I. M. Dharmadasa

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• BSc(2.1) BSc(1st) PhD Senior Staff Grade Professor
• >meritus Professor at Sheffield Hallam University

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 pr...

In this study, a two-electrode electrodeposition technique was employed to grow thin films of antimony selenide (Sb2Se3) on glass/fluorine-doped tin oxide (FTO) substrates. The highest quality thin films were consistently obtained within the range of 1600 mV to 1950 mV. Subsequent electrodeposition experiments were conducted at discrete voltages to...

The electrodeposition ͑ED͒ of CdS ͑continuous process͒ was investigated in detail with the aim of replacing chemical bath deposited ͑CBD͒ CdS ͑batch process͒ from the solar cell production process. This avoids the daily production of toxic waste and, hence, drastically reduces manufacturing cost. Material studies were carried out using voltammetry,...

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...

This study has attempted for the first time to electrochemically fabricate PV cells based on both p-type and n-type window layers of the same materials and compare the performance. CdTe, the only commercially successful material for thin-film PV has been used as the absorber. Two graded-band-gap devices having glass-FTO/n-ZnTe/n- CdTe/i-CdTe/p-CdTe...

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...

Cathodic electrodeposition technique has been successfully used to achieve the growth of polycrystalline CdMnTe ternary compound thin films at different cathodic potentials. The choice of various cathodic potentials used in this work was made from the cyclic voltammogram results. The CdMnTe thin films were electroplated from electrolytes containing...

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 liter...

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 scient...

Perovskite solar cells have shown an impressive efficiency improvement over the past ~ 10 years achieving ~ 23% to date. However, the lifetime and instability of device characteristics are real issues to understand and solve before scaling up and commercialisation of these devices. Researchers have attempted to understand the hysteresis behaviour o...

Electrodeposition of cadmium telluride (CdTe) on fluorine doped tin oxide (FTO) using two electrode configurations was successfully achieved with the main focus on the growth temperature. The electroplating temperatures explored ranged between 55 and 85 • C for aqueous electrolytes containing 1.5 M cadmium nitrate tetrahydrate (Cd(NO 3) 2 ·4H 2 O)...

This project aims to develop next-generation electrodeposited graded bandgap solar cells with p-type window material for a higher open circuit voltage, thus higher conversion efficiency. In search of wide bandgap p-type window, Mg incorporation to the CdTe electrolytic bath has been carried out, which has given a rise in typical CdTe bandgap from 1...

Electrodeposition of cadmium telluride (CdTe) on fluorine doped tin oxide (FTO) using two electrode configuration was successfully achieved with the main focus on the growth temperature. The electroplating temperatures explored ranges between (55 and 85)℃ for aqueous electrolytes containing 1.5 M cadmium nitrate tetrahydrate (Cd(NO3)2 •4H2O) and 0....

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 respe...

Ga doping of CdS thin films has been achieved using a simplified cathodic electrodeposition method and with glass/indium tin oxide (glass/ITO) as a substrate. CdCl2, Na2S2O3 and GaCl3 were used as precursors. The Ga-doped and un-doped CdS films obtained were characterized for their structural, optical, luminescence, compositional and morphological...

This chapter describes the characteristic structural and electrical properties of solid-state materials with emphasis on semiconductors, surfaces and interfaces, junctions, charge carrier transport mechanisms, electrical contacts and devices. An overview of semiconductor growth techniques is also included in this chapter for readers to familiarise...

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 diffracti...

The sun offers mankind virtually unlimited energy potential with photovoltaics being one of the energy-harnessing technologies. New understanding of semiconductor material issues, processing steps, graded bandgap device architectures and device physics paves the way to achieving high-energy conversion efficiency. Although the photovoltaic market is...

The main absorber material used in solar cells described in this book is CdTe. This chapter provides an insight to the electrodeposition of cadmium telluride (CdTe) layers. CdTe thin films were electrodeposited on glass/fluorine-doped tin oxide (FTO) using a two-electrode system from an acidic and aqueous solution containing 1.5 M Cd(NO3)2·4H2O and...

This chapter provides an insight into next-generation graded bandgap photovoltaic device fabrication. All-electrodeposited devices were fabricated using n-p, n-n-p, n-n + large Schottky barrier (SB) and n-n-n + SB architecture using ZnS, CdS and CdTe thin layers. The fabricated devices were evaluated using both current-voltage (I-V) and capacitance...

This chapter provides an insight to the electrodeposition of CdS layers from electrolytic bath without precipitation. CdS layers used in thin-film solar cells as window layers and other electronic devices are usually grown by wet chemical methods using CdCl2 as the cadmium source and either Na2S2O3, NH4S2O3 or NH2CSNH2 as sulphur sources. Obviously...

This chapter covers introductory topics providing a broad overview of the different aspects of energy and energy resources with a focus on solar energy and photovoltaic technology. A consideration of the energy distribution of the solar spectrum, photovoltaic solar energy conversion techniques and the operating configuration of photovoltaic solar c...

Zinc sulphide (ZnS) layers have been used as buffer layers in the solar cells described in this book, and this chapter provides an insight into the electrodeposition of ZnS layers. Electrodeposition of zinc sulphide (ZnS) was achieved from an electrolytic bath containing zinc sulphate monohydrate (ZnSO4·H2O) and ammonium thiosulphate ((NH4)2S2O3) i...

Perovskite solar cells exhibiting ~ 14–15% efficiency were experimentally measured using current–voltage (I–V) and capacitance–voltage (C–V) techniques in order to extract material and device properties, and understand the action of photovoltaic (PV) operation. Deep analyses were carried out on dark- and illuminated I–V curves, and dark C–V curves....

In order to develop wide bandgap p-type window materials to use in graded bandgap devices, the effects of magnesium (Mg) in n-CdTe layers were explored. In this work, magnesium-incorporated cadmium telluride (CdTe:Mg) layers were electroplated using two-electrode method. The layers were deposited on glass/FTO (flourine doped tin oxide) substrates,...

This book will guide Photovoltaics researchers in a new way of thinking about harvesting light energy from all wavelengths of the solar spectrum. It closes the gap between general solar cells books and photovoltaics journal articles, by focusing on the latest developments in our understanding of solid-state device physics. The material presented is...

The electrodeposition of polycrystalline I-doped CdTe was successfully performed from aqueous solutions containing cadmium nitrate (Cd(NO3)2) and tellurium oxide (TeO2). The effects of different I-doping concentrations in an electrolytic bath on the CdTe layers deposited were evaluated structurally, optically, morphologically and electronically usi...

Electrodeposition of zinc sulphide (ZnS) was achieved from electrolytic bath containing zinc sulphate monohydrate (ZnSO4·H2O) and ammonium thiosulphate ((NH4)2S2O3) in a two-electrode electroplating configuration. The cyclic voltammetric studies show that ZnS layers can be electroplated between (1350 and 1550) mV. The grown layers were characterist...

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 spect...

In order to develop wide bandgap p-type window materials to use in graded bandgap devices, the effects of magnesium (Mg) in n-CdTe layers were explored. In this work, magnesium incorporated cadmium telluride (CdTe:Mg) layers were electroplated using two-electrode method. The layers were deposited on glass/FTO (flourine doped tin oxide) substrates,...

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 spectr...

In order to produce high efficiency solar cells based on CdTe, CdCl2 post-growth treatment is an essential processing step. This treatment can be further improved by adding elements such as Fluorine and Gallium into the CdCl2 solution. Through systematic experimentation, it has been found that the pH value of the treatment solution also affect the...

Electrodeposition (ED) has been recognized as a low cost and scalable technique available for fabrication of CdS/CdTe solar cells. Photovoltaic activity of these electrodeposited semiconductor materials drastically depends on the ED growth parameters namely; electrodeposition potential, concentrations and ratios of concentrations of precursors used...

CdS/CdTe/Au thin film solar cells have been fabricated on different transparent conducting oxide (TCO) substrates/front contacts to study the influence of these different TCOs on the performance of the devices. The TCOs used were ZnO, ZnO:Al and SnO2:F. Under dark condition, all three device structures of the type glass/TCO/n-CdS/n-CdTe/Au n–n hete...

Cadmium sulfide (CdS) is a well-known window material used for fabrication of second generation thin film solar cells including CdS/CdTe and CdS/CuInGaSe2. Among the CdS fabrication techniques, electrodeposition is a simple, cost effective and scalable method that has been stepped towards large scale commercialization. However, the presence of prec...

Abstract All-electrodeposited ZnS, CdS and CdTe thin layers have been incorporated in a graded bandgap solar cell structure of glass/FTO/n-ZnS/n-CdS/n-CdTe/Au have been fabricated and an average conversion efficiency of 14.18% was achieved under AM1.5 illuminated condition. Based on former work in which 10% conversion efficiency was reported, optim...

Electrochemical deposition and characterization of nanocrystallite-CdS thin films for thin film solar cell application are reported. The two-electrode system used provides a relatively simple and cost-effective approach for large-scale deposition of semiconductors for solar cell and other optoelectronic devices application. Five CdS thin films were...

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 h...

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 spectr...

Deposition of cadmium telluride (CdTe) from cadmium chloride (CdCl2) and tellurium oxide has been achieved by electroplating technique using two-electrode configuration. Cyclic voltammetry shows that near-stoichiometric CdTe is achievable between 1330 and 1400 mV deposition voltage range. The layers grown were characterised using X-ray diffraction...

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 CdC...

Photovoltaic devices are developed mainly based on p–n or p–i–n type device structures, and these devices can utilise only a fraction of the solar spectrum. In order to further improve device parameters and move towards low-cost and high-efficiency next generation solar cells, device architectures capable of harvesting all photons available should...

The role of Chlorine-based activation in the production of high quality CdS/CdTe photovoltaic have been well discussed and explored with an overlook of the effect of Cadmium chloride (CdCl2) post-growth treatment acidity on the property of the fabricated devices. This work focuses on the optimisation of CdCl2 post-growth treatment pH as it affects...

The inclusion of gallium into the well-known CdCl2 post-growth treatment shows drastic improvement in both CdTe material and electrical properties of the fully fabricated CdS/CdTe-based solar cell as compared with the regular CdCl2 treatment. The optical, morphological, compositional and electronic properties the glass/FTO/n-CdS/n-CdTe/p-CdTe were...

Ga-doped CdTe polycrystalline thin films were successfully electrodeposited on glass/fluorine doped tin oxide substrates from aqueous electrolytes containing cadmium nitrate (Cd(NO3)2·4H2O) and tellurium oxide (TeO2). The effects of different Ga-doping concentrations on the CdTe:Ga coupled with different post-growth treatments were studied by analy...

CdCl2 treatment is a crucial step in development of CdS/CdTe solar cells. Although this processing step has been used over a period of three decades, full understanding is not yet achieved. This paper reports the experimental evidence for improvement of composition of CdTe layers during CdCl2 treatment. This investigation makes use of four selected...

The effect of electrodeposition technique on CdS thickness incorporated in CdS/CdTe-based solar cell has been investigated using all-electrodeposited g/FTO/n-CdS/n-CdTe/p-CdTe multilayer device configuration. The optical, morphological and structural properties of the electroplated CdS were investigated for CdS thicknesses between 50 and 200 nm. Th...

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. S...

The fabrication of multi-junction graded bandgap solar cells have been successfully implemented by electroplating three binary compound semiconductors from II-VI family. The three semiconductor materials grown by electroplating techniques are ZnS, CdS and CdTe thin films. The electrical conductivity type and energy bandgap of each of the three semi...

This experiment reports the study on CdS/CdTe thin film solar cells for military application. In this work, CdS/CdTe thin film solar cell has been heat-treated with various device structures and chemical treatments in order to activate the properties of CdTe for optimum solar cell device performance. These treatments are such as CdCl2 treatment, Cd...

At present, cadmium telluride (CdTe) is one of topmost thin film nanocrystalline materials in the arena of photovoltaics (PV) with a considerable market share. However, it is essential to have a profound understanding of effects and mechanisms of post deposition treatments on the quality of CdTe material in order to improve its PV activities furthe...

Cadmium telluride (CdTe) thin films have been deposited on glass/conducting glass (FTO) substrates using low-cost two electrode system and aqueous electrodeposition method. The glass/FTO substrates were used to grow the CdTe layers at different deposition voltages. The structural, electrical, optical and morphological properties of the resulting fi...

Fluorine doped tin oxide (FTO) thin films with adequate properties to be used as transparent electrical contact for PV solar cells were synthesised using the spray pyrolysis technique, which provides a low cost operation. The deposition temperature and the fluorine doping have been optimized for achieving a minimum resistivity and maximum optical t...

The incorporation of GaCl3 into the usual CdCl2 post-deposition treatment solution of CdTe-based solar cells has been investigated. Both CdS and CdTe layers used in this work were prepared by electroplating technique and they are n-type in electrical conduction as observed from photoelectrochemical cell measurement technique. Before applying the ch...

CdS thin films were cathodically electrodeposited by means of a two-electrode deposition system for different durations. The films were characterised for their structural, optical, morphological and compositional properties using X-ray diffraction (XRD), spectrophotometry, scanning electron microscopy and energy dispersive X-ray (EDX) respectively....

Making use of previously designed and experimentally tested results of graded bandgap devices, and the comprehensive electrodeposition of semiconducting materials knowledge, a three layer n-n-p device structure was fabricated and tested for their electronic properties and solar cell performance. Glass/FTO/n-CdS/n-CdTe/p-CdTe/Au devices were fabrica...

The fabrication of a one-sided p-n hetero-junction (HJ) diodes have been successfully carried out using both p-type ZnTe and n-CdS semiconductors. Chemical bath deposition (CBD) and electrodeposition (ED) techniques have been used in the deposition of n-CdS and p-ZnTe layers respectively. Before the fabrication of the one-sided p-nHJ diodes, the el...

Abstract: Thin films of CdTe semiconductor materials were grown on fluorine doped tin oxide (FTO) conducting glass substrates using the technique of electrodeposition. CdSO4 at high concentrations and CdCl2, TeO2 at low concentrations were used as precursor salts for electrodeposition. The range of deposition potentials was estimated using cyclic v...

Fluorine which is an n-type dopant of cadmium telluride thin films was included during growth from a cadmium nitrate [Cd(NO3)2·4H2O] bath using an electrodeposition technique. The fluorine concentration in the Cd(NO3)2·4H2O baths were varied between 0.5 ppm and 50 ppm in order to determine its effect on the optical, structural, morphological and el...

CdS thin films have been successfully electrodeposited on glass/FTO substrates using acidic and aqueous solution of CdCl2.xH2O and thiourea (SC(NH2)2). The electrodeposition of CdS thin films were carried out potentiostatically using a 2-electrode system. The prepared films were characterised using X-ray diffraction, Raman spectroscopy, Scanning el...

Thin films of CdTe semiconductor were electrochemically deposited using two-electrode and three-electrode configurations in potentiostatic mode for comparison. Cadmium sulphate and tellurium dioxide were used as cadmium and tellurium sources respectively. The layers obtained using both configurations exhibit similar structural, optical and electric...

Thin films of CdTe semiconductor were electrochemically deposited using two-electrode and three-electrode configurations in potentiostatic mode for comparison. Cadmium sulphate and tellurium dioxide were used as cadmium and tellurium sources respectively. The layers obtained using both configurations exhibit similar structural, optical and electric...

The CdCl2 treatment used in the development of high efficiency CdTe solar cells is an essential processing step but remains fully unexplored. What really happens during this treatment is not yet fully understood. The changes in doping concentrations during this processing step are a key parameter to investigate. Determination of the position of the...

CdS is the most matching window material available for the CdTe absorber layer of CdS/CdTe solar cells and electrodeposition is a promising technique adaptable for fabrication of thin films of CdS owing to its simplicity, low cost, scalability and manufacturability. The quality of electrodeposited thin film semiconductor layers depends significantl...

CdS layers used in thin film solar cells and other electronic devices are usually grown by wet chemical methods using CdCl2 as the Cadmium source and either Na2S2O3, NH4S2O3 or NH2CSNH2 as Sulphur sources. Obviously, one of the sulphur precursors should produce more suitable CdS layers required to give the highest performing devices. This can only...

Thin film structure of CdS/CdTe heterojunction is a promising device for solar to electricity conversion. A low-cost electroplating technique is known to produce device quality thin films for application in both mono- and multi-junction solar cells. Multi-junction solar cell devices show better performance due to their ability in harvesting photons...

Multi-Layer devices consisting of glass/FTO/n-CdS/n-CdTe/p-CdTe/Au have been fabricated using all-electroplated CdS and CdTe in an n-n-p device configuration. The effects of incorporation of graded bandgap technology were explored, and improved solar cell device parameters were observed. The fabricated device shows an average conversion efficiency...

Zinc sulphide (ZnS) thin films with both n- and p-type electrical conductivity were grown on glass/fluorine-doped tin oxide-conducting substrates from acidic and aqueous solution containing ZnSO4 and (NH4)2S2O3 by simply changing the deposition potential in a two-electrode cell configuration. After deposition, the films were characterised using var...

Thin films of CdS and CdTe semiconductor materials were electrodeposited onto glass/fluorine doped tin oxide conducting glass surfaces using a potentiostat/galvanostat equipped with a three electrode cell. Aqueous electrolytic bath containing CdCl2 and (NH4)2S2O3 was used for the electrodeposition of CdS thin films. CdTe thin films were electrodepo...

The growth of n- and p-type ZnTe thin films have been achieved intrinsically by potentiostatic electrodeposition method using a 2-electrode system. Cyclic voltammogram have been used to obtain range of growth voltages required to form stoichiometric thin films of ZnTe. The ZnTe thin films have been electrodeposited (ED) on glass/fluorine-doped tin...

Using intrinsic doping, n- and p-type ZnTe thin films have been electrodeposited (ED) on glass/fluorine-doped tin oxide (FTO) conducting substrate in aqueous solutions of ZnSO4 · 7H2O and TeO2. The intrinsic doping was achieved by simply varying the deposition potential. The films have been characterised for their structural, optical, electrical, m...

Cadmium telluride (CdTe) thin films have been successfully prepared from an aqueous electrolyte bath containing cadmium chloride (CdCl2)·H2O and tellurium dioxide (TeO2) using an electrodeposition technique. The structural, electrical, morphological and optical properties of these thin films have been characterised using X-ray diffraction (XRD), Ra...

Cadmium telluride (CdTe) thin films were electrodeposited on glass/fluorine-doped tin oxide (FTO) using a two electrode system from an acidic and aqueous solution containing 1.0M Cd(NO 3) 2 ·4H 2 O, low level of TeO 2 solution and 500 ppm CdF 2 as a dopant at pH=2.00±0.02. Photoelectrochemical (PEC) cell measurement, X-ray diffraction (XRD), Raman...

Cadmium sulphide is widely used as a heterojunction partner and a window layer material in the fabrication of polycrystalline CdTe thin film solar cells. Cadmium sulphide films were prepared by continuous bath deposition technique using CdCI 2 as cadmium precursor salt, and ammonium thiosulphate or thiourea as the sulphur precursor salt. The growth...

Fluorine which is an n-type dopant of Cadmium Telluride (CdTe) thin films was included during growth from a cadmium nitrate (Cd (NO3)2 4H2O) bath using electrodeposition technique. The fluorine concentration in the Cd (NO3)2 4H2O baths were varied between 0.5 ppm to 30 ppm in order to determine its effect on the optical, structural, morphological a...

CdTe thin films were electrodeposited (ED) using acidic aqueous solution containing 1.0 M Cd(NO3)2 4H2O and 1.0 mM TeO2. The deposition of the CdTe thin films were carried out cathodically using 2-electrode system on the glass/FTO substrate. The ED-CdTe layers were heat treated with CdCl2 and CdCl2+CdF2 at three different temperatures of 385oC, 420...

Current solar cells under research and development utilise mainly one absorber layer limiting the photon harvesting capabilities. In order to develop next generation solar cells, research should move towards effective photon harvesting methods utilising low-cost solar energy materials. This will lead to reduce the $W⁻¹ figure for direct solar energ...

Intense pulsed light (IPL) treatment was used for rapid thermal processing of electroplated CdTe layers, with and without CdCl2. Electroplated CdTe layers consist of small grains showing highly preferential orientation along the (111) planes. IPL processing improves the crystallinity keeping the (111) preferred orientation until an energy input thr...