Thin Film Solar Cells Research Articles

Improving the power conversion efficiency of RbPbBr3 absorber based solar cells through the variation of efficient hole transport layers

Novel rubidium-lead-bromide (RbPbBr3) hybrid perovskite solar cells (HPSCs) are gaining attention from researchers because of their exceptional semiconductor qualities. Researchers have been examining RbPbBr3-based single junction photovoltaic cells in a number of configurations, including two different hole transport layers (HTL) made of V2O5 and MoTe2 and an electron transport layer (ETL) made of CdS. We investigated elements including band alignment, defect density, layer thickness, doping concentration, interface defect density, carrier concentration, generation, recombination, open circuit voltage (VOC), short circuit current (JSC), fill factor (FF), and power conversion efficiency (PCE) through extensive numerical analysis using SCAPS-1D simulation software. According to the research, the V2O5 HTL design, with a VOC of 1.1433 V, a JSC of 34.3969 mAcm−2, and an FF of 86.63 %, attained the maximum PCE at 34.06 %. By contrast, the MoTe2 HTL configuration's PCE was 31.66 %, with a VOC of 1.0388 V, a JSC of 34.4977 mAcm−2, and an FF of 88.35 %. These results provide insightful information and a workable strategy for creating RbPbBr3-based, reasonably priced thin-film solar cells.

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.

Understanding phase evolution in CuSbS2 absorbers via rapid sulfurization of Cu/Sb/Cu stacks

Copper-antimony-sulfide (CuSbS2) is a promising absorber for use in thin-film solar cells. In this study, we report the fabrication of CuSbS2 films by sulfurizing sequentially evaporated Cu/Sb/Cu stacks at 450 °C for 5 min and investigate the influence of Cu thickness (Cu-poor, Cu-correct, and Cu-rich) on the phase evolution. The film prepared with a Cu-poor composition exhibited the formation of phase-pure CuSbS2 with several micron-sized grains uniformly grown on the surface, a bandgap energy of 1.55 eV, an electrical resistivity of 16.8 Ω cm, and a carrier concentration of 7.27 × 1017 cm−3. The CuSbS2 film fabricated with the stoichiometric and Cu-rich composition contained a minor Cu12Sb4S13 and Cu3SbS4 secondary phases with increased grain size, decreased bandgap (1.55–1.51 eV), electrical resistivity (8.63–5.59 Ω cm), and increased carrier concentration (1.63–2.28 × 1018 cm−3 cm−3). This investigation reveals that a slightly Cu-poor composition is required for the growth of phase-pure CuSbS2 films suitable for thin-film solar cells.

Impact of nanoscale Cu (I) precursors prepared by solution process on large-area CdTe solar cells

In recent years, the study of Cu (Ӏ) precursors in high-performance CdTe thin-film solar cell devices has received increasing attention. However, few studies have been reported on nanoscale Cu (I) precursors in large-area CdTe devices (≥1 cm2). Here, three different Cu (Ӏ) nano precursors have been rapidly prepared by solution method (CuCl ethanol solution, CuI acetonitrile solution, and CuSCN aqueous ammonia solution) and their effects on the performance of commercial large-area CdTe thin-film solar cells have been investigated. The results show that the distribution amount and uniformity of the nano precursor particles on the CdTe back surface have a large impact on the device performance. The CuCl nanoparticles are more uniformly distributed and the device performance is more excellent. CuI nanoparticles easily formed clusters at grain boundaries. Denser distribution of CuSCN nanoparticles. The thermal diffusion conditions (temperature, time and precursor concentration) have a significant effect on the device performance, but the most reasonable thermal diffusion conditions tend to be the same for all devices. This suggests that the thermal diffusion conditions are determined by the nature of the CdTe absorber layer itself and are not interfered by different nano precursors.

A Revisit of Crystallization in Tin Halide Perovskite Thin Films: From Nucleation, Intermediate to Crystal Growth

AbstractPerovskite solar cells (PSCs) are exuding unique charm in the third generation of thin film solar cell technology with high power conversion efficiency (PCE) and low production cost. Recently, the lead‐free tin halide perovskite solar cells (TPSCs) have drawn significant research interests due to the advantages of low toxicity, near‐ideal bandgap and high carrier mobility. However, the rapid crystallization and easy oxidation limits the film quality and final performance of the solar cells. Therefore, the deposition of high‐quality tin halide perovskite films is key to the advance of TPSCs. In this review, the classical theory of solution nucleation and crystal growth is reviewed and correlated to the practical deposition of tin perovskite film. The physicochemical properties of tin perovskite with those of lead counterpart and the differences in the crystallization process is carefully compared. On this basis, recent regulation strategies are systematically summarized in terms of the nucleation management, intermediate phase engineering and crystal growth regulation. In addition, the preparation of mixed tin‐lead (Sn‐Pb) PSCs toward high performance is also discussed, as well as the limiting factors for device performance and stability. Finally, the future challenges and prospects of the crystallization regulation are discussed toward more efficient and stable TPSCs.

Effect of annealing temperature on the structural, morphological, compositional, and optical characteristics of CNCTS thin films for solar cells

The compound Cu2Ni0.75Co0.25SnS4 (CNCTS) was synthesized using the spin-coating technique. Analysis via X-ray diffraction and Raman spectroscopy revealed the formation of a cubic structure at 350 °C, with a lattice parameter of 5.40 Å and a crystallite size of 51 A°, with no secondary phase detected. Scanning electron microscopy and energy dispersive spectroscopy examination showed that the annealed CNCTS sample at 350 °C for 1 h displayed surface morphologies that were nearly uniform, dense, and rough, with a composition close to stoichiometric. UV–Visible–Near infrared analysis indicated that the bandgap energy of the annealed CNCTS at 350 °C is 1.39 eV, rendering it highly suitable for low-cost photovoltaic applications.

A theoretical investigation of MoS2-based solar cells with CdS electron transport layer and V2O5 hole transport layer for boosting performance

Researchers are becoming more interested in molybdenum disulfide (MoS2)-based photovoltaic cells because of their exceptional semiconducting qualities. The use of CdS ETL and V2O5 HTL in thin-film solar cells based on MoS2 has been studied. The effects of electron and hole concentration, generation and recombination, FF, VOC, JSC, band alignment, defect density, absorber layer thickness, buffer layer thickness, interface defect density, and PCE have all been thoroughly numerically analyzed. The SCAPS-1D simulation software was applied to conduct the aforementioned investigation. The study found that the V2O5 HTL design reached the maximum PCE at 35.13 % with a VOC of 1.0738 V, a JSC of 36.8308 mAcm−2, and a FF of 88.83 %. On the other hand, without HTL configuration, the PCE was 23.05 %, the VOC was 0.9049 V, the JSC was 29.4614 mAcm−2, and the FF was 86.45 %. These findings offer useful data and a practical plan for developing inexpensive, MoS2-based thin-film solar cells.

Disorder induced band gap lowering in kesterite type Cu2ZnSnSe4 and Ag2ZnSnSe4: a first-principles and special quasirandom structures investigation

Quaternary chalcogenides, i.e. Cu2ZnSnS4, crystallising in the kesterite crystal structure have already been demonstrated as potential building blocks of thin film solar cells, containing only abundant elements and exhibiting power conversion efficiencies of about 14.9% so far. However, due to the potential presence of several structurally similar polymorphs, the unequivocal identification of their ground state crystal structures required the application of more elaborate neutron diffraction experiments. One particular complication arose from the later identified Cu–Zn disorder, present in virtually all thin film samples. Subsequently, it has been shown experimentally that this unavoidable Cu–Zn disorder leads to a band gap lowering in the respective samples. Additional theoretical investigations, mostly based on Monte-Carlo methods, tried to understand the atomistic origin of this disorder induced band gap lowering. Here, we present theoretical results from first-principles calculations based on density functional theory for the disorder induced band gap lowering in kesterite Cu2ZnSnSe4 and Ag2ZnSnSe4, where the Cu–Zn and Ag–Zn disorder is modelled via a supercell approach and special quasirandom structures. Results of subsequent analyses of structural, electronic, and optical properties are discussed with respect to available experimental results, and will provide additional insight and knowledge towards the atomistic origin of the observed disorder induced band gap lowering in kesterite type materials.

Broadband light absorption enhancement in a–Si:H ultrathin film solar cells with nanophotonic light trapping structures

Light trapping over a wide wavelength range is critical for applications such as thin-film solar cells (TFSCs). Therefore, in this paper, we report a plasmonic light trapping scheme as a solution to overcome the limited absorption of light in hydrogenated amorphous silicon (a-Si:H) thin film solar cells. Here we propose plasmonic nanostructures, which have periodic nanodisks added to the front surface of the cell. These structures combine a variety of photonic effects to reduce reflection, improve light trapping, and increase absorption over a broadband solar spectrum. Initially, to test whether the suggested plasmonic nanoparticles can enhance light-trapping within the absorber layers of the cell, we used the 3D finite difference time domain method to simulate the propagation of electromagnetic waves and the absorbed light in each layer of the cell. Additionally, the obtained optical properties after the FDTD simulation are used to design electrical model simulations using SCAPS software. The results show that the front surface of nanodisk-shaped solar cells with only a 100-nm-thick a-Si:H layer can absorb light at wavelengths ranging from 300 to 800 nm, which is greater than that of flat a-Si:H film devices. With optimized structural parameters, the short circuit current density Jsc could be enhanced by 98 % and 71 % with the addition of Au and Cu nanodisks, respectively. Additionally, the conversion efficiency is improved by 28 % and 26 % for Au and Cu, respectively. The proposed design of the light trapping structure can provide guidelines for ultra-TFSCs with high performance.

Nanosecond laser-induced crystallization of SiOx/Au bilayers in air and vacuum

High-quality polycrystalline silicon films on low-cost and low-temperature substrates have attracted much attention as promising materials for high-speed thin-film transistors and thin-film solar cells fabrication. To obtain poly-Si films on low temperature substrates, several concepts have been proposed. Usually the amorphous material undergoes crystallization which can be achieved by various methods including solid-phase crystallization, metal-induced crystallization or liquid-phase crystallization. In this work, we tried to combine the advantages of metal-induced crystallization and liquid-phase crystallization. To achieve this we explored the nanosecond laser crystallization of a bilayer structure consisting of Au and SiO0.1 layers with thicknesses of 30 nm and 130 nm, respectively. The study reveals that when exposed to 532 nm wavelength radiation leads to its destruction due to rupture. On the other hand, when subjected to 1064 nm wavelength radiation, no similar material behavior is observed, and the measured modification threshold is 0.15 J/cm2, representing a 40 % reduction compared to SiO0.1 film without gold. It is demonstrated that at laser fluences of 0.35 J/cm2 and higher, the treatedsurfaceinair becomes enriched with silicon dioxidenanoporous coating, attributed to the return of evaporation products to the target surface. Theoretical modeling, assuming thermal evaporation of the coating, suggests that the undesirable nanoporous layer formation can be avoided.

Impact of stacking sequence and sulfurization duration on the growth of pyrargyrite Ag3SbS3 absorber layers

Pyrargyrite Ag3SbS3 is a promising absorber for thin-film solar cells. In this study, the impact of precursor stacking sequence and sulfurization duration on the growth and properties of Ag3SbS3 films was investigated. Initially, the Ag3SbS3 films produced by depositing Sb/Ag and Ag/Sb/Ag metal stacks and then sulfurizing at 300 °C crystallized in rhombohedral structure with (113) preferred orientation. The film produced from the Sb/Ag stack had a uniform and large-grained morphology up to a thickness of 1150 nm, and a direct bandgap of 1.65 eV; whereas the film prepared with the Ag/Sb/Ag stack exhibited nonuniform grain morphology with decreased film thickness, and increased bandgap energy (1.70 eV). Secondly, the Ag3SbS3 films produced from the Sb/Ag stack by increasing sulfurization duration from 10 to 90 min increases the crystallite size from 26 to 27 nm, enhances the grain compactness and uniformity, varies the bandgap in the range of 1.65–1.69 eV, and electrical resistivity. The solar cells fabricated using the films produced by sulfurizing the Sb/Ag stack for 30 min duration exhibited a maximum power conversion efficiency of 0.52% with an VOC of 471.6 mV, JSC of 2.0 mA/cm2, and FF of 55.0%. This study offers a pathway for the advancement of Ag3SbS3 thin-film solar cells.

Numerical modelling and performance investigation of inorganic Copper-Tin-Sulfide (CTS) based perovskite solar cell with SCAPS-1D

Perovskite solar cells (PSCs) are a favorable option for the upcoming generation of photovoltaic systems due to their simplicity and high energy conversion efficiency. The third iteration of thin-film solar cells including copper-tin-sulphide (CTS) is easily accessible on Earth, possesses excellent optoelectrical properties, and does not include any harmful substances, making it environmentally sustainable. Using the solar cell capacitance simulator (SCAPS), this study examines the performance of a PSC based on copper oxide (Cu2O) and zinc selenide (ZnSe). The study investigates the factors that influence the performance of CTS-based SCs, such as absorber layer thickness, absorber defect density, interface defect densities, doping densities, and working temperature on the performance of the PSC. The results show that 30.37 % perovskite cell efficiency (PCE) increased from 20.94 % after optimization with 0.9403 V of open circuit voltage, 37.2682 mA/cm2 of short circuit current and 86.67 % of fill factor.

Low-temperature influence on the properties and efficiency of thin-film perovskite solar cells fabricated by the PVco-D technique

The study discussed in this publication aimed to develop a perovskite solar cell adapted to operating conditions at reduced temperature and pressure and less than 1 μm thick. The physical vapor co-deposition technique was proposed and successfully used to create a solar cell structure with a thin layer of hybrid perovskite as an energy-collecting material. A comprehensive analysis of methylammonium lead iodide behavior in a wide temperature range from 10 K to 320 K was carried out to implement this project. The initial phase included assessing the degradation of the perovskite material layer after cooling to the temperature of liquid helium and then re-heating it to room temperature. Then, using spectroscopic techniques, the characteristics of the layers' optical and electrical properties were determined. The obtained results allowed the design of the complete structure of a thin-film perovskite cell, which was made using only the vacuum sublimation process. Simulations using the SCAPS-1D program and experimental results showed high agreement and allowed for obtaining an efficiency of approximately 18.5 % in the interested temperature range. Perovskite solar cell stability tests over six months confirmed the positive impact of the proposed technique for depositing the complete cell structure on its temporal stability. The research results are optimistic for the applications of perovskite cells in space.

Combined Charge Extraction by Linearly Increasing Voltage and Time-Resolved Microwave Conductivity to Reveal the Dynamic Charge Carrier Mobilities in Thin-Film Organic Solar Cells.

This article reports a purely experiment-based method to evaluate the time-dependent charge carrier mobilities in thin-film organic solar cells (OSCs) using simultaneous charge extraction by linearly increasing the voltage (CELIV) and time-resolved microwave conductivity (TRMC) measurements. This method enables the separate measurement of electron mobility (μe) and hole mobility (μh) in a metal-insulator-semiconductor (MIS) device. A slope-injection-restoration voltage profile for MIS-CELIV is also proposed to accurately determine the charge densities. The dynamic behavior of μe and μh is examined in five bulk heterojunction (BHJ) OSCs of polymer:fullerene (P3HT:PCBM and PffBT4T:PCBM) and polymer:nonfullerene acceptor (PM6:ITIC, PM6:IT4F, and PM6:Y6). While the former exhibits fast decays of μh and μe, the latter, in particular, PM6:IT4F and PM6:Y6, exhibits slow decays. Notably, the high-performing PM6:Y6 demonstrates both a balanced mobility (μe/μh) of 1.0-1.1 within 30 μs and relatively large CELIV-TRMC mobility values among the five BHJs. The results exhibit reasonable consistency with a high fill factor. The proposed new CELIV-TRMC technique offers a path toward a comprehensive understanding of dynamic mobility and its correlation with the OSC performance.

Study on optoelectronic properties of CuInSe2/CuInSSe films and PN junctions

CuInSe2 (CIS) is a semiconductor with a direct bandgap of about 1.04 eV. Its potential applications in the field of flexible thin-film solar cells are vast and promising. Improving cell performance through the sulfidation of the CIS absorber layer is a vital method. Furthermore, the bandgap can be adjusted through ideal element doping and interfacial state recombination can be decreased. In this study, the mixed source vacuum evaporation is used to prepare CIS, CuInS1.5Se0.5 and CuInS0.5Se1.5 films, followed by annealing under N2, S, and Se atmospheres. Subsequently, Mo/CIS/CdS PN junction and Mo/CuInSxSe2-x (x = 0.5 or 1.5)/CdS PN junctions are fabricated. The results demonstrate that Se-annealing of CIS films reduces hetero-phase formation, improves crystallization quality and yields high intensities of transmittance and reflectance. S-annealing of CISSe films results in enhanced intensities of transmittance and reflectance. The intensities of the primary XRD peaks of CuInS0.5Se1.5 film are greater than those of the CuInS1.5Se0.5 film. The morphologies of the CISSe films become flatter and smoother as annealing in S-atmosphere. The CuInS1.5Se0.5 film shows a higher photocurrent compared to the CuInS0.5Se1.5 film, suggesting that a greater proportion of S can enhance photo carrier concentration of CISSe films. Additionally, the carrier transport in S-annealed CuInS0.5Se1.5/CdS PN junction is predominantly governed by tunneling current mechanism, while carrier transports of other PN junctions are regulated by leakage current mechanism.

The role of interface energetics in Sb2Se3 thin film solar cells

We comprehensively simulated the interface energetics at the Sb2Se3/CdS interfaces and showed its impact on device performance. The interface discontinuity, band bending at interface and energy level alignment generates interfaces issues and must be optimized for an optimal device performance. The design parameters for controlling interface. Metal contact work function preferably higher than electron affinity (EA) and Fermi level (EF) combined (EA + EF), should result in near Ohmic behaviour of contact. Secondly electron affinity of buffer could be tuned to achieve small positive conduction bandoffset (spike barrier) at absorber/buffer interface which lowers the chances of recombination through interface states. A pn + configuration with highly doped buffer layer, as compared to p-absorber, is favourable as it will extend depletion in absorber, providing additional drift to photo-generated carriers. Lastly, acceptor defect at Sb2Se3-CdS interface generate surface inversion and detrimental to performance. Donor defects occupying interface states are preferred condition for optimal device performance. We have compiled the optimal ranges for these controlling parameters, to achieve theoretically ideal values of energy level alignment and energetics, leading to optimal performance.

Antimony doping strategy enables efficiency and bending durable flexible Cu2ZnSn(S,Se)4 thin film solar cells

Suppressing the open-circuit voltage deficit and residual stress caused by stubborn defects is crucial for achieving efficiency flexible Cu2ZnSn(S,Se)4 solar cell coexisting with bending stability. The strategy of sputtering Sb2Se3 layer in CZTS precursor followed by selenization is proposed to realize Sb doping in CZTSSe. Benefitting from the role of Sb doping in suppressing SnZn defects, improved mechanical flexibility with decreased porosity and released residual stress declining from −5.75 GPa to −3.45 GPa of CZTSSe absorber is achieved, which can effectively inhibit carrier recombination in CZTSSe/CdS heterojunctions during harsh bending environment. Consequently, an enhanced efficiency from 3.06 % to 4.63 % is achieved with the optimal Sb2Se3 thickness of 80 nm, which can retain 90 % of its initial efficiency after harsh bending. The inspiring results provide a new route to stress regulation for flexible copper-based thin film solar cells.

An optical study on the enhanced light trapping performance of the perovskite solar cell using nanocone structure

Photon management strategies are crucial to improve the efficiency of perovskite thin film (PTF) solar cell. In this work, a nano-cone (NC) based 2D photonic nanostructure is designed and simulated aiming at achieve superior light trapping performance by introducing strong light scattering and interferences within perovskite active layer. Compared to the planar PTF solar cell, the NC nanostructured device with 45 degrees half apex angle obtains highest short-circuit current density, which improved over 20% from 15.00 mA/cm2 to 18.09 mA/cm2. This work offers an alternative design towards effective light trapping performance using 2D photonic nanostructure for PTF solar cell and could potentially be adopted as the nano-structuring strategy for the future perovskite solar cell industry.

Investigation of structural, morphological and optoelectronic properties of (Ni, Co)-doped and (Ni/Co) co-doped SnO2 (110) sprayed thin films

The manuscript details the application of spray pyrolysis for the deposition of an economically viable transparent conductive oxide film comprised of (Ni/Co) co-doped SnO2 on a glass substrate. The primary objective of this research was to systematically examine the impact of Ni/Co co-doping on diverse properties of the SnO2 thin film. These properties encompassed the film's structural composition, surface morphology, optical response, and electrical behaviors. A comparison was made with pure SnO2 film, as well as SnO2 films doped with 3 %Ni and 1 %Co. The results indicate that all the samples exhibited a tetragonal structureThe introduction of Co and Ni atoms had no impact on the favored alignment of the (110) plane or the crystal structure of the SnO2 film. The crystallite size of the pure SnO2 film, as well as the (Co, Ni)-doped and (Ni/Co) co-doped SnO2 films, varied within the range of 11 to 20 nm. Scanning electron microscopy (SEM) images were employed to assess how doping and co-doping influenced the surface characteristics of the films. The presence of pores and/or roughness on the surface resulted in a hydrophilic character and a decrease in the contact angle for the doped films (Ni, Co). However, the co-doped film exhibited a hydrophobic characteristic due to the surface enhancement provided by SnO2:3 %Ni:1 %Co. The research also focused on the optical characteristics of the films, showing a positive impact with the proper incorporation of Ni and Co atoms into the SnO2 lattice. It was notably observed that the addition of Ni and Co atoms improves the optical properties of the undoped transparent SnO2 film in the visible spectrum, with a high transmittance of 87 % achieved for the Ni-doped film. Furthermore, the hydrophobic nature achieved by adding a concentration of 3 %Ni to the SnO2:1 %Co film enhances its optical transmission in the range of 300 nm to 750 nm. The SnO2 film shows an improvement in the electrical resistivity upon doping and co-doping with low resistivity value of 2.22 × 10−2 Ω.cm for the film (3 %Ni/1 %Co)-SnO2. Drawing from these insightful results, the study proposes the potential utilization of (Ni/Co) co-doped SnO2 films as transparent electrodes in optoelectronic applications, especially in the manufacturing of thin film solar cells.

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.