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Cadmium telluride PV module manufacturing at BP Solar
Abstract
BP Solar has built a 10 MW capacity CdTe thin-film (Apollo®) manufacturing plant in Fairfield, California. The plant is on the verge of commercialization and is expected to produce several megawatts of 61 × 155 cm (24 × 61-inch) thin-film modules (nominally 80 W) in 2001. This paper describes the basic Apollo® process steps, the recent advances made in the Apollo® CdTe technology, the state of the art CdTe reactor with its sophisticated design and control features and various techniques used to characterize the semiconductor materials. Module performance and reliability results are also summarized. An NREL-confirmed module efficiency of 10.6% is reported for a 0.94 m2 module with a maximum power of 91.5 W. Indoor stress testing and outdoor performance test beds are described, and the data presented show good indoor stability under various stress conditions. Copyright © 2002 John Wiley & Sons, Ltd.
... The scalability and manufacturability of electroplating has been demonstrated on an industrial scale by British Petroleum (BP) Solar in the 1980s and 1990s [78,79]. BP Solar manufactured CdTebased solar cells with a solar panel area ~1 m 2 with a conversion efficiency of ~10% [78,79]. ...
... The scalability and manufacturability of electroplating has been demonstrated on an industrial scale by British Petroleum (BP) Solar in the 1980s and 1990s [78,79]. BP Solar manufactured CdTebased solar cells with a solar panel area ~1 m 2 with a conversion efficiency of ~10% [78,79]. As compared to the laboratory scale setup as shown in Figure 2, scaling up requires a larger tank to contain the electrolyte and multi-plate cathode attached to multiple conducting substrates. ...
... The scalability and manufacturability of electroplating has been demonstrated on an industrial scale by British Petroleum (BP) Solar in the 1980s and 1990s [78,79]. BP Solar manufactured CdTe-based solar cells with a solar panel area~1 m 2 with a conversion efficiency of~10% [78,79]. ...
The attributes of electroplating as a low-cost, simple, scalable, and manufacturable semiconductor deposition technique for the fabrication of large-area and nanotechnology-based device applications are discussed. These strengths of electrodeposition are buttressed experimentally using techniques such as X-ray diffraction, ultraviolet-visible spectroscopy, scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy, and photoelectrochemical cell studies. Based on the results of structural, morphological, compositional, optical, and electronic properties evaluated, it is evident that electroplating possesses the capabilities of producing high-quality semiconductors usable for producing excellent devices. In this paper we will describe the progress of electroplating techniques mainly for the deposition of semiconductor thin film materials and their treatment processes, and fabrication of solar cells.
... In order to achieve this, any research programme should be focused on low-cost, scalable and manufacturable growth method. During the late 1990s, BP Solar successfully demonstrated this by manufacturing nearly 1.0 m 2 solar panels with conversion efficiencies greater than 10% [21]. Since the electrodeposition of semiconductors fulfils all these three criteria, authors' work is mainly based on electroplated semiconductors and the work presented in this paper is on electroplated CdS and CdTe materials and devices. ...
... CdCl 2 addition to the thin films of CdTe was carried out in many different ways. One method was to add CdCl 2 into the CdSO 4 electrolyte in the case of electroplating [21]. For many other growth methods, CdTe thin films were immersed in a CdCl 2 solution and allowed to dry before heat treatment. ...
... This method is particularly suitable for manufacturing large area electronic devices such as PV solar panels and display devices. The CdS/CdTe project completed by BP Solar successfully proved the manufacturability of large solar panels in the 1980s and 1990s by producing ~1.0 m 2 solar panels with efficiencies over 10% using electroplated CdTe [21]. The current aim of the research at SHU solar energy group is to develop next generation solar cells based on graded bandgap device structures utilising electroplated materials. ...
Thin film solar cells based on CdS/CdTe hetero-structure has shown a drastic improvement changing from 16.5 to 22.1% efficiency during a short period of time from ~2013 to ~2016. This has happened in the industrial environment and the open research in this field has stagnated over a period of two decades prior to ~2013. Most of the issues of this hetero-structure were not clear to the photovoltaic (PV) community and research efforts should be directed to unravel its complex nature. Issues related to materials, post-growth treatment, chemical etching prior to metallisation and associated device physics are the main areas needing deeper understanding in order to further develop this device. After a comprehensive research programme in both academia and in industry on these materials, surfaces and interfaces and fully fabricated devices over a period of over three decades by the main author, the current knowledge as understood today, on all above mentioned complex issues are presented in this paper. Full understanding of this structure will enable PV developers to further improve the conversion efficiency beyond 22.1% for CdS/CdTe based solar cells.
... conversion [1][2][3][4][5] and radiation detection [6][7][8]. The most crucial properties of this material for these applications include; optical, structural, chemical composition and electronic properties. ...
... The overall response of the material to the incident light is connected to its complex refractive index according to Eq. (2). ...
... Figure 9a-d show the graph of (αhν) 2 vs photon energy for all the samples. Again, the highest absorption (αhν) 2 and the best absorption edges are displayed by the samples treated with CdCl 2 + CdF 2 followed by those treated with only CdCl 2 and then by the samples annealed without chemical treatment. These results bring out the overall positive effect of annealing on electrodeposited CdTe. ...
CdTe thin films of different thicknesses were electrodeposited and annealed in air after different chemical treatments to study the effects of thickness and the different chemical treatments on these films for photovoltaic applications. The thicknesses of the samples range from 1.1 to 2.1 μm and the annealing process was carried out after prior CdCl2 treatment and CdCl2 + CdF2 treatment as well as without any chemical treatment. Detailed optical and structural characterisation of the as-deposited and annealed CdTe thin films using UV–Vis spectrophotometry and X-ray diffraction reveal that incorporating fluorine in the well-known CdCl2 treatment of CdTe produces remarkable improvement in the optical and structural properties of the materials. This CdCl2 + CdF2 treatment produced solar cell with efficiency of 8.3% compared to CdCl2 treatment, with efficiency of 3.3%. The results reveal an alternative method of post-deposition chemical treatment of CdTe which can lead to the production of CdTe-based solar cells with enhanced photovoltaic conversion efficiencies compared to the use of only CdCl2.
... The development progress became slow, and it took nearly another decade to increase the efficiency only by 0.7-16.5% by Wu et al. [14]. In parallel to this scientific research, BP Solar initiated a scaling up process in the mid-1980s using electroplated CdTe and successfully manufactured 0.96-m 2 solar panels with an efficiency of 10.6% [15]. Although BP Solar was in the forefront of this technology, termination of this manufacturing work together with other solar energy activities around 2000 was a real setback for the development of CdS/CdTe solar cells. ...
... For the growth of CdTe layers, there are about 14 different growth techniques [24], but the commercially successful methods have been CSS and electrodeposition (ED). First Solar Company is successfully using modified CSS to produce high-efficiency devices, and the manufacturability of ED-CdTe has also been successfully proven by BP Solar [15]. Because of the comprehensive research carried out by the authors of this article on electrodeposition of semiconductors, most of the examples given in this paper will be based on ED-CdTe thin films [25,26], but the principles can also be applied to CdTe layers grown by other techniques. ...
Cadmium telluride-based solar cell is the most successfully commercialised thin film solar cell today. The lab-scale small devices have achieved ~22% and commercial solar panels have reached ~18% conversion efficiencies. However, there are various technical complications and some notable scientific contradictions that appear in the scientific literature published since early 1970s. This review paper discusses some of these major complications and controversies in order to focus future research on issues of material growth and characterisation, post-growth processing, device architectures and interpretation of results. Although CdTe can be grown using more than 14 different growth techniques, successful commercialisation has been taken place using close-space sublimation and electrodeposition techniques only. The experimental results presented in this review are mainly based on electrodeposition. Historical trends of research and commercial successes have also been discussed compared to the timeline of novel breakthroughs in this field. Deeper understanding of these issues may lead to further increase in conversion efficiencies of this solar cell. Some novel ideas for further development of thin film solar cells are also discussed towards the end of this paper.
... The scalability and manufacturability of electroplating has been demonstrated on an industrial scale by BP solar in the 1980s and 1990s [67,68]. BP solar manufactured CdTebased solar cells with solar panel area ~1 m 2 with a conversion efficiency of ~10% [67,68]. ...
... The scalability and manufacturability of electroplating has been demonstrated on an industrial scale by BP solar in the 1980s and 1990s [67,68]. BP solar manufactured CdTebased solar cells with solar panel area ~1 m 2 with a conversion efficiency of ~10% [67,68]. ...
The attributes of electroplating as a low-cost, simple, scalable and manufacturable semiconductor deposition technique for the fabrication of large-area and nanotechnology-based device applications are discussed. These strengths of electrodeposition are buttressed experimentally using techniques such as X-ray diffraction, Ultraviolet-visible spectroscopy, Scanning electron microscopy, Atomic force microscopy, Energy-dispersive X-ray spectroscopy and photoelectrochemical cell studies. Based on the structural, morphological, compositional optical, and electronic properties evaluated results, it is evident that electroplating possesses the capabilities of producing high-quality semiconductors usable in producing excellent devices. In this paper, we will describe the progress of electroplating technique mainly for the deposition of semiconductor thin film materials, their treatment processes and fabrication of solar cells.
... The history of CdTe growth based on electrodeposition using an aqueous electrolyte was first demonstrated by Mathers and Turner in 1928 [13]. A more elaborate work on the electrodeposition of CdTe was carried out by Panicker and Knaster in 1978 [12], and thereafter, many researchers [1,[15][16][17][18][19] have electrodeposited CdTe from aqueous solutions. Usually, the electrodeposition of CdTe is carried out using CdSO 4 and TeO 2 , which serve as the Cd and Te precursors, respectively. ...
... Usually, the electrodeposition of CdTe is carried out using CdSO 4 and TeO 2 , which serve as the Cd and Te precursors, respectively. The research program continued by BP in the 1980s successfully demonstrated the scaling up of this technology by manufacturing nearly 1.0 m 2 in area solar panels with over 10% conversion efficiency [18]. The successful deposition of CdTe and comprehensive material characterization have also been carried out recently using CdCl 2 [14] and Cd(NO 3 ) 2 precursors [19] for selecting the best cadmium precursor for electroplating. ...
Electrodeposition of CdTe thin films was carried out from the late 1970s using the cadmium sulphate precursor. The solar energy group at Sheffield Hallam University has carried out a comprehensive study of CdTe thin films electroplated using cadmium sulfate, cadmium nitrate and cadmium chloride precursors, in order to select the best electrolyte. Some of these results have been published elsewhere, and this manuscript presents the summary of the results obtained on CdTe layers grown from cadmium sulphate precursor. In addition, this research program has been exploring the ways of eliminating the reference electrode, since this is a possible source of detrimental impurities, such as K ⁺ and Ag ⁺ for CdS/CdTe solar cells. This paper compares the results obtained from CdTe layers grown by three-electrode (3E) and two-electrode (2E) systems for their material properties and performance in CdS/CdTe devices. Thin films were characterized using a wide range of analytical techniques for their structural, morphological, optical and electrical properties. These layers have also been used in device structures; glass/FTO/CdS/CdTe/Au and CdTe from both methods have produced solar cells to date with efficiencies in the region of 5%–13%. Comprehensive work carried out to date produced comparable and superior devices fabricated from materials grown using 2E system. View Full-Text
... With theoretical calculations indicating that quantum dot solar cells have the potential to reach a maximum thermodynamic conversion efficiency of up to 66% 11 , the development of hybrid photoactive ink formulations which are compatible with inkjet printing processes presents one of the key challenges in advancing this technology. Thus far, hybrid cells have, for the most part, relied on the II-VI semiconductor cadmium-selenide (CdSe) for the inorganic component 12,13 , while the closely related compound cadmium-telluride (CdTe) has received little attention despite the fact that it is the foremost photovoltaic material for the thin film solar cell industry [14][15][16] . Here, we present our studies focused on fabricating a photoactive CdTe ink formulation which is compatible with the inkjet printing process. ...
... These days, solar cells are often made using the electrodeposition approach, such as the CIGS solar cells created with France's CISEL [27] and the CdTe cells made via BP plc [28]. Although thiourea was utilized as a precursor for the electrodeposition of CdS [29], Finding a reliable sulfur supply for the electrodeposition of CZTS proved challenging. ...
CMTS is a quaternary semiconductor similar to copper zinc tin sulfide (CZTS) which is nontoxicand abundant on Earth and is a P-type light absorbent material which is suitable for thinfilmsolar cell fabrication and achieves better conversion efficiency of 0.78% , as well as havinga direct energy gap estimated at (1.76 eV) and a high optical absorption coefficient [20] (α≥ 104cm-1). In this paper, the development cases of a Cu2MgSnS4 composite in the thin-film industry,as well as its use in solar cell applications, are summarized. Illustrated and explained thedifficulty related to processing the raw material, the manufacturing procedure, andmanufacturing equipment. Finally, the potential for development of Cu2MgSnS4. Where thefocus was on thin films.
... In thermal evaporation, the precursor substance is heated in a vacuum chamber until it vaporizes, and then allowed to deposit onto a substrate, where it condenses into a solid film. High-quality CZTS films with good crystallinity and purity can be produced using this technique [9,10]. Pulsed laser deposition (PLD) is a process that ablates a target material with a high-energy laser before depositing it onto a substrate. ...
The research referred to in this study examines the morphological, structural, and optical characteristics of kesterite (Cu1−xAgx)2ZnSnS4 (CAZTS) thin films, which are produced using a process known as thermal evaporation (TE). The study’s main goal was to determine how different Ag contents affect the characteristics of CAZTS systems. X-ray diffraction (XRD) and Raman spectroscopy were used to confirm the crystal structure of the CAZTS thin films. Using a mathematical model of spectroscopic ellipsometry, the refractive index (n) represented the real part of the complex thin films, the extinction coefficient (k) portrayed the imaginary part, and the energy bandgap of the fabricated thin films was calculated. The energy bandgap is a crucial parameter for solar cell applications, as it determines the wavelength of light that the material can absorb. The energy bandgap was found to decrease from 1.74 eV to 1.55 eV with the increasing Ag content. The ITO/n-CdS/p-CAZTS/Mo heterojunction was well constructed, and the primary photovoltaic characteristics of the n-CdS/p-CAZTS junctions were examined for use in solar cells. Different Ag contents of the CAZTS layers were used to determine the dark and illumination (current–voltage) characteristics of the heterojunctions. The study’s findings collectively point to CAZTS thin layers as potential absorber materials for solar cell applications.
... Then, for the case of the n-type semiconductor (ZnO), the refractive index equals 1.75 at 350 nm, and it decreases exponentially to 1.6 at 800 nm as shown in Fig. 2. Moreover, its extinction coefficient equals the value of 0.17 at a wavelength of 300 nm and decreases exponentially to the value of 0.02 at 400 nm as shown in Fig. 3. Therefore, this layer is assumed to possess high absorbance values at shorter wavelengths corresponding to its extinction coefficient [51,52]. Meanwhile, the bandgap of ZnO between 3.1 and 3.2 eV is obtained as in [53,54]. ...
In this research, a front layer of indium tin oxide (ITO) is added on the top surface of copper zinc tin sulfide (CZTS)/zinc oxide (ZnO) thin film solar cell. The goal of this paper is to improve the absorption values against the angle of incidence through visible wavelengths. The transfer matrix approach and the finite element method were extensively used in the design and simulation process. The numerical findings are investigated with the help of COMSOL multiphysics software as well. Recently, it has been found that the angle of incidence significantly reduces the solar cell absorption. To prevent such increment of absorption losses as the angle of incidence rises, the numerical findings have deduced that it may therefore be of interest to include an anti-reflecting coating of ternary one-dimensional photonic crystals on a single unit cell. Meanwhile, the anti-reflective coating is designed with three different geometries: planar, convex, and concave. The investigated results demonstrated that the concave geometry is efficient in controlling the absorption losses of the designed CZTS/ZnO thin film solar cell against the increase in the angle of incidence. In this regard, for an angle of incidence less than 50°, the solar cell absorption values remain greater than 0.9055 all over the visible spectrum. Therefore, a relatively high performance of this cell is strongly expected.
... High-energy ions are used to bombard a target material in this process, causing atoms to be expelled and deposited onto a substrate. The composition and qualities of the CZTS film can be controlled by sputtering with a variety of gases, such as argon [9][10][11]. In thermal evaporation, the precursor substance is heated in a vacuum chamber until it vaporizes, and then allowed to deposit onto a substrate where it condenses into a solid film. ...
The research that we are referring to examines the morphological, structural, and optical characteristics of kesterite (Cu1-xAgx)2ZnSnS4 (CAZTS) thin films, which are produced using a process known as thermal evaporation (TE). The study's main goal was to determine how different Ag contents affect the characteristics of CAZTS systems. X-ray diffraction (XRD) and Raman Spectroscopy: were used to confirm the crystal structure of the CAZTS thin films. Using a mathematical model of spectroscopic ellipsometry, the refractive index (n) represented the part of the complex refractive index, the extinction coefficient (k) portrayed the imaginary one, and also the energy band gap of the fabricated films were all calculated. The energy band gap of the thin films was also calculated. This is a crucial parameter for solar cell applications, as it determines the wavelength of light that the material can absorb. The energy band gap was found to decrease from 1.74 eV to 1.55 eV with increasing Ag content. The ITO/n-CdS/p-CAZTS/Mo heterojunction was well constructed, and the primary photovoltaic characteristics of the n-CdS/p-CAZTS junctions were examined for use in solar cells. Different Ag contents of the CAZTS layers were used to determine the dark and illumination (current-voltage) characteristics of the heterojunctions. The study's findings collectively point to CAZTS thin layers as potential absorber materials for solar cell applications.
... To decrease the number of cations in a liquid substance or product, one effective strategy is using electrochemical precipitation or hot-plunge liquid at the cathode by utilizing the power of the external circuit. In the 1970s, people began experimenting with semiconductor material electrochemical explanations [82,83].Electrodeposition is presently utilized to produce solar cells, such as CIGS solar cells manufactured by France's CISEL [84] and CdTe cells manufactured by BP plc [85]. However, employing thiourea as an alternative for CdS in the electrodeposition process has proven difficult in identifying areas of strength for this source efficiency of 0.8% [87][88]. ...
For the past ten years, copper-based quaternary chalcogenide semiconductor materials have also been studied and classified in a variety of ways. The majority of research and academic works on quaternary chalcogenides are devoted to solar cell PV studies, where, as the material first gained popularity as a less expensive option in contrast to Si for Solar PV systems. . Such components have all of the desirable characteristics for becoming an effective PV material in the thin films or nanomaterials configuration, like effective and non-toxic unique materials, effective charge carrier, best possible energy band, as well as higher adsorption co-effectiveness. Cu2MIMIIX4 (where X = S or/and Se; MII = Si, Sn, and Ge; MI = Zn, Mn, Fe, Co, Ni, Cd, and Hg) is a new class of quaternary materials that has just emerged and found use in electrochemistry, thermal, sensor systems, power banks, and some other technologies. The unique combination characteristics of this class of chalcogenides, like optoelectronic and electrical; magnetic and optoelectronic; as well as thermo-electric, make their potentially useful importance for a variety of usages. Even though many of the papers have already covered the PV characteristics of such quaternary chalcogenides, this material has many various uses that remain investigated. This article touches on the multi-functional systems of novel dissimilar quaternary copper-based chalcogens, including the fabrication, the doping impact on their physical and chemical characteristic, and their use in many applications, including solar cells.
... In recent times, the electrochemical deposition techniques or the electro-deposition techniques have been followed widely to prepare thin-film solar cell materials [68,69]. The first semiconductor electrochemical deposition method was carried out almost four decades ago [70]. ...
In the renewable energy sector, solar energy has emerged as a very abundant resource, which has its implementation from very large-scale industries to household uses. The market of solar cells has been monopolized by thick-film Silicon solar cells ever since its initial development. However, with recent advancements, thin film has become the preferred design for solar cells because of several upper hands it proved over the thick cells. CIGS (Copper Indium Gallium Diselenide) and CdS (Cadmium Selenide) have shown tremendous performances in the thin-film sector. But with toxicity and cost factors, these cells are never that feasible. So, CZTS (CuZnSn Sulfide) which has come as a replacement for CIGS, has shown extraordinary photovoltaic nature with very high light absorption characteristics. Further, the constituents of CZTS are abundant in nature which reduces the cost involved. To enhance efficiency, numerous structural and material features have been experimentally modified. The single-junction CZTS solar cell, however, has yet to achieve an efficiency of more than 13%, despite numerous attempts. This article presents a thorough analysis of the advancements made and potential applications for the CZTS thin-film solar cell (TFSC). This manuscript outlines the development of the TFSC, the fabrication process, the design of the TFSC, the defects in the CZTS, and the potential use of the TFSC as a solar cell.
... 59,107 All-laser-scribed thin-film solar module interconnection is an industrial standard and applied already for decades in amorphous silicon (a-Si), CdTe, and tandem thin-film a-Si-based modules. 108,109 The process provides high throughput due to fast scanning speeds, low maintenance, and is compatible with flexible substrates due to noncontact processing. 43,110 Consequently, laser scribing is of key interest for perovskite solar module interconnections, enabling the fabrication of scribing lines of only few tens of micrometers lateral extension and of good electrical properties. ...
Given the outstanding progress in research over the past decade, perovskite photovoltaics (PV) is about to step up from laboratory prototypes to commercial products. For this to happen, realizing scalable processes to allow the technology to transition from solar cells to modules is pivotal. This work presents all‐evaporated perovskite PV modules with all thin films coated by established vacuum deposition processes. A common 532‐nm nanosecond laser source is employed to realize all three interconnection lines of the solar modules. The resulting module interconnections exhibit low series resistance and a small total lateral extension down to 160 μm. In comparison with interconnection fabrication approaches utilizing multiple scribing tools, the process complexity is reduced while the obtained geometrical fill factor of 96% is comparable with established inorganic thin‐film PV technologies. The all‐evaporated perovskite minimodules demonstrate power conversion efficiencies of 18.0% and 16.6% on aperture areas of 4 and 51 cm2, respectively. Most importantly, the all‐evaporated minimodules exhibit only minimal upscaling losses as low as 3.1%rel per decade of upscaled area, at the same time being the most efficient perovskite PV minimodules based on an all‐evaporated layer stack sequence. Here, we report on the concept of all‐evaporated perovskite solar modules with all‐laser‐scribed monolithic interconnections. Fabricated minimodules exhibit power conversion efficiencies of 18.0% and 16.6% on aperture areas of 4 and 51 cm2, respectively. Minimal upscaling losses of 3.1%rel per decade of upscaled area are demonstrated.
... At a cathodic potential above ~ 1300 mV, there seems to be stability in the forward current density from ~ 1320 mV to 1450 mV. Within this voltage range, co-deposition of Te, Cd and Mn takes place and hence the CdMnTe semiconductor compound starts to deposit on the cathode according to the chemical reaction shown in Eq. (4), which is a summation of Eq. (1), (2) and (3). ...
Growth of polycrystalline CdMnTe ternary compound thin films has been carried out using cathodic electrodeposition technique at different cathodic potentials. The range of the cathodic potentials used in this work has been chosen according to the cyclic voltammogram results. The CdMnTe thin films were electroplated from electrolyte containing CdSO 4 , TeO 2 and MnSO 4 in an acidic aqueous medium. Glass/fluorine-doped tin oxide (FTO) substrates have been used to electrodeposit the semiconductor layers. The structural, compositional, morphological, optical and electrical properties of the CdMnTe thin films were studied using X-ray diffraction (XRD), Sputtered neutral-mass spectroscopy (SNMS), Scanning electron microscopy (SEM), UV-Vis spectroscopy and Photo-electro-chemical (PEC) cell measurements respectively. The primarily grown as-deposited (AD) layers went through two different post-growth surface treatment conditions-heat-treated in air in the presence of CdCl 2 (CCT) and heat-treated in air in the presence of GaCl 3 (GCT). Results from the XRD indicated the polycrystalline nature of the electrodeposited films. The electroplated films have cubic crystal structures and the preferred orientation was found to be along the (111) plane of CdMnTe. Inclusion of Mn has been qualitatively observed using SNMS measurement. The optical energy bandgaps of the thin films were found to be varying between ~ 1.90 and ~ 2.20 eV. Though all the layers after post-treatment showed p-type electrical conduction, both p and n-type conductivity were obtained at different cathodic potentials for as-deposited materials. Comparison of the deposited layers to other electrodeposited ternary compounds has also been discussed.
... The potential of CdTe thin films in the fabrication of radiation detectors with room temperature capability has been attributed to their unique properties such as atomic number (Cd: 48 and Te: 52), good chargetransport, high resistivity (109 X), high density (5.85 g/cm 3 ), and relatively large energy band gap (1.44 eV) [4][5][6][7]. Different deposition techniques have been employed in the growth of CdTe thin films such as chemical bath deposition (CBD), sputtering, thermal evaporation, electrodeposition (ED) etc., [8][9][10][11]. Among these various techniques, electrodeposition has been reported as one of the simplest techniques in the synthesis of CdTe based solar cells [12]. ...
In this research, cadmium telluride (CdTe) thin films were fabricated using electrodeposition technique at 1400 mV cathodic potential. CdTe films were deposited on fluorine doped tin oxide (FTO) substrate of dimension 2.3 by 2.4 cm² at varied time of deposition. X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet visible spectrophotometer (UV-vs), photoelectrochemical cell measurement (PEC), and energy dispersive X-ray spectroscopy (EDX) were used to characterize the structural, morphological, optical, electrical conductivity and elemental composition of electrodeposited films respectively. The particle average crystallite size was estimated as 11.98 nm. The energy band gap of as deposited films decreases as the period of deposition increases for both annealed and unannealed samples. Furthermore, the period of deposition was found to constitute major factor in the dominance of the constituent elements, thereby influencing the electrical conductivity and band gap properties of the films. Consequently, the conductivity of CdTe can be reasonably tuned when heat-treated and the tunability of the energy band gap can be achieved by varying the period of deposition in the electrodeposition technique. Despite the potential of electrodeposited CdTe in solar cells applications, synthesis of p-type CdTe in a stable way place a bottleneck to the utilization of CdTe as a good absorber layer in preventing front surface recombination when CdTe form a heterojunction with any window layer material.
... This is made possible by the electrical in-series integration of the cells directly inside the production process (monolithically integrated) by means of a robotic laser scribing. This technology realized a 11% efficient module in 2002 by depositing the CdTe thin film with the electrodeposition technique [79]. In the years 2010-2011, the number of factories able to produce tens of megawatts/years of CdTe modules were 10 units worldwide. ...
Among thin-film photovoltaic technology, cadmium telluride (CdTe) has achieved a truly impressive development that can commercially compete with silicon, which is still the king of the market. Solar cells made on a laboratory scale have reached efficiencies close to 22%, while modules made with fully automated in-line machines show efficiencies above 18%. This success represents the result of over 40 years of research, which led to effective and consolidated production processes. Based on a large literature survey on photovoltaics and on the results of research developed in our laboratories, we present the fabrication processes of both CdTe polycrystalline thin-film solar cells and photovoltaic modules. The most common substrates, the constituent layers, their interaction, the interfaces and the different “tricks” necessary to obtain highly efficient devices will be analyzed. A realistic industrial production process will be analytically described. Moreover, environmental aspects, end-of-life recycling and the life cycle assessment of CdTe-based modules will be deepened and discussed.
... Cadmium chloride treatment or the activation step is a wellknown processing step to increase the efficiency of CdS/ CdTe thin film solar cells [38][39][40][41]. Numerous publications are available on this treatment that includes the introduction of CdCl 2 on to the CdTe surface and heat treatment in air at an optimised temperature for optimised time period. ...
Cadmium telluride-based solar cell is the most successfully commercialised thin film solar cell today. The laboratory-scale small devices have achieved ~ 22%, and commercial solar panels have reached ~ 18% conversion efficiencies. However, there are various technical complications and some notable scientific contradictions that appear in the scientific literature published since the early 1970s. This review paper discusses some of these major complications and controversies in order to focus future research on issues of material growth and characterisation, post-growth processing, device architectures and interpretation of the results. Although CdTe can be grown using more than 14 different growth techniques, successful commercialization has been taken place using close-space sublimation and electrodeposition techniques only. The experimental results presented in this review are mainly based on electrodeposition. Historical trends of research and commercial successes have also been discussed compared to the timeline of novel breakthroughs in this field. Deeper understanding of these issues may lead to further increase in conversion efficiencies of this solar cell. Some novel ideas for further development of thin film solar cells are also discussed towards the end of this paper.
... The major growth techniques used for large area CdS/CdTe-based solar cell fabrication are, close spaced sublimation (CSS) [3], sputtering [4] and electrochemical deposition (ED) [5]. However, with respect to deposition process continuity, doping simplicity, self-purification, scalability, manufacturability, economic viability and Cdcontaining waste reduction, electrodeposition (ED) is considered one of the leading techniques [6][7][8][9][10][11]. ...
Cadmium sulphide (CdS) thin-films have been electrodeposited using two electrode system to be used as the hole back diffusion barrier (hbdb) layer for graded bandgap solar cells with p-type windows. Cadmium acetate dihydrate [Cd(CH3COO)2·2H2O] and ammonium thiosulphate [(NH4)2S2O3] have been used as the cadmium (Cd) and sulphur (S) precursors respectively. In this work, CdS layers have been grown on glass/FTO (fluorine doped tin oxide) substrates at cathodic potentials ranging from 1300 to 1460 mV in order to find the best growth voltage. N-type conductivity is observed for all the layers and band-gap ranged between ~ 2.36 and ~ 2.40 eV for as-deposited layers and ~ 2.31 and ~ 2.36 eV for air-annealed layers. X-ray diffraction (XRD) analysis revealed cubic/hexagonal mixed crystallinity for the as-grown layers which indicates a tendency of transiting towards hexagonal structure upon annealing. Compositional and morphological characteristics of the layers have been investigated with energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) respectively.
... The main focus of the PV community is to reduce the Watt per hour ($W -1 ) cost using low-cost materials and processing methods. Electrodeposition, a low-cost method of semiconductor growth has shown the flexibility of semiconductor growth from both aqueous and non-aqueous solutions (Sasikala, Dhanasekaran and Subramanian, 1997) and has been proven to be manufacturable in the production of solar panels (Cunningham, Rubcich and Skinner, 2002). It also provides advantage for the control of deposition parameters, and hence material properties. ...
Cadmium sulphide thin films have been grown from acidic electrolyte prepared from analytical grade reagent using electroplating technique. The films were grown on glass/FTO substrate in an acidic medium of pH 2.50 and temperature of 85 o C. The layers were intended for use as window layers in CdTe thin film solar cells. The structural study show that the films were crystalline with the preferred orientation along the (100)H phase of cadmium sulphide (CdS). The optical study shows that the bandgaps matched well with the bulk bandgap of CdS (2.42 eV) after the cadmium chloride (CdCl2) treatment. The films also show improved morphology after CdCl2 with increased roughness than in the case of the as-deposited films. Photoelectrochemical (PEC) cell study indicate that all the layers in both the as-deposited and after the CdCl2 were n-type in electrical conduction.
... In addition, the work will concentrate on the possible application of these films in solar cells, although they can be applied in other optoelectronic devices such as photodiodes, photoresistors and light-emitting diodes, as mentioned earlier. This becomes important as electrochemical deposition has proven to be a reliable and scalable technique for growing semiconductor materials that produce high-efficiency solar cells [10,17,31,32] in recent times. It therefore becomes pertinent to mention that for solar cell application, as window material, CdS is preferably grown using the CBD method while the absorber material (CdTe, CIGS or CZTS) can be grown by a variety of techniques other than CBD. ...
Thin film CdS materials for possible optoelectronic devices application have been synthesized by the electrochemical deposition method, using two different cadmium salts and sodium thiosulphate as precursors. In order to keep the synthesis process as simple as possible, no additional chemicals were added as complexing agents or buffers, and a two-electrode set-up was used. The qualities of the resulting films from the different cadmium precursors were compared by characterizing them for their physico-chemical properties using state-of-the-art glancing incidence X-ray diffraction, UV–Vis spectrophotometry, scanning electron microscopy and energy dispersive X-ray spectroscopy (EDX). The results obtained show significant influence of cadmium precursor on the structural, optical and chemical properties of the films. Whereas CdCl2 precursor produced CdS with purely hexagonal structure in both as-grown and heat-treated conditions, Cd(CH3COO)2 produced CdS with purely cubic crystal structure, with films from both precursors showing clear difference in physical appearance. Energy bandgap values estimated for the films are in the range (2.49–2.57) eV and (2.22–2.23) eV in as-deposited form, with CdCl2 and Cd(CH3COO)2 precursors respectively. After annealing, these values become 2.42 eV with CdCl2 and (2.30–2.31) eV with Cd(CH3COO)2. Although CdS from both precursors show similar surface morphology, EDX results reveal that CdS films from CdCl2 precursor are more stoichiometric with Cd/S atomic ratios of (0.90–0.93) compared to films from Cd(CH3COO)2 precursor with Cd/S values of (0.87–0.88).
... Other subdivisions of chemical vapour deposition (CVD) include metalorganic CVD (MOCVD), atmospheric pressure CVD (APCVD), etc. [3]. However, based on the simplicity of technique, columnar growth, selfpurification, ease of extrinsic doping [5] and ease of depositing n-type, i-type and p-type semiconductors (for semiconductor materials whose conductivity type depends on stoichiometry) by varying the deposition potential, scalability, manufacturability [6][7][8] and economic viability [9] amongst other advantages, electrodeposition is considered as one of the leading thin-film deposition techniques [10]. Electrodeposition is not without its challenges; this includes requirements for a conducting substrate, pinhole generation (due to its nucleation mechanism [11]), low process temperature (as improved crystallinity is achievable at higher deposition temperature [12]), comparatively longer deposition time, etc. ...
Further to the semiconductor material and electronic properties discussed in Chap. 2, the evaluation of semiconductor materials can be examined for structural, morphological, compositional, optical and electronic properties to facilitate research towards optimisation. This chapter describes the physics and the basic functionality of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy and photoelectrochemical (PEC) cell measurement equipment. Current-voltage (I-V) and capacitance-voltage (C-V) techniques were utilised for the evaluation to facilitate research towards solar cell device performance in order to understand the factors affecting the performance of device materials.
... Maybe, electrodeposition is one of the more exploited large area L-T technique, since the 90's when PV modules based on ED-CdTe was fabricated in BP Solar's laboratories (Turner et al., 1994;Cunningham et al., 2002). However, electrodeposition of semiconducting materials was firstly introduced in the 70's (Danaher and Lyons 1978;Kröger, 1978;Panicker et al., 1978) and in the early 1980's (Fulop and Taylor, 1985;Ortega and Herrero, 1989) a thin film ED-CdTe-based solar cell with a remarkable efficiency above 8% was successfully obtained (Basol, 1984). ...
Recently, the CdTe solar cell technology reached a high-tech level able to realize devices showing efficiencies close to 22%. Nowadays, this technology acquires more and more market share, becoming the most promising among the thin film technologies. These important achievements are the result of more than 40 years of studies and researches that have synergically group together the photovoltaic module manufacturing technology with semiconductor and interfaces physics, modeling, characterization and measurements on electronic devices.
This paper shows the main steps of the production process of the thin film CdTe/CdS-based solar cells both from a technological and from a physical point of view.
In particular, the main differences between cells fabricated in superstrate and in substrate configuration will be highlighted. For each of these two structures the fundamental layers, their main alternatives, chemical and thermal treatments, interfaces, the won challenges and the still open-problems will be presented and discussed.
... The main focus of the PV community is to reduce the Watt per hour ($W -1 ) cost using low-cost materials and processing methods. Electrodeposition, a low-cost method of semiconductor growth has shown the flexibility of semiconductor growth from both aqueous and non-aqueous solutions (Sasikala, Dhanasekaran and Subramanian, 1997) and has been proven to be manufacturable in the production of solar panels (Cunningham, Rubcich and Skinner, 2002). It also provides advantage for the control of deposition parameters, and hence material properties. ...
In this work, we present a theoretical investigation on the structural, electronic and optical properties of Bi2Se3 via density functional theory (DFT) approach in conjunction with a many-body perturbation theory (MBPT) formalism. It was found that inclusion of van der Waals (vdW) correction reproduce experimental interlayer distances, lattice parameters and atomic coordinates of Bi2Se3 material. Also, band structure calculations show that correction leads to a band gap closer to the experiment. On the other hand, excitonic effects and optical properties, namely, imaginary and real parts of dielectric function, refractive index, absorption coefficient, extinction coefficient, reflectivity, electron energy loss function and optical conductivity are investigated using Bethe-Salpeter equation (BSE) approach. Our first time reported results of Bi2Se3 with inclusion of electron-hole interaction show a good agreement with the available experimental measurements. The obtained results of the exciton energy show that the title material can absorb a photon within infrared wavelengths.
Thin-film solar cells (TFSCs) represent a promising frontier in renewable energy technologies due to their potential for cost reduction, material efficiency, and adaptability. This literature review examines the key materials and advancements that make up TFSC technologies, with a focus on Cu(In,Ga)Se2 (CIGS), cadmium telluride (CdTe), and Cu2ZnSnS4 (CZTS) and its sulfo-selenide counterpart Cu2ZnSn(S,Se)4 (CZTSSe). Each material’s unique properties—including tuneable bandgaps, high absorption coefficients, and low-cost scalability—make them viable candidates for a wide range of applications, from building-integrated photovoltaics (BIPV) to portable energy solutions. This review explores recent progress in the enhancement of power conversion efficiency (PCE), particularly through bandgap engineering, alkali metal doping, and interface optimization. Key innovations such as silver (Ag) alloying in CIGS, selenium (Se) alloying in CdTe, and sulfur (S) to Se ratio optimization in CZTSSe have driven PCE improvements and expanded the range of practical uses. Additionally, the adaptability of TFSCs for roll-to-roll manufacturing on flexible substrates has further cemented their role in advancing renewable energy adoption. Challenges remain, including environmental concerns, but ongoing research addresses these limitations, paving the way for TFSCs to become a crucial technology for transitioning to sustainable energy systems.
Incorporating mesoporous structures into various materials can provide abundant active sites and facilitate smooth diffusion, and their effectiveness has been demonstrated across a range of material types. However, despite the development of numerous mesoporous materials, first-generation mesoporous materials (e.g., silica-based compositions) have limited applications due to their poor electrical conductivity and limited compositional diversity, necessitating additional processing for widespread utilization. Our group first proposed the synthesis of mesoporous metals using a solution-based soft-templating method based on self-assembly of micelles, marking a significant advancement in mesoporous materials. This effective process has recently been extended to the synthesis of mesoporous metals and chalcogenides. Chalcogenides have garnered significant attention due to their intriguing optical, electrical, and electrochemical properties arising from their distinctive electronic structures. Mesoporous chalcogenides have been found to effectively enhance these properties. This paper provides a comprehensive review of the synthesis of mesoporous metals and chalcogenides—representing second-generation mesoporous materials (mesoporous materials 2.0)—with specific examples. Our goal is to inform readers about second-generation mesoporous materials and provide insights for further research.
Cadmium Telluride (CdTe) thin film solar cells have demonstrated high efficiency and cost-effectiveness in generating clean electricity. However, the commonly used CdS buffer layer in these cells poses environmental and health concerns due to its cadmium content. This study investigates the performance of CdTe solar cells with various Cd-free zinc chalcogenide-based buffer layers (ZnO, ZnSe, ZnS) using numerical simulations with the Silvaco-Atlas software. The baseline CdS/CdTe solar cell structure was first validated, yielding a conversion efficiency of 22.14%, in good agreement with previous experimental and theoretical results. Replacing the CdS buffer layer with ZnO, ZnSe, and ZnS, resulted in improved efficiencies of 23.04%, 23.13%, and 24.48%, respectively. Further optimization of the absorber and buffer layer thicknesses and doping densities enabled achieving best efficiencies of 25.23% and 25.04% for the ZnS and ZnSe buffer layers. The superior performance of the Zn-based buffers is attributed to their larger bandgaps compared to CdS, allowing more photons to reach the CdTe absorber layer, and their reduced susceptibility to detrimental interactions with chlorine during cell fabrication. These findings demonstrate the potential of Cd-free zinc chalcogenide buffer layers, as high-efficiency and environmentally friendly alternatives to CdS in CdTe thin film solar cells. The results motivate further experimental studies to validate the simulation outcomes and accelerate the development of Cd-free CdTe photovoltaic devices for sustainable clean energy generation.
Electrodeposited cadmium telluride (CdTe) solar cells are conventionally fabricated with high-purity (≥99%) cadmium precursors. Thecurrent record efficiency of 15.3% was achieved from 99.997% pure cadmium nitrate precursors. This work aims to test the utility oflower-cost, lower-purity precursors and compare the performances as a function of the precursor purity. Initially, CdTe thin filmswere electroplated from an electrolyte containing 98% pure cadmium nitrate tetrahydrate and tellurium dioxide in an acidic aqueousmedium. Glass/fluorine-doped tin oxide (FTO) substrates have been used to electrodeposit the semiconductor layers. The as-deposited (AD) layers were heat-treated in the air with CdCl2. The structural, compositional, electrical, optical, and morphologicalcharacterizations of the CdTe thin films were studied, and the optimal growth voltage for achieving stoichiometric CdTe has beenidentified. The optimized layers have been used in fabricating thin-film solar cells having glass/FTO/n-CdS/n-CdTe/p-CdTe/Auarchitecture, which currently holds the record efficiency. The solar cells have been investigated with illuminated current-voltageanalysis. A comprehensive comparison with the previous works carried out with higher-purity chemicals has been performed for boththe material properties and device parameters achieved using low-purity Cd precursors. The optimal growth voltage for CdTe withlow-purity precursors was found to be 1,315 mV and a ~6.0% device efficiency was achieved. It has been observed that the use of veryhigh-purity precursors can ensure considerably higher performance; however, it is possible to play an important role in theperformance versus cost trade-off using low-purity chemicals too.
1.0 cm ² large copper oxide solar cells are fabricated using a solution-based approach and the contributions of the semiconductor contacts to the photovoltage are observed with Kelvin probe surface photovoltage spectroscopy.
This paper introduces a novel design of a thin-film solar cell based on CZTS and ZnO composite materials with the help of ITO as the front contact layer. This study primarily focuses on how the cells’ optical absorbance at visible wavelengths can be improved. COMSOL Multiphysics is employed as a powerful tool for the investigation of the numerical simulation. The numerical findings showed that the optimum thicknesses of the ITO and ZnO are 80 and 350 nm, respectively. In this regard, with a normal incidence, a wide range of incoming light wavelengths from 450 nm to 800 nm might result in optical absorption of the examined cell of above 0.9. However, this value decreased significantly to reach less than 0.75 when the angle of incidence increased to 50o. To minimize this reduction, on the top surface of the cell, a texture-designed anti-reflective coating designed from a single period of well-known one-dimensional photonic crystals is deposited. The findings demonstrated that the cell’s absorption at normal incidence could reach over 0.96 through the overall incident wavelengths. Therefore, CZTS/ZnO thin-film solar cells with an anti-reflecting coating of texturing configuration showed enormous potential for manufacturing effective solar cells.
In this chapter we will show how much appreciated were the electro-optical characteristics of one of the most widely used semiconductors of the II-VI family, Cadmium Telluride or CdTe. High quality single crystals with industrially appreciable dimensions have been easily obtained since the beginning of the CdTe epopee. Exploiting its very high transparency in the mid-infrared it was firstly employed as window for i.r. laser applications. Its role, as a material for developing electro-optical modulators needed for the evolution of power CO2-based lasers, was crucial. In more modern times, with the advent of nanotechnologies, CdTe has found considerable success as a UV-Vis photodetector if used in the form of dots, ribbons, belts and, more in general, when it is possible to exploit quantum confinement in reduced dimensions. But where CdTe has been most successful is in the photovoltaic field, where solar cells and photovoltaic modules, with conversion efficiency greater than 22% and 19% respectively, have been made. To date, among thin-film technologies, CdTe-based modules occupy the first place on the market and more than 8% globally. We will talk about this and much more in the rest of this chapter by going into the detail of the photodetectors and, mainly, of the solar cells, revealing the smartest tricks normally used to make these devices sustainable, efficient and cost-effective.
This review paper summarises the key issues of CdTe and CdS/CdTe solar cells as observed over the past four decades, and focuses on two growth techniques, electrodeposition (ED) and closed space sublimation (CSS), which have successfully passed through the commercialisation process. Comprehensive experience in electrical contacts to CdTe, surfaces & interfaces, electroplated CdTe and solar cell development work led to the design and experimentally test grading of band gap multilayer solar cells, which has been applied to the CdS/CdTe structure. This paper presents the consistent and reproducible results learned through electroplated CdTe and devices, and suggestions are made for achieving or surpassing the record efficiency of 22.1% using the CSS material growth technique.
Collaborations and co-creations within the “Holy Triangle of Science, Technology and Industry” have been governing the unprecedented progress in each and every part of the value chain of the photovoltaic solar energy conversion sector since the first discovery of the photovoltaic effect in 1839 by French physicist Alexander Edmond Becquerel (Becquerel in C R 9:561–567, 1839). Intentionally or accidentally discovered effects leading to converting solar energy directly to electrical energy were initiated innovation cycles in the photovoltaic power industry aimed at delivering workable, economically feasible products to serve end users. Despite the growing interest in photovoltaic conversion, the level of scientific understanding of interaction between light and matter had been somewhat unclear up to the end of nineteenth centuries. The frontline of scientific and technological developments in the field of converting solar energy directly to electrical energy were pushed forward continuously in the early twentieth century, with the better understanding of light and matter interaction combined with the discovery of the electron and nucleus. Despite the low converting efficiencies, scientist, technologists and entrepreneurs kept their faith in the emergence of a commercially feasible device to convert solar energy to electricity in the first half of twentieth century. At the beginning of the second half of the twentieth century, the Bell Telephone Company engaged in controlling the properties of semiconductors by introducing impurities for silicon rectifiers and they discovered that illumination of a p-n heterojunction constructed between silicon containing gallium impurities and lithium creates a current in the external circuit. Following this observation, the innovation ecosystem at Bell laboratories surrounding fundamental research and development, technological progress as well product development focused their effort to improve the properties of silicon semiconductors and fabricating a solar cell based on silicon p-n junctions. In 1954 they designed a “solar battery” by serial connection of a solar cell to power the radio transmitter (Chapin et al. in J Appl Phys 25(5):676–677, 1954). Since then the extensive basic research and technological development efforts have been offering innovative solutions for photovoltaic conversion in efficiency, stability and manufacturing cost to compete with conventional power production technologies as well as other clean energy technologies. The progress in the each corner of the holy triangle follow complex and evolutionary road maps and the parameters of solar cells, modules and systems have being improved using innovative materials, devices, technologies for solar power sector different combinations. The emerging and novel technologies have been advancing in the technology readiness level (TRL) index from the blue sky research level (TRL1) to the system demonstration over the full range of expected conditions level (TRL9). This work aims to summarize the relationships in the holy triangle of science, technology and industry in the quest to convert solar energy into electricity since the first discovery of the photovoltaic effect in 1839 (Becquerel in C R 9:561–567, 1839).KeywordsPhotovoltaic conversionPhotovoltaic power systemsRecyclingCircular economy
The article analyzes the charge transfer mechanism in a new type of selectable (adjustable spectrum) injection photodetector based on the Si-CdTe-CdS structure of electronic processes. This structure shows that there is a mutual compensation of the drift and diffusion currents of the charge carriers. The Si-CdTe-CdS heterostructures were formed by the growth of the pCdTe-CdS layer on a nSi-pCdTe substrate using heat evaporation in a vacuum under a residual pressure of 10⁻⁴ Pa. studied and obtained the current-voltage curves and spectral characteristics of the nSi-pCdTe-nCdS heterostructures.
Metal halide perovskite solar cells (PSCs) have been considered to be one of the most promising next‐generation energy harvesters over the past decades due to remarkably rapid improvement of power conversion efficiency in photovoltaics. However, energy harvesters based on the solar energy source have an intrinsic environment limitation for indoor applications. A feasible solution to the limitation is to add non‐solar energy harvesting functions to the solar energy harvesters. Here, the piezoelectric properties of two types of metal halide PSCs are investigated, the 3D only and the 3D/2D structure, showing PCEs of 21.3% and 23.2%, respectively. Piezo‐response force microscopy and synchrotron‐based X‐ray diffraction demonstrate that both types of PSC sample have piezoelectricity. Remarkably, the 3D/2D structure has considerably higher piezoelectric amplitude than the 3D‐only. The deep level transient spectroscopy results reveal that the enhancement in the piezoelectricity of the 3D/2D structure originates from PbBr defects. This study unravels the role of defects in the piezoelectricity of metal halide PSCs and provides a direction to develop the multi‐function energy harvesters based on the PSCs.
The introduction of selenium in the CdTe solar cells has been responsible for high performance CdTe thin film solar cells in recent years. It is an approach to form CdSexTe1-x alloys by the interdiffusion using precursor CdSe layer during the CdTe high-temperature deposition process. Nevertheless, the compositionally gradient CdSexTe1-x formed by the diffusion makes it difficult to absorb long-wavelength photons adequately. So close-spaced sublimation deposited CdSexTe1-x interlayer was incorporated in the CdTe thin film solar cells. It is found that 600 nm CdSexTe1-x absorber is useful to increase long-wavelength photons absorption and extend the long-wavelength QE response. Meanwhile, the synergetic effects of the primary absorber deposition processing on CdTe solar cell performance were investigated. The substrate temperature of CdTe deposition has an obvious impact on the cell efficiency. The much higher substrate temperature can efficiently gain larger grain size, increase the crystal quality and promote the interdiffusion of different semiconductor layers. These improvements can efficiently decrease the carrier recombination to obtain a much higher fill factor and open-circuit voltage.
A comparative study of the performance of glass/FTO/CdS/CdTe/Au thin film solar cells was carried out for solar cells fabricated with CdTe electrochemically grown using 2-electrode and 3-electrode set-ups. Structural, optical and morphological characterization of the CdTe films prior to solar cell fabrication show that both electrode set-ups produce CdTe with similar X-ray diffraction patterns, optical absorption properties and surface morphologies. Current density-voltage characterization of resulting solar cells also shows that CdTe from both electrode systems produced solar cells with comparable conversion efficiencies. The open-circuit voltage, short-circuit current density and fill factor of cells from both systems were in the ranges of (410–630) mV, (15.2–33.0) mAcm⁻² and (0.32–0.49), respectively. These results indicate that the 2-electrode set-up can go a long way in reducing production cost by eliminating the reference electrode, which is also a potential impurity source, as well as ensuring a simplified deposition system.
In the first stage of this study, various metallic stacking order layers were utilized and the most suitable one determined. In the second stage of this study, the effect of pre-annealing treatment of Mo/Cu/Sn in the determined stacking order (Mo/Cu/Sn/Zn/Cu) on the properties of Cu2ZnSnS4 (CZTS) thin films was investigated. CZTS thin films were grown on Mo coated glass by DC magnetron sputtering deposition of metallic precursor layers, followed by a thermal annealing step in Rapid Thermal Processing (RTP) system. Mo/Zn/Sn/Cu and Mo/Cu/Sn/Zn/Cu were used as metallic stacking order layers, 500, 550, and 600 °C values were selected as the reaction temperatures. The GDOES data showed that increasing the reaction temperature gave rise to enhancement in the homogeneity of the films and Mo/Cu/Sn/Zn/Cu stacking order was appeared more promising one in terms of the homogeneity of the film. XRD and Raman spectra of the films exhibited and proved formation of CZTS structure and other secondary phases. In the second stage of this study, the Mo/Cu/Sn structure of the Mo/Cu/Sn/Zn/Cu stacking order was exposed to pre-annealing treatment at 200 and 380 °C to see impact of the pre-annealing treatment and pre-annealing temperature. XRD and Raman spectra of the films proved formation of CZTS structure. GDOES data revealed that pre-annealing treatment enhanced homogeneity of films. PL and optical band gap values showed that the pre-annealing treatment did not change the optical properties of the films. The best solar cell performance was achieved with 2.2 % conversion efficiency in the CZTS samples which are pre-annealed at 200 °C.
CdTe photovoltaic technology is one of the first being brought into production together with amorphous silicon (already in the mid 90s Solar Cells Inc. in USA, Antec Solar and BP Solar in Europe were producing 60 × 120cm modules) and it is now the largest in production among thin film solar cells (Photovoltaics Report, 2014).CdTe has high chemical stability and a large variety of successful preparation methods available, which makes this technology one of the most suitable for large area module production.Historically there are two large categories of CdTe photovoltaic devices depending on the substrate deposition temperature, typically low temperature processes are considered when substrate temperature is below 450 °C.In this paper we will describe the last progress of CdTe based thin film solar cells, fabricated with low substrate temperature process, and their pros and cons.
The effects of the type of anode material on the properties of electrodeposited CdTe thin films for photovoltaic application have been studied. Cathodic electrodeposition of two sets of CdTe thin films on glass/fluorine-doped tin oxide (FTO) was carried out in two-electrode configuration using graphite and platinum anodes. Optical absorption spectra of films grown with graphite anode displayed significant spread across the deposition potentials compared to those grown with platinum anode. Photoelectrochemical cell result shows that the CdTe grown with graphite anode became p-type after post-deposition annealing with prior CdCl2 treatment, as a result of carbon incorporation into the films, while those grown with platinum anode remained n-type after annealing. A review of recent photoluminescence characterization of some of these CdTe films reveals the persistence of a defect level at (0.97–0.99) eV below the conduction band in the bandgap of CdTe grown with graphite anode after annealing while films grown with platinum anode showed the absence of this defect level. This confirms the impact of carbon incorporation into CdTe. Solar cell made with CdTe grown with platinum anode produced better conversion efficiency compared to that made with CdTe grown using graphite anode, underlining the impact of anode type in electrodeposition.
Owing to their suitable band gaps and high absorption coefficients, Cd-based compounds such as CdTe and CdS are the most promising photovoltaic materials available for low-cost high-efficiency solar cells. Additionally, because of their large atomic number, Cd-based compounds such as CdTe and CdZnTe, have been applied to radiation detectors. For these reasons, preparation techniques for these materials in the polycrystalline films and bulk single crystals demanded by these devices have advanced significantly in recent decades, and practical applications have been realized in optoelectronic devices. This chapter mainly describes the application of these materials in solar cells and radiation detectors and introduces recent progress.
Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) has recently attracted a great amount of interest as a potential absorber for next generation thin film solar cells, owing to its decent optical and electronic properties comparable to traditional Cu(In, Ga)Se2 (CIGSe) and CdTe materials, and constituents of earth-abundant and low-toxic elements. Similar to CIGSe and CdTe, kesterite CZTSSe can be fabricated by both vacuum and solution based processes. Typical vacuum based processes such as evapora tion and sputtering may suffer from scaling issues and high intrinsic costs. In this regard, solution based processes are desirable and are actively being developed. The solution processed approach permits the use of low-cost and high-through put equipment and the deployment of large-scale production facilities with lower capital investment. This chapter discusses the fundamental aspects of kesterite thin film solar cells at first. Then, the deposition strategies of CZTSSe are reviewed. The last part of the text deals with solution processes including electrodeposition and direct solution coating used for the preparation of CZTSSe absorbers and solar cells. Today's state-of-the-art performance as well as challenges to achieve low-cost and environmentally friendly mass production are also discussed.
Thin-film PV has attracted much attention and considerable R&D effort since early 1980s because of its low cost potential. Although barriers to market dominance for thin-film products have been increasing because of the precipitous drop in the wafer Si module prices, thin-film technologies have been increasing their module efficiencies and manufacturing capacity. In this chapter we present a brief review of two important polycrystalline thin-film technologies in large-scale manufacturing: one based on cadmium telluride (CdTe), and the other on copper indium gallium selenide/sulfide (CIGS) as the absorber material.
The influence of ultrasonic irradiation (USI) on the load characteristics of the In–n⁺CdS–nCdSxTe1–x–pZnxCd1–xTe–Mo heterostructure was studied under different illuminance levels of monochromatic light (λ = 632.8 nm) and white light. It was established that the efficiency of the heterostructure increases under the increase in the laser irradiation power and under the action of ultrasound.
Films of cadmium telluride made by cathodic electrodeposition from an electrochemically purified solution containing readily available chemicals were of greater purity than single crystals purchased as high purity materials from three suppliers, as determined by positive secondary ion mass spectroscopy. The conditions of the electrodeposition and some properties of the films are described.
We have induced recrystallization of small grain CdTe thin films deposited at low temperatures by close-spaced sublimation (CSS), using a standard CdClâ annealing treatment. We also studied the changes in the physical properties of CdTe films deposited by radio-frequency magnetron sputtering after the same post-deposition processing. We demonstrated that the effects of CdClâ on the physical properties of CdTe films are similar, and independent of the deposition method. The recrystallization process is linked directly to the grain size and stress in the films. These studies indicated the feasibility of using lower-temperature processes in fabricating efficient CSS CdTe solar cells. We believe that, after the optimization of the parameters of the chemical treatment, these films can attain a quality similar to CSS films grown using current standard conditions. {copyright} {ital 1999 American Vacuum Society.}
Large area 300 mm x 300 mm CdS/CdTe solar cells with record efficiencies over 10% have been fabricated using a reproducible, safe and low cost electrodeposition route for CdTe deposition. CdS window layers have been grown using chemical bath deposition which produces uniform adherent films by a cost effective route. Electrical characterization of small area (0.02 cm) devices confirms that the structure is p-n rather than p-i-n. Module reliability tests show efficiency stability for more than 16,000 hours outside, and very little change using indoor environmental tests.
Thin films of cadmium sulfide
have major applications in optoelectronic devices. Several techniques have been developed for the deposition of
films. Among these, growth of
films from an aqueous solution is the low‐cost technique suitable for many applications. In this work, the deposition of
device quality
films on glass and
substrates from an aqueous solution containing cadmium acetate, ammonia, ammonium acetate, and thiourea has been investigated.
The structural and electrical properties of
films have been characterized. The doping of
films with boron and the properties of boron‐doped
films have also been studied. High efficiency thin film
solar cells have been prepared from solution‐grown
films.
By analyzing CdTe/CdS devices fabricated by vacuum evaporation, a self consistent picture of the effects of processing on the evolution of CdTe cells is developed which can be applied to other fabrication methods. In fabricating CdTe/CdS solar cells by evaporation, a 400°C CdCI2 heat treatment is used which recrystallizes the CdTe and interdiffuses the CdS and CdTe layers. The interdiffuson can change the bandgap of both the CdTe and CdS which modifies the spectral response of the solar cell. After this heat treatment a contacting/doping procedure is used which converts the CdTe conductivity to p-type by diffusion from Cu from the contact. Finally, the cell is treated with Br2CH3,OH which improves both Voc and FF. Analogous process steps are used in most fabrication processes for CdTe/CdS solar cells.
This paper describes the work performed at BP Solar, Fairfield,
California highlighting advances in the Apollo(R) CdTe technology. The
paper describes the eight basic process steps involved in making the
module. The state of the art CdTe reactor is also detailed with its
sophisticated design and control features. Various techniques were
utilized to characterize the semiconductor materials. Using AFM and
X-ray diffraction, the morphology and crystallographic properties of the
films were investigated. This work showed the grain structure was small,
even after post deposition air anneals. Optical characterization
determined quantum efficiency of the device and helped optimize window
layer thickness for record performances. NREL confirmed module
efficiency of 10.8% is reported for a 0.55m2 module and a
maximum power of 91.5 W for a 0.94m2 monolithic module.
Indoor stress testing and outdoor performance test beds are also
described. The data presented shows good indoor stability at various
stress conditions
Progress in Photovoltaics
- Mccandless Be Moulton Lv
- Birkmire
McCandless BE, Moulton LV, Birkmire RW. Progress in Photovoltaics: Research and Applications 1997; 5: 249–260.
Proceedings of the 12th EC PV Solar Energy Conference
- Woodcock JM
- Ozsan ME
- Johnson DR
- Oktik S
- Patterson MH
Proceedings of the 12th European Photovoltaic Solar Energy Conference
- Woodcock JM
- Ozsan ME
- Turner AK
- Cunningham DW
- Johnson DR
- Marshall RJ
- Mason NB
- Oktik S
- Patterson MH
- Roberts S
- Sadeghi M
- Sherborne JM
- Sivapathasundaram D
- Walls IA
- McCandless
- McCandless