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Radiation sensor based on thin-film CdTe/CdS device structure and its radiation resistance under high-intensity hydrogen plasma
Journal of Applied Physics
Abstract
In this work, the ability of CdTe/CdS thin-film device structures prepared by the hot-wall method to detect ionizing radiation was investigated. The samples were fabricated with a structure typical of CdTe/CdS-based solar cells and exhibit radiation sensitivity even without the application of an external voltage. This allows such structures to be used as low-voltage radiation sensors. An investigation of the radiation resistance of the structures, namely, the effect of irradiation with high-intensity hydrogen plasma H 2 ⁺ on the crystal structure and performance, was carried out. It was shown that the device structures remained operational after two plasma pulses at an ion density of 2 × 10 ²³ m ⁻² and an energy density of up to 0.2 MJ/m ² . With further exposure to plasma, the device structures deteriorated, first, due to gradual sputtering off of the back contact, and, second, as a result of diffusion processes that occurred when the structures were heated to high temperatures, due to which the entire volume of the CdTe base layer got converted into a CdS x Te 1−x solid solution.
... At the same time, it follows from such studies, that the primary influence on degradation is not so much the energy of the particles in the flow as the accumulated radiation dose. In Ref. [13], we began our investigation of influence of high-intensity plasma flows on CdS/CdTe, with the focus on the irradiation with hydrogen plasma and its effects on the photoelectric properties and crystal structure of these device structures. In that study, the irradiation doses were established, at which structural changes at the CdS/CdTe interface begin to occur, which causes a decrease in the output photoelectric parameters of such device structures. ...
... In the initial state, the device structures had photosensitivity and could be used as SCs and radiation sensors of -particles [13]. The free surface of the cadmium telluride films was smooth, had a typical grey colour, and the average grain size of the layers was 1 -3 µm. ...
The influence of pulsed helium plasma irradiation, with a 10 ms duration and a surface energy load of 0.2 MJ m-2, on the elemental and phase composition, surface morphology and crystal structure of thin-film heterosystems based on CdS/CdTe was studied. The cadmium sulphide and cadmium telluride layers were deposited by condensation via a hot wall method onto a glass substrate covered with an FTO layer. It was found that after one pulse, the device structure remains in working condition. An increase in the irradiation dose leads to surface sputtering, the formation of through pores 0.5-2 m in size, and a microcracks network with two characteristic scales. One crack network is formed in the glass substrate, and the second network is formed with cracks in the CdTe film. It is shown that the thermal effect of plasma stimulates the diffusion of sulphur; as a result, the proportion of CdTe1-xSx solid solutions formed in the process of obtaining the CdS/CdTe heterosystem increases. In addition, the sulphur content increases in these solid solutions, which leads to their decomposition with the separation of the CdS1-yTey solid solution phase. These solid solutions migrate to the CdTe surface through cracks and are observed as separate crystals.
... Group ⅡB-ⅥA semiconductors have garnered considerable interest due to their unique photoelectric, photochemical, and photocatalytic characteristics [1,2]. These semiconductor materials are extensively used in modern solid-state electronic devices, such as solar panels [3], light-emitting diodes [4,5], photodetectors [6,7], nuclear radiation detectors [8,9], lasers [10,11] and photoelectric chemical cell gas sensors [12]. These semiconductor materials may experience various complex environments during the utilization of devices. ...
Based on the local bond average approach and the definition of the thermal expansion coefficient, the temperature-dependent thermal expansion coefficient for Group ⅡB-ⅥA semiconductors has been established. The consistency in theoretical results and reported values confirms that the higher the Debye temperature, the wider the nonlinear range of the thermal expansion coefficient at low temperatures, and the lower the change rate for the temperature-dependent thermal expansion coefficient. The bigger the ionicity, the shorter the bond length, and the smaller the thermal expansion coefficient. The influence of ionicity on the thermal expansion coefficient is greater than those of both Debye temperature and cohesive energy. The present analytical function is beyond the scope of available approaches, which not only provides a new understanding of the physical mechanism of the thermal expansion coefficient response to temperature but also is helpful in the quantitative design of semiconducting optoelectronic devices.
... Among them, the correction of radiation intensity signal is particularly prominent (Pokutnii 2023). Due to the complexity and variability of the marine environment, the radiation intensity signals received by the LiDAR system are often affected by many factors (Meriuts et al. 2022), such as atmospheric attenuation, water absorption, scattering, wave fluctuations, marine biological activities, etc. These factors will not only lead to attenuation and distortion of signal strength (Kotarba 2022), but also may introduce noise and interference, thus seriously affecting the accuracy and reliability of surveying and mapping results. ...
In order to maintain the continuity and consistency of 3D ocean spatial data and enhance the robustness of mapping radiometric signal correction, the calibration method of LiDAR mapping radiometric signal in 3D ocean space is studied. The environmental impact of the radiation intensity signal is corrected by establishing the radar equation of 3D ocean space LiDAR mapping. By using the method of homonymous points screening based on coherent information, the homonymous laser feet of adjacent navigation belts are automatically screened to determine the overlap area of navigation belts. On the basis of the overlapping zone of the navigation belt and the radar equation, the calibration model of the radiation intensity signal of the LiDAR mapping in 3D ocean space is established. The nonlinear weighted total least squares method is used to solve the correction parameters of the correction model and complete the correction of the radiation intensity signal of the LiDAR mapping in 3D ocean space. The experiment shows that this method can effectively and automatically screen the laser feet of the same name in adjacent navigation belts. This method can effectively correct the radiation intensity signal of 3D ocean space LiDAR mapping. After correction by this method, the laser feet of the same name in the overlapping area of the flight belt basically coincide, that is, the correction effect is better.
... The stability of CdTe is due to its high binding energy of 6 eV per atom and its high melting point of 1041 • C [13]. Its potential applications include various types of semiconductor devices like solar cells [14], sensors [15], medical imaging [16], and X-ray and γ -ray detectors [17]. ...
Cadmium Telluride (CdTe) thin films were synthesized using a low-cost two-electrode electrodeposition configuration in potentiostatic mode and from an aqueous acidic solution. More commonly used cadmium salts for electrodeposition of CdTe include CdSO4 , CdCl2 and Cd (NO 3) 2. In the present work, a less commonly used salt, cadmium acetate, was used as a cadmium precursor for the growth of CdTe thin films. The thin films were deposited on a coated glass fluorine-doped tin oxide (FTO) substrates. The deposition voltage was varied from 1230 to 1270 mV with a 10 mV increment. The structure, optical, conductivity, surface morphological, elemental composition, and surface roughness properties of the as-deposited thin films were investigated by using X-ray diffraction (XRD), UV-VIS spectrophotometry, Photoelectrochemical cell analysis (PEC), scanning electron mi-croscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and scanning probe microscopy (SPM), respectively. The XRD results showed that the CdTe thin films displayed a higher intensity at 1250 mV deposition voltage. UV-VIS spectroscopy measurements revealed that the band gap of the CdTe thin films was near that of the bulk CdTe at 1250 mV deposition voltage. The PEC measurement indicated that at a low voltage of 1230 mV, the conductivity of the film was p-type and Te-rich. When the deposition voltage was 1270 mV, the CdTe films became n-type and Cd-rich. EDS results confirmed the presence of both Cd and Te with more stoichiometric values at the growth voltage of 1250 mV. The SEM images showed that the surface morphology changed with deposition voltage. SPM results indicated that the highest average surface roughness value of 94.9 nm was obtained with a deposition voltage of 1250 mV. These results indicate that the film prepared at a deposition voltage of 1250 mV, may have better potential application as an absorber layer in solar cell device.
ABSTRACT Thin film samples of cadmium telluride were obtained using thermal vacuum evaporation to study the diffusion length of minority charge carriers. Initial state analysis was conducted through X-ray structural studies of cadmium telluride condensed on glass substrates. The analysis revealed two diffraction reflections corresponding to the crystallographic planes (111) and (333). Calculations showed that the sizes of coherent scattering regions were 93 nm and 56 nm, while microstrain values were determined as 11.6×10 −3 and 4.8×10 −3 , respectively, for these planes. Electron diffraction studies identified the zone axis of the formed film structures as [110]. Additionally, twinning and forming a layered substructure within the cadmium telluride thin films were observed. Microscopic surface studies provided insights into the surface relief, measured at approximately 130 nm, and the polycrystalline grain size, determined to be 1 micrometer. The method of spectral dependence of small-signal surface photovoltage was employed to investigate the electrophysical properties of cadmium telluride thin films. The diffusion length of minority charge carriers was calculated to be 0.45 micrometers, which is half the size of the grain dimensions. Furthermore, the transmittance coefficient of cadmium telluride was examined in the wavelength range of 800-900 nm. The optical bandgap energy was 1.4 eV, slightly lower than the 1.5 eV observed for monocrystalline cadmium telluride. In conclusion, cadmium telluride film structures produced by thermal vacuum evaporation exhibit electrophysical and electrical parameters inferior to monocrystalline cadmium telluride. These characteristics, particularly the low diffusion length of minority carriers and short electrical signal decay times make such film structures suitable for use in devices requiring long-term stability under the influence of time, extreme temperatures, electric fields, and radiation.
Cadmium telluride (CdTe) thin films were synthesized by using a two-electrode electrodeposition method on a conductive glass fluorine-doped tin oxide (FTO) substrate. The structural analysis revealed that the deposited CdTe thin films have mixed-phase cubic zinc blends and hexagonal structures in as-prepared and annealed forms with pH depositions of 1.8, 2.5, and 3.5. When the deposition pH is 3.0, only a single-phase cubic structure is observed. The crystallite sizes were 6, 14, 17, and 14 nm for as-prepared and 12, 20, 23, and 19 nm heat-treated samples for corresponding pH values of 1.8, 2.5, 3.0, and 3.5, respectively. The energy bandgaps were recorded in the range 1.38–1.58 eV for as-deposited samples and 1.35–1.5eV for annealed samples for pH values of 1.8–3.5, respectively. The surface image showed that CdTe thin films uniformly covered the glass substrate while the surface morphology of CdTe changed with pH. The availability of both Cd and Te was verified by compo- sitional analysis. The average surface roughness recorded 50.08, 52.08, and 24.00 nm for as-prepared samples and 56.46, 78.73, and 47.17 nm for heat-treated samples for the pH values of 2.5, 3.0, and 3.5, respectively. The overall result shows that the pH value of 3.0 produced a CdTe film of good quality for solar cell application.
The article is dedicated to the numerical simulations of thin-layer structures based on CdTe semiconductors, which can be fabricated by using low-cost technologies. Structures Mo/Au/CdS/CdTe/Au, and their modifications, with different thicknesses of the main layers are investigated. The possibility of creating a detector of ionizing radiation based on these structures, which has selective properties with respect to the radiation type, and very low operation voltage, is shown. The detection efficiencies of α-, β-, and γ-radiation in different energy ranges were calculated based on the obtained values of energy losses of ionizing particles, which are proportional to the output signal of the detector. The use of such detectors, together with a solid-state converter made of boron carbide containing either natural boron natB or boron enriched with the 10B isotope up to 95%, for the detection of thermal neutrons was also studied. It was shown that the structures could be used to create α-particle spectrometers, given that the CdTe thickness is tailored to the highest expected α-particle energy. Detectors with thin CdTe (1–5 μm) can be successfully used in the counting mode. For neutron detection, stacking multiple single structures into sandwich structures was proposed and investigated. In such a configuration, the detector qualities were markedly improved: the efficiency of neutron detection reached ∼60%, while the sensitivity to the background γ- and β-radiation was ∼100 times lower than that for neutrons. The very low sensitivity of the simulated neutron detectors to the neutron incidence angle was shown.
This study investigates the properties of CdS thin films, obtained by DC magnetron sputtering, specifically focusing on their elastic properties and structural parameters. The analysis of the XRD patterns indicates a uniform thickness for the hexagonal crystal structure CdS layers. The average crystallite size of the CdS nanostructured thin films is estimated to be 28 nm using the Scherrer equation. The lattice strain is calculated for FTO/CdS sample using the Williamson-Hall (W-H) equation and the uniform deformation model (UDM). The UDM analysis suggests an average strain of 4.04 × 10-3. The strain analysis using the modified Williamson-Hall equation and the size-strain plot (SSP) method yields consistent results. The average strain obtained from the W-H plot is 0.92 × 10-3, while the SSP method gives a particle size of 67 nm. The different analysis methods employed in the study exhibit good consistency and correlation.
The Chinese Hα Solar Explorer (CHASE) is designed to test a newly developed satellite platform and conduct solar observations. The scientific payload of the satellite is an Hα imaging spectrograph (HIS), which can, for the first time, acquire full-disk spectroscopic solar observations in the Hα waveband. This paper briefly introduces CHASE/HIS including its scientific objectives, technical parameters, scientific application system, etc. The CHASE mission is scheduled to launch in 2021. It will complement the observations by on-orbit solar spacecraft (such as SDO, IRIS, STEREO and PSP), as well as future solar missions of the Solar Orbiter and Advanced Space-based Solar Observatory (ASO-S).
We evaluated the durability of cadmium telluride (CdTe) solar cells upon proton beam irradiation as well as the possibility of achieving a dosimeter usable in proton beam therapy by applying 100 MeV of pencil beam scanning (PBS) irradiation. Specifically, a 100 MeV proton PBS beam was applied at irradiation doses of 0, 10¹², 10¹³, 10¹⁴, and 10¹⁵ cm⁻². According to the results, the remaining factors (defined as the ratio of the degraded value to the initial value) of open-circuit voltage (Voc), short-circuit current (Jsc), fill-factor (FF), and efficiency (ƞ) which are solar cell performance parameters, were approximately 89%, 44%, 69%, and 30%, respectively, compared to those of the reference cell (without irradiation) at the highest dose of 1×10¹⁵ cm⁻². In particular, the conversion efficiency, which is the main factor, was approximately 70% of that of the reference cell even at a high fluence of 1×10¹⁴ cm⁻². In addition, we observed the projected range of the hydrogen atoms based on the PBS beam energy using the Tool for Particle Simulation software and assessed the amount of fluence accumulated in a CdTe cell. As the energy increased, the fluence accumulated inside the cell tended to decrease owing to the characteristics of the Bragg peak of the proton. Thus, the radiation damage to the cell induced by the proton beam was reduced. The results of this study are expected to provide valuable reference information for research on dosimetry sensors composed of thin-film solar cells, serving as the basis for future application in proton beam therapy with CdTe solar cells.
Space photovoltaics is dominated by multi-junction (III-V) technology. However, emerging applications will require solar arrays with high specific power (kW/kg), flexibility in stowage and deployment, and a significantly lower cost than the current III-V technology offers. This research demonstrates direct deposition of thin film CdTe onto the radiation-hard cover glass that is normally laminated to any solar cell deployed in space. Four CdTe samples, with 9 defined contact device areas of 0.25 cm2, were irradiated with protons of 0.5-MeV energy and varying fluences. At the lowest fluence, 1 × 1012 cm−2, the relative efficiency of the solar cells was 95%. Increasing the proton fluence to 1 × 1013 cm−2 and then 1 × 1014 cm−2 decreased the solar cell efficiency to 82% and 4%, respectively. At the fluence of 1 × 1013 cm−2, carrier concentration was reduced by an order of magnitude. Solar Cell Capacitance Simulator (SCAPS) modelling obtained a good fit from a reduction in shallow acceptor concentration with no change in the deep trap defect concentration. The more highly irradiated devices resulted in a buried junction characteristic of the external quantum efficiency, indicating further deterioration of the acceptor doping. This is explained by compensation from interstitial H+ formed by the proton absorption. An anneal of the 1 × 1014 cm−2 fluence devices gave an efficiency increase from 4% to 73% of the pre-irradiated levels, indicating that the compensation was reversible. CdTe with its rapid recovery through annealing demonstrates a radiation hardness to protons that is far superior to conventional multi-junction III-V solar cells.
The provision of a particle and power exhaust solution which is compatible with first wall components and edge plasma conditions is a key area of present-day fusion research and mandatory for a successful operation of ITER and DEMO. The work package plasma-facing components (WP PFC) within the European fusion programm complements with laboratory experiments i.e. in linear plasma devices, electron, and ion beam loading facilities, the studies performed in toroidally confined magnetic devices: JET, ASDEX Upgrade, WEST etc. The connection of both groups is done via common physics and engineering studies, including the qualification and specification of plasma-facing components, and by modelling codes simulating the edge plasma conditions and the plasma-material interaction as well as the study of fundamental processes. WP PFC is addressing these critical points in order to ensure reliable and efficient use of conventional, solid PFCs in ITER (Be and W) and DEMO (W and steel) with respect to heat load capabilities (transient and steady-state heat and particle loads), lifetime estimates (erosion, material mixing, and surface morphology), and safety aspects (fuel retention, fuel removal, material migration, and dust formation) in particular for quasi-steady-state conditions. Alternative scenarios and concepts (liquid Sn or Li as PFCs) for DEMO are developed and tested in the case that the conventional solution turns out not to be functional. Here, we present an overview of the activities with emphasis on a few key results: (i) the observed synergistic effects in particle and heat loading of ITER-grade W with the available set of exposition devices on material properties such as roughness, ductility and microstructure, (ii) the progress in understanding of fuel retention, diffusion, and outgassing in different W-based materials including the impact of damage and impurities like N, and (iii) the preferential sputtering of Fe in EUROFER steel providing in-situ a W surface and a potential first wall solution for DEMO.
Thin film semiconductor neutron detectors are an attractive candidate to replace He-3 neutron detectors, due to the possibility of low cost manufacturing and the potential for large areas. Polycrystalline CdTe is found to be an excellent material for thin film charged particle detectors-an integral component of a thin film neutron detector. The devices presented here are characterized in terms of their response to alpha and gamma radiation. Individual alpha particles are detected with an intrinsic efficiency of >80%, while the devices are largely insensitive to gamma rays, which is desirable so that the detector does not give false positive counts from gamma rays. The capacitance-voltage behavior of the devices is studied and correlated to the response due to alpha radiation. When coupled with a boron-based neutron converting material, the CdTe detectors are capable of detecting thermal neutrons. (c) 2014 AIP Publishing LLC.
Recent developments in photovoltaics created a commercially viable technology of large area uniform thin-film structures, potentially extendable to the field of medical imaging, where the capability of producing large area x-ray detectors is essential for the successful diagnosis and treatment of cancer. We propose a large area thin-film CdTe structure suitable for radiation detection and discuss its main characteristics under x-ray beams used in radiation therapy. While based on the same principle, the details of its operations are very dissimilar from that of photovoltaics.
CdTe/CdS solar cells of 10% efficiency, developed with a vacuum deposition method were irradiated with high-energy protons of different fluences. The V oc and f.f. of irradiated cells increase or decrease depending on the fluence. The normal soda lime glass substrate darkens under the irradiation; therefore low Isc is measured. Measurements suggest that CdTe solar cells are highly stable under proton flux. Flexible and lightweight solar cells were developed in a superstrate configuration on polymer substrates. 8.6 % efficiency cells with Voc770 mV and Isc of 20.3 mA/cm 2 were achieved.
CdTe thin films, deposited on different substrate structures by physical vapor deposition, sputtering, and close‐spaced sublimation, have been treated with CdCl 2 at several temperatures. The morphology of the films has been studied by atomic force microscopy, and the observations were correlated to results obtained from x‐ray diffraction, cathodoluminescence, and minority‐carrier lifetime measurements. The samples treated at 400 °C resulted in the best device‐quality films, independent of deposition method and underlying substrate structure. For the first time, a nanograin structure was observed in CdTe sputtered samples. © 1995 American Vacuum Society
Tungsten samples were exposed to sequential steady-state (particle flux of 10 22 m-2 s −1 , heat flux of 1.7 MW/m 2) and pulsed (surface heat load of 0.45 MJ/m 2 , pulse duration of 0.25 ms) hydrogen plasmas. Several steps of the steady-state irradiation and pulsed loading were carried out. The samples were studied between the stages of the irradiation with SEM and XRD methods. It has been found that crack network and blisters developed on the surface under irradiation strongly depend on the initial structure of tungsten samples.
Presence of interfaces between high and low atomic number (Z) materials, often encountered in diagnostic imaging and radiation therapy, leads to radiation dose perturbation. It is characterized by a very narrow region of sharp dose enhancement at the interface. A rapid falloff of dose enhancement over a very short distance from the interface makes the experimental dosimetry nontrivial. We use an in‐house‐built inexpensive thin‐film Cadmium Telluride (CdTe) photodetector to study this effect at the gold‐tissue interface and verify our experimental results with Monte Carlo (MC) modeling. Three‐micron thick thin‐film CdTe photodetectors were fabricated in our lab. One‐, ten‐ or one hundred‐micron thick gold foils placed in a tissue‐equivalent‐phantom were irradiated with a clinical Ir‐192 high‐dose‐rate (HDR) source and current measured with a CdTe detector in each case was compared with the current measured for all uniform tissue‐equivalent phantom. Percentage signal enhancement (PSE) due to each gold foil was then compared against MC modeled percentage dose enhancement (PDE), obtained from the geometry mimicking the experimental setup. The experimental PSEs due to 1, 10, and 100 μm thick gold foils at the closest measured distance of 12.5 μm from the interface were 42.6±10.8, 137.0±11.9, and 203.0±15.4, respectively. The corresponding MC modeled PDEs were 38.1±1., 164±1, and 249±1, respectively. The experimental and MC modeled values showed a closer agreement at the larger distances from the interface. The dose enhancement in the vicinity of gold‐tissue interface was successfully measured using an in‐house‐built, high‐resolution CdTe‐based photodetector and validated with MC simulations. A close agreement between experimental and the MC modeled results shows that CdTe detector can be utilized for mapping interface dose distribution encountered in the application of ionizing radiation.
PACS number(s): 29.40.Wk, 73.50.Pz, 87.53.Jw, 87.55.K‐
In the present study, nondoped CdS crystal with a size of 5 × 5 × 0.5mm3 was investigated on the optical and scintillation properties. The optical transmittance was 70% at wavelength longer than 500 nm, and the absorption edge was around 490 nm. The photoluminescence emission peak appeared around 490nm under 340nm excitation with 6.6 ns fast decay time. In X-ray induced radioluminescence spectrum over the temperature range of 7-300 K, it showed four emission bands around 490, 500-540 with several peaks, 600, and 750 nm. Temperature dependences of each emission band were different. The scintillation decay time was reproduced by two exponential decay components of 8 and 67 ns, and that for X-ray induced afterglow was approximately 0.1% at 20ms after switching of the X-ray irradiation.
In this paper, the effects of electron beam irradiation on the CdTe thin films are studied. The CdTe thin films are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and contact angle measurements for different bath concentration. The thin film layers are subjected to irradiation of 6 MeV electrons. Finally the effect of irradiation is correlated to crystal size, grain size and contact angle measurements of the CdTe thin films
A post-deposition process for optimizing the efficiency of thin film CdTe/CdS solar cells deposited by physical vapor deposition has been developed and the effects of the individual process steps on the materials and device properties have been analyzed. A 400 °C heat treatment with CdCl2 restructures the CdTe resulting in enhanced grain size and crystallographic reorientation. Structural and optical measurements indicate interdiffusion of sulfur and tellurium during the heat treatment resulting in formation of a CdSxTe1−x layer with a narrower band gap than CdTe. Bifacial current-voltage and quantum efficiency analysis of the CdTe devices at various stages of the optimization process shows the evolution of the device from a p-i-n structure to a heterojunction. A chemical treatment improves the open circuit voltage ( ) and Cu/Au contact to the CdTe. The optimization process can be applied to cells using CdTe and CdS deposited by different methods.
Output parameters and diode characteristics under illumination of flexible thin-film solar cells ITO/CdS/CdTe/Cu/Au formed on polyimide films by vacuum methods are studied. Using mathematical modeling of the effect of diode characteristics under illumination on the efficiency, the physicothechnical parameters of such structures are optimized. This made it possible to obtain laboratory samples of flexible solar cells based on cadmium sulfide and telluride with an efficiency of 11.4%. Solar modules with an efficiency of 4.5% based on the developed flexible solar cells are formed for the first time.
Development of flexible and lightweight solar cells is interesting for terrestrial and space applications that require a very high specific power (kW/kg) and flexibility for curved shaping or rolling. Flexible CdTe/CdS solar cells of 11% efficiency in superstrate and 7.3% efficiency in substrate configurations have been developed with a “lift-off” approach. However, roll-to-roll manufacturing is desired in future.Therefore, flexible superstrate solar cells were directly grown on commercially available ∼10μm thin polyimide (Upilex™) foils. A process for the deposition of ITO (front contact) has been developed to have a stable front contact on the Upilex™ foil. Post-deposition annealing treatments of the ITO/polyimide stacks bring a significant stability to the front contact, having almost the same sheet resistance at the beginning and at the end of the cell fabrication process. Solar cells with AM1.5 efficiency of 11.4% on Upilex™ foils (highest efficiency recorded for flexible CdTe cell) have been developed. A comparison of the cells prepared on different polyimides is presented.
Hot-wall vacuum deposited n-CdS/p-CdTe thin-film solar cells with the graded-gap CdTe1−xSx interfaces have been investigated. The CdTe1−xSx interfaces have been studied by means of the measurement and subsequent computer simulation of the spectral photoresponse curves, as well as by the layer-by-layer laser mass-spectrometry analysis of the cells. The p-n junction optimization according to the simulation results has been carried out by means of the open-air annealing of the fresh-prepared solar cells.
Phase control is critical for achieving high-performance CdTe cells when CuxTe is used as a back-contact for CdTe cells. CuxTe phases are mainly controlled by the Cu/Te ratio, and they can also be affected by post-heat-treatment temperature. Although Cu2Te has the highest conductivity, it is unstable and provides more Cu diffusion into the CdS and CdTe films. Cu diffusion into the CdS causes “cross-over”, and Cu diffusion into the CdTe film creates Cu-related defects that lower photogenerated carrier lifetime and result in voltage-dependent collection. A “recontact” experiment clearly indicated that the mechanism giving rise to “roll-over” is the formation of Cu-related oxides, rather than the loss of Cu on the back-contact.
Polycrystalline CdTe/CdS solar cells are used in space, as well as terrestrial, applications. The results of the studies on the effect of 8MeV electron irradiation on p-CdTe/n-CdS thin film solar cells prepared by radio frequency (RF) sputtering are presented in this article. Solar cell parameters like short circuit current (Isc), open circuit voltage (Voc), fill factor (FF), conversion efficiency (η), saturation current (Is) and ideality factor (n) have been considered. CdTe thin film solar cells exhibit good stability against electron irradiation up to 100kGy.
Problems related to the dosimetry of γ-radiation, in particular of high intensity, are investigated together with operational performances of detectors, their temperature stability, reproducibility and reliability of detector measurements. A comprehensive study was carried out of CdTe detectors, obtained by the Bridgman growth method, and CdZnTe detectors, crystallized by the Bridgman method at high pressure of inert gas. All the investigated ingots were of p-type conductivity. The current–voltage characteristics and dynamic resistance of detectors from CdTe and CdZnTe were measured over a wide range of operational temperatures (−30 to +70°C) and bias voltages . The dosimetry performance of CdTe and CdZnTe γ-radiation detectors was tested with standard calibration dosimetry rigs of different intensity. The relation between the detector count rate (count mode of operation) or detector anode current (integrated, or current mode of operation) and the exposure dose rate (EDR) of the γ-radiation was established. The count rate of the radiation registered from different sources (, , ) in the count mode depends linearly on EDR in the EDR range from up to . In high-intensity radiation fields a measurement of the current induced by the γ-radiation, i.e. with the detector operating in “current mode”, is preferable. In this case, our researches have shown that the EDR dependence of the output voltage of the current–voltage converter is linear in the range from up to . Several designs of “detector-absorbing filter” sets were proposed for the correction of the energy dependence of the CdTe and CdZnTe detector absorption efficiency. An experimental detector unit equipped with an optimized “detector-filter” set had a discrete sensitivity of (±20%) in the energy range .
Detectors using CdTe photoconductors are being used with great success in LEP to monitor the vertical beam emittance. They can withstand tremendous irradiation, of up to 10^13 Gy, from hard X-rays. For the LHC, monitors measuring the relative luminosity will be placed inside absorbers located 142 m from the interaction points, where they will receive about 10^8 Gy per year due to gamma radiation and neutrons.
Thick-polycristalline-CdTe detectors were recently tested for speed, sensitivity and radiation resistance before and after receiving up to 10^15 neutrons per cm^2. The test results are presented here, along with a comparison of the calculated charge deposition in Silicon, Diamond and GaAs detectors.
Radiation resistance of semiconductor detectors of corpuscular and gamma radiation
- L N Davydov
- A A Zakharchenko
- D V Kutny
- V E Kutny
- I M Neklyudov
- A V Rybka
- I N Shlyakhov
L.N. Davydov, A.A. Zakharchenko, D.V. Kutny, V.E. Kutny, I.M. Neklyudov, A.V. Rybka,
I.N. Shlyakhov, "Radiation resistance of semiconductor detectors of corpuscular and gamma
radiation," Bulletin of KhNU Physical series "Nuclei, particles, fields" 627, 3-22 (2005). [in Russian].
Investigation of characteristics of semiconductor detectors of alpha radiation
- A S Sokolov
- D D Burdeiny
- A O Pudov
- A A Zakharchenko
- A V Rybka
- V E Kutny
Using of closed box deposition technique for preparation of cadmium telluride thin films
- M Kharchenko
M. Kharchenko, "Using of closed box deposition technique for preparation of cadmium
telluride thin films," Physics and chemistry of solid state. 8(4), 718-721 (2007). [in Ukraine]
http://page.if.ua/uploads/pcss/vol8/0804-10.pdf.
Radiation hardness of cadmium telluride solar cells in proton therapy beam mode
- J Y Nam
- Song
Nam, J.Y. Song, "Radiation hardness of cadmium telluride solar cells in proton therapy beam mode,"