Thin Films For Solar Cell Applications Research Articles

Investigation of thermally induced surface composition and morphology variation of magnetron sputtered Sb2Se3 absorber layer for thin film solar cells

One of the most promising semiconductor materials for the development of sustainable thin-film solar cell technology is antimony selenide (Sb2Se3). Its excellent optical and electrical properties have drawn attention lately for potential application in thin-film solar cells. In this study, Sb2Se3 films deposited using the direct current (DC) magnetron sputtering technique have been subjected to a post-annealing process without an extra selenium supply at temperatures between 150 and 450 °C. Without an extra selenium supply, the impact of post-annealing temperature on the surface composition as well as the physical properties of the fabricated films was investigated. The overall evaluations revealed that the post-annealing temperature is highly efficient in altering the physical properties of the Sb2Se3 absorber thin films. We further observed that the post-annealing process improved the crystallization and the heat treatment temperature quite affected preferential orientation. The surface morphology of films exhibited structural deformation at high post-annealing temperatures (> 350 °C). According to optical and electrical characterizations, respectively, the optical energy gap and the resistivity of Sb2Se3 films reduced with an increment in the post-annealing temperature. Based on the XPS result, the variation in temperature of post-annealing led to a change in the surface composition of the films. The findings on the growth of Sb2Se3 thin films indicate the existence of an intermediate growth temperature that permits the growth of Sb2Se3 films to be optimized. The study’s conclusions can serve as a guide to the growth of Sb2Se3 thin films with the desired crystallinity, surface morphology, and composition for thin film solar cell applications.

Ecodesign of Kesterite Nanoparticles for Thin Film Photovoltaics at Laboratory Scale.

This manuscript investigates the efficient synthesis of copper zinc tin sulfide (CZTS) nanoparticles for CZTS thin film solar cell applications with a primary focus on environmental sustainability. Underpinning the investigation is an initial life-cycle assessment (LCA) analysis. This LCA analysis is conducted to evaluate the environmental impact of different synthesis volumes, providing crucial insights into the sustainability of the synthesis process by considering the flows of material and energy associated with the process. Life-cycle assessment results demonstrate that significant reductions to the environmental impact can be made by increasing the synthesis volume of CZTS nanoparticle ink. Using a 5-fold increase in volume can reduce all 11 investigated environmental impacts by up to 35.6%, six of these impacts demonstrating reductions >10% and the amount of global warming potential is reduced by 21.4%. Motivated by the LCA results, COMSOL simulations are employed to understand the fluid flow patterns in large-scale fabrication. Various sizes and speeds of stirrer bars are investigated in these simulations, and it is determined that a 50 mm stir bar at 200 rpm represents the optimal configuration for the synthesis process in a 500 mL flask. Subsequently, large-batch CZTS nanoparticle inks are synthesized using these parameters and compared to small-batch samples. The light absorbers are characterized using Raman spectroscopy and X-ray diffraction, confirming favorable properties with close-to-ideal elemental ratios in large-batch synthesis. Finally, solar cell devices fabricated utilizing CZTSSe absorbers from the large volume synthesis process demonstrate comparable performance to those fabricated using small-batch synthesis, with uniform power conversion efficiencies of around 5% across the substrate. This study highlights the potential of large-volume CZTS nanoparticle synthesis for efficient and environmentally friendly CZTS solar cell fabrication, contributing to the advancement of sustainable renewable energy technologies.

Theoretical Design of Tellurium-Based Two-Dimensional Perovskite Photovoltaic Materials.

In recent years, the photoelectric conversion efficiency of three-dimensional (3D) perovskites has seen significant improvements. However, the commercial application of 3D perovskites is hindered by stability issues and the toxicity of lead. Two-dimensional (2D) perovskites exhibit good stability but suffer from low efficiency. Designing efficient and stable lead-free 2D perovskite materials remains a crucial unsolved scientific challenge. This study, through structural prediction combined with first-principles calculations, successfully predicts a 2D perovskite, CsTeI5. Theoretical calculations indicate that this compound possesses excellent stability and a theoretical efficiency of up to 29.3%, showing promise for successful application in thin-film solar cells. This research provides a new perspective for the design of efficient and stable lead-free 2D perovskites.

Silicon nanohole based enhanced light absorbers for thin film solar cell applications

We proposed a nanohole-based silicon (Si) absorber structure to enhance the light absorption of thin-film Si solar cells. Our proposed structures exhibited excellent performances harnessing the light-matter interaction phenomenon with a few microns of thick Si (3 µm). We employed the finite-difference time-domain method to analyze the optical properties and solved Poisson’s, continuity, and heat transfer equations to analyze the electrical and thermal properties of our proposed structures, operating in the wavelength range from 300 to 1100 nm. We obtained a maximum average absorption of 72.6% for our proposed square hole Si absorber structure. The power conversion efficiency and short circuit current density were calculated to be 20.74% and 39.91 mA/cm2. We achieved polarization-insensitive performance due to the symmetrical nature of the structure. The temperature of our proposed structure was increased by ∼10 K due to light absorption for different ambient temperatures. Moreover, we found our proposed structure was thermally stable over time. Our proposed structures can enhance the absorption of Si nanostructures, which can be conducive to designing Si-thin solar cells for energy harvesting.

Light-absorber engineering induced defect passivation for efficient antimony triselenide solar cells

Antimony selenide (Sb2Se3) has attracted considerable attention thanks to non-toxic, earth-abundant and exceptional optoelectrical properties. Post-selenization treatment is a widely used approach to improve crystallization and passivate defects for chalcogenide thin-film solar cells. The overall performance of the final device is often significantly affected by the process conditions. Herein, we have systematically explored the influence of selenization pressure on Sb2Se3 thin-film solar cells fabricated via sputtering and post-selenization. High-quality Sb2Se3 thin films without visible voids and blisters have been obtained at an optimized selenization pressure of 0.05 Pa. The optimized Sb2Se3 absorber thin film not only mitigates charge carrier recombination but optimizes the back contact of the device. Consequently, a remarkable efficiency of 7.42 % was obtained for the champion device, paving a simple and effective way to fabricate superior Sb2Se3 absorber thin films and highly efficient solar cells. This study is expected to give insights into post-selenization operating conditions for device efficiency enhancement and to further expand the commercial application of Sb2Se3 thin-film solar cells.

AlZnO magnetron sputtered thin film for photovoltaic application

Aluminum zinc oxide (AZO) is a nontoxic and a low-cost material that finds application as a transparent conducting electrode in photovoltaic devices. In this study the (direct current) DC magnetron sputtering of AZO films is carried out at different deposition times of 5, 10, 15, 20 and 25 min’s at room temperature and it’s structural, optical, electrical and morphological properties are studied for its use as a front contact for thin film solar cell application. The structural study suggests that the preferred orientation of grains along (002) plane having hexagonal structure and the optical and the electrical studies suggest that the films show an average transmission of 70% and a resistivity of the order of 10-4Ωcm. On the other hand, the scanning electron microscopy (SEM) images suggest the formation of packed grains having a homogeneous surface. Moreover in order to study the optoelectronic properties of prepared samples, the electronic and optical calculations of the AZO are performed by the first-principles calculations using density functional theory (DFT).

Heterojunction interface engineering of C60 electron transport layer insertion enables efficient Cd-free Sb2Se3 solar cells

Antimony selenide (Sb2Se3) emerges as a promising semiconductor for solar energy conversion, attributed to its high light absorption and excellent photoelectric properties, coupled with notable stability and consistent stoichiometry. Yet, its application in thin-film solar cells is limited by non-radiative recombination losses at suboptimal heterojunction interfaces. Addressing this, we propose a strategy employing a C60 electron transport layer (ETL), thermally evaporated between the Sb2Se3 absorber and SnOx buffer layer. This approach not only increases the carrier density in SnOx but also passivates harmful defects like VO and OH−, thus reducing interfacial recombination. Incorporating C60 ETL improves the fill factor (FF) and open-circuit voltage (VOC) of the Sb2Se3 device, achieving a maximum power conversion efficiency (PCE) of 6.65 %. This finding highlights the significance of ETL-dependent interfacial engineering in enhancing Sb2Se3 solar cell performance, offering a novel and accessible solution to the primary challenge in developing Cd-free Sb2Se3 solar cells.

Monolithic Use of Inert Gas for Highly Transparent and Conductive Indium Tin Oxide Thin Films.

Due to its excellent electrical conductivity, high transparency in the visible spectrum, and exceptional chemical stability, indium tin oxide (ITO) has become a crucial material in the fields of optoelectronics and nanotechnology. This article provides a thorough analysis of growing ITO thin films with various thicknesses to study the impact of thickness on their electrical, optical, and physical properties for solar-cell applications. ITO was prepared through radio frequency (RF) magnetron sputtering using argon gas with no alteration in temperature or changes in substrate heating, followed with annealing in a tube furnace under inert conditions. An investigation of the influence of thickness on the optical, electrical, and physical properties of the films was conducted. We found that the best thickness for ITO thin films was 100 nm in terms of optical, electrical, and physical properties. To gain full comprehension of the impact on electrical properties, the different samples were characterized using a four-point probe and, interestingly, we found a high conductivity in the range of 1.8-2 × 106 S/m, good resistivity that did not exceed 1-2 × 10-6 Ωm, and a sheet resistance lower than 16 Ω sq-1. The transparency values found using a spectrophotometer reached values beyond 85%, which indicates the high purity of the thin films. Atomic force microscopy indicated a smooth morphology with low roughness values for the films, indicating an adequate transitioning of the charges on the surface. Scanning electron microscopy was used to study the actual thicknesses and the morphology, through which we found no cracks or fractures, which implied excellent deposition and annealing. The X-ray diffraction microscopy results showed a high purity of the crystals, as the peaks (222), (400), (440), and (622) of the crystallographic plane reflections were dominant, which confirmed the existence of the faced-center cubic lattice of ITO. This work allowed us to design a method for producing excellent ITO thin films for solar-cell applications.

Nitrogen doped single layer graphene for CZTS-based thin film solar cells

CdS thin films are commonly utilized as a buffer layer in chalcopyrite thin-film solar cells. However, due to the toxic nature of Cadmium (Cd), ongoing efforts are being directed towards exploring alternative options. In this contribution, doped graphene film with remarkable optical and electrical properties has been introduced for the first time as an alternative buffer layer, replacing CdS in CZTS thin-film solar cell application. In this study, nitrogen-doped graphene (N-doped graphene) film was utilized as a substitute buffer layer in the CZTS thin-film solar cell structure, replacing the conventional CdS thin film. For comparative analysis, CZTS/N-doped graphene and CZTS/CdS traditional solar cell structures were fabricated and separately characterized. The CZTS thin films produced were examined through EDX, XRD, SEM, Raman, optical transmission and PL spectroscopy measurements. According to performed analyses, the Cu-poor and Zn-rich kesterite CZTS thin films exhibited a uniform and dense polycrystalline microstructure as observed in surface and cross-sectional SEM images. XRD spectra of the kesterite CZTS thin film displayed predominant peaks corresponding to the (112), (220/204), and (312/116) diffraction planes of the kesterite CZTS phase. Raman spectra showed a dominant peak at ∼336 cm−1 associated with the kesterite CZTS phase. PL emission spectra indicated transitions from the conduction band to defect levels. The CVD-grown doped graphene film exhibited a 3.43 I2D/IG ratio and a 25 cm−1 FWHM of the 2D peak, indicating a single-layer graphene according to Raman analysis. Permanent nitrogen doping with a 2% atomic concentration was confirmed by XPS measurement. The optical transmission measurement of the single layer doped graphene film showed a 95% transmittance value. Nitrogen doping was contributed to decrease the sheet resistance of the graphene film. The Glass/Mo/CZTS/N-doped graphene/i-ZnO/ITO/Al solar cell displayed a VOC of 0.267 V, JSC of 24.6 mA/cm2, FF of 36.46, and η of 2.37%, showing higher FF and Jsc values but lower conversion efficiency compared to the Glass/Mo/CZTS/CdS/i-ZnO/ITO/Al traditional solar cell structure. Hence, the superior working function and transparency properties position the N-doped graphene film as a competitive buffer layer for use in CZTS-based thin-film solar cells.

Nanocrystalline Silicon Layers for the Application in Silicon Heterojunction Solar Cells

After application in thin-film silicon tandem solar cells and in lab-scale silicon heterojunction (SHJ) devices, doped nanocrystalline silicon (nc) layers now arrived on the industrial stage. Despite their challenging deposition, the benefits they hold with respect to even higher device performance compared to their amorphous counterparts are significant and justify additional effort. In this contribution we report on developments towards industrially applicable processes for n- and p-doped silicon layers, nc-Si(n) and nc-Si(p), and their implementation in SHJ cells. Our investigation focuses on the impact of deposition temperature (Tdep) and the need for a thin oxide layer to promote fast nucleation of thin, sufficiently crystalline, doped nc-Si films in a single deposition chamber powered at 13.56 MHz. We identified main challenges for thin film and contact engineering and reached efficiencies of 23.0% with n- and 23.1% with p-type nc-Si approaching cell performances of our process of record based on amorphous Si (a-Si) layers.

Investigation of structural and optical properties of doped and undoped Cd0.75Se0.25 chalcogenide material for thin-film solar cell application

Investigation of structural and optical properties of doped and undoped Cd0.75Se0.25 chalcogenide material for thin-film solar cell application

Effect of Temperature to Fabrication Cigs Solar Cell Using the Sputtering Method

Copper-indium-gallium diselenide (CuInGaSe2) or CIGS is one of the most promising materials for thin film solar cell applications. CIGS solar cells were deposited by sputtering method on ZnO/ZnS/CIGS/Mo arrays. Various parameters in sputtering greatly influence the efficiency of CIGS solar cells such as temperature. Thermal parameters are used to compare the effect of the CIGS layer on optimizing the efficiency of CIGS solar cells. The results show that the CIGS layer deposited using temperature has a crystalline structure, besides that the resulting efficiency is also higher than CIGS solar cells deposited without temperature, namely 0.177%.

Deposition time dependent physical properties of semiconductor CuO sprayed thin films as solar absorber

This study aims to develop copper oxide (CuO) films on standard glass substrates using the spray pyrolysis technique and investigate the effect of different deposition times on their structural, morphological, wettability, optical, and electrical properties to enhance their optoelectronic characteristics. CuO thin films were fabricated at different deposition times (5 to 20 min) with a substrate temperature of 400 °C. X-ray diffraction (XRD) analysis confirmed the crystalline structure of all deposited CuO films, showing a monoclinic phase with preferential orientation along the (111) direction, indicating a well-ordered atomic arrangement. Atomic force microscopy (AFM) examination revealed the influence of deposition time on the surface morphology, with a low roughness value of 13.315 nm observed for the 10 min film compared to 19.432 nm for the 20 min film. Contact angle (CA) analysis showed a transition from hydrophilic to hydrophobic behavior as the deposition time increased, indicating significant changes in surface properties. This transition to a hydrophobic nature (CA = 105°) for the 20 min sample is important for protecting photovoltaic devices from humidity-related degradation, ensuring long-term reliable operation even in challenging conditions. The transmittance of the film in the visible region was low, indicating high absorbance of CuO. The optical gap decreased from 1.98 to 1.61 eV with increasing deposition time, making films suitable as absorber layers in solar cells. Electrical analysis showed improved conductivity with increasing deposition time, leading to a decrease in electrical resistivity (3.77 Ω.cm) and high charge density (1.269 × 1016 cm−3) for the 20 min film. Therefore, the 20 min deposition film with a hydrophobic character exhibited good p-type electrical semiconductor properties and efficient absorption of solar light, making it promising for thin film solar cell applications.

Influence of Hubbard U correction on the structural, electronic and optical properties of Kesterite Cu2XSnS4 (X= Zn, Fe)

The new materials like quaternary chalcogenides semiconductors is an approach towards environment-friendly photovoltaic materials due to their promising potential as thin film solar cell absorbers. This work investigates the density functional theory (DFT) and density functional theory plus Hubbard U (DFT + U) approach on the kesterite phase of sulfide-based chalcogenides, Cu2XSnS4, CXTS (X = Zn and Fe) materials. The inclusion of the potential correlation term, U, plays a vital role in aiding the understanding of the complex many-electron problem, which LDA and GGA from DFT might not adequately describe. It was found that, by applying Hubbard U terms on p and d orbital states, the value of electronic band gaps can be significantly fixed close to the experimental value (∼1.3 eV–1.5 eV). The parametrized dependence of the band gap was well explained. The investigation of optical properties associated with the thin film applications on imaginary parts of the dielectric function shows that both structures have greater absorption at the energy range of 0–5 eV. Moreover, the refractive index and optical absorption show good results for both kesterite CXTS in the most effective wavelength of light to absorb sunlight (visible spectrum), which could exhibit a better finding for a suitable candidate for cost-effective new thin film solar cell application.

Halogenated graphene derivatives as an absorber layer for solar cell applications : A DFT study with vdw correction

Due to the flexible nature and high transparency of Graphene (G) in the ultraviolet to infrared spectrum, it is ideal for thin-film solar cell applications. To use graphene for such a purpose, there is a need to tune its band gap at Fermi level, and the most convenient method is chemical functionalization. So, in this study, we will investigate electronic and mechanical properties, along with the structure and stability analysis of halogenated (X) bilayer and trilayer graphene B(T)LG using density functional theory with van der Waals correction (vdw-GGA). These halogenated B(T)LGs are designed by adsorbing the top and bottom surfaces with fluorine (F) and chlorine (Cl) at the maximum possible separation. BLGs are designed as X/graphene/graphene/X with bernal (AB) and non-bernal (AA) stacking. TLGs are designed as X/graphene/graphene/graphene/X as AAA, ABA, and ABC stacking with 50% X termination at the top and 50% on the bottom side. Chlorination results in weak physisorption while fluorination results in chemisorption. Binding energies Eb found quite higher for fluorinated bilayer graphene derivatives. Halogenation of TLG disturbs Dirac cones at Fermi level in case of fluorine adsorption while remaining unaffected under chlorination. Due to repositioning of some states above EF, provide an additional path for intraband transition, made systems more conductive except for fluorinated bilayer graphenes F-BLGs. A small band gap of 0.2 meV and 0.04 eV appeared at Fermi level of fluorinated non-bernal and bernal configuration, respectively. An E-field applied normal to the plane of F-BLGs can further tune the band gap. Due to underestimation of Band gap using GGA, hybrid functionals HSE06 were used for better estimation.

Study of thermally evaporated Sb2Se3-based substrate-configured solar cell

Antimony selenide (Sb2Se3) has emerged as a promising absorber material for thin film solar cell (TFSC) application. In this work, a (120) oriented substrate-configured Sb2Se3 based TFSC has been fabricated using the thermally evaporated Sb2Se3 thin films. Pre-synthesized bulk Sb2Se3 was used as a source material and the films were subjected to post-deposition selenization. TFSCs were fabricated in a device configuration of Glass/Mo/Sb2Se3/CdS/ITO/Ag. It was found that there is a significant increment in the power conversion efficiency (PCE) with increased Voc and Jsc in the devices, wherein the Sb2Se3 absorber films were subjected to post-deposition selenization compared to the devices made with as-deposited films. TFSC with as grown Sb2Se3 film was showing an efficiency of ∼ 1% with Voc ∼ 208 mV, Jsc∼16 mA cm−2 and fill factor (FF) ∼ 29.9%. The device with selenized Sb2Se3 films showed a power conversion efficiency of 3.38% with Voc, Jsc and FF values of 362 mV, 18.54 mA cm−2 and 50.39%, respectively. The increase in PCE for selenized films is attributed to better grain growth and suppression of selenium vacancy defects. Overall, the findings of this work demonstrate the potential prospects of Sb2Se3 as an absorber material for TFSCs applications and suggest that post-deposition selenization plays a significant role in the enhancement of device efficiency. The obtained results are contributive in the understanding and development of low-cost Sb2Se3-based TFSCs.

Germanium Selenide: A Critical Review on Recent Advances in Material Development for Photovoltaic and Photoelectrochemical Water‐Splitting Applications

Germanium selenide (GeSe), a new 2D semiconductor material, is an attractive material due to its excellent optoelectronic properties, which hold tremendous promise in a wide range of applications, including thin‐film solar cells (TFSCs) and photoelectrochemical (PEC) water splitting. Several attempts have been made to date in theoretical studies, high‐quality GeSe material synthesis, evaluating absorber properties, and developing efficient TFSCs and PEC devices. Using existing device topologies for chalcogenide materials, TFSCs with 5.2% efficiency and a PEC device with 3.17% solar‐to‐hydrogen efficiency have been recently developed. To enable its potential in high performances of TFSCs and PEC devices for future large‐scale applications, further improvement in materials quality, device design, and development is required. In this regard, this review provides a comprehensive overview of current advances made in GeSe material development and applications in TFSCs and PEC devices. First, the fundamental properties of GeSe material, theoretical studies, as well as in‐depth synthesis methods, are outlined. Then, key developments in GeSe‐based TFSCs and PEC devices are discussed with an emphasis on device designs. Finally, the most prominent impediments to a fundamental understanding of materials are highlighted, and perspectives on future research directions for improving material quality and device efficiency are provided.

Design of CZTS/CZTSe tandem solar cells with enhanced performance

The replacement of toxic and expensive materials with non-toxic, earth-abundant alternatives is an urgent necessity in the field of solar cells. Due to their environmentally friendly and optical properties, CZTS and CZTSe kesterite materials have been proposed as promising alternative compounds in thin film solar cell applications. In this study, a numerical investigation of a CZTS/CZTSe tandem solar cell structure is conducted using SILVACO software. In this structure, CZTS and CZTSe serve as the main absorbers in the top and bottom sub-cells, respectively. However, the bottom sub-cells require thick absorbers, which leads to a decrease in overall performance due to the limited diffusion length of minority carriers in the applied materials. A separate study of individually top and bottom cells was conducted, and their results closely matched those reported by world champions. Effects of the top absorber thickness were examined for the tandem configuration, which resulted in a conversion efficiency (η) of 15.71%. In order to enhance the performance of the tandem solar cell, a creation of a diffusion electric field in the absorbers of the sub-cells through gradient doping is proposed. The results demonstrated a significant improvement in performance, with gradient doping densities of 2 × 1014-1019 cm−3 and 1.5 × 1015-1019 cm−3 in the CZTS and CZTSe layers, respectively, yielding a remarkable conversion efficiency of 23.38%.

A comparative study of Cu2ZnSn(SxSe1−x)4 nanoparticles for solar cells: From chemical synthesis to devices

Thin-film solar cells using quaternary compounds Cu2ZnSn(SxSe1−x)4 (0 ≤ x ≤ 1; CZTSe, CZTSSe, or CZTS) as absorber materials have attracted a lot of attention from the photovoltaic research community. Traditionally, vacuum-based techniques have been used for the synthesis of Cu2ZnSn(SxSe1−x)4 absorbers. In this work, an easy, less toxic, non-vacuum, single-reaction chemical route is used for the synthesis of Cu2ZnSn(SxSe1−x)4 (x = 0.0,0.4,1.0) nanoparticles. Using structural characterization techniques, the presence of kesterite phase in the as-synthesised nanoparticles is confirmed. The surface micrographs revealed increase in nanoparticle grain size with the selenium doping and nearly stoichiometric composition with compact morphology of nanoparticles. Further, the optical characterization of as-synthesised nanoparticles exhibited bandgaps in the range 1.52 – 1.02 eV which are optimal for thin film solar cell applications. The fabricated solar cells using synthesised compounds exhibited promising photo response capabilities with a highest efficiency of 0.752% for Cu2ZnSn(S0.4Se0.6)4 absorber-based device under AM1.5 illumination without any buffer layer. Results presented in this work indicate the suitability of the kesterite compounds synthesized through the chemical route as absorber materials for cheap solar cells.

A periodic corrugated metallic nanomesh for broadband light absorption enhancement

Plasmonic nanostructures have been demonstrated for their application in thin film solar cells to enhance absorption. Of particular concern is the novel design, enabling the broadband absorption enhancement. Here, we proposed and implemented a periodic corrugated Au nanomesh for broadband light absorption enhancement. By combining plasmon treatment of pre-stretched substrate and nanosphere lithography, the Au nanomesh on the nanocorrugation with different period has been realized. Compared to the planar nanomesh, the periodic corrugated nanomesh exhibits observable absorption enhancement at broad wavelength range, especially from 700[Formula: see text]nm to 1000[Formula: see text]nm, which is of significance in bring solar energy up to more utilization due to poor absorption of thin film solar cells at the near-infrared band. The enhancement attributes to the spatially geometry deformation of nanomesh supported more plasmonic resonance at the different adjacent frequency. Also, the absorption enhancement is relative to the period of corrugation, which caused by the variation of geometry deformation amplitude of nanomesh. This periodic corrugated metallic nanomesh provides an alternative nanostructured electrode to broadband absorption enhancement for thin film solar cell application.