Solar Cell Structure Research Articles

Optical properties study of a perovskite solar cell film stack by spectroscopic ellipsometry and spectrophotometry

Spectroscopic ellipsometry is a reproducible and non-invasive characterization technique that allows the evaluation of multilayered structures. However, it is an indirect technique and requires the use of well-calibrated models to correctly analyze the materials. In this work, we report a multilayer modeling approach to investigate the optical properties of the three layers of interest typically employed on an inverted perovskite solar cells structure, namely, indium-tin-oxide (ITO) as a transparent anode, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as a hole transport layer, and methylammonium lead iodide (MAPbI3) as the perovskite layer. The parameterized optical constants based on oscillator models were simultaneously fitted to ellipsometry and intensity-transmission data and validated with ultraviolet–visible (UV–Vis) spectroscopy and profilometry. We propose this multilayer modeling approach as a method to be employed throughout the different stages of the fabrication process to study the distinct mechanisms that impact the final performance of a photovoltaic device.

All-Inorganic Hydrothermally Processed Semitransparent Sb2S3 Solar Cells with CuSCN as the Hole Transport Layer.

An inorganic wide-bandgap hole transport layer (HTL), copper(I) thiocyanate (CuSCN), is employed in inorganic planar hydrothermally deposited Sb2S3 solar cells. With excellent hole transport properties and uniform compact morphology, the solution-processed CuSCN layer suppresses the leakage current and improves charge selectivity in an n-i-p-type solar cell structure. The device without the HTL (FTO/CdS/Sb2S3/Au) delivers a modest power conversion efficiency (PCE) of 1.54%, which increases to 2.46% with the introduction of CuSCN (FTO/CdS/Sb2S3/CuSCN/Au). This PCE is a significant improvement compared with the previous reports of planar Sb2S3 solar cells employing CuSCN. CuSCN is therefore a promising alternative to expensive and inherently unstable organic HTLs. In addition, CuSCN makes an excellent optically transparent (with average transmittance >90% in the visible region) and shunt-blocking HTL layer in pinhole-prone ultrathin (<100 nm) semitransparent absorber layers grown by green and facile hydrothermal deposition. A semitransparent device is fabricated using an ultrathin Au layer (∼10 nm) with a PCE of 2.13% and an average visible transmittance of 13.7%.

Study and simulation of GaInP single junction solar cell

This study aims to improve the electrical performances of the GaxIn1-xP single junction solar cell. To this objective, a single-junction solar cell GaxIn1-xP has been simulated with different doping concentrations and thicknesses of the emitter and base region in order to improve its conversion efficiency. The simulations have been done taking into account the optical, electrical and physical properties of the GaxIn1-xP according to the indium composition. The physical models such as the radiative, Auger and Shockley–Read–Hall (SRH) recombination were also considered. The optimized single junction Ga0.04In0.96P (1.39 eV) solar cell structure achieved, showed, under standard conditions (1-sun, AM1.5, 300 K), a maximum conversion efficiency of 23.73%. Moreover, the effects of the thickness and the doping concentration of each region on the electrical parameters of the Ga0.04In0.96P solar cell were also studied.

Photoconductivity and bandgap of binary impurity - doped crystalline silicon

The paper presents the results of study of the photoconductivity spectra of sulfur- and <sulfur+manganese>-doped samples of silicon (Si<S>, Si<MnS>) under dark conditions and while samples were subjected to constant light in forward and reverse switching modes. The paper also presents the calculation results of the value of the band gap (Eg ) of <sulfur+zinc> -doped silicon samples (Si<ZnS>). Spatial analogues of generally accepted GaAs structure such as Si2Mn2S and Si2Zn2S are hypothesized to be brought up in the result of above mixed dopings. Tentative investigations of the short-circuit current and open-circuit voltage of p-n-structures, as well as the photoconductivity of such structures, together with the analysis of their lux-ampere characteristic might serve for proposing potential varying band structures for solar cells.

A A highly efficient InGaP thin film solar cell structure, optimization and characteristics

Inorganic solar cells based on III-V semiconductor materials are widely used owing to their high efficiencies. In this work, we aim to improve the performance of the single heterojunction solar cell InGaP. The InGaP cell is constituted of a back surface field (BSF), a base, an emitter and a window layer with InAlAsP material. The simulation is done after optimization, modeling, and choice of the used materials and the thickness of different layers constituting the solar cell. The choice of materials whose gap energy is decreasing allows the absorption of the solar spectrum in its almost totality. Then, we varied the temperature to know its effects on the gap energy and the efficiency of the InGaP cell. The InGaP and solar cell with optimal parameters are illuminated by an AM1.5 solar spectrum through InAlAsP window layer. The simulation and optimization at 300K of short circuit current parameters (Jsc), open circuit voltage (Voc), fill factor (FF) and efficiency (?) are done using Tcad Silvaco software. The characteristics obtained are: the minimized thickness of 665 nm, electrical efficiency is about ? = 21.87% for InGaP cell, Jsc = 14.43 mA/cm2, Voc = 1.63 V, and FF = 91.21 %.

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.

Numerical Investigation of Copper Zinc Tin Sulphide Based Solar Cell with Non‐Toxic Zn (O, S) Buffer Layer

Zinc oxide sulphide Zn (O, S) buffer layer has attracted enormous attention due to its composition of non‐toxic, low cost, and earth abundant elements, unlike cadmium sulphide (CdS) used in copper zinc tin sulphide (CZTS) solar cells. Zn (O, S) possesses a direct optical bandgap that's adjustable between 2.7 and 3.6 eV related to the mole fraction , making it a potential candidate as a buffer layer with CZTS based solar cells. In this work, the Zn (O, S)/CZTS‐based solar cell structure is numerically studied and compared with CdS/CZTS. The existence of defects and traps along the layers and interfaces is taken in consideration. To achieve optimal results, this research has focused on; effects of the element composition (x = S/(S + O)) ratio of Zn (O, S) buffer layer, the addition of a back surface field (BSF) layer, the influence of Zn (O, S)/CZTS and CdS/CZTS interfaces defect density, varying thicknesses and doping concentrations of the layers (absorber, buffer, BSF) on open‐circuit voltage (Voc), short‐circuit density (Jsc), fill factor (FF), and power conversion efficiency. Findings illustrate that the highest conversion efficiency of the Zn (O, S)/CZTS solar cell reached 14.65% with Voc = 0.9972 V, Jsc = 18.37 mA cm−2 and FF = 79.96% which is better than the CdS/CZTS structure.

Surface recombination and peltier heat generation in Kesterite thin film solar cells due to defect increment under elevated heat

Thermal instability is the major barrier against the commercialization and upscaling of thin film solar cells. Heat generation in thin film solar cells occurs both at normal operation conditions and under stress conditions. In this paper, we developed a simulation model to investigate the heat generation in CZTSSe Kesterite thin film solar cells by coupling the optical, electrical, and thermal modules in the COMSOL simulation package. This strongly coupled model allows investigation of the two main heat generation factors in solar cell structure: Surface recombination heat and Peltier heat. These factors have been rarely analyzed in literature but can be significantly detrimental to the solar cell structure especially when the temperature of the cell rises over time under operation conditions. We extended our simulation to insert the defect growth at the Surface and bulk of the CZTSSe layer of the cell for elevated temperatures (400 °C. for 1000 h) and calculate the heat generation at CZTSSe/Mo(S,Se)2 and CZTSSe/CdS interfaces and at the deletion width of the junction where Surface recombination heat and Peltier heat generated from electrons and holes are generated. The simulation shows that Peltier heat generation from electrons is more dominant than Peltier heat from holes while the surface recombination heat is significantly more dominant compared to Peltier heat generation.

Enhancing Surface Modification and Carrier Extraction in Inverted Perovskite Solar Cells via Self-Assembled Monolayers.

Perovskite solar cells (PSCs) have been significantly improved by utilizing an inorganic hole-transporting layer (HTL), such as nickel oxide. Despite the promising properties, there are still limitations due to defects. Recently, research on self-assembled monolayers (SAMs) is being actively conducted, which shows promise in reducing defects and enhancing device performance. In this study, we successfully engineered a p-i-n perovskite solar cell structure utilizing HC-A1 and HC-A4 molecules. These SAM molecules were found to enhance the grain morphology and uniformity of the perovskite film, which are critical factors in determining optical properties and device performance. Notably, HC-A4 demonstrated superior performance due to its distinct hydrophilic properties with a contact angle of 50.3°, attributable to its unique functional groups. Overall, the HC-A4-applied film exhibited efficient carrier extraction properties, attaining a carrier lifetime of 117.33 ns. Furthermore, HC-A4 contributed to superior device performance, achieving the highest device efficiency of 20% and demonstrating outstanding thermal stability over 300 h.

Growth of nano-polycrystalline CuIn1-xAlxSe2 thin films and its photovoltaic cell formation

Nano-polycrystalline thin films of CuIn1-xAlxSe2 (CIAS) chalcopyrite material are re-grown on annealing the 700 nm thick Cu/In/Al/Se stack at temperatures ranging from 523 to 623 K. The stack is obtained at room temperature by sequentially evaporated layer deposition (SELD) technique. The grown films show a tetragonal crystal system of CIAS having unit cell parameters a; b = 5.781(5) Å, c = 11.593 (7) Å, with cell volume (V) = 387.523(4) Å3. The micrographs of the films show grains of spherical and cylindrical shapes. Raman spectra of the layers indicate A1 mode at 180.72(7) cm−1, which confirms the CIAS phase. The thin film's energy dispersive X-ray analysis (EDAX) establishes CuIn0.63Al0.37Se2 stoichiometry at 523 K. The direct allowed bandgap (Eg) value varies between 1.35 and 1.50 eV with a change in TA from 523 to 623 K; the values are near the optimum PV cell. The grown thin film samples exhibit absorption coefficient (α) ≥ 1 × 105 cm−1. The solar cell structure of FTO/p-CIAS/n-CdS/In exhibits a photovoltaic (PV) response.

Optimisation and numerical analysis of highly efficient CGSe-based thin film solar cell

Among the various chalcopyrites compounds used in photovoltaic devices, Copper Gallium Selenium (CGSe) turns out as an underperformer due to its limited photovoltaic performance, So far highest efficiency measured is about 11.9%. This paper investigates the possibilities for efficiency enhancement for the CuGSe layer in Cu2O/CGSe/TiO2/ZnO thin film solar cell structure using the SCAPS-1D simulation program. The short circuit current (Jsc) and power conversion efficiency (PCE) is 30.77 mA cm−2 and 27.10%, with open-circuit voltage (Voc) and fill factor (FF) of 1.03 V and 84.72% respectively. Furthermore, we evaluated some specific parameters of TiO2/CGSe heterostructure, such as the influence of layer thickness, operating temperature, the effect of defect density and acceptor density of CGSe layer, metal work function, and the effect of series and shunt resistance on cell performance. We investigated that combining TiO2 as an ETL and Cu2O as HTL with a CGSe absorber layer is novel and promising, which results in higher power conversation efficiency and improves other PV parameters. The application of CGSe/TiO2 heterojunction in a simulated model offers a viable method for the development of high-efficiency solar cell devices.

Zinc sulfide thin films deposited by chemical bath: Tuning consideration of structural, optical band gap, and electrical properties for CIGS solar cells application

Zinc sulfide (ZnS) is widely employed in a solar cell structure as a buffer layer due to its excellent physical and chemical properties. ZnS elements discovered in the earth's crust are safe. This study examined the performance characteristics of ZnS thin films deposited on soda lime glass substrate via chemical bath deposition. The ZnS thin films were annealed at temperatures of 300, 400, and 500 °C in a vacuum environment. XRD showed the ZnS thin films with high annealing temperatures are composed of a wurtzite structure. Increased annealing temperature improved crystallization, average crystallite sizes, film thickness, and low dislocation density as well as lattice strain. The FESEM analysis reveals that the morphology of annealed thin film at high temperatures has larger grains compared to the deposited films. EDS spectra confirm that zinc and sulfur are present in the ZnS thin film. Annealed films have an average transmission of 20–50 % in the visible spectrum of 300–1100 nm. Films exhibit 103 Ωcm resistivity, and the bulk carrier density ranges between 1012 and 1014 cm−3. The annealed film at 500 °C has a direct band gap of 3.47 eV, a resistivity of 1.79 × 103 Ωcm, and a bulk concentration of 1.19 × 1014 cm−3. All ZnS thin films have n-type conductivity.

Nanotextured highly efficient optical and light trapping strategies using efficient hole transport-free structure for perovskite solar cells

Device modelling of CH3NH3PbI3-based hole transport layer (HTL)-free nanotextured perovskite solar cells (PSC) was performed. In recent years, HTL-free PSCs have grown tremendously and gained widespread attention. Also, using nanostructures in PSCs significantly affected this type of solar cell's power conversion efficiency (PCE). Light trapping (LT) by nanostructures is a promising approach to optimizing the performance of PSCs in this work. We employed coupled optical and electrical modelling to optimize these nanostructures. In the current simulation, all parameters impacting the PSC were accurately examined and considered using the finite element technique (FEM). First, we obtained the photovoltaic results for two planar and free-HTL structures. The simulation results show that not using HTL reduces the PCE of PSC by up to 15 %. In this article, we emphasized nanostructures and their key features that minimize losses related to light by managing and optimizing light to achieve high PCE for the PSC. Using nano-texture at the surface of the active layer with ZnO material and optimizing the height, we were able to bring the lost efficiency in the free-HTL structure to 14.87 %, and also the short-circuit current density and open-circuit voltage for the proposed structure were 18.16 (mA/cm2) and 0.98 (V), respectively.

Comparative study on perovskite solar cells using P_ZnO, Al_ZnO and In_ZnO as ETMs by SCAPS-1D

This study uses the SCAPS 1D software to analyze solar cells with lead iodide perovskite (CH3NH3PbI3) as the active material and three different types of ZnO doping: undoped (P_ZnO), aluminum-doped (Al_ZnO), and indium-doped (In_ZnO) as the electron transport layer (ETL). This study aims to investigate the effects of charge carrier density on the J-V characteristics and electrical properties (Jsc, Voc, FF, Eff) of a solar cell structure made up of FTO/ETL/CH3NH3PbI3/CuInSe2/Au. Gold makes up the back contact, and tin oxide doped with fluorine (FTO) makes up the front contact. These two compounds have work roles are 5.47 eV and 4.4 eV respectively. Zinc oxide, both undoped and doped, makes up the electron transport layer, whereas methyl ammonium lead iodide makes up the absorber layer. Thin sheets, indium diselenide, and copper make up the hole transport layer. An optimal perovskite layer was obtained by decreasing the electron transportation layer's thickness (ETL) from 500 to 100 nm. For the In_ZnO ETL, this optimization was accomplished at 300K working temperature. Reduced ETL thickness was shown to result in higher efficiency (above 27%), as well as higher fill factor (above 87%). With a Voc value of 1.180V, a FF value of 87.55%, and a Jsc value of 26.276mA/cm2, the greatest efficiency performance of 27.15% was found. Using an absorber layer made of CH3NH3PbI3 with a thickness of 800 nm and indium-doped oxide of zinc (In_ZnO) is the layer that transports electrons, this performance was achieved. The results are obtained at a constant irradiance level of 1000 W/m2, under the AM1.5G spectrum.

Computational analysis on the role of an AGT current enhancer in a CZTS-based thin film solar cell

This paper gives a synopsis of a CZTS-based n-CdS/p-CZTS/p + -AgGaTe2/p++-MoS2 thin film solar cell that has been designed and explored by the simulation technique with the help of a solar cell capacitance simulator (SCAPS-1D). The design utilizes CdS as the window layer, CZTS as the first absorber layer, AgGaTe2 as the second absorber layer, and MoS2 as the BSF layer. The influencing parameters of these materials such as thickness, doping concentration, and defect density have been adjusted to achieve the right balance between the proposed structure and to see the changes that affect the device's overall performance. In ideal condition, the single n-CdS/p-CZTS heterojunction structure shows power conversion efficiency (PCE) of 17.75% with short circuit current, JSC of 24.82 mA/cm2, open circuit voltage, VOC of 0.88 V and fill factor (FF) of 81.3%. But, with the inclusion of MoS2 as the BSF, the overall PCE is elevated to 25.84% with VOC of 1.09 V, JSC of 26.96 mA/cm2 and FF of 87.64%. Finally, with the fusion of AgGaTe2 as a current augmenting layer the JSC gets a huge boost and is enhanced to 34.7 mA/cm2 with a PCE of 33.89%. These simulation findings unveil the potential of the proposed solar cell structure with CZTS as the absorber layer and AgGaTe2 as the current boosting layer in creating an environment-friendly, affordable and highly efficient thin film solar cell.

Cost-effective polymer donors with simple structure for organic solar cells

This review summarized recent advances in cost-effective polymer donors with a simple structure for organic solar cells.

Improving the efficiency of a CIGS solar cell to above 31% with Sb2S3 as a new BSF: a numerical simulation approach by SCAPS-1D.

The remarkable performance of copper indium gallium selenide (CIGS)-based double heterojunction (DH) photovoltaic cells is presented in this work. To increase all photovoltaic performance parameters, in this investigation, a novel solar cell structure (FTO/SnS2/CIGS/Sb2S3/Ni) is explored by utilizing the SCAPS-1D simulation software. Thicknesses of the buffer, absorber and back surface field (BSF) layers, acceptor density, defect density, capacitance-voltage (C-V), interface defect density, rates of generation and recombination, operating temperature, current density, and quantum efficiency have been investigated for the proposed solar devices with and without BSF. The presence of the BSF layer significantly influences the device's performance parameters including short-circuit current (Jsc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (PCE). After optimization, the simulation results of a conventional CIGS cell (FTO/SnS2/CIGS/Ni) have shown a PCE of 22.14% with Voc of 0.91 V, Jsc of 28.21 mA cm-2, and FF of 86.31. Conversely, the PCE is improved to 31.15% with Voc of 1.08 V, Jsc of 33.75 mA cm-2, and FF of 88.50 by introducing the Sb2S3 BSF in the structure of FTO/SnS2/CIGS/Sb2S3/Ni. These findings of the proposed CIGS-based double heterojunction (DH) solar cells offer an innovative method for realization of high-efficiency solar cells that are more promising than the previously reported traditional designs.

Thermal Runaway in Thin Film PV: temperature profile modeling

Thermal runaway is a well known phenomena in degradation analysis of the CdS/CdTe thin film solar cells. The thin thickness of such devices can be deteriorated by the temperature fluctuations after a long enough time. We modeled the temperature profile of thin film devices considering the uniform and nonuniform distribution for temperature of the glass substrate and current flowing through TCO layer. In addition, the temperature profile of a hot spot at the edge of the device has been formulated and compared with the real data and fitting functions represented in a few literature. All the above modeling was based on the heat transfer equation considering the importance of thermal resistances. The convection and conduction resistances were introduced in the considered Biot number optimized for PV applications. The modeling presented in this paper can be extended to other solar cell structures or large scale modules. The current study suggests that the thickness and temperature dependencies of the thermal conductivity, convection and conduction resistance might be taken into account and be optimized in thermal runaway issues of thin film devices. The hot spot modeling suggests that the current flowing across the TCO layer can assist the thermal runaway and deformation of neighboring area.

A novel investigation of pressure-induced semiconducting to metallic transition of lead free novel Ba3SbI3 perovskite with exceptional optoelectronic properties.

The structural, electronic, mechanical, and optical characteristics of barium-based halide perovskite Ba3SbI3 under the influence of pressures ranging from 0 to 10 GPa have been analyzed using first-principles calculations for the first time. The new perovskite Ba3SbI3 material was shown to be a direct band gap semiconductor at 0 GPa, but the band gap diminished when the applied pressure increased from 0 to 10 GPa. So the Ba3SbI3 material undergoes a transition from semiconductor to metallic due to high pressure at 10 GPa. The Ba3SbI3 material also exhibits an increase in optical absorption and conductivity with applied pressure due to the change in band gap, which is more suitable for solar absorbers, surgical instruments, and optoelectronic devices. The charge density maps confirm the presence of both ionic and covalent bonding characteristics. Exploration into the mechanical characteristics indicates that the Ba3SbI3 perovskite is mechanically stable. Additionally, the Ba3SbI3 compound becomes strongly anisotropic at high pressure. The insightful results of our simulations will all be helpful for the experimental structure of a new effective Ba3SbI3-based inorganic perovskite solar cell in the near future.

Hole-transport materials based on β-cyanodiarylethene core structure for efficient inverted perovskite solar cells

Three hole-transport materials (MT1–3) were successfully used in inverted perovskite solar cells, and the MT1-based device exhibited excellent efficiency.