CdTe Thin Films Research Articles

Copper doping effect in the back surface field layer of CdTe thin film solar cells

In this work, the Solar Cell Capacitance Simulator (SCAPS-1D) is employed to evaluate the characteristics of CdTe thin films with ZnTe as the Back Surface Field (BSF) layer and estimate the effective copper doping ratio at both the atomic scale and the device operational response perspective. The electrical characteristics of ZnTe, at varying levels of copper doping, were derived using density functional theory (DFT) by applying the generalized gradient approximation (GGA) and Hubbard U corrections (DFT+U). The performance of ZnTe with different Cu concentrations as a BSF layer was evaluated by analysing the values of four key parameters that are open circuit voltage (VOC), short circuit current density (JSC), fill factor (FF), and conversion efficiency (η). The results indicate that an increase in Cu concentration from 0% to 3%, 6%, 10%, and 12% resulted in a reduction of the energy band gap. Specifically, the energy band gap decreased from 2.24 eV to 2.10 eV, 1.98 eV, 1.92 eV, and 1.88 eV, respectively. Optimal Cu doping promotes the favourable shift in the valence band maxima (VBM) and formation of p + -ZnTe, lowering thermionic emission and improving carrier lifetime, which results in an improved ohmic contact, η = 18.73% for 10% of Cu content. Excessive doping in contrast degraded the overall device performance by forming an unmatched carrier band offset at the front interface with CdS, increasing the acceptor type defect and CdTe compensation rate. Overall, the findings suggest that incorporating a controlled level of Cu, which in this case is around 10%, promotes the efficiency and stability of the proposed CdTe device configuration to a certain extent.

Chemically processed CdTe thin films for potential applications in solar cells – Effect of Cu doping

Thin films of cadmium telluride (CdTe) have attained the attention of researchers due to the potential application in solar cells. However, cost-effective fabrication of solar cells based on thin films along with remarkable efficiency and control over optical properties is still a challenging task. This study presents an analysis of the structural, optical and electrical properties of undoped and Cu-doped CdTe thin films fabricated on ITO coated glass substrates using an electrodeposition process with a focus on practical applications. Electrolytes of cadmium (Cd), tellurium (Te) and copper (Cu) are prepared with a low molarity of 0.1 M. Thin films are deposited by keeping current density in the range of 0.12–0.3 mA/cm2. Copper doping is varied (2-10 wt%) for the optimized sample. X-ray diffraction crystallography indicates that both undoped CdTe and Cu-doped CdTe films crystallize into a dominant hexagonal lattice. Direct energy band gap is observed for both undoped and doped conditions. The study revealed a drop in the optical band gap energy to ∼1.46 eV with the increase in doping (Cu) concentration from 2 to 10 wt%. Increase in mobility and conductivity is observed with the increase in current density of the deposited undoped CdTe thin films. Whereas, Cu doping of 6 wt% produced thin films with acceptable mobility and conductivity for the doped samples. Furthermore, photoluminescence (PL) spectroscopy unveiled a multitude of emission peaks encompassing the visible spectrum, arising from the combination of electrons and holes through both direct and indirect recombination processes. Findings of this study suggest that chemically produced CdTe thin films would be suitable for use as low-cost applications pertaining to solar cells.

A Review on the Third-Generation Solar Cells: Model, Materials, and Performance.

The present solar cells – first and second generation solar cells are very expensive. They are formed from single crystal and poly-crystal silicon (Si) and Si base, CIGS, CdTe and III-V thin films respectively. This led to the idea of third generation photovoltaic modules. This paper presents works on different types of third generation solar cells. This includes organic photovoltaics (OPVs), copper zinc tin sulfide (CZTS), perovskite solar cells, dye-sensitized solar cells (DSSCs), and quantum dot solar cells.

Property enhancement of a close-spaced sublimated CdTe thin film by a post-growth activation step with CdCl2 and MgCl2

The activation of CdTe thin films using MgCl2 after growth demonstrates superior texture, optical characteristics, and structural properties compared to the hazardous CdCl2, particularly in the context of large-scale production.

Prospects of Taiwan's solar energy development and policy formulation

Taiwan lacks energy stock and has been paying great attention to developing renewable energy to improve energy security and sustain economic growth. Solar energy is attractive to Taiwan's government as the recorded radiation is substantial, and a significant amount of fallow land is available for panel installation. This study investigates the potential solar energy production from Crystalline silicon (c-Si) and cadmium Telluride thin-film (CdTe) cell systems, estimates each system's capital requirement, and compares the economic and environmental benefits to explore effective investment strategy. The results show that, on average, the c-Si module could produce 10,644 GWh per year while the CdTe mode would yield a total electricity of about 9365 GWh. The useful life also plays an essential role in the investment requirement. With a 30-year useful life, the systems can reduce the annualized installation and maintenance cost to about NT$3.16 billion. In terms of offset efficiency, every MWh produced would result in at least 13.63–15.49 metric ton of carbon emission offset, and the offset value per GWh can be up to NT$5.77 million, which provide attractive economic incentives to energy suppliers. We point out that the acquisition of low-cost financing sources such as green bonds, as well as the improvement of current emission trading systems (ETS), would greatly benefit solar energy development.

Simulation and performance analysis of CdTe thin film solar cell using different Cd-free zinc chalcogenide-based buffer layers

In this study, the performance of a Cadmium Telluride (CdTe) thin-film solar cell was evaluated with various buffer layers (CdS, ZnSe, ZnO, ZnS) using the Silvaco-Atlas semiconductor device simulator. The impact of these buffer layers on the functionality of the CdTe solar cell was scrutinized at a temperature of 300 K under standard AM1.5G illumination. Initially, the modeling and simulation results of CdS/CdTe solar cell were examined, in comparison with the experimental and simulation results previously reported, to validate our reference structure and to explore its performance. The baseline CdS/CdTe solar cell, serving as a benchmark, yielded a conversion efficiency of 22.14 %. Then we attempted to identify an environmentally friendly alternative buffer layer for the CdTe thin film solar cell by substituting CdS with various Cd-free zinc chalcogenide-based materials (Zn(O,S,Se)) to boost efficiency. By trimming the layer thickness to approximately 0.01 μm, conversion efficiencies of 23.04 %, 23.13 % and 24.48 % were attained for the ZnO, ZnSe, and ZnS buffer layers, respectively. In order to investigate the performance of each proposed structure, thickness and doping density of the absorber and buffer layer were varied. Best efficiency around 25.23 % and 25.04 % are achieved for the optimized solar cells for ZnS and ZnSe buffer layer, respectively. As a result, ZnS and ZnSe are promising materials can be used as an alternative to the commonly used CdS buffer layer in CdTe solar cell. The influence of the operating temperature on solar cell performance was also investigated.

Power Generation Performance of CdTe Thin Film Solar Modules in Lhasa

With the increasing energy consumption of buildings, reducing the energy consumption of buildings has become a key link to achieving the goal of carbon neutrality. Building integrated photovoltaic (BIPV) is an important research direction. Based on the CdTe thin film solar modules power generation system on the south-facing wall of a building in Lhasa, the article collected the annual power generation data for 2022. The characteristics and variation patterns of the total monthly power generation and typical monthly daily power generation are analyzed. Furthermore, the correlation between power generation performance and the main influencing factors was analyzed. The differences in power generation characteristics between CdTe thin films solar modules and single crystal silicon solar modules were compared and analyzed. The results show that the annual power generation of the CdTe thin film solar modules power generation system exhibits a “U” shaped distribution, and the power generation in winter is greatly affected by weather conditions. The peak power of 1kWp CdTe thin film solar modules is lower than that of single crystal silicon solar modules. The generation duration is longer than single crystal silicon solar modules. The total power generation is greater than single crystal silicon solar modules.

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.

Photodegradation of CdTe thin film via PVD for water splitting to generate hydrogen energy

The cost-effective catalysts are attracting attention in the field of water-splitting hydrogen generation for their effective light utilization and charge separation activity. In this work, CdTe has introduced this promising photocathodic material among the few photocatalysts with a low band gap. This photocatalyst has a high activity for the PEC hydrogen evolution under simulated sunlight irradiation. XRD study reveals the confirmation of the prepared CdTe thin film. SEM study provided the morphology and surface structure for the absorption of the solar spectra, the optical properties of CdTe thin film confirmed the absorption of solar spectra for the hydrogen production. FTIR provided the functional group of the CdTe thin film. Electrochemical impedance spectroscopy showed that the charge transfer at the electrode–electrolyte interface for CdTe thin film is much better than another semiconductor. The LSV for STH% was noted to be 1.07% for CdTe thin film and the production of hydrogen generation of CdTe thin film was observed at 4953.21 mol.g−1.h−1.

Effects of Quantum Confinement Energy on the Transmittance of Cadmium Telluride (CdTe) Within the Near Infrared Region (700-2500nm)

This study investigates how the energy of quantum confinement affects the transmittance of cadmium telluride, because of the importance of this substance, as it crystallizes in the form of cubes as thin films that are used in solar cells and liquid crystal imaging devices, as well as in infrared optics [1]. The MATLAB computer program version (2012a) was used, which is based on the characteristic matrix theory and Brus model, in addition to the quantum confinement energy equation. We found that the transmittance value of the nano CdTe thin film at normal incidence reaches 96.4% at a quantum confinement energy Eco = 2.7eV and at a particle size PS =2.6nm, while the value reaches 73.6% at a quantum confinement energy Eco = 0.01eV and at a particle size of PS=50nm.

Investigation of electrodeposited CdTe thin films for solar cell development

Investigation of electrodeposited CdTe thin films for solar cell development

Outdoor Experimental Investigation of the Temperature Effect on the Performance of Different PV Modules Materials

Desert locations are of great interest for photovoltaic applications due to their high solar availability. However, in these regions, harsh climatic conditions can have a significant impact on the performance and reliability of photovoltaic panels. In the present study, the effect of temperature on the performance of the two PV technologies, Polycrystalline Silicon (pc-Si) and thin film Cadmium Telluride (CdTe), in a hot desert climate was investigated. To accomplish this, one module from each technology was installed in Benguerir city and exposed to outdoor conditions during the hot season of the year (May to October). Results indicate that although pc-Si exhibits higher module efficiency than CdTe, the latter was less temperature-sensitive under high ambient temperature values. In fact, during the monitoring period, CdTe technology demonstrated lower module temperatures than pc-Si, with a daily average temperature deviation of 1.75°C. In addition, the performance ratio and conversion efficiency for pc-Si were reduced by 8.7% and 1.35%, respectively, when the daily average ambient temperature increased from 25°C to 40°C. While with the thin film CdTe technology, the decline in these performance parameters did not exceed 6.8% and 1.05%, respectively.

Effect of Antireflection Coating on the Efficiency of an ITO/SnO2/CdS/CdTe Thin Film Solar Cell

Effect of Antireflection Coating on the Efficiency of an ITO/SnO2/CdS/CdTe Thin Film Solar Cell

Study of carrier mobility in CdTe and PbTe thin films as a function of temperature

The temperature dependency of kinetic parameters in p-PbTe and p-CdTe thin films formed on glass substrates has been investigated. The surface mobility of current carriers in PbTe films was computed as a function of temperature under the assumption of diffuse scattering of charge carriers. The mechanisms of intergranular current carrier transfer related with thermoelectronic emission are established. The role of surface scattering and intergranular boundaries in thin films of lead and cadmium tellurides is addressed.

Optimization physical properties of CdTe /Si solar cell devices fabricated by vacuum evaporation

We investigated at the optical properties, structural makeup, and morphology of thin films of cadmium telluride (CdTe) with a thickness of 150 nm produced by thermal evaporation over glass. The X-ray diffraction study showed that the films had a crystalline composition, a cubic structure, and a preference for grain formation along the (111) crystallographic direction. The outcomes of the inquiry were used to determine these traits. With the use of thin films of CdTe that were doped with Ag at a concentration of 0.5%, the crystallization orientations of pure CdTe (23.58, 39.02, and 46.22) and CdTe:Ag were both determined by X-ray diffraction. orientations (23.72, 39.21, 46.40) For samples that were pure and those that were doped with silver, the optical band gap shrank by (1.52-1.47) eV (400–1100)nm resulting in a drop in the absorption coefficient. An incident power density of (100 mW/cm2) was used to examine the I-V properties of heterojunctions created by light on a variety of clean and doped materials. In accordance with the X-ray diffraction analysis, the films had a cubic structure and dominated grain growth along the (111) crystallographic direction.

Ultrafast nonlinear optical properties of Ag-CdTe thin films by co-sputtering in the near-infrared region

Metal-doped CdTe has become a heated topic in recent years due to its ultrafast nonlinear optical properties. Herein, Ag-CdTe thin films with different doping amount (1W, 3W and 5W) and pure CdTe thin films were fabricated on quartz substrates by magnetron sputtering. The effects of Ag doping on the morphology, optical band gap and nonlinear optical properties of the thin films were systematically investigated. The nonlinear optical properties were investigated by femtosecond(fs) Z-scan technique under 800 nm. The results indicated that the Ag-CdTe thin films exhibit good nonlinear optical properties in the near-infrared region due to free carrier absorption and two-photon absorption. The results showed that the dopant content and the variation of the incident laser energy can control the RSA intensity, the nonlinear absorption coefficient, and the nonlinear refractive index of Ag-CdTe thin films. These results can provide new support for their applications in the field of nonlinear optoelectronic devices.

Vertical nanostructures thin films of CdS and CdTe using low temperatures GLAD

This research develops a distinct method for obtaining of thin films of CdS and CdTe with vertical nanostructure morphology grown at low temperatures on the substrate of about 100 °C, were obtained by RF sputtering and sublimation from a vapor effusion source, respectively, both methods were combined with the glancing angle deposition technique. The CdS thin film exhibited a hexagonal structure with preferential plane orientation (002) under compressive stress and a crystallite size of approximately 45 nm. The CdTe film showed a cubic Zinc-Blende structure with an expansive lattice of the unit cell and with preferential plane orientation (111). The size of the crystallites in CdTe was approximately 56 nm. Scanning electron microscopy showed porous nanocolumn structures with vertical nanorods with a width of approximately 16 nm for the CdS and 80 nm for the CdTe, respectively with thicknesses of approximately 335 nm for the CdS and 1330 nm for the CdTe. Using open-source software ImageJ obtained a porosity measurement of approximately 10.4% for CdS and 9.4% for CdTe, respectively. The bandgap energy of the CdS and CdTe thin films was 2.47 eV and 2.51 eV, respectively. The refractive index was 2.5 for CdS and 3.5 for CdTe, respectively. The Urbach energy of the CdS and CdTe was 146 meV and 62 meV respectively. Our results are optimal for possible applications in photovoltaic devices, especially in solar cells and flexible solar cells.

Thermally evaporated CdTe thin films on glass and (100) silicon substrates for solar cells applications

Thermally evaporated CdTe thin films on glass and (100) silicon substrates for solar cells applications

Structural and optical properties of smooth radio frequency sputtered XTe (X=Cd, Zn) thin films

Zinc telluride (ZnTe) and cadmium telluride (CdTe) thin films, with smooth surfaces, were prepared by the radio frequency sputtering method. X-ray diffaction patterns revealed the formation of pure cubic phases and allowed the access of the structural properties. The lattice mismash between the two compounds is found to be around 6%.UV–visible spectroscopy showed a significant absorption coefficient within the visible spectrum, accompanied by an energy band gap measuring 1.9 eVfor the ZnTe film and 1.42 eV for the CdTe film. This study may be benificial for using these materials together of separately in photovoltaic and photocatalytic devices.

Morphology and structure of CdCl2-Containing CdTe films deposited by discrete vacuum thermal evaporation

The impact of discrete vacuum thermal evaporation (DVTE)-produced CdTe thin films after thermal annealing and CdCl2 treatment is discussed in the present article. As a result of simultaneous DVTE of CdCl2 and CdTe, CdCl2 was added straightly into the bulk of the formed CdTe film at the 270 °C substrate temperature in a single procedure. The DVTE approach deposits CdTe thin films with a high crystalline structure, which can be utilized effectively for the production of high efficiency solar cell applications, according to the results of X-ray diffraction, scanning electron microscopy with focused ion beam, transmission electron microscopy, and atomic force microscopy measurements.