Bulk Defect Density Research Articles

Exploring the correlation between the bandgap engineering and defect density toward high CTS solar cell efficiency

Ternary chalcogenide Cu2SnS3 (CTS) has emerged as a relevant compound for solar energy harvesting owing to its favorable optoelectronic properties. The aim of this study was to conduct a numerical investigation using SCAPS-1D software to determine the optimal conditions for an efficient CTS solar cell. The research focused on how the bandgap (Eg) design affects the optical properties and photovoltaic performance (PV) of a CTS solar cell. The correlation between the Eg width and bulk defect density (Nt), as well as the CTS/CdS interface defect density (Nit) of CTS thin films, was also investigated. The results revealed that the increase in Eg significantly improves the external quantum efficiency (EQE), power conversion efficiency (PCE), and open-circuit voltage (Voc) of the solar cells. In addition, a remarkable decrease in recombination rate was observed. For Eg values of 1.1 eV and 1.18 eV, the solar cell demonstrated a minimal recombination rate of 5 × 1020 cm−3 and a high PCE of 5%. The contour plot of Nt as a function of Eg confirmed that Eg and Nt values of 1.18 eV and 5 × 1016 cm−3, respectively, provide higher efficiency. Furthermore, the results highlighted the importance of limiting Nit to below 5 × 1014 cm−3 at the CTS/CdS junction. Under optimum conditions, the output parameters of the CTS solar cell were calculated to be 6.30% for the PCE, 46.64% for the fill factor (FF), 33.89 mA/cm2 for the short-circuit current (Jsc), and 398.2 mV for Voc.

Surface-Mediated Charge Transfer of Photogenerated Carriers in Diamond.

Solvated electrons are highly reductive chemical species whose chemical properties remain largely unknown. Diamond materials are proposed as a promising emitter of solvated electrons and visible light excitation would enable solar-driven CO2 or N2 reductions reactions in aqueous medium. But sub-bandgap excitation remains challenging. In this work, the role of surface states on diamond materials for charge separation and emission in both gaseous and aqueous environments from deep UV to visible light excitation is elucidated. Four different X-ray and UV-vis spectroscopy methods are applied to diamond materials with different surface termination, doping and crystallinity. Surface states are found to dominate sub-bandgap charge transfer. However, the surface charge separation is drastically reduced for boron-doped diamond due to a very high density of bulk defects. In a gaseous atmosphere, the oxidized diamond surface maintains a negative electron affinity, allowing charge emission, due to remaining hydrogenated and hydroxylated groups. In an aqueous electrolyte, a photocurrent for illumination down to 3.5eV is observed for boron-doped nanostructured diamond, independent of the surface termination. This study opens new perspectives on photo-induced interfacial charge transfer processes from metal-free semiconductors such as diamonds.

Chlorine‐doped perovskite materials for highly efficient perovskite solar cell design offering an efficiency of nearly 29%

AbstractThe new form of renewable energy attracts enormous attention from researchers for its immense importance and impact on our daily life. A fossil energy is a non‐renewable source that will end shortly because of its immense use in houses and industries. Among the renewable sources, solar cells based on perovskite (PVK) materials exponentially increase their efficiency from 3.8% to 25.8% rapidly in a diminutive period of time. In the present study, doped and undoped PVK layers (MAPbI3, MAPb[I1‐xClx]3) are considered and optimized for solar cell application by using the SCAPS‐1D device simulator. A detailed investigation is done in terms of PVK absorber layer (PAL) thickness variation with different electron and hole transport layers, temperature, and bulk defect density to optimize the device performance. The MAPb(I1‐xClx)3‐based device delivered the highest conversion efficiency of ~29% with JSC of 25.59 mA/cm2, VOC of 1.348 Volt, and an FF of about 83.68%. Results reported in this work may pave the way for the development of advanced high‐efficiency PVK solar cells.

Optimizing the performance of Cs2AgBiBr6 based solar cell through modification of electron and hole transport layers

This work investigates the potential of Cs2AgBiBr6 as an absorber layer for solar cell applications and explores ways to advance the PV performance of cells by studying different electron transport layers (ETLs) and hole transport layers (HTLs). The energy band diagrams of the Cs2AgBiBr6 based cell are analyzed with different ETLs and HTLs to illustrate how electrons and holes flow within the cell. Specifically, one of the proposed cells substitutes TiO2 with chlorine passivated tin oxide (Cl@SnO2), while the other uses phenyl-C60 -butyric acid methyl ester on tin oxide (C60 -SnO2) as the ETL. The PV characteristics of the Cs2AgBiBr6-based solar cell is evaluated using SCAPS 1D. The PV performance parameters of Cs2AgBiBr6-based solar cells has been analyzed in search of optimum thickness of Cs2AgBiBr6 layer. Subsequently, the impact of bulk defect density in Cs2AgBiBr6 layer at the obtained optimum thickness i.e., 611 nm has also been explored. C60-SnO2 is found to have higher electron mobility, work function, and stability than Cl@SnO2, making it a better choice for the ETL. The resulting PV parameters for the cell Cl@SnO2/CS2AgBiBr6/Me4PACz are: VOC - 1.527 V, JSC - 10.42 mA/cm2, FF − 75.66%, and PCE - 12.08%. While the cell SnO2-C60/Cs2AgBiBr6/Me4PACz delivers PV parameters VOC- 1.53 V, JSC- 12.81 mA/cm2, FF - 79.15%, and PCE - 13.43%.

Examining the potential of non-toxic stable double perovskite solar cells based on Cs2CuSbX6

The main issues impeding the commercialization of perovskite solar cells are their toxicity and long-term stability. Thus, it is essential to find a robust and reliable alternative light absorber that is environmentally friendly and provides stability. Herein, we present stable and lead-free Cs2CuSbX6 (where X = Cl, Br, and I) double perovskite light harvesters as a substitute, which can render excellent efficiency and long-term stability. The double perovskite solar cells based on the Cs2CuSbX6 light harvester, the aluminium-doped ZnO electron transport layer, and the MoO3 and Cu2O hole transport layers are critically evaluated using the SCAPS-1D software package. The densities of defects and dopants as well as the thickness of the succeeding layers of the double perovskite solar cells are altered to extract high efficiency. With aluminium-doped ZnO serving as the electron transport layer, the optimized Cs2CuSbI6-based double perovskite solar cells attain a power conversion efficiency (PCE) of about ∼29% for both MoO3 and Cu2O hole transport layers. Several potential back electrodes are also investigated, and their impact on performance is assessed. The fluctuation in PCE concerning operating temperature is computed for authentic analysis of the double perovskite solar cells during real-time operation. Overall, in order to achieve high PCEs in Cs2CuSbI6-based double perovskite solar cells, it is crucial to consider both the thickness of the light harvester layer and the bulk defect density.

CsPbI3-perovskite quantum dot solar cells: unlocking their potential through improved absorber layer characteristics and reduced defects

Perovskite quantum dots (CsPbI3-PQDs), a translucent material, have gained great interest in the PV industries owing to their unified virtues of perovskites and quantum dots. However, researchers have found that perovskite solar cells (PSCs) suffer from issues like low stability at high relative humidity, energy states imbalance, severe hysteresis, and an easy decomposition under ultraviolet (UV) radiation that severely restrict their industrialization. Quantum dots (QDs) are excellent materials with numerous admirable traits that have been extensively employed in PSCs to overcome the aforementioned problems. To achieve high performance of the examined device, the CsPbI3-PQDs has been stacked between two charge transport layers, i.e., Cl@SnO2 (to facilitate electrons towards cathode) and P3HT (to facilitate holes towards anode). In this context, study of variations in different parameters such as thickness and acceptor density of the CsPbI3-PQDs absorber layer has been done. After varying the thickness and acceptor density of the CsPbI3-PQDs layer, the cell’s performance is optimized at thickness of 400 nm and acceptor density of 1 × 1017/cm3 delivering higher PV parameters power conversion efficiency (PCE):16.17%, open circuit voltage (VOC):1.02 V, short circuit density (JSC):18.06 mA cm−2 and fill factor (FF): 87.06% respectively. Thereafter, the effects of bulk defects in CsPbI3-PQDs and the interface between CsPbI3-PQDs and Cl@SnO2 have been explored in this work. For the cell to work at its best, the bulk defect density and interface defect density, respectively, should not be more than 1 × 1014 /cm3 and 1 × 1013 /cm2. Afterwards, a comprehensive study has been done by varying the front electrode transparency (from 40% to 95%) to improve the device performance. With 95% of front electrode transparency, the performance of device is improved due to increase in the photon coupling.

Design and Performance Enhancement of a GaAs-Based Homojunction Solar Cell Using Ga0.5In0.5P as a Back Surface Field (BSF): A Simulation Approach

The GaAs semiconductor is a solar energy promising material for photovoltaic applications due to its good optical and electronic properties. In this work, a homojunction GaAs solar cell with AlxGa1-xAs and GayIn1-yP solar energy materials as window and back surface field (BSF) layers, respectively, was simulated and investigated using SCAPS-1D software. The performance of the GaAs-based solar cell is evaluated for different proportions ofxandy, which allowed us to obtain the values of 0.8 and 0.5 forxandy, respectively, as the best values for high performance. We then continued the optimization by taking into account some parameters of the solar cell, such as thickness, doping, and bulk defect density of the p-GaAs base, n-GaAs emitter, and Ga0.5In0.5P BSF layer. Solar cell efficiency increases with emitter thickness, but the recombination phenomenon is more pronounced than that of electron-hole pair generation in the case of a thicker base. The effect of variation in the work function of the back contact has also been studied, and the best performance is for a platinum (Pt) electrode. The optimized GaAs-based solar cell achieves a power conversion efficiency of 35.44% (JSC=31.52 mA/cm2,VOC=1.26 V,FF=89.14%) and a temperature coefficient of -0.036%/°C. These simulation results provide insight into the various ways to improve the efficiency of GaAs-based solar cells.

Analysis of absorber layer for wide-bandgap double perovskite solar cell using SCAPS-1D

The development of lead-free perovskite is seen as a windfall for the future of photovoltaic (PV) technology. The use of double perovskite as a solution to the problem of lead toxicity that plagues the PV sector is an intriguing possibility. Lead-free perovskite (Cs2AgBi0.75Sb0.25Br6) solar cells with a large bandgap of 1.8 eV have been modeled using SCAPS-1D device simulation software. In this simulation work, firstly, the device is calibrated to reach the experimental work. We studied the optimal thickness of the absorber layer, and we examined the diffusion length as a measure of absorber quality by varying the bulk defect density (1 × 1013 cm−3 to 1 × 1017cm−3) of the absorber layer. Both of these analyses were performed in conjunction with one another. The thickness of the absorber layer is a primary aspect of a high-performing device. The results revealed that the high carrier diffusion length of 1 µm and carrier lifetime of 200 ns is enough for high conversion efficiency. We have achieved 10.10% PCE (Power conversion efficiency), a high Voc of 1.123 V and Jsc of 15.28 mA-cm−2 with optimized parameters of the proposed model.

Design and numerical analysis of CIGS-based solar cell with V2O5 as the BSF layer to enhance photovoltaic performance

Copper indium gallium selenide (CIGS)-based solar cells have exhibited greater performance than the ones utilizing cadmium telluride (CdTe) or hydrogenated amorphous silicon (a-Si: H) as the absorber. CIGS-based devices are more efficient, considering their device performance, environmentally benign nature, and reduced cost. In this article, we proposed a potential CIGS-absorber-based solar cell with an FTO/ZnSe/CIGS/V2O5/Cu heterostructure, with a V2O5 back-surface field (BSF) layer, SnO2:F (FTO) window layer, and ZnSe buffer layer. Using the solar cell capacitance simulator one-dimensional simulation software, the effects of the presence of the BSF layer, the thickness, bulk defect density, and acceptor density of the absorber layer, buffer layer thickness, interfacial defect density, device resistance, and operating temperature on the open-circuit voltage, short-circuit current, fill factor, and efficiency, as well as on the quantum efficiency and recombination and generation rate, of the device have been explored in detail. The simulation results revealed that only a 1 μm-thick-CIGS absorber layer with V2O5 BSF and ZnSe buffer layers in this structure offers an outstanding efficiency of 31.86% with a VOC of ∼0.9 V. Thus, these outcomes of the CIGS-based proposed heterostructure provide an insightful pathway for fabricating high-efficiency solar cells with performance more promising than the previously reported conventional designs.

Design and Performance Exploration of a Lead‐Free All‐Inorganic Hydrogenated Cs2AgBiBr6‐Based Double Perovskite Solar Cell: A Numerical Modeling Study

Lead‐free double perovskite Cs2AgBiBr6 has attracted wide attention owing to its nontoxic and stable properties. Recently, hydrogenated Cs2AgBiBr6 (HCABB) films have been shown to possess superior optoelectronic properties than pristine Cs2AgBiBr6, and the double perovskite solar cell (DPSC) based on the films broke the efficiency record of DPSCs as soon as it was proposed. However, its poor energy band alignment and thin absorber layer thickness prevent HCABB from realizing its full photovoltaic potential. In this article, we design a lead‐free all‐inorganic HCABB‐based DPSC for application purposes. To explore its photovoltaic potential, we numerically optimize the transport layer materials, the thickness and bulk defect density of the absorber layer, the interface defect densities, the back contact material, and the parasitic series and shunt resistances step by step for the HCABB‐based DPSC. We predict the HCABB‐based DPSC with the structure of FTO/Nb2O5/HCABB/CuI/Cu can achieve an open‐circuit voltage of 1.139 V, short‐circuit current density of 22.40 mA cm−2, fill factor of 83.35%, and power conversion efficiency of 21.28%. Overall, our work explores the photovoltaic potential of HCABB and provides guidance for fabricating more efficient HCABB‐based DPSCs.

Defect Engineering in Earth‐Abundant Cu2ZnSnSe4 Absorber Using Efficient Alkali Doping for Flexible and Tandem Solar Cell Applications

To demonstrate flexible and tandem device applications, a low‐temperature Cu2ZnSnSe4 (CZTSe) deposition process, combined with efficient alkali doping, was developed. First, high‐quality CZTSe films were grown at 480 °C by a single co‐evaporation, which is applicable to polyimide (PI) substrate. Because of the alkali‐free substrate, Na and K alkali doping were systematically studied and optimized to precisely control the alkali distribution in CZTSe. The bulk defect density was significantly reduced by suppression of deep acceptor states after the (NaF + KF) PDTs. Through the low‐temperature deposition with (NaF + KF) PDTs, the CZTSe device on glass yields the best efficiency of 8.1% with an improved VOC deficit of 646 mV. The developed deposition technologies have been applied to PI. For the first time, we report the highest efficiency of 6.92% for flexible CZTSe solar cells on PI. Additionally, CZTSe devices were utilized as bottom cells to fabricate four‐terminal CZTSe/perovskite tandem cells because of a low bandgap of CZTSe (~1.0 eV) so that the tandem cell yielded an efficiency of 20%. The obtained results show that CZTSe solar cells prepared by a low‐temperature process with in‐situ alkali doping can be utilized for flexible thin‐film solar cells as well as tandem device applications.

A comprehensive photovoltaic study on tungsten disulfide (WS2) buffer layer based CdTe solar cell

Transition metal di-chalcogenides (TMCDs)-Tungsten disulfide (WS2) exhibit excellent optoelectronic properties such as suitable bandgap, high absorption coefficient, good conductivity, high carrier mobility, etc. to be used as a photovoltaic material for thin-film solar cells. In the present work, we have replaced the traditional buffer CdS and ITO/ZnO window layer in CdTe solar cells with the non-toxic, earth-abundant WS2 buffer and SnO2 window layer, respectively. The SCAPS-1D solar simulator is used to investigate the potentiality of WS2 as buffer material in CdTe solar cells. This numerical study provides a comparison of the performances between the proposed structure: SnO2/WS2/CdTe/Au and the baseline structure: ITO/ZnO/CdS/CdTe/Au. The impacts of the charge carrier generation rate, spectral response, current-voltage characteristics, bulk defect density, defect density at buffer/absorber interface, operating temperature, and capacitance-voltage characteristics on the solar cell performance parameters have also been analyzed. The tolerance level of defect density in WS2 bulk and WS2/CdTe interface are found to be 1017 cm−3 and 1012 cm−3, respectively. The temperature study reveals the poor structural robustness and thermal stability of the proposed cell. The conversion efficiency of the proposed cell has found to be 20.55% at the optimized device structure. Nevertheles, these findings may provide an insight to fabricate viable, environment friendly, and inexpensive CdTe thin-film solar cells.

Halide Composition Engineered a Non-Toxic Perovskite–Silicon Tandem Solar Cell with 30.7% Conversion Efficiency

Since the conversion efficiency of silicon (Si)-based solar cells stagnates at 26.7% in the literature, extensive research and development activities are carried out on perovskite silicon-based tandem solar cells. However, the presence of lead (Pb) and the instability of perovskite prevent their large-scale implementation in the photovoltaic industry. Therefore, it is important to replace the hazardous material (Pb) in perovskite top cells to design non-toxic perovskite–silicon tandem solar cells. The current work yields much-needed studies to develop a non-toxic perovskite–silicon-based tandem solar cell. For the first time, methylammonium tin mixed halide (MASnI3–xBrx)-based materials are comprehensively investigated and optimized with respect to different halide compositions, absorber layer thickness, and bulk defect density in standalone configurations, followed by the development of a lead-free MASnI2Br1–Si-based tandem solar cell. The transfer matrix method and current matching techniques are used to design the two-terminal monolithic tandem cell, which showed a maximum conversion efficiency of 30.7% with an open circuit voltage (VOC) of 2.14 V. The results outlined in this manuscript will pave the way for the progress of highly efficient, non-toxic perovskite–silicon tandem solar cells.

Back contact optimization for Sb<sub>2</sub>Se<sub>3</sub> solar cells

Antimony selenide (Sb<sub>2</sub>Se<sub>3</sub>) has advantages of low-toxicity, abundant and excellent photoelectric properties. It is widely considered as one of the most promising light-harvesting materials for thin-film solar cells. However, the power conversion efficiency of the Sb<sub>2</sub>Se<sub>3</sub> thin-film solar cell is still far inferior to that of cadmium telluride, copper indium gallium selenium and perovskite solar cells. As is well known, the Sb<sub>2</sub>Se<sub>3</sub> solar cell performance is closely related to the light absorber layer (crystallinity, composition, bulk defect density, etc.), PN heterojunction quality (charge carrier concertation, energy band alignment, interface defect density, etc.) and back-contact barrier formation, which determines the process of carrier generation, excitation, relaxation, transfer and recombination. The low fill factor is one of the core problems that limit further efficiency improvement of Sb<sub>2</sub>Se<sub>3</sub> solar cells, which can be attributed to the high potential barrier at the back contact between the Mo electrode and Sb<sub>2</sub>Se<sub>3</sub> absorption layer. In this work, a heat treatment is applied to the Mo electrode to generate a MoO<sub>2</sub> buffer layer. It can be found that this buffer layer can inhibit MoSe<sub>2</sub> film growth, exhibiting better Ohmic contact with Sb<sub>2</sub>Se<sub>3</sub>, and reducing the back contact barrier of the solar cell. The Sb<sub>2</sub>Se<sub>3</sub> thin film is prepared by an effective combination reaction involving sputtered and selenized Sb precursor. After introducing the MoO<sub>2</sub> buffer layer, it can also promote the formation of (<i>hk</i>1) (including (211), (221), (002), etc.) preferentially oriented Sb<sub>2</sub>Se<sub>3</sub> thin films with average grain size over 1 μm. And the ratio of Sb to Se is optimized from 0.57 to 0.62, approaching to the stoichiometric ratio of Sb<sub>2</sub>Se<sub>3</sub> thin film and inhibiting the formation of V<sub>se</sub> and Sb<sub>Se</sub> defects. Finally, it enhances the open-circuit voltage (<i>V</i><sub>OC</sub>) of solar cells from 0.473 to 0.502 V, the short-circuit current density (<i>J</i><sub>SC</sub>) from 22.71 to 24.98 mA/cm<sup>2</sup>, and the fill factor (FF) from 46.90% to 56.18%, thereby increasing the power conversion efficiency (PCE) from 5.04% to 7.05%. This work proposes a facile strategy for interfacial treatment and elucidates the related carrier transport enhancement mechanism, thus paving a bright avenue to breaking through the efficiency bottleneck of Sb<sub>2</sub>Se<sub>3</sub> thin film solar cells.

Evaluating the Potential of Lead‐Free Nontoxic Cs2BiAgI6‐Based Double Perovskite Solar Cell

Recently, the efficiency of single‐junction perovskite solar cells has been competing with the crystalline Si solar cells. However, the perovskite absorbers are toxic and susceptible to moisture. Herein, the performance of an environmentally benign and durable Cs2BiAgI6 light harvester using the 1D Solar Cell Capacitance Simulator (SCAPS‐1D) software package is evaluated. The primary physical parameters, namely, defect and doping densities and thickness of the subsequent layers, are varied to achieve high efficiencies. The optimized Cs2BiAgI6‐based double perovskite solar cells with three distinct hole‐transporting layers (HTLs) (i.e., MoO3, CuSCN, and spiro‐OMeTAD) deliver a power conversion efficiency of ≈29% with AZnO as electron transport layer (ETL). Further, a variety of possible rear electrodes are explored, and their effect on the performance is estimated. For real‐time examination of the Cs2BiAgI6‐based double perovskite solar cells, the variation of power conversion efficiency (PCE) concerning the operating temperature is estimated. The thickness of the Cs2BiAgI6 light harvester layer and the bulk defect density are the key aspects in attaining high power conversion efficiencies in Cs2BiAgI6‐based double perovskite solar cells.

Concurrent investigation of antimony chalcogenide (Sb2Se3 and Sb2S3)-based solar cells with a potential WS2 electron transport layer

Antimony (Sb) chalcogenides such as antimony selenide (Sb2Se3) and antimony sulfide (Sb2S3) have distinct properties to be used as absorber semiconductors for harnessing solar energy including high absorption coefficient, tunable bandgap, low toxicity, phase stability. The potentiality of Sb2Se3 and Sb2S3 as absorber material in Al/FTO/Sb2Se3(or Sb2S3)/Au heterojunction solar cells (HJSCs) with 2D tungsten disulfide (WS2) electron transport layer (ETL) layer has been investigated numerically using SCAPS-1D solar simulator. A systematic investigation of the impact of physical properties of each active material of Sb2Se3, Sb2S3, and WS2 on photovoltaic parameters including layer thickness, carrier doping concentration, bulk defect density, interface defect density, carrier generation, and recombination. This study emphasizes the exploration of causes of low performance of actual devices and demonstrates the individual variation in the open-circuit voltage (VOC), short-circuit current density (JSC), fill factor (FF), power conversion efficiency (PCE) and quantum efficiency (QE). Thereby, highly potential heterostructures of Al/FTO/WS2/absorber (Sb2Se3 or Sb2S3)/Au proposed, in which, the PCE over 28.20 and 26.60% obtained with VOC of 850 and 1230 mV, Jsc of 38.0 and 24.0 mA/cm2, and FF of 86.0 and 89.0% for Sb2Se3 and Sb2S3 absorber, respectively. These detailed findings revealed that the Sb-chalcogenide heterostructure with potential WS2 ETL can be used to realize the fabrication of feasible thin film solar cells and thus the design of high-efficiency high-current (HEHC) and high-efficiency high-voltage (HEHV) solar panels.

The Impact of Electrostatic Interactions Between Defects on the Characteristics of Random Telegraph Noise

Random telegraph noise (RTN) is one of the most challenging defect-related reliability concerns in emerging HfO2-based devices due to the higher bulk defect density compared to SiO2. Despite many research efforts, the physical mechanisms determining complex signals (e.g., multilevel, anomalous, temporary RTN) are still unclear and need a deeper investigation. With this driving force, we performed physic-based kinetic Monte Carlo (kMC) simulations in a TiN/HfO2/TiN cell to directly analyze the role of defects which promote RTN, both in steady state and transient regime. The nonmonotonic trends of the ratio of the RTN dwell times with the applied bias frequently found in the literature are found to be caused by changes with the applied voltage of the preferential capture/emission source/destination of traps. The in-depth analysis sheds new light on the conventional methods for defect classification and vertical position estimation. Moreover, such source/destination changes also occur over time due to the dynamics of the local electric field, which varies with the evolution of the surrounding electrostatic landscape. Notably, the local field is given by the overlap of the applied voltage and of the trapped charge contributions, the latter being dominant at low voltages. The analysis of the Markov chains of closely spaced defects shown interdependencies and alterations of the RTN capture and emission times. A new method is proposed to include the impact of electrostatic interactions between defects on RTN.

Performance evaluation of WS2 as buffer and Sb2S3 as hole transport layer in CZTS solar cell by numerical simulation

AbstractThis study reports on performance enhancement of a Cu2ZnSnS4 solar cell introducing Sb2S3 as hole transport layer (HTL) along WS2 as buffer layer. We have investigated photovoltaic (PV) characteristics by utilizing SCAPS‐1D. A comparative analysis on PV performances between conventional CZTS/CdS and proposed Ni/Sb2S3/CZTS/WS2/FTO/Al solar cells is presented. It is revealed that “spike like” band structure at the CZTS/WS2 interface having smaller conduction band offset makes it potential alternative to commonly used CdS buffer. This report also evaluates that the Sb2S3 as an HTL inserted at the rear of CZTS enhances performances by reducing carrier recombination at back interface with appropriate band alignment. The impacts of thickness, carrier concentration of different layers, and bulk defect density in CZTS as well as the interface defects on cell outputs are analyzed. The influences of temperature, work function, and cell resistances are also examined. Optimum absorber thickness of 1.0 μm along doping density of 1017 cm−3 is selected. A maximum efficiency of 30.63% is achieved for the optimized CZTS cell. Therefore, these results suggest that Sb2S3 as HTL and WS2 as buffer layer can be employed effectively to develop highly efficient and low‐cost CZTS solar cells.

Performance enhancement of Sb2Se3-based solar cell with hybrid buffer layer and MoSe2 as a hole transport material using simulator device

In this work, we first compared the experimental and simulated J-V characteristics of the Sb2Se3-based solar cell without and with a hybrid buffer layer using SCAPS-1D software. The introduction of a second buffer layer reduces the current leakage caused at the front contact of the solar cell and the power conversion efficiency (PCE) increases from 3.75% to 5.18%; and the use of the ternary compound cadmium zinc sulfide (CdZnS), as an alternative electron transport layer (ETL) to the traditional cadmium sulfide (CdS), increases the PCE from 5.18% to 7.13%. Thereafter, different thicknesses of the SnO2/CdZnS hybrid buffer layer were simulated, and the optimization resulted in a value of 50 nm, with thicknesses of 10 nm and 40 nm for the SnO2 and CdZnS layers respectively. Furthermore, the optimization of the Sb2Se3 absorber allows to obtain a bulk defect density of 1011 cm−3 and a carrier capture cross section of 10–14 cm2. Finally, the low doping problem of the absorber is solved by forming a MoSe2 layer at the Sb2Se3/Mo interface. MoSe2 acts as a hole transport material (HTM) and is used for high mobility of charge carriers within it; moreover, its presence improves the performance of the Sb2Se3-based solar cell and a PCE of 18.77% (JSC = 34.37 mA/cm2, VOC = 660 mV, FF = 82.78%) is obtained. Our simulation results also show that the n-i-p configuration of the Sb2Se3-based solar cell is more stable.

Numerical simulation and optimization of physical properties for high efficiency CuSbS2 thin film solar cells

Here we present numerical modeling of copper antimony sulfide (CuSbS2) solar cells to analyze the impact of several interrelated physical parameters of the absorber layer and absorber/buffer interface such as bulk vs interface defect density, energy band gap vs electron affinity of CuSbS2, absorber thickness vs acceptor density together with device shunt vs series resistance on the device efficiency. A benchmark simulation of the experimental CuSbS2 solar cell is initially performed in SCAPS-1D (Solar Cell Capacitance Simulator in one dimension) environment considering a suitable defect model, which gave an efficiency of 3.19 % comparable to the experimental value. After the systematic optimization of different materials properties and interface defect density, the power conversion efficiency is increased up to 10.71 % with a remarkable upgrade in open circuit voltage, photocurrent, and fill factor. A detailed analysis of heterojunction features such as built-in potential, depletion width, diffusion length, and carrier recombination was performed to understand the impact of the aforementioned physical parameters on the performance of this solar cell. The present results give an important guideline to find out the shortcomings of CuSbS2 solar cells, which in turn help the researchers for designing and feasible fabrication of more efficient CAS solar cells.