Photovoltaic Absorber Research Articles

Investigation of a potential photovoltaic absorber based on first principles spectroscopic screening of chalcogenide perovskites: CaZrX3 (X = S, Se)

Investigation of a potential photovoltaic absorber based on first principles spectroscopic screening of chalcogenide perovskites: CaZrX3 (X = S, Se)

Structural, electronic, magnetic, optical and thermoelectric properties of ferromagnetic double perovskites K2ScCoX6 (X = F, Cl): A first-principles study

To identify a promising alternative to lead-based materials for solar cell application, we investigated the different physical properties of K2ScCoX6 (X = F, Cl) perovskites. Both materials have ferromagnetic ground state. The obtained optimize lattice constants are found to be 8.48 Å and 10.04 Å for K2ScCoF6 and K2ScCoCl6 respectively. Our finding indicate that these materials exhibit excellent structural, mechanical, the thermal stability, as evidenced by their Goldsmith’s tolerance factor, elastic parameters, and negative formation energies. The formation energy is found to be -2.4 and -2.1 eV/atom for K2ScCoF6 and K2ScCoCl6 respectively. The electronic properties reveals that both materials have semiconducting nature. Notably, we observed low direct bandgap of 0.93 eV for K2ScCoF6 and 1.22 eV for K2ScCoCl6, which contrast with the typically large bandgap values reported for most halide double perovskite. The calculated values of Poisson’s and Pugh’s ratios, along with positive Cauchy’s pressure, suggest a ductile nature for these compounds. Additionally, the optical properties show high absorption and optical conductivity, coupled with low reflectivity and minimal energy loss in lower energy ranges. These results suggest that the halogen-based double perovskite materials have significant potential as photovoltaic absorber materials in solar cell applications. Furthermore, their higher Seebeck coefficients, power factors and low thermal conductivity at room temperature underscore their potential for thermoelectric applications.

Electronic and optical properties of Sb2Se3 and Sb2S3: theoretical investigations

Abstract In recent developments in solar energy research, Sb2Se3 and Sb2S3 emerge as environment friendly photovoltaic absorber materials, distinguished by their narrow bandgap and high absorption coefficient. Theoretical investigations to determine the electronic structure, effective density of states, dielectric function, and absorption coefficient of Sb2Se3 and Sb2S3 crystals have been performed using first-principle methods. The results reveal band gap values of about 0.822 and 1.757 eV (PBE method), 1.114 and 1.778 eV (HSE06 method) for Sb2Se3 and Sb2S3, respectively. The valence band and conduction band edges are primarily formed by Se 4p, S 3p, and Sb 5p hybridized orbitals. The effective density of states (DOS) exhibit magnitudes on the order of 1019 cm−3. Notably, anisotropic characteristics are observed in the real and imaginary parts of the dielectric function. Furthermore, the absorption coefficient surpasses 105 cm−1 at 1 and 1.2 eV for both Sb2Se3 and Sb2S3. The result indicates that these highly efficient absorber materials are suitable in collecting solar energy.

Comprehensive review of CZTS deposition techniques and experimental insights into low-temperature chemical synthesis of CZTS thin film solar cells

This review describes various deposition methods and subsequent processes for synthesizing Cu₂ZnSnS₄ thin films, a promising chalcogenide photovoltaic absorber material from an earth-abundant, non-toxic element inventory. CZTS promises a benign alternative route in contrast to conventional CIGS and CdTe photovoltaics based on rare and expensive elements. The review classifies CZTS fabrication as either a one-step or a two-step process and then elaborates on the different processes involved, such as PLD, electrodeposition, spray pyrolysis, spin coating, and sputtering. Investigation has been carried out in this work for each technique with respect to respective advantages and deficiencies regarding scalability, film quality, and any need for sulfurization to improve crystallinity and phase purity for efficient photovoltaic performance. This work also gives an insight into the experimental study through low-temperature chemical synthesis methodology for depositing CZTS films, while combining techniques such as spin coating and sulfurization in a controlled manner in order to achieve optimized material composition and electronic properties. Characterization through XRD and XPS revealed optimal stoichiometry with minor secondary phases. From this, one can consider that CZTS could be a very promising material candidate toward a scalable, efficient solar cell. The aim of this work is to underpin further advances in CZTS-based photovoltaics by optimization of deposition strategies and improvement in film quality for sustainable energy applications.

Prediction of the physics properties of solar material Cu2BaSnS4

Recently, there has been a suggestion that Cu2BaSnS4 could be a promising candidate for a photovoltaic absorber with a wide band gap. The study primarily examined the structural, along with the mechanical and thermodynamic characteristics of Cu2BaSnS4. In addition, a study was performed to examine the presentation and representation of three-dimensional (3D) characteristics related to linear compressibility, shear modulus, and Young's modulus. The investigation into thermodynamic characteristics was calculated and analyzed.

Interface-enhanced germanium selenide solar cells comprising an ultrathin and uniform antimony selenide buffer layer via hydrothermal approach

Germanium selenide (GeSe) is a promising thin film photovoltaic absorber material owing to its excellent optoelectronic properties, high stability, and low toxicity. Interface engineering by introducing an ultrathin antimony selenide (Sb2Se3) buffer layer between the CdS electron transport layer and GeSe absorber layer is an effective technique for enhancing solar cell performance. However, the key to this technique is the fabrication of a uniform and smooth Sb2Se3 buffer layer with minimal thickness. In this study, instead of the conventional closed-space sublimation method, a hydrothermal method was employed to slowly grow an Sb2Se3 buffer layer with a thickness of approximately 8 nm. The Se/Na2SO3 molar ratio in the selenium source during the hydrothermal synthesis was adjusted; a molar ratio of 1:2 led to an uneven Sb2Se3 buffer layer thickness, whereas a molar ratio of 1:10 resulted in the formation of Sb2O3 particles on the buffer layer surface. When the Se/Na2SO3 molar ratio was 1:6, a smooth, uniform, dense, and impurity-free Sb2Se3 buffer layer was obtained, achieving the highest efficiency of 3.33 % in a GeSe solar cell. Moreover, GeSe solar cells with hydrothermally grown Sb2Se3 buffer layers demonstrated superior device interface properties and efficiency comparable with those using Sb2Se3 buffer layers deposited via closed-space sublimation. This technique offers an effective method for steadily improving the performance of GeSe solar cells.

Cu2ZnSnS4 Nanoparticles as an Efficient Photocatalyst for the Degradation of Diclofenac in Water

Dangerous emerging water micropollutants like Diclofenac are harming ecosystems all over the planet, and immediate action is needed. The large bandgap photocatalysts conventionally used to degrade them need to be more efficient. Cu2ZnSnS4, a well-known light absorber in photovoltaics with a bandgap of 1.5 eV, can efficiently harvest an abundant portion of the solar spectrum. However, its photocatalytic activity has so far only been reported in relation to the degradation of organic dyes, and it is usually used as a benchmark to assess the activity of a photocatalyst without testing its actual potential on a hazardous water micropollutant conventionally encountered in primary and secondary waters. Here, we report the promising photocatalytic activity of Cu2ZnSnS4 nanoparticles in the degradation of Diclofenac, chosen as a benchmark for dangerous emerging water micropollutants.

A-Site Cation Chemistry in Halide Perovskites.

Metal halide perovskites are an important class of semiconductors now being implemented as photovoltaic absorbers and explored for light emission, among other device applications. The semiconducting properties of halide perovskites are deeply intertwined with their composition and structure. Specifically the symmetry, tilting, and distortions of the metal halide octahedra impact the band structure and other optoelectronic properties. In this review, we examine the various compositions of monovalent A-site cations in three-dimensional (3D) halide perovskites AMX3 (M = divalent metal; X = halide). We focus on how the A-site cation templates the inorganic metal-halide perovskite framework, resulting in changes in the crystal structure symmetry, as well as M-X bonding parameters, summarized in a comprehensive table of AMX3 structures. The A-site cation motion, effects of alloying, and 2D Ruddlesden-Popper perovskite structures with unique A-site cations are further overviewed. Correlations are shown between these A-site cation dominated structural parameters and the resulting optoelectronic properties such as band gap. This review should serve as a reference for the A-site cation structural chemistry of metal halide perovskites and inspire continued research into less explored metal halide perovskite compositions and structures.

Introduction of the distribution of Cs in Cu(In,Ga)Se2 photovoltaic absorbers following post-deposition treatment with CsF

In recent years, the device performance of Cu(In,Ga)Se2 (CIGS) solar cells has been improved by heavy alkali element post-deposition treatment (Alkali-PDT). Therefore, it is of great significance to study the mechanism of enhancing CIGS device performance through Alkali-PDT. One aspect to be studied is the distribution of heavy alkali elements in the absorber. In this work, the distribution of the heavy alkali element Cs in the absorber after post deposition treatment of CsF (CsF-PDT) and its effect on the device performance are investigated. The experimental results indicate that Cs can enter both the grain interior (GI) and grain boundaries (GB) via the Cu vacancy (VCu). By comparing the distribution of Na and Cs in the film, it can be noticed that Na is mainly distributed at the GB, while Cs is not differently distributed between the GB and GI. This is mainly due to the fact that the presence of Na at GB inhibits the accumulation of Cs there. The distribution of Cs is beneficial in improving the device’s performance by passivating defects, such as InCu.

Exploring optoelectronic, optical thin films, mechanical and thermal transport properties of bromide double perovskites Rb2Ag(Ga/In)Br6 for photovoltaic and thermoelectric applications

Lead-free double halide perovskites like Rb2Ag(Ga/In)Br6 have demonstrated themselves potential candidates in solar cell research owing to their environmental friendliness, stability, and exceptional performance. This study comprehensively analyzes the structural, mechanical, optoelectronic and optical coating features, as well as thermodynamic and thermoelectric properties of two Rb2AgGaBr6 and Rb2AgInBr6 compounds. Using the Wien2k code with GGA + mBJ exchange-correlation potentials, we confirm their structural stability in cubic phase Fm-3m and identifying them as direct band gap semiconductors (Γ → Γ) of 0.38 eV and 1.0644 eV, respectively. Then, optical analysis reveals broad absorption bands across visible and ultraviolet wavelengths, making them suitable for photovoltaic absorbers. Finally, the thermoelectric investigations under varying temperatures show favourable properties, such as a high Seebeck coefficient with poor electronic thermal conductivity. This also yields exceptional value (0.96 and 0.994 for Rb2AgGaBr6, Rb2AgInBr6, respectively) of figure of merit (ZT) at room temperature and chemical potential μ-μ0 = - 0.09eV near the Fermi energy level, enhancing their potential for thermoelectric applications. These findings underscore the versatility and promising future of Rb2Ag(Ga/In)Br6 as important semiconductors processing for optoelectronic, thermoelectric, and mechanical devices.

Theoretical Optimization of an Earth-Abundant and Environmentally Friendly Photovoltaic Absorber Cu3PSe4 from First-Principles Study to Device Simulation.

To seek an earth-abundant and environmentally friendly absorber for thin-film solar cells, Cu3PSe4 is investigated by first-principles calculations and device simulations. We demonstrate that the compound has a suitable band gap width of 1.3 eV as well as a high sunlight absorption coefficient. However, drawbacks like small electron affinity, high hole concentration, large lattice mismatch with CdS, etc., are revealed, which may degrade the photovoltaic performance. To address those shortcomings, we propose (1) to optimize the carrier concentration by preparing the samples at low temperature and under a Cu-rich environment, (2) to replace the CdS buffer layer by a more suitable wide-gap semiconductor with smaller lattice mismatch, and (3) that the selected buffer layer should have small electron affinity in order to reduce the open-circuit voltage losses. After implementation of these optimization approaches, the device simulations demonstrate that the power conversion efficiency reaches 17.7% for a solar cell with the configuration Mo/Cu3PSe4/WS2/n-ZnO. The combination of first-principles calculations at the atomistic level and device simulations at the macroscopic level provides an appropriate approach to design ideal solar cells.

DFT electronic structure investigation of chromium ion-implanted cupric oxide thin films dedicated for photovoltaic absorber layers

This study explores the enhancement of cupric oxide (CuO) thin films for photovoltaic applications through chromium doping and subsequent annealing. Thin films of CuO were deposited on silicon and glass substrates using reactive magnetron sputtering. Chromium was introduced via ion implantation, and samples were annealed to restore the crystal structure. The optical and structural properties of the films were characterized using X-ray diffraction, spectrophotometry, and spectroscopic ellipsometry. Results indicated that implantation reduced the absorbance and conductivity of the films, while annealing effectively restored these properties. Sample implanted with 10 keV energy and 1 × 1014 cm−2 dose of Cr ions, after annealing had sheet resistance of 1.1 × 106 Ω/sq compared to 1.7 × 106 Ω/sq for non implanted and annealed CuO. Study of crystalline structure confirmed the importance of annealing as it reduced the stress present in the material after deposition and implantation. Density Functional Theory (DFT) calculations were performed to investigate the electronic structure and optical properties of CuO with varying levels of chromium doping. Calculations revealed an energy gap of 1.8 eV for undoped CuO, with significant changes in optical absorption for doped samples. Energy band gap determined using absorbance measurement and Tauc plot method had value of 1.10 eV for as deposited CuO. Samples after implantation and annealing had energy band gap value increased to about 1.20 eV. The study demonstrates that chromium doping and subsequent annealing can enhance the optical and electronic properties of CuO thin films, making them more efficient for photovoltaic applications.

Evaluating Photovoltaic Conversion Performance under Artificial Indoor Lighting

Several photovoltaic technologies, based on different semiconductor absorbers with band-gap energy in the range Eg = 1.0–1.5 eV are currently sharing the market for outdoor applications. These photovoltaic cells are designed to achieve an optimal photovoltaic conversion under solar illumination (represented by the standard AM1.5 global spectrum), but their performance changes under different artificial indoor lights. Here, the detailed balance principle that was first applied for an ideal photovoltaic absorber under solar radiation is now used by considering the actual spectra of four typical indoor lamps: incandescent, halogen, metal halide and white LED. For each particular illumination source, the theoretical maximum for short-circuit current, open-circuit voltage and maximum power point have been calculated and represented as a function of the absorber band-gap energy. Furthermore, the optical absorption spectra of some semiconductors with optimal solar conversion efficiencies are used to estimate their comparative performance under the various artificial light sources. It has been found that wide band-gap absorbers (Eg~1.9 eV) are needed to achieve a light-to-electricity conversion efficiency of 60% under LED illumination or 31% with metal halide bulbs, while a lowest band-gap energy of about 0.8 eV is required to obtain a maximum efficiency of 24% with incandescent and halogen lamps.

A first-principles investigation on a new group of diamond-like semiconductors Cu4-II-Ge2-VI7 (II = Zn, Cd and VI = S, Se) as photovoltaic absorbers

Many diamond-like semiconductors with tetrahedral bonds, such as Si, CdTe and Cu(In,Ga)Se2, have been utilized as absorbers in photovoltaics (PV). In this work, a novel group of diamond-like compounds, namely Cu4-II-Ge2-VI7 with II = Zn/Cd and VI = S/Se, have been explored by first-principles means. From the calculations of the electronic structures and related optical properties, we have demonstrated that all these quaternaries have direct-type band structures, while their band gap energies are not suitable for PV applications. By anionic alloying, however, the width of the band gaps can be tuned to the desired energy. For example, the Cu4ZnGe2S4Se3 alloy has a suitable band gap of 1.34 eV. Our work provides the support and perspective for further experimental research on this group of semiconductors and their alloys as potential candidates in PV technologies.

Real-Time Spectroscopic Ellipsometry for Flux Calibrations in Multi-Source Co-Evaporation of Thin Films: Application to Rate Variations in CuInSe2 Deposition.

Flux calibrations in multi-source thermal co-evaporation of thin films have been developed based on real-time spectroscopic ellipsometry (RTSE) measurements. This methodology has been applied to fabricate CuInSe2 (CIS) thin film photovoltaic (PV) absorbers, as an illustrative example, and their properties as functions of deposition rate have been studied. In this example, multiple Cu layers are deposited step-wise onto the same Si wafer substrate at different Cu evaporation source temperatures (TCu). Multiple In2Se3 layers are deposited similarly at different In source temperatures (TIn). Using RTSE, the Cu and In2Se3 deposition rates are determined as functions of TCu and TIn. These rates, denoted Reff, are measured in terms of effective thickness which is the volume per planar substrate area and accounts for surface roughness variations with deposition time. By assuming that all incident metal atoms are incorporated into the films and that the atomic concentrations in the deposited material components are the same as in single crystals, initial estimates of the Cu and In atom fluxes can be made versus TCu and TIn. Applying these estimates to the co-evaporation of a set of CIS films from individual Cu, In, and Se sources, atomic concentration corrections can be assigned to the Cu and In2Se3 calibration films. The corrections enable generation of a novel calibration diagram predicting the atomic ratio y = [Cu]/[In] and rate Reff within the TCu-TIn plane. Using this diagram, optimization of the CIS properties as a PV absorber can be achieved versus both y and Reff.

Computational Investigation of Structural, Electronic and Optical Properties of Ternary Chalcogenide TLGaQ2 Monoclinic Compounds: a First Principle Study

Purpose: This paper aim to investigate and predict by simulation the impact of the substitution of Q-site atom (Q꞊S, Se) on the TIGaQ2 monoclinic compounds for the first time, along the three main polarizations of the incident wave directions [100], [010] and [001]. Theoretical Framework: This study focuses mainly on ternary chalcogenide compounds TlGaQ2 (Q= S, Se) from ABQ2 family to highlight the objective resources aimed at promising prospects offered for them. Design/Methodology/Approach: A series of ab-initio calculations based on the (PW+PP) method within the density functional theory DFT framework were carried out with CASTEP code for the simulation of their physical properties (structural, electronic-optical). The exchange correlation potential was treated within the generalized gradient approximation (GGA) implemented in the CASTEP code and expressed by the PBE functional. Findings: The equilibrium lattice parameters are in good agreement with the available experimental results. The calculated band structure shows that are direct bandgap semiconductor nature 1.92eV (1.41eV) for TlGaS2 and TlGaSe2 respectively with a great potential for photovoltaic solar cell absorber materials. A set of optical parameters were calculated including the complex dielectric function, the reflective index, reflectivity, the absorption coefficient and loss function. The optical properties obtained revealed very interesting optical properties exhibiting strong optical absorption in UV range up to (~2x105cm-1) for both compounds making them appropriate for photovoltaic solar-cell absorber materials. Furthermore, low reflectivity and energy loss function are shown within in the visible and ultraviolet energy range, allowing them to be promising materials in several optoelectronics applications likes photosensitive devices. Implications: All these findings results show a successful accurately prediction for chalcogenide materials behavior and will be helpful for future studies allowing a better understanding of their potential applications in modern photovoltaic technologies as well as within UV ranges for optoelectronics applications.

Dependence of Crystal‐Field Energy on Strain/Stress Sensed by Temperature Variation of Chalcopyrite Semiconductor (Optical) Band‐Gap for Efficient Band‐Gap Tuning in the CIS/CIGS Photovoltaic

Chalcopyrite selenide single crystals and epitaxial layers (CuIn1−xGaxSe2, x = 0.00, 0.08, 0.19, 1.00) were characterized by temperature‐dependent photoreflectance (PR), photoluminescence (PL), photoluminescence–excitation (PLE), and variable excitation‐energy photoluminescence (VEPL) spectroscopy. The transition energies Ea, Eb, and Ec of both CuInSe2 (CIS) and CuGaSe2 (CGS) layers sensed by PR were higher than the energies of single crystals. CuInSe2 and CuGaSe2 grown on GaAs(001) underlie compressive and tensile stresses, respectively, which lead to band‐gap broadening in CIS and band‐gap narrowing in CGS. The increase of the Ea, Eb, Ec energies of tensely stressed CuGaSe2 layers to energies higher than those of the bulk originates from the stress dependence of the non‐cubic crystal field. Band‐gap scanning of the CuGaSe2 layer with continuous‐wave Ti:sapphire‐laser confirmed the absence of correlation between band‐gap readjustment and intrinsic defects. The energy of the band‐edge exciton EFE, in the PL‐spectra, was lower than the Ea transition energy, in the PR‐spectra, which is assigned to partial quenching of ΔCF with the increase of external tensile stress by gallium‐segregation at the chalcopyrite/GaAs‐interface. The stress dependence of ΔCF is negligible in CuInSe2 and linear, with a rate of 9 meV/100 MPa, in CuGaSe2. It is revealed that the energy band‐gap of photovoltaic chalcopyrite absorbers can be tuned by simultaneous built‐in and external lattice‐tuning.

Structure-Property Correlations in CZTSe Domains within Semiconductor Nanocrystals as Photovoltaic Absorbers.

Semiconductor nanocrystals (NCs) are promising materials for various applications. Two of four recently identified CuαZnβSnγSeδ (CZTSe) domains demonstrate metallic character, while the other two exhibit semiconductor character. The presence of both metallic and semiconductor domains in one NC can hugely benefit future applications. In contrast to traditional band gap studies in the NC community, this study emphasizes that NC domain interfaces also affect the electronic properties. Specifically, the measured band gap of a tetrapod-shaped CZTSe NC is demonstrated to originate from two specific domains (tetragonal I and monoclinic P1c1 Cu2ZnSnSe4). The heterojunction between these two semiconductor domains exhibits a staggered type-II band alignment, facilitating the separation of photogenerated electron-hole pairs. Interestingly, tetrapod NCs have the potential to be efficient absorber materials with higher capacitance in photovoltaic applications due to the presence of both semiconductor/semiconductor interfaces and metal/semiconductor "Schottky"-junctions. For the two photo-absorbing domains, the calculated absorption spectra yield maximum photon-absorption coefficients of about 105 cm-1 in the visible and UV regions and a theoretical solar power conversion efficiency up to 20.8%. These insights into the structure-property relationships in CZTSe NCs will guide the design of more efficient advanced optical CZTSe materials for various applications.

Investigating the preparation process of excellent Cu3VSe4 absorption layer prepared by amine-thiol system

Cu3VSe4 material has become a new kind of photovoltaic absorber due to its optical bandgap matching light-absorbing, abundant elements in crust, and high light absorption coefficient. Here, we prepared Cu3VSe4 thin films by amine-thiol method and investigated the preparation process of excellent Cu3VSe4 absorption layer for the first time. The effects of various Cu/V ratios on the morphology, structure, and electrical properties of the films are studied. XRD and Raman results show that pure-phase Cu3VSe4 films are obtained with the Cu/V ratios lower than 2.9. SEM results simply adjusting the Cu/V ratio cannot obtain a compact selenized Cu3VSe4 thin films. The best crystallinity of thin film with 2.8 of Cu/V ratio is named as Cu2.8VSe4 and selected as the representative. Though optimizing the selenization conditions, a dense morphology and good electrical properties of the absorption layer can be prepared under 570 °C of the high-temperature process. Our findings can lay the favorable foundation for high-efficiency Cu3VSe4 devices.

Influence of PVP on the properties of solvothermally synthesized famatinite nanoparticles: Structural, morphological and optical insights

Famatinite (Cu3SbS4) nanoparticles were synthesized through a solvothermal approach using various polyvinylpyrrolidone (PVP) ratios as a capping agent with a binary solvent of ethylene glycol and water in equal parts. Incremental additions of PVP, ranging from 0 to 1.5 g, exerted significant influence on the material's characteristics. Through comprehensive analysis involving X-ray diffraction, Raman spectroscopy, Scanning electron microscopy (SEM) with Energy dispersive spectrometer (EDS), and UV diffuse reflectance spectroscopy, critical insights were obtained. XRD analysis confirmed the tetragonal crystal structure and revealed reduced crystallite sizes due to the incorporation of PVP. Raman spectroscopy validated the presence of pure famatinite phase with 0.5 g and 1.0 g PVP. SEM analysis uniformly depicted a spherical morphology in all samples, emphasizing PVP's role in mitigating nanoparticle agglomeration. UV diffuse reflectance spectroscopy disclosed direct bandgaps falling within the 0.88 – 0.97 eV range. The collective findings highlighted the substantial impact of PVP in the binary solvent on the structural, morphological, and optical properties of Cu3SbS4 nanoparticles. These results underscore the potential application of these tailored nanoparticles as promising candidates for advanced photovoltaic absorber materials.