CdTe Research Articles

Lattice mismatch alleviation in p-CdTe/n-Si heterostructure by surface engineering on Si substrate

The study used magnetron sputtering to investigate the growth of cadmium telluride (CdTe) thin films on surface treated n-type silicon (n-Si) substrates. The n-Si substrates were textured using potassium hydroxide (KOH) before the sputter deposition of CdTe. This was followed by cadmium chloride treatment to reduce the strain at the interface of CdTe and Si, which is caused by the incompatible lattice and thermal expansion mismatch (CTE). X-ray diffraction (XRD) analysis showed that the lowest FWHM and dislocation densities were obtained for CdCl2/CdTe/txt-nSi, which aligns with the scanning electron microscopy (SEM) results. In the SEM images, the interface bonding between the CdTe and Si surfaces was visible in the cross-sections, and the top-view images revealed sputtered CdTe thin films conforming to the patterns of pyramidal textured Si as an engineered surface to capture more light to maximize absorption in the CdTe/Si tandem design. The Energy dispersive X-ray (EDX) results showed that all the CdTe deposited on textured n-Si exhibited more Te atoms than Cd atoms, irrespective of the CdCl2 treatment. The presented results suggest that the texturization and CdCl2 treatment improved the morphology and grain boundary passivation of the sputtered CdTe. The adhesiveness of CdTe on the n-Si substrate was also significantly enhanced. Our findings further demonstrate that proper surface treatment of the Si substrate can greatly improve the quality of CdTe grown on Si by reducing the strain that occurs during the growth process. This study demonstrates a valuable method for enhancing the integration of CdTe with Si for two-junction tandem solar cell applications.

A Comprehensive Review on the Recent Strategy of Cation Substitution in CZTS(Se) Thin Films to Achieve Highly Efficient Kesterite Solar Cells

Kesterite Cu2ZnSnS4 (CZTS) and selenized CZTS (CZTSSe) are the most potential replacements of Cu(InxGa1−x)Se2 as absorber layers in thin‐film solar cells, aligning with modern green energy policies. In spite of a reported power conversion efficiency (η) of nearly 14.9%, their efficiency still lags much behind their predecessors like cadmium telluride and CIGS. Major obstacles hindering the performance of CZTS‐based thin‐film solar cells pertain to the formation of CuZn and ZnCu antisite defects, along with high density of 2CuZn + SnZn donor defects, which adversely affects open‐circuit voltage and η. To combat these challenges, researchers have explored cation substitution by incorporating alternative isovalent atoms, such as substituting Ag/Li for Cu, Mn/Cd for Zn, and Ge/Ti for Sn, as a potent strategy to inhibit severe potential fluctuations and undesirable tail states caused by Cu–Zn disorder and Sn‐related defects. Recently single‐cation substitution in CZTS (or CZTSSe) has garnered considerable attention, while dual‐cation incorporation has emerged as an intriguing avenue to enhance device performance, although in its nascent stage of research and development. This review discusses recent progress on cation substitution to suppress antisite defects in CZTS (or CZTSSe), leading to high‐efficiency thin‐film solar cells.

Signal-difference-to-noise comparison of temporal subtraction, kV-switching dual-energy and photon-counting dual-energy x-ray angiography.

Dual-energy (DE) x-ray angiography with photon-counting detectors (PCDs) may enable single-exposure DE imaging of coronaryvasculature. To compare the iodine signal-difference-to-noise ratio (SDNR) of single-exposure DE angiography with digital subtraction angiography (DSA) and kV-switching DE angiography for matched patient x-rayexposure. In a phantom study, we determined the technique parameters that maximized the iodine SDNR per root entrance air kerma for DSA, kV-switching DE angiography and single-exposure DE angiography. We measured SDNR from images of a phantom consisting of an iodine step-wedge immersed in a water tank of either 20 or 30cm in thickness. We also imaged a phantom with simulated vessels embedded in background clutter and measured vessel SDNR. For this second phantom, we also applied anti-correlated noise reduction (ACNR) and calculated the resulting iodine SDNR. All images were acquired using a cadmium telluride PCD with two energy bins and analog charge summing for charge sharing suppression. The energy-discrimination capabilities were only used for the single-exposure DE approach. Optimized techniques were compared in terms of SDNR per root air kerma for two levels of x-rayscatter. For the same patient x-ray exposure, the SDNR of single-exposure DE imaging without ACNR was 75% to 85% of that of kV-switching DE imaging (also without ACNR) and DSA, the latter two of which had nearly equal SDNR. The single-exposure DE approach required ∼50% of the tube load of the kV-switching approach to achieve the same SDNR. For matched patient air kermas, the single exposure approach required only ∼25% of the tube load of the kV-switching approach. ACNR increased SDNR by 2.4 and 3.0 for kV-switching and single-exposure DE imaging,respectively. Photon-counting, single-exposure DE angiography can suppress soft tissues and provide iodine SDNR levels comparable to DSA and kV-switching DE angiography for matched patient radiation exposures. When ACNR is used to reduce DE image noise, the SDNR of single-exposure DE imaging and kV-switching DE imaging exceed that of DSA by more than a factor of two. Compared to kV-switching DE imaging, single-exposure DE imaging requires substantially lower tube loading to achieve the sameSDNR.

Dual‐emission ratiometric fluorescence sensors based on silica, molecularly imprinted polymers and carbon quantum dots for high‐sensitivity and high‐selectivity detection of sulfadiazine

AbstractIn this work, a dual‐emission ratiometric fluorescence sensor was prepared and used for the detection of sulfadiazine (SDZ) drug. The hydrothermal method was used to synthesize carbon quantum dots (CQD) (fluorescence response signal) and sulfhydryl‐modified cadmium telluride quantum dots (fluorescence reference signal), and a molecularly imprinted polymer was subsequently synthesized. After eluting the template molecule SDZ, the blot recognition site remains on the surface of the imprinted polymer. During the process of detection, due to electron transfer between SDZ and CQDs, holes of stimulated electrons are filled. This leads to fluorescence quenching at around 430 nm, which greatly improves sensor selection performance. Compared with traditional single‐emission fluorescence sensors, ratiometric fluorescence sensors have a wider linear range and higher detection accuracy. Under the optimal conditions, the sensor exhibited excellent performance in terms of low detection limit (4.2 nmol L−1) and satisfactory linear range (2–20 μmol L−1). This intelligent response change mode also provides prospect for detection of other sulfonamide antibiotics and offers a reference to signal transform for other molecular imprinting technologies. © 2023 Society of Industrial Chemistry.

Effect of various layers on improving the photovoltaic efficiency of Al/ZnO/CdS/CdTe/Cu2O/Ni solar cells

The photovoltaic (PV) cell structure containing Al/ZnO/CdS/CdTe/Cu2O/Ni has been simulated using the SCAPS-1D software. The PV device includes a zinc oxide (ZnO) transparent conductive oxide (TCO) window layer, a cadmium sulfide (CdS) buffer layer, and a cadmium telluride (CdTe) absorber layer. Additionally, an electron reflected-hole transport layer (ER-HTL) comprising cuprous oxide (Cu2O) is introduced between the absorber layer and the back metal contact. Aluminum (Al) and nickel (Ni) serve as the upper/top and back contact materials, respectively, interconnecting the layers. The back contact materials, the thickness of the absorber, buffer, and window layers, the acceptor density of the absorber layer, the donor density of the buffer layer, the series and shunt resistance, as well as temperature, were all modified to investigate the PV performance of this structure. The PV performance parameters are evaluated through the open-circuit voltage (VOC), short-circuit current (JSC), fill factor (FF), and power conversion efficiency (PCE). To achieve optimal performance, it is recommended to set the acceptor and donor densities for the absorber and buffer layers at 1017 cm−3. These desired densities can be attained by using a window and buffer layer thickness of 100 nm, an absorber layer thickness of 2500 nm, and an ER-HTL of 50 nm. The optimized model demonstrates PV performance characteristics of 1.4811 V for VOC, 28.682434 mA/cm2 for JSC, 74.91 % for FF, and 31.82 % for PCE under the AM 1.5 G spectrum. Furthermore, it exhibits a quantum efficiency of around 100 % at visible wavelengths.

A novel radiometric calibration of an infrared thermometer

A new temperature calibration scheme was proposed and implemented on the National Physical Laboratory infrared radiometer Absolute Measurements of Blackbody Emitted Radiance (AMBER) operating in the wavelength range from 9 µm to 11 µm and equipped with a cryogenically cooled mercury cadmium telluride detector. The scheme involves measurements of the relative spectral responsivity of the filter radiometer including the spectral transmittance of the window and lens. It requires calibration at two reference temperatures, but does not involve measurement of the zero-radiance signal. The scheme uses a Ga-point blackbody as one reference point, and a variable temperature blackbody source at close to −30 °C with its temperature measured with a standard platinum resistance thermometer as the other. The measured temperature was compared using the variable temperature blackbody as the source against the temperature measured by the standard platinum resistance thermometer and agreement within the uncertainties was confirmed at intermediate temperatures. The scheme has the advantage that it makes full use of the small uncertainty realised by the fixed-point blackbody. The scheme was successfully implemented in an international comparison of sea surface temperature measuring radiometers where AMBER served to provide the reference.

High Spectral Efficiency Long-Wave Infrared Free-Space Optical Transmission With Multilevel Signals

This study explores the potential of long-wave infrared free-space optical (FSO) transmission that leverages multilevel signals to attain high spectral efficiency. The FSO transmission system consists of a directly modulated-quantum cascade laser (DM-QCL) operating at 9.15 μm and a mercury cadmium telluride (MCT) detector. To fully understand the system, we conduct measurements on the DM-QCL chip and MCT detector and assess the overall amplitude response of the DM-QCL, MCT detector, and all electrical components. We apply various signals, including on-off keying (OOK), 4-level pulse amplitude modulation (PAM4), 6-level PAM (PAM6), and 8-level PAM (PAM8) to maximize the bit rate and spectral efficiency of the FSO transmission. Through a two-dimensional sweeping of the laser bias current and MCT detector photovoltage, we optimize the transmission performance. At the optimal operation point, the FSO system achieved impressive results which are up to 6 Gbaud OOK, 3.5 Gbaud PAM4, 3 Gbaud PAM6, and 2.7 Gbaud PAM8 signal transmissions, with a bit error rate performance below 6.25% overhead hard decision-forward error correction limit when the DM-QCL operates at 10°C. We also evaluate the eye diagrams and stability of the system to showcase its remarkable transmission performance. Our findings suggest that the DM-QCL and MCT detector-based FSO transceivers offer a highly competitive solution for the next generation of optical wireless communication systems.

Functionalized graphene, quantum dots, and PEDOT:PSS based screen-printed electrode for the endocrine disruptor bisphenol A determination

Strategies aimed for the monitoring the endocrine disruptor bisphenol A (BPA) become essential due to the high toxicity that this substance can cause in the environment. In this sense, a screen-printed electrode with functionalized graphene, cadmium telluride quantum dots, and polymer (PEDOT:PSS) was manufactured for the determination of the BPA in environmental matrices. The materials that compose the sensor were characterized by fluorescence spectroscopy, X-ray diffraction, FEG-SEM, TEM and FTIR. The electrochemical behavior of the analyte was performed by cyclic voltammetry and the quantification by square-wave voltammetry, respectively. The electroanalytical method showed a linear response in the BPA concentration range from 0.020 to 9.0 µmol L−1 with a limit of detection of 3.4 nmol L−1. Finally, the electroanalytical method was successfully applied to environmental samples for the determination of BPA, with a recovery close to 100%. This demonstrates its good applicability and sensitivity for this type of sample.

Modeling of dark current in semispherical quantum dot structures for infrared photodetection

Due to its tunable heterojunction bandgap and great sensitivity to normal incident illumination, the Quantum Dot Infrared Photodetectors (QDIPs) have received a lot of attention for the purpose of infrared sensing. It could be a very promising replacement for conventional infrared photodetectors made with established technology, including mercury cadmium telluride and quantum well infrared photodetectors. In this work, a model for the dark current in semispherical QDIP has been developed, resolves the primary semiconductor Poisson's and continuity equations, where the wave function and the bound states effects are investigated. In this study, Boltzmann transport equation in the photodetector active layer with embedded QDs is solved using the finite difference time domain method to determine the photodetector carrier mobility and its degradation due the quantum dot scattering. The outcomes of the presented have been contrasted with truncated conical QDIPs showing that smaller volume QDs had less noisy dark current. Investigations have been done into how the semispherical QDIP's dark current characteristics are affected by the QD volume, density, and operating temperature.

Optimizing the Charge Carrier Dynamics of Thermal Evaporated TexSe1‐x Films for High‐Performance Short‐Wavelength Infrared Photodetection

AbstractShort‐wavelength infrared photo‐sensing materials are dominated by germanium, indium gallium arsenide, indium antimonide, and mercury cadmium telluride. However, the complex fabrication process and high production cost hinder their widespread applications. Recently, TexSe1‐x has shown great potential for infrared photodetection, but TexSe1‐x‐based devices are still suffering from extremely high dark current and poor device performance. In this work, high‐quality TexSe1‐x films are fabricated by thermal evaporation and low‐temperature annealing. The optoelectronic properties of the TexSe1‐x thin films are systematically investigated and optimized. The absorption spectrum is carefully tuned to cover the broad range from 300 to 1600 nm by modulating the ratio of Te and Se. Photodiodes based on the optimized TexSe1‐x thin films are also fabricated, and achieve high responsivity, reduced dark and low noise current density, and a fast response time of <850 ns. Then, prototypical devices based on Te0.65Se0.35 thin films are demonstrated for optical communications, indicating the great potential for next‐generation, low‐cost short‐wavelength infrared photodetection.

Solar harvesting through multiple semi-transparent cadmium telluride solar panels for collective energy generation

Among major energy conversion methods, photovoltaic (PV) solar cells have been the most popular and widely employed for a variety of applications. Although a PV solar panel has been shown as one of the most efficient green energy sources, its 2D surface solar light harvesting has reached great limitations as it requires large surface areas. There is, therefore, an increasing need to seek solar harvest in a three-dimensional fashion for enhanced energy density. In addition to a conventional 2D solar panel in the x-y area, we extend another dimension of solar harvesting in the z-axis through multiple CdTe solar panels arranged in parallel. The high transparency allows sunlight to partially penetrate multiple solar panels, resulting in significantly increased solar harvesting surface area in a 3D fashion. The advantages of the 3D multi-panel solar harvesting system include: i) enlarged solar light collecting surface area, therefore increased energy density, ii) the total output power from multiple panels can exceed that of the single panel, and iii) significantly reduced surface area needed for densely populated cities. With five CdTe solar panels of different transparencies in parallel, the multilayer system can produce collective output power 233% higher than that of the single solar panel under the same surface area when arranged in descending (i.e., PV panel with the highest transparency on top and lowest at bottom). The PCE of the multi-panel system has also increased 233% in descending order indicating the viability of 3D solar harvesting. The multi-panel system will dimensionally transform solar harvesting from 2D to 3D for more efficient energy generation.

A Comprehensive and Sustainable Recycling Process for Different Types of Blended End-of-Life Solar Panels: Leaching and Recovery of Valuable Base and Precious Metals and/or Elements

The production of photovoltaic modules is increasing to reduce greenhouse gas emissions. However, this results in a significant amount of waste at the end of their lifespan. Therefore, recycling these solar panels is important for environmental and economic reasons. However, collecting and separating crystalline silicon, cadmium telluride, and copper–indium–gallium–selenide panels can be challenging, especially in underdeveloped countries. The innovation in this work is the development of a process to recycle all solar panel waste. The dissolution of all metals through the leaching process is studied as the main step of the flowchart. In the first step of leaching, 98% of silver can be recovered by 0.5 M nitric acid. Then, the second and third step involves the use of glycine for base metal dissolution, followed by the leaching of valuable metals with hydrochloric acid. The effect of parameters such as the initial pH, acid concentration, solid/liquid ratio, and hydrogen peroxide concentration is studied. The results show that up to 100% of Cu, Pb, Sn, Zn, Cd, In, Ga, and Se can be recovered under optimal conditions. The optimal conditions for the dissolution of Cu, Zn, and Cd were a glycine concentration of 0.5 M, a temperature of 25 °C, a solid/liquid ratio of 10 gr/L, and 1% of hydrogen peroxide. The optimized glycine concentration for the leaching of lead and tin was 1.5 M. Indium and gallium were recovered at 100% by the use of 5 M hydrochloric acid, S/L ratio = 10 gr/L, and T = 45 °C. Separation of selenium and tellurium occurred using 0.5 M HCl at a temperature of 60 °C. Additionally, for the first time, a general outlook for the recycling of various end-of-life solar panels is suggested.

Numerical Investigation on the Effects of Grain Size and Grinding Depth on Nano-Grinding of Cadmium Telluride Using Molecular Dynamics Simulation.

Cadmium telluride (CdTe) is known as an important semiconductor material with favorable physical properties. However, as a soft-brittle material, the fabrication of high-quality surfaces on CdTe is quite challenging. To improve the fundamental understanding of the nanoscale deformation mechanisms of CdTe, in this paper, MD simulation was performed to explore the nano-grinding process of CdTe with consideration of the effects of grain size and grinding depth. The simulation results indicate that during nano-grinding, the dominant grinding mechanism could switch from elastic deformation to ploughing, and then cutting as the grinding depth increases. It was observed that the critical relative grain sharpness (RGS) for the transition from ploughing to cutting is greatly influenced by the grain size. Furthermore, as the grinding depth increases, the dominant subsurface damage mechanism could switch from surface friction into slip motion along the <110> directions. Meanwhile, as the grain size increases, less friction-induced damage is generated in the subsurface workpiece, and more dislocations are formed near the machined groove. Moreover, regardless of the grain size, it was observed that the generation of dislocation is more apparent as the dominant grinding mechanism becomes ploughing and cutting.

N-type CdTe:In for photovoltaics: in situ doping, type verification and compensation effects

We explored the in-situ doping of cadmium telluride thin films with indium to produce n-type absorbers as an alternative to the near-universal choice of p-type for photovoltaic devices. The films were grown by close space sublimation from melt-synthesised feedstock. Transfer of the indium during film growth was limited to 0.0014%–0.014%—unless reducing conditions were used which yielded 14%–28% efficient transport. While chunks of bulk feedstock were verified as n-type by the hot probe method, carrier type of thin film material was only able to be verified by using hard x-ray photoelectron spectroscopy to determine the Fermi level position within the band gap. The assignment of n-type conductivity was consistent with the rectification behaviour of a p-InP/CdTe:In junction. However, chloride treatment had the effect of compensating n-CdTe:In to near-intrinsic levels. Without chloride, the highest dopant activation was 20% of the chemical concentration of indium, this being for a film having a carrier concentration of n = 2 × 1015 cm−3. However, the activation was often much lower, and compensation due to over-doping with indium and native defects (stoichiometry) are discussed. Results from preliminary bifacial devices comprising Au/P3HT/ZnTe/CdTe:In/CdS/FTO/glass are presented.

Exploring the time-resolving capabilities of XIDer assemblies

The XIDer R&D project, between the European Synchrotron Radiation Facility (ESRF) and Heidelberg University, is developing state-of-the-art detectors for the high-energy, high-flux beamlines of the ESRF Extremely Brilliant Source (EBS). In particular, the XIDer detector aims to tackle the significant challenges posed by time-resolved experiments analysing the pattern of diffracted or scattered X-rays.To fulfil the needs of these experiments, a novel on-chip incremental digital integration readout scheme with per-pixel digital data output has been implemented. The EBS beam operates with different time structures: from a near-100% duty cycle X-ray beam to an up to 5.7MHz pulsed X-ray beam. For the latter EBS mode, the XIDer ASIC has been designed to have a fast front-end and memory storage cells, such that the pulsed EBS beam can be exploited by time-resolved experiments. Recent measurements of the time-resolving capabilities of XIDer ASICs hybridised cadmium telluride and cadmium zinc telluride sensors are presented.

Enzyme-free nucleic acid and luminescent material cascade amplifications enable urinary dual miRNAs assay for non-invasive bladder cancer diagnosis

We presented a facile biosensing strategy for the detection of dual microRNAs (miRNA-21 and miRNA-126) in urine samples from bladder cancer (BC) patients. The fluorescent homogeneous detection of miRNAs was achieved by elaborate parallel catalytic hairpin assembly (CHA) integrated with material cascade amplifications. The continuous release of G-quadruplex (G4) sequences and Hg2+ was attributed to the specific recognition between the miRNAs and the corresponding hairpin oligonucleotides. Assisted by the streptavidin-(T-Hg2+-T-biotin)4 structures, more Hg2+ emission was obtained, and the spatial site block effect was used to order its distribution, significantly improving the selective recognition performance of cadmium telluride quantum dots (CdTe QDs) (1.4–2.9 times). Furthermore, the peroxidase-like activity of G4-hemin was used to catalyze the oxidation of dopamine (DA) to fluorescence-enhanced polydopamine (PDA). The generated PDA signal and the Hg2+-quenched CdTe QDs signal completed the synchronous detection to achieve a high-sensitivity analysis of the dual miRNAs. The limit of detection (LOD) of both miRNAs was as low as the fM level. Eventually, 56 clinical urine samples were quantified. The results showed satisfying specificity (100%) and sensitivity (92%) with a strong clinical agreement, including computed tomography (CT) and pathology findings, indicating a rapid non-invasive solution for early diagnosis of BC.

Mercaptosuccinic acid capped cadmium telluride quantum dots as luminescent thermometer over a wide temperature range of −100 to 60℃

Thermal-sensitive photoluminescence (PL) properties of cadmium telluride quantum dots capped with mercaptosuccinic acid (MSA-CdTe QDs) were investigated by collecting QDs’ PL steady-state spectra and decay curves from a cryogenic temperature of −100℃ to 60℃. These QDs display peak wavelength redshift and shorten fluorescence lifetime with the increase of temperature. In situ XRD patterns showed that the QDs’ grain size increases due to thermal expansion induced by the increasement of temperature, which further leads to the redshift of luminescence peak wavelength position. The results prove MSA-CdTe QDs are excellent candidates for luminescence thermometry over a broad temperature range of −100 to 60℃.

Modelling the spectral influence on photovoltaic device performance using the average photon energy and the depth of a water absorption band for improved forecasting

Accurate forecasts of solar panel performance can improve grid penetration, enable cost evaluation prior to project implementation, and improve fault detection during operation. Spectral correction functions (SCFs) used to model the influence of the solar spectrum in such forecasting models are typically based on either proxy representations of the spectrum, using parameters such as air mass, or parameters derived directly from the spectrum, such as the average photon energy (APE). Although the latter is more accurate, the APE is argued in some studies not to be a unique characteristic of the spectrum and to suffer from increased uncertainty when analysing spectra at longer wavelengths. This study first derives APE spectral correction function coefficients for three PV technologies — multicrystalline (mSi), triple junction amorphous silicon (aSi-T), and cadmium telluride (CdTe). Based on an analysis of uncertainty in the SCF for each of the three devices, this study proposes a new spectral correction function based on the average photon energy, φ, and the depth of a water absorption band, ɛ. The additional index enables spectra to be characterised by unique combinations of φ and ɛ. Several water absorption bands are tested and the 650–670 nm band is found to yield the most accurate SCF for all three PV devices. An optimal parameterisation of the SCF for each PV device, as well as a cost-accuracy-balanced parameterisation, is presented. Improvements in the prediction accuracy of up to 60% for both the mSi and aSi-T modules, and around 20% for the CdTe module, are achieved by the proposed model with respect to a comparable two-variable proxy SCF, namely the air mass and precipitable water function. Compared with the single-variable APE SCF, f(φ), the proposed model improves the prediction accuracy by around 10% for the aSi-T and mSi modules, and by around 2% for the CdTe module. No new data are required for the proposed model compared with f(φ) as the same spectra used to calculate the APE are used to calculate ɛ. The proposed spectral correction function can easily be integrated into wider photovoltaic performance models for improved forecasting.

Inorganic Thin-Film Solar Cells: Challenges at the Terawatt-Scale

Thin-film solar cells have been referred to as second-generation solar photovoltaics (PV) or next-generation solutions for the renewable energy industry. The layer of absorber materials used to produce thin-film cells can vary in thickness, from nanometers to a few micrometers. This is much thinner than conventional solar cells. This review focuses on inorganic thin films and, therefore, hybrid inorganic–organic perovskite, organic solar cells, etc., are excluded from the discussion. Two main families of thin-film solar cells, i.e., silicon-based thin films (amorphous (a-Si) and micromorph silicon (a-Si/c-Si), and non-silicon-based thin films (cadmium telluride (CdTe) and copper–indium–gallium diselenide (CIGS)), are being deployed on a commercial scale. These commercial technologies, until a few years ago, had lower efficiency values compared to first-generation solar PV. In this regard, the concept of driving enhanced performance is to employ low/high-work-function metal compounds to form asymmetric electron and hole heterocontacts. Moreover, there are many emerging thin-film solar cells conceived to overcome the issue of using non-abundant metals such as indium (In), gallium (Ga), and tellurium (Te), which are components of the two commercial thin-film technologies, and therefore to reduce the cost-effectiveness of mass production. Among these emerging technologies are kesterite CZTSSE, intensively investigated as an alternative to CIGS, and Sb2(S,Se)3. In this review, after a general overview of the current scenario of PV, the three main challenges of inorganic thin-film solar cells, i.e., the availability of (safe) metals, power conversion efficiency (PCE), and long-term stability, are discussed.

Effect of the Diffusion of Copper Atoms in Polycrystalline CdTe Films Doped with Pb Atoms

The process of diffusion of labeled copper atoms in p-CdTe&lt;Pb&gt; coarse-block films with a columnar grain structure has been studied. The CdTe&lt;Pb&gt; film is a p-type semiconductor, where an increase in the Pb concentration in the composition of the CdTe films increases the resistivity ρ of the structure. When the Pb concentration in CdTe changes from 1018 to 5·1019 cm-3, the hole concentration decreases by more than 3 orders of magnitude at a constant operating level depth of EV + (0.4 ± 0.02) eV. This may indicate that the concentration of acceptor defects, which are formed in the films due to self-compensation upon doping with a PbCd donor, exceeds the number of the latter. Electrical measurements by the Hall method were carried out at a direct current and a temperature of 300 K. As a result, an increase in the temperature of films on a Mo-p-CdTe&lt;Pb&gt; substrate during annealing affects the electrical parameter of charge carrier mobility µ, it decreases significantly. X-ray diffraction analysis showed that on the diffraction patterns of samples of p-CdTe&lt;Pb&gt; films, all available reflections correspond to the CdTe phase and up to х = 0.08 do not contain reflections of impurity phases and have a cubic modification. Based on the results of the calculation, it was established that the low values of the diffusion coefficient of Cu atoms are due to the formation of associates of the A type , which are directly dependent on the concentration of atoms. Diffusion length Ln and lifetime τn of minority current carriers in large-block p-type cadmium telluride films, which can also be controlled by introducing lead atoms into cadmium telluride.