Absorber Layer Material Research Articles

Mapping Surface-Defect and Ions Migration in Mixed-Cation Perovskite Crystals.

Single crystal perovskites have garnered significant attention as potential replacements for existing absorber layer materials. Despite the extensive investigations on their photoinduced charge-carriers dynamics, most of the time-resolved techniques focus on bulk properties, neglecting surface characteristic which plays a crucial role for their optoelectronic performance. Herein, 4D ultrafast scanning electron microscopy (4D-USEM) is utilized to probing the photogenerated carrier transport at the first few nanometers, alongside density functional theory (DFT) to track both defect centers and ions migration. Two compositions of mixed cation are investigated: FA0.6MA0.4PbI3 and FA0.4MA0.6PbI3, interestingly, the former displays a longer lifetime compared to the latter due the presence of a higher surface-defect centers. DFT calculations fully support that revealing samples with higher FA content have a lower energy barrier for iodide ions to migrate from the bulk to top layer, assisting in passivating surface vacancies, and a higher energy diffusion barrier to escape from surface to vacuum, resulting in fewer vacancies and longer-lived hole-electron pairs. These findings manifest the influence of cation selection on charge carrier transport and formation of defects, and emphasize the importance of understanding ion migrations role in controlling surface vacancies to assist engineering high-performance optoelectronic devices based on single crystal perovskites.

Analysis and design of 25.3% efficient Sb2Se3 solar cells by numerical simulation

Sb2Se3 has a high absorption coefficient of 105 cm−1 in the visible light range, which is an excellent absorber layer material. Currently, a better band alignment between conventional CdS and Sb2Se3 has led to the widespread adoption of CdS as the electron transport layer (ETL) in Sb2Se3 solar cells. However, CdS is toxic, necessitating the exploration of alternative ETL materials that are eco-friendly and possess an appropriate energy band with Sb2Se3. In this study, we endeavor to pioneer an all-inorganic, green solar cell structure of Au/MoS2/Sb2Se3/WS2/ITO by employing MoS2 as the hole transport layer (HTL) and WS2 as the ETL. We primarily optimized Sb2Se3 thickness and its hole doping concentration (NA) by SCAPS-1D numerical simulation. Based on the analysis of built-in electric field and carrier recombination rate along Sb2Se3, the optimal thickness and NA ranges of Sb2Se3 are determined, which are 0.9–1.1 μm and 1016-1018 cm−3 respectively. Through a series of optimization, the structure achieves the highest power conversion efficiency (PCE) of about 25.3 % in the current simulation of Sb2Se3 solar cells. After comparing the novel WS2 ETL with the conventional CdS ETL, we find that WS2 has a larger built-in potential (Vbi) and charge recombination resistance (Rrec). In addition, from the analysis of energy band structure, the spike-like band at Sb2Se3/WS2 interface can effectively inhibit the carrier recombination, which makes the device obtain a larger open circuit voltage (VOC) of 0.69 V. This study can provide theoretical reference for the development of non-toxic and efficient Sb2Se3 solar cells.

Effects of palladium doping on structural, mechanical，and opto-electronic behavior of Cs2Pt1-xPdxBr6 double perovskites

Stability in structure and mechanical properties, along with an appropriate band structure, plays a pivotal role in enhancing the performance of the absorber layer materials in perovskite solar cells. In this study, we have employed first-principles calculations to explore the effects of palladium (Pd) doping on the structural, mechanical, and optoelectronic properties of Cs2PtBr6 perovskite. The aim is to explore and identify absorber layer materials for solar cells with superior physical characteristics. Results demonstrated that pristine and Pd4+ doped Cs2PtBr6 are mechanically and dynamically stable, and they all belong to ductile materials. Electronic structure calculations show that Pd4+doping can induce the transition of Cs2PtBr6 from an indirect bandgap to a direct bandgap. Concurrently, with the increase of Pd4+doping concentration, the bandgap decreases, which is beneficial for light absorption. Optical property analyses have also confirmed that with the increase in Pd4+ doping concentration, there is a significant improvement in the optical absorption of Cs2PtBr6 within the visible light range. Particularly, double perovskite Cs2Pt0.25Pd0.75Br6 and Cs2PdBr6 stand out as the best candidates for the solar cell absorption layer due to their close proximity to the ideal bandgap (∼1.5 eV) and strong light absorption coefficients (exceeding 105 cm−1). The findings contribute to the development of light absorption layer materials in perovskite solar cells.

Enhanced structural and optical properties of Cs0.1FA0.9PbI3 perovskite thin film with potassium doping for perovskite solar cells

Hybrid halide perovskite (HHP) materials have been rigorously explored since last decade specially for their potential use as absorber layer material in perovskite solar cells. Formamidinium (FA) based HHP materials show many fascinating properties and exhibit thermal stability. However, photoactive cubic phase of formamidinium lead iodide (FAPbI3) material is unstable at room temperature. To overcome the phase stability issue, substitution of Cs+ or MA+ (methylamine) ion has been found useful. Further, to enhance the material properties of FA-MA or FA-Cs based HHP materials, alkali ion doping is widely explored. In this study, the role of K+ ion doping in enhancing the optoelectronic properties of Cs-FA based HHP material is studied thoroughly by structural and optical characterizations. The XRD results show the suppression of yellow non-perovskite phase after Cs doping in FAPbI3 material. The SEM results predict increased grain size with small K+ content in Cs0.1FA0.9PbI3 material. The PL and TRPL results predict the increase in radiative recombination and charge carrier lifetime with small K-doping and detrimental effects of doping concentration above 3 % of K. The solar cell simulation results yield a maximum power conversion efficiency of 18.21 % in K0.03(Cs0.1FA0.9)0.97PbI3 absorbing layer-based device.

Graphene oxide-titanium oxide-polyaniline hybrid materials for high-performance dye-sensitized solar cells

A new solar cell that comprises a graphene oxide and titanium oxide nanoparticle (NP) composite with graphitized polyaniline (PANI) has been tested in polymer solar cells (PSCs). In this study, a series of conjugated polymers were synthesized and evaluated as the absorber and hole-transport layer materials in organic solar cells, demonstrating the significant impact of the chemical structure of the polymers on solar cell performance. The incorporation of graphene oxide (GOX) and titanium oxide TiO2 NP in conjugated polymers, particularly when graphitized within the PANI layer, led to improved open-circuit voltages compared to structurally similar polymers without NP. The morphology of the composite films was analyzed and related to the photovoltaic performance of polymers synthesized with polyaniline PANI-base and PANI-salt. Optimal NP addition in PANI-salt, PANI-base, PANI-base-TiO2, and PANI-base-GOX resulted in open-circuit voltages and efficiencies of 433 mV and 3.67%, 250 mV and 0.595%, 310 mV and 1.358%, and 520 mV and 2.366%, respectively. This study underscores the importance of polymer film uniformity in the performance of PSCs, with the highest efficiency obtained using a conjugated polymer with the best PANI-salt and PANI-base-GOX films. The research sheds light on the relationship between polymer structure and device photovoltaic performance, which is crucial for the design of new polymeric materials for efficient use and stable OSCs and PSCs.

Performance evaluation of an eco-friendly and highly efficient FASnI3-based perovskite solar cell using Mg-doped CuCrO2 as HTL

Perovskite-based solar cells have emerged as promising photovoltaic devices. However, challenges involving unstable and toxic materials hinder their commercial use. Addressing these issues, the investigation incorporates a non-toxic tin-based absorber layer and specific inorganic charge transporter materials. The focus is on formamidinium tin iodide (FASnI3) based perovskite solar cells (PSCs), known for their efficiency, lead-free composition, and environmental friendliness. Zinc oxy-sulphide (ZnO0.25S0.75) serves as the electron transport layer (ETL) due to its 3.03 eV band gap. Magnesium doped copper delafossite (Mg–CuCrO2) acts as the hole transport layer (HTL) for its 3.3 eV band gap and its ability to maintain device stability. The proposed structure Au/Mg–CuCrO2/FASnI3/ZnO0.25S0.75/TCO was analyzed using numerical simulation conducted with the solar cell capacitance simulator (SCAPS-1D). Performance parameters of the structure were assessed by varying FASnI3 absorber layer thickness, defect density, and doping concentration. Variations in ETL and HTL thickness, defect density, and electron affinity were also explored. Effects of interface defects, series resistance, shunt resistance, and temperature on the device were examined. The optimized device achieved Voc of 1.2462 V, Jsc of 27.98 mA/cm2, FF of 89.33%, and PCE of 31.16%. This level of efficiency holds significant promise as an alternative for a highly effective environmentally friendly solar absorber material in photovoltaic applications.

Novel buffer layer on the performance of CZTS solar cells by numerical simulation

Cu2ZnSnS4 as the promising absorber layer material, has received great attention in the application of highly efficient and low-cost thin film solar cells. The theoretical photovoltaic conversion efficiency of the CZTS thin-film solar cells reaches up to around 32%. Conventionally, CdS or CdSe have been used as buffer layers in these cells. However, cadmium's toxicity and volatility pose environmental concerns. This paper explores TiNxOy and CrNxOy as buffer layers in CZTS solar cells, investigated through numerical simulations using SCAPS-1D. Thickness and carrier concentration on the solar cell performance are mainly investigated. Effects of conduction band offset and defect density on photovoltaic parameters of CZTS/TiNxOy and CZTS/CrNxOy solar cells are also simulated based on the optimal thickness and carrier concentration. The simulation results point out that the photovoltaic conversion efficiency of both systems achieves 22% when TiNxOy or CrNxOy is used as buffer layers. Notably, compared with the CZTS/CrNxOy solar cell structure, TiNxOy as the buffer layer provides a more compatible band offset with the CZTS layer.

Photovoltaic properties of novel quaternary chalcogenides based on high-throughput screening and first-principles calculations

<sec>In recent decades, the demand for clean energy has promoted extensive research on solar cells as a key renewable energy source. Among the various emerging absorber layer materials, Kesterite-type semiconductors have aroused significant interest. Especially, Kesterite Cu<sub>2</sub>ZnSnS<sub>4 </sub>(CZTS) stands out as a promising candidate for low-cost thin-film solar cells due to its direct bandgap, high optical absorption coefficient, suitable bandgap (1.39–1.52 eV), and abundance of constituent elements. However, the power conversion efficiency (PCE) of CZTS-based solar cells currently lags behind that of Cu(In,Ga)Se<sub>2</sub> (CIGS) cells, mainly due to insufficient open-circuit voltage caused by a large number of disordered cations and defect clusters, resulting in non-radiative recombination and band-tail states.</sec><sec>To address these challenges, partial or complete cation substitution has become a viable strategy for altering the harmful defects in CZTS. This study proposes a heterovalent substitution of Zn in CZTS and explores the potential of novel quaternary chalcogenide compound <i>A</i><sub>2</sub><i>M</i><sub>2</sub><i>M'Q</i><sub>4</sub> (<i>A</i> = Na, K, Rb, Cs, In, Tl; <i>M</i> = Cu, Ag, Au; <i>M'</i> = Ti, Zr, Hf, Ge, Sn; <i>Q</i> = S, Se, Te) as absorbers for solar cells. By substituting elements in five prototype structures, a comprehensive material database comprising 1350 <i>A</i><sub>2</sub><i>M</i><sub>2</sub><i>M'Q</i><sub>4</sub> compounds is established.</sec><sec>High-throughput screening and first-principles calculations are used to evaluate the thermodynamic stabilities, band gaps, spectroscopic limited maximum efficiencies (SLMEs), and phonon dispersions of these compounds. Our research results indicate that 543 compounds exhibit thermodynamic stability (<i>E</i><sub>hull</sub> < 0.01 eV/atom), 202 compounds possess suitable band gaps (1.0–1.5 eV), and 10 compounds meet all the criteria for thermodynamic and dynamic stability, suitable band gaps, and high optical absorption performance (10<sup>4</sup>–10<sup>6</sup> cm<sup>–1</sup>), with theoretical SLME values exceeding 30%.</sec><sec>Notably, <i>Ibam</i>-Rb<sub>2</sub>Ag<sub>2</sub>GeTe<sub>4</sub> exhibits the highest SLME (31.8%) in these candidates, featuring a band gap of 1.27 eV and a small carrier effective mass (< <i>m</i><sub>0</sub>). The electronic structures and optical properties of these compounds are comparable to those of CZTS, which makes them suitable for highly efficient single-junction thin-film solar cells.</sec><sec>All the data presented in this work can be found at <ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.doi.org/10.57760/sciencedb.j00213.00006">https://www.doi.org/10.57760/sciencedb.j00213.00006</ext-link>.</sec>

Effect of uniaxial strain on Hole mobility of Sb<sub>2</sub>Se<sub>3</sub>

Antimony selenide (Sb<sub>2</sub>Se<sub>3</sub>) is a simple-phase, element-rich, and economically friendly material for solar cell absorption layers, with broad application prospects. However, the weak conductivity of Sb<sub>2</sub>Se<sub>3</sub> has become a significant factor limiting the performance of solar cell devices. Carrier mobility is an important electrical parameter for both materials and devices, and strain can change carrier mobility. Therefore, studying the effect of strain on the carrier mobility of Sb<sub>2</sub>Se<sub>3</sub> is of practical significance. In this work, using density functional theory and deformation potential theory, we systematically investigate the influence of uniaxial strain on the band structure, bandgap width, iso-surface, and effective mass of Sb<sub>2</sub>Se<sub>3</sub>. We analyze the effects of three types of uniaxial strains along the <i>x-</i>, <i>y-</i>, and <i>z-</i>direction on the carrier mobilities along the <i>x-</i>, <i>y-</i>, and <i>z-</i>direction, which are denoted by <i>μ</i><sub><i>x</i></sub>, <i>μ</i><sub><i>y</i></sub>, and <i>μ</i><sub><i>z</i></sub>, respectively. It is found that under these strains, the valence band maximum (VBM) position of Sb<sub>2</sub>Se<sub>3</sub> remains unchanged, and the bandgap decreases with the increase of strain along the <i>y</i>- and <i>z</i>-direction, while it increases along the <i>x-</i>direction. The variation in bandgap may be related to the coupling strength between the Sb-5p orbital and Se-4p orbital of the conduction band minimum (CBM). For fully relaxed Sb<sub>2</sub>Se<sub>3</sub>, its iso-surface exhibits a distorted cylindrical shape, with low dispersion along the <i>z</i>-axis and high dispersion along the <i>x</i>- and <i>y</i>-axis, where <i>μ</i><sub><i>x</i></sub> is greater than <i>μ</i><sub><i>y</i></sub> and <i>μ</i><sub><i>z</i></sub>, suggesting that the <i>x</i>-direction should be considered as the specific growth direction for Sb<sub>2</sub>Se<sub>3</sub> experimentally. When the strain is applied along the <i>x</i>- and <i>z</i>-direction, <i>μ</i><sub><i>x</i></sub> gradually increases with strain increasing, while it decreases when the strain is applied along the <i>y-</i>direction. Taking into account the combined effects of strain on bandgap, iso-surface, density of states, and mobility, this study suggests that the optimal performance of Sb<sub>2</sub>Se<sub>3</sub> solar cell absorber layer material can be realized when the strain is applied along the <i>y</i>-axis, with a compressive strain of 3%.

Improvement in spectral range of Sb 2 Se 3 absorption layer on Bi addition

Antimony selenide (Sb 2 Se 3) is a versatile material used in solar cells. The alteration in the physical properties of Sb 2 Se 3 alloys on Bi addition has been analysed. (Sb 2 Se 3)100-x Bi x (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0, and 1.2) system has been studied to examine the structural alterations by computing physical parameters. The increase in parameters, i.e., average coordination number 〈Z〉, total number of constraints per atoms (N c ), and crosslinking density (D cl ) reflect an increase in rigidity of the Sb 2 Se 3 on Bi incorporation. The computed band gap decreases on Bi addition, from 1.095 eV to 1.079 eV, indicating an approximate increase in absorption wavelength from 1132.42 nm to 1149.21 nm. An increase in rigidity reflects reduction in defect states decreasing the recombination rate within absorption layer. There are variations in cohesive energy, electronegativity, and average single-bond energy. The study reveals that this composition can be utilized to develop novel solar absorber layer materials.

Synthesis and characterization of lithium-doped copper zinc tin sulfide (CZTS) thin films

The non-toxic nature and remarkable optoelectronic properties of kesterite (Cu2ZnSnS4 and CZTS) make CZTS a potential candidate for solar cell absorber layer material. Since alkali metal doping has shown a performance boost of active layers of solar cells, this work investigates the effects of significant lithium doping on sol-gel-produced CZTS thin films. CZTS- and lithium (Li)-doped CZTS thin films were prepared using the spin coating technique. The variation of structural, morphological, and optical properties of CZTS due to Li-doping has been studied by x-ray diffraction, scanning electron microscopy, and UV–visible spectroscopy techniques. All the synthesized LixCu2−xZnSnS4 (x = 0, 0.2, 0.4, 0.6) films showed fine crystallinity with average crystallite sizes of 4.745, 6.013, 6.255, and 6.404 nm, respectively. The average grain size decreases from 0.336 to 0.310 µm via increasing Li concentration. The inclusion of Li increased the bandgap energy ranges from 1.5 to 1.808 eV. The Li0.6Cu1.4ZnSnS4 thin showed the highest absorption coefficient of 3.505 × 104 cm−1 among all the prepared thin films. A high optical conductivity over 1014 s−1 was observed for CZTS, which further increased with an increased Li concentration. The synthesized structures showed enhanced characteristics suitable for solar cell application.

Modeling and Investigation of Highly Efficient Environment Friendly Perovskite Solar Cell with CuSbS2 as Hole Transport Layer

The presence of lead and its associated toxicity represents a hindrance to the broad commercial production of lead halide perovskites and their utilization in solar photovoltaic devices. Although lead halide perovskites have found extensive application in solar cell technology, questions have arisen regarding the hazardous nature and durability of lead (Pb) in photovoltaic systems. This research seeks to address these concerns by exploring alternative materials, such as tin-based perovskites, to pave the way for cleaner and more sustainable energy solutions. The scientific community has shown increased interest in tin-based perovskites due to their superior efficiency and stability compared to lead-based perovskite solar cell. This research introduces a planar heterojunction solar cell utilizing tin-based perovskites that are free of lead. The simulation task was conducted using SCAPS-1d software. Device parameters for a lead-free PSC (perovskite solar cell) using significant framework FTO/WS2/CH3NH3SnI3(perovskite)/CuSbS2 included an examination of factors like perovskite layer thickness, the obsession of acceptors in the perovskite layer, defects density of perovskite layer, and the band gap of the perovskite layer. In this setup, WS2 served as the ETL material, CuSbS2 functioned as the HTL material, and the CH3NH3SnI3(Perovskite) was used as the absorber layer material. This configuration achieved an impressive PCE 32.5%, along with a Jsc34.1mAcm-², Voc1.02V and FF85.5%. These optimized results likelihood indicates the strong prospect for development of an eco-friendly and efficient model of PSC (perovskite solar cell).

Cu2GeS3/Cd0.5Zn0.5S Heterojunction Thin Film Solar Cells

Ternary compounds such as Cu2GeS3(CGS) and Cu2SnS3(CTS) semiconductor materials have been considered as lower defects and environmentally friendly absorber layer materials for solar cells. In this work, the band offsets for CGS/CdS and CTS/CdS heterointerface are calculated by the first-principles calculation method. The valence band maximum (VBM) of CdS is below CGS (valence band offset ΔEV =1.4 eV), and the conduction band minimum (CBM) of CdS is below CGS (conduction band offset ΔEC =0.5 eV), i.e., the CGS/CdS is type II interface. The VBM of CdS is below CGS (ΔEV =1.4 eV), and the CBM of CdS is above CTS(ΔEC =-0.1 eV), i.e., the CTS/CdS heterojunction is type I. We also obtained the type I of CGS/Cd1−x Zn x S heterointerface with a favorable barrier height of 0.2 eV by adjusting the composition of x in Cd1−x Zn x S alloy with 0.5.

Scrutinizing the effect of substrate temperature and enhancing the multifunctional attributes of spray deposited copper gallium sulfide (CuGaS2) thin films

ABSTRACT Polycrystalline chalcopyrite CuGaS2 thin films were prepared using a spray pyrolysis route has been considered a potential material for the solar cell absorber layer. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) studied the impact of substrate temperature in the range of 200–300˚C on surface profile and roughness. Powder X-ray diffraction disclosed that the films were polycrystalline at all examined substrate temperatures, with crystallite size increasing with increased substrate temperature. The UV-Vis displays the cut-off wavelength in 550–880 nm for varied substrate temperatures of CuGaS2 thin films, and the observed band gap is 2.75 eV–1.89 eV. The electrical attributes showed the enhancement in mobility (4.632 cm2 V−1 s−1) for varied substrate temperatures of CuGaS2 thin films. The 300˚C temperature sprayed CuGaS2 polycrystalline films are a decent candidate to be apposite as an absorber layer in thin film photovoltaic solar cells.

Performance evaluation and the optimization of an inverted photo-voltaic cell with lead-free double perovskite material and inorganic transport layer materials

The research on the solar cell structure based on various inorganic, organic and hybrid type of perovskite absorbing materials is increasing due to their legion features. Various inorganic titanium (Ti) based double perovskite absorbing materials like, Cs2TiCl6, Cs2TiBr6, and Cs2TiI6 are examined. Cs2TiBr6 is chosen to be the most promising absorbing layer material alternative suitable for a stable environmentally friendly solar cell application due to its larger spectrum response and tunable band gap than the other promising absorbing materials. The primary objective of this work aims for investigating the functioning of Cs2TiBr6 with various inorganic charge transport materials under simulated conditions using the simulation software, SCAPS-1D (a Solar Cell Capacitance Simulator), Solar Cell Capacitance Simulator, and its functioning is evaluated by varying the interface defect density, thickness, defect density, etc. of various layer materials of the solar cell device. The basic input parameters, like electron-affinity, thickness, band-gap, charge mobility, permittivity, and defect density, of different layer materials are used in the simulation software to accomplish the modelling of the novel structure of solar cell device. A highly efficient environmentally friendly perovskite solar cell structure is the focus of this numerical research. Analysis results are compared with the existing data for substantiation. Finally, one planar inverted, high performance device structure, Glass/MoO3/Cs2TiBr6/SnO2/Au, is evolved, which is a promising eco-friendly device that can be used for making solar panels without any toxic consequences. The short circuit current density, the open circuit voltage, power conversion efficiency, and the fill-factor of this innovative inverted solar cell structure are observed to be 16.589 mA/cm2, 1.1 V, 15.68 %, and 85.76 %, which are significantly better parameters than those previously reported.

Simulation and Numerical Investigation of the Effect of Temperature and Defect on ZnTe/ZnSe/ZnO Thin-Film Photovoltaic Solar Cell Performance Efficiency

Thin film-based solar cell semiconductor emerges as a promising candidate for solar photovoltaic future applications. A proposed heterojunction ZnTe/ZnSe/ZnO thin film-based solar cell has been simulated by using Solar Cell Capacitance Simulator-One Dimension (SCAPS-1D) in order to study the impact of temperature and defect layers on its efficiency parameters. The heterojunction thin film-based solar cell has been selected for simulation due to its low cost, availability, and reduced toxicity compared to other absorber layer materials. Numerical modeling has been used to comprehend device properties before fabrication. The results indicate that the efficiency parameters (Jsc, VOC, FF, and η) have been significantly affected by temperature and the presence of defect layers. The simulated J-V characteristics demonstrate how defect density affects solar cell efficiency parameters. In the defect system, the efficacy parameters have been reduced except for a slight increase in VOC at 300 K. The findings of this study are significant as they demonstrate the importance of understanding the impact of temperature and defect layers on the performance of thin film-based solar cells. The use of numerical modeling tools like SCAPS-1D can aid in the design and development of new solar cell technologies, which could ultimately lead to the widespread adoption of solar energy as a clean and sustainable energy source.

Numerical simulation of germanium selenide heterojunction solar cell

One of the research hotspots in thin film solar cell technology is to seek the suitable absorber layer materials to replace cadmium telluride and copper indium gallium selenium. Recently, germanium selenide (GeSe) with excellent photoelectric property has entered the field of vision of photovoltaic researchers. The main factors affecting the performance of heterojunction solar cell are the material properties of each functional layer, the device configuration, and the interface characteristics at the heterostructure. In this study, we utilize GeSe as the absorber layer, and assemble it with stable TiO<sub>2</sub> as electron transport layer and with Cu<sub>2</sub>O as hole transport layer, respectively, into a heterojunction solar cell with the FTO/TiO<sub>2</sub>/GeSe/Cu<sub>2</sub>O/Metal structure. The TiO<sub>2</sub> and Cu<sub>2</sub>O can form small spike-like conduction band offset and valence band offset with the absorber layer, respectively, which do not hinder majority carrier transport but can effectively suppress carrier recombination at the heterointerface. Subsequently, the wxAMPS software is used to simulate and analyze the effects of functional layer material parameters, heterointerface characteristics, and operating temperature on the performance parameters of the proposed solar cell. Considering the practical application, the relevant material parameters are selected carefully. After being optimized at 300 K, the proposed GeSe heterojunction solar cell can reach an open circuit voltage of 0.752 V, a short circuit current of 40.71 mA·cm<sup>–2</sup>, a filling factor of 82.89%, and a conversion efficiency of 25.39%. It is anticipated from the results that the GeSe based heterojunction solar cell with a structure of FTO/TiO<sub>2</sub>/GeSe/Cu<sub>2</sub>O/Au has the potential to become a high-efficiency, low toxicity, and low-cost photovoltaic device. Simulation analysis also provides some references for designing and preparing the heterojunction solar cells.

The effect of polyvinyl alcohol (PVA) on the optical, electrical and solid state properties of copper zinc tin sulfide (CZTS) deposited by sensitive spray pyrolysis (SSP)

Recently, the use of CZTS as the basis for other generation of low cost thin films solar cells has stimulated further researches. Its excellent p-type absorber nature, relatively high absorption coefficient and ideal energy band-gap of 1.5eV motivated these efforts. Additionally, CZTS consist of earth-abundant, cheap and non-toxic elements with very low manufacturing cost. Initially, copper indium gallium selenide (CIGS) solar cell device emerged but suffered limitations in further development because of rare indium and gallium in the device structure therefore, CZTS is recently preferred as an alternative to CIGS commercial solar cell absorber layer. In this work, solution mixture of CZTS and PVA was deposited on a substrate at temperature of 150 °C. Sensitive spray pyrolysis was used to grow the thin films where calculated amount of the precursor mixture was allowed to fall and be deposited on a heated substrate to form CZTS/PVA thin films. Subsequently, the thin film samples were annealed at a temperature of 200oCfor 1 h to achieving pure crystalline thin film formation. SEM, XRD analysis, Optical, Solid State properties and Raman analysis were studied. The XRD analysis showed that the thin films fell into the pure kesterite structure of CZTS. Results show that produced thin films exhibited higher absorption coefficient and optical conductivity than pure CZTS, 106 m−1 and 1014(S−1) against 104cm−1 and 1012(S−1) respectively. The band-gap is between 1.53eV and 1.73eV. Using a PVA concentration of 0.05 M yielded highest absorbance and optical conductivity with lowest real dielectric constant and transmittance. These improved optical, electrical and solid state properties suitably qualify these thin films as absorber layer material for solar cell applications.

Numerical Simulations on CZTSSe-Based Solar Cells with GaSe as an Alternative Buffer Layer Using SCAPS-1D

In recent years, because of non-toxic characteristic, relatively high efficiency, and adjustable band gap, the research on thin film solar cells using Cu2ZnSn (SxSe1-x)4 (CZTSSe) as the absorber layer material has been in full swing. But its large band gap width makes it easy to form an excessive potential barrier with other materials, which leads to the raise of the recombination probability of carriers. Therefore, it is necessary to select a suitable buffer layer to optimize such solar cells. Compared with the common buffer material CdS, GaSe crystal has a high damage threshold, strong anisotropy, and nonlinear optical properties. In this paper, a safe and efficient material, GaSe, was selected as the buffer layer of the solar cell with CZTSSe as the absorber layer. At the same time, traditional holes transport layer was removed to save its complex manufacturing process. The addition of GaSe also adjusted the energy band arrangement of the battery, which alleviated the strong potential barrier between the absorber layer and the window layer to improve the carrier transport effectively. The effects of the impurity ratio, thickness, temperature, and defect density on the device performance were also discussed in detail, which provides a reference for experimental preparation and industrial application.

Photovoltaic performance of mixed cation K0.005MA0.995PbI3‐based perovskite solar module

AbstractHybrid halide perovskites (HHPs) are attracting large attention due to their excellent photovoltaic characteristics. MAPbI3 (MA = CH3NH3) based solar cells are widely studied both on experimental and theoretical fronts. Alkali metal ion doping in the absorbing layer material (MAPbI3) of HHP solar cells is helpful for enhancing the photovoltaic performance and stability of the complete solar module. In present work, a complete perovskite solar module with K‐doped MAPbI3 absorbing layer has been simulated numerically. The effect of various parameters such as thickness, defect density, series, and shunt resistances on device performance has been studied. After optimizing these parameters, a device with the maximum possible efficiency (20.69%) has been reported. The reproducibility of solar cells before and after optimization has also been compared with respect to the variation in carrier mobilities in absorber layer material. Higher reproducibility of the optimized device has been obtained as compared to the pristine device. This present work contains adequate information to run an experimental trial for designing solar module containing K‐doped MAPbI3 absorbing layer.