Absorber Layer In Solar Cells Research Articles

Numerical investigation of CuSbS2 thin film solar cell using SCAPS-1D: enhancement of efficiency on experimental films by defect studies

The study of photovoltaic solar cells has been an exciting field of research because of their environmentally friendly nature. Scientists are continuously searching for new methods to develop solar cells that are highly efficient and cost-effective. One promising option is the use of Copper Antimony Sulphide (CuSbS2) based ternary compound semiconductor in ultrathin film photovoltaic cells. This material has a high absorption coefficient, low cost, and is readily available in the earth’s crust. These characteristics make it an ideal candidate for use as a thin-film absorber layer in solar cells. In this work, FTO/CdS/In2S3/CuSbS2/Spiro-OMeTAD/Au device is proposed to improve the efficiency of experimentally designed CuSbS2-based thin film solar cells using numerical modeling. Device simulation was carried out using SCAPS-1D software, and the illumination spectrum used for this optimization was 1.5 AM. The simulated results from SCAPS-1D were compared to the experimental data. After optimizing the device parameters all the electrical parameters of the solar cell were improved. The optimized CuSbS2-based device shows power conversion efficiency (PCE) of 21.11% with short circuit current density (Jsc) of 20.96 mA cm−2, open circuit voltage (Voc) of 1.23 V, and fill factor (FF) of 81.84%. Based on the simulation results, it is possible to increase the performance of the device by varying different parameters such as the defect density of each layer, interfacial defect density, thickness, and doping concentration.

Enhancing the properties of Cd-free MgZnS buffer for solar cells by co-sputtering ZnS and Mg targets

The buffer is an essential component that connects the window and absorber layers in thin film solar cells, which has significant impacts on the performance of cell device. CdS is widely used buffer material, but it has drawbacks of toxicity and narrow band gap of 2.4 eV. This work explores the fabrication of a novel Cd-free MgZnS buffer layer through co-sputtering ZnS and Mg targets. The grain size, morphology, phase composition, transmittance and band gap of MgZnS films are manipulated by adjusting the substrate temperature, sputtering power of ZnS target and sputtering current of Mg target. The MgZnS film exhibits remarkable characteristics, including high crystallinity with grain size of about 35 nm, high transmittance of over 80%, and high band gap of 3.44 eV. The process parameters with favorable outcomes include substrate temperature of 300 °C, ZnS sputtering power of 100 W, and Mg sputtering current of 0.05 A. Furthermore, compared with the CdS buffer, the MgZnS buffer has better compactness and transmittance. This method provides a promising new and effective avenue to fabricate Cd-free buffers for solar cells.

New highly efficient perovskite solar cell with power conversion efficiency of 31% based on Ca3NI3 and an effective charge transport layer

The fascinating structural, optical, and electronic features of calcium nitrogen iodide (Ca3NI3) make it an attractive material for developing absorbers for efficient and reasonably priced applications involving solar cells. Potential applications as an absorber layer in heterostructure solar cells for the perovskite material Ca3NI3 have been thoroughly studied theoretically. For the Ca3NI3 absorber-based cell structure with CdS as the ETL layer, the best PV values were discovered using the SCAPS-1D simulator. Working temperatures, interface densities of active materials, doping densities, and layer thicknesses were all carefully considered while analyzing the PV performance. It was also possible to find the quantum efficiency (QE), generation and recombination rates, and current density-voltage (J-V). The structure composed of Al/FTO/CdS/Ca3NI3/Ni demonstrated a remarkable power conversion efficiency (PCE) of 31.31%. With CdS serving as the electron transport layer (ETL), the high efficiency was matched by a current density (JSC) of 43.590813 mA/cm2, a fill factor (FF) of 81.68%, and an open-circuit voltage (VOC) of 0.8793 V. This work contributes to a better understanding of the potential of Ca3NI3 in heterostructure perovskite solar cells, which will facilitate the creation of more robust and efficient PSC devices.

Investigating inorganic perovskite as absorber materials in perovskite solar cells: machine learning analysis and optimization

This work investigates the potential of inorganic perovskites AgBiSCl2 and Al2Cu2Bi2S3Cl8 as absorber layers in perovskite solar cells, followed by the application of supervised machine learning models. Extensive exploration and optimization of device architectures FTO/SnO2/AgBiSCl2/Spiro-OMeTAD/Au and FTO/SnO2/Al2Cu2Bi2S3Cl8/Spiro-OMeTAD/Au are conducted, involving variations in absorber layer thickness (d), bulk defect density (Nt), and carrier mobility (μ n,p). The AgBiSCl2-based device achieves an optimized conversion efficiency of 10.06%, while the Al2Cu2Bi2S3Cl8-based device achieves 12.27%. To train different machine learning models, 1600 datasets are collected for each device, and Neural Networks (NN), Random Forests (RF), and XGBoost (XGB) models are employed. The performance parameters, evaluated using mean squared error (MSE) and high R-squared (R2) values, demonstrate that XGB performs the best, achieving an MSE of 0.210 and R2 of 97.1% for AgBiSCl2 and 0.671 and 90.6% for Al2Cu2Bi2S3Cl8. Additionally, the impact of each variable (d, Nt, and μ n,p) on the output is analyzed using Shapley Additive Explanations (SHAP) plots for each model. The results presented in this study pave the way for the advancement of perovskite material-based solar cells without relying on complex optoelectronic semiconducting equations and device simulators.

Exploring the impact of defect energy levels in CdTe/Si dual-junction solar cells using wxAMPS

A numerical analysis of a CdTe/Si dual-junction solar cell in terms of defect density introduced at various defect energy levels in the absorber layer is provided. The impact of defect concentration is analyzed against the thickness of the CdTe layer, and variation of the top and bottom cell bandgaps is studied. The results show that CdTe thin film with defects density between 1014 and 1015 cm−3 is acceptable for the top cell of the designed dual-junction solar cell. The variations of the defect concentrations against the thickness of the CdTe layer indicate that the open circuit voltage, short circuit current density, and efficiency (ƞ) are more affected by the defect density at higher CdTe thickness. In contrast, the Fill factor is mainly affected by the defect density, regardless of the thin film’s thickness. An acceptable defect density of up to 1015 cm−3 at a CdTe thickness of 300 nm was obtained from this work. The bandgap variation shows optimal results for a CdTe with bandgaps ranging from 1.45 to 1.7 eV in tandem with a Si bandgap of about 1.1 eV. This study highlights the significance of tailoring defect density at different energy levels to realize viable CdTe/Si dual junction tandem solar cells. It also demonstrates how the impact of defect concentration changes with the thickness of the solar cell absorber layer.

Performance evaluation of 2D MoS2-based solar cells and realization of transparent ultra-thin devices

Molybdenum disulfide (MoS2) is an alternate absorber layer in 2D solar cells owing to its potential of proficient sunlight harvesting. The optimum electrical and optical properties of MoS2 validate it as a suitable photovoltaic absorber material. This work investigates the performance of 2D (and multi-layer) MoS2-based vertically stacked solar cell by numerical simulation process using one dimensional solar cell capacitance simulator (SCAPS). Two device configurations based on Schottky junction (ITO/n-MoS2/Au) and pn junction (ITO/n-MoS2/p-MoS2/Au) have been theoretically analyzed. The feasibility of ultra-thin transparent solar cells is also demonstrated, which is motivating from a technological outlook. Initially, the properties of the active layers are optimized to give the highest performance. The findings are explained on the basis of band alignment between the electrodes and the different layers. The potential barrier developed at the interface of different materials governs the output of the cells. The calculations forecast the material properties, which need to be tuned to fabricate solar cells with enhanced efficiency. After optimization, the highest efficiency obtained for single n-MoS2-based solar cell is 10.22%, while for the pn junction solar cell it is 16.86%. The optimized cells exhibit high open circuit voltages of ∼1.2 V, which is an essential factor for commercial realization of solar cells. Lastly, the performance of transparent solar cells based on thin 2D MoS2 films has been predicted which showcases the efficiency in the range of 0.78%–4.36%. These homo-junction device investigations of solely MoS2 layer along with employment of a strict control on the defects during deposition and fabrication of MoS2-based solar cells can ensure better performance of the device. Thus, it can open ways to develop next generation feasible solar cells with higher power density as compared to existing technology.

Doping and precoating by Cu-metal and annealing impacts on some physical properties and applications of MnS thin films

We prepared thin films of manganese sulfide (MnS) using a thermal evaporation technique. These films were pre-coated and doped with Cu ((MnS)1-xCux, x = 0.05 g). A lot of work was done on these films using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV/VIS/NIR spectrophotometry, and a two-probe approach to figure out their structure, shape, optical properties, and electrical properties. We investigated various factors including the optical energy gap (Eg), refractive index (n), extinction coefficient (k), Urbach energy (Eu), dielectric constants (εr), dispersion parameters, activation energy (ΔE), mobility, photocatalytic analysis, and Seebeck coefficient. The XRD analysis showed that the thin films were amorphous. The direct optical energy gaps of the pure, Cu pre-coated layer, and Cu-doped MnS films were measured at 3.17 eV, 1.88 eV, and 2.45 eV, respectively. Annealing the films at different temperatures showed normal refractive index dispersion in the NIR region. The addition of copper, both as a pre-coating layer and as doping, resulted in a decrease in film resistivity, indicating their semiconducting nature. FE-SEM analysis provided valuable insights into the morphology of the thin films, revealing a uniform and smooth surface. The electrical characteristics showed that film resistivity decreased with copper addition, confirming enhanced conductivity. These properties hold significance in the development of absorber layers for second-generation solar cells, thermoelectric characteristics, and photocatalysis applications.

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.

Carrier mobility in doped Sb<sub>2</sub>Se<sub>3</sub> based on deformation potential theory

Antimony selenide (Sb<sub>2</sub>Se<sub>3</sub>) is an element-rich, cost-effective, and non-toxic material used as an absorber layer in solar cells. The performance of solar cells is significantly influenced by the transport characteristics of charge carriers. However, these characteristics in Sb<sub>2</sub>Se<sub>3</sub> have not been well understood. In this work, through density functional theory and deformation potential theory, we investigate the hole transport properties of pure Sb<sub>2</sub>Se<sub>3</sub> and As-, Bi-doped Sb<sub>2</sub>Se<sub>3</sub>. The incorporation of as element and Bi element does not introduce additional impurity levels within the band gap. However, the band gaps are reduced in both As-Sb<sub>2</sub>Se3 and Bi-Sb<sub>2</sub>Se<sub>3</sub> due to the band shifts of energy levels. This phenomenon is primarily attributed to the interactions between the unoccupied 4p and 6p states of the doping atoms and the unoccupied 4p states of Se atoms, as well as the unoccupied 5p states of Sb atoms. In this study, we calculate and analyze three key parameters affecting mobility: effective mass, deformation potential, and elastic constants. The results indicate that effective mass has the greatest influence on mobility, with Bi-Sb<sub>2</sub>Se<sub>3</sub> exhibiting the highest average mobility. The average effective mass is highest in As-Sb<sub>2</sub>Se<sub>3</sub> and lowest in Bi-Sb<sub>2</sub>Se<sub>3</sub>. The elastic constants of the As- and Bi-doped Sb<sub>2</sub>Se<sub>3</sub> structures show minimal differences compared with that of the intrinsic Sb<sub>2</sub>Se<sub>3</sub> structure. By comparing the intrinsic, As-doped, and Bi-doped Sb<sub>2</sub>Se<sub>3</sub>, it is evident that doping has a minor influence on deformation potential energy along various directions. The study reveals that the hole mobility in Sb<sub>2</sub>Se<sub>3</sub> displays significant anisotropy, with higher mobilities observed in the <i>x</i>-direction and the <i>y</i>-direction than in the <i>z</i>-direction. This discrepancy is attributed to stronger covalent bonding primarily in the <i>x</i>- and <i>y</i>-direction, while in the <i>z</i>-direction weaker van der Waals forces is dominant. The directions with enhanced charge carrier transport capability contribute to efficient transfer and collection of photo-generated charge carriers. Therefore, our research theoretically underscores the significance of controlling the growth of antimony selenide along specific directions.

Optimizing the structure and optoelectronic properties of cuprite thin films via a plasma focus device as a solar cell absorber layer

Solar cells are of growing importance as a renewable energy source, and cuprite (Cu2O) stands out as a promising material due to its cost-effectiveness, abundance, and appealing optoelectronic characteristics.

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

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

First-principles study on the structural, electronic, elastic, optical and thermodynamic properties of double antiperovskites X6BiSbN2 (X = Mg, Ca, Sr)

The perovskite materials have been widely used because of their excellent properties. Based on density functional theory, the structural, electronic, elastic, optical and thermodynamic properties of double antiperovskites X6BiSbN2 (X = Mg, Ca, Sr) are calculated. The results show that X6BiSbN2 (X = Mg, Ca, Sr) have stable crystal structures, and their band gaps are 1.172eV, 1.303eV and 0.965eV, respectively. Mg6BiSbN2 is an indirect bandgap semiconductor, which may be more suitable for use as a photocatalyst. Ca6BiSbN2 and Sr6BiSbN2 are direct bandgap semiconductors with high polarization and absorption coefficients, low reflectivity in the visible light region and good mechanical durability, which may be suitable candidates for the absorption layer of perovskite solar cells. In addition, X6BiSbN2 (X = Mg, Ca, Sr) have broad absorption range and high absorption coefficient in the ultraviolet region, which indicates that they may be potential photodetector materials. Sr6BiSbN2 has no entanglement between acoustic and optical branches in the phonon spectrum and a low Debye temperature, which helps to improve the thermoelectric coefficient, so it may be suitable for thermoelectric devices. The calculation results in this paper show that X6BiSbN2 (X = Mg, Ca, Sr) are expected to be used in the absorption layer of solar cells and photodetector field, and Sr6BiSbN2 may also be suitable for thermoelectric devices.

Enhancing charge carrier extraction and energy band alignment in perovskite solar cells using interfacial passivation with polar organic molecules

The wide utilization of perovskite material as an absorber layer in solar cells necessitates favorable alignment with the perovskite's conduction band, governed by FTO/TiO2 (SnO2). Instead of an ideal electric-selective contact, further improvement of the hole-selective contact is crucial to enhance hole extraction and minimize carrier recombination at the interface between perovskite and spiro-OMeTAD. In this study, we employed series of polar organic molecules [2,4-dimethyl-6,8-bis(4-(methylthio)phenyl)pyrrolo [1,2-a]pyrimidine-7-carbonitrile (PCNS), 2,4-dimethyl-6,8-diphenylpyrrolo [1,2-a]pyrimidine-7-carbonitrile (PCN), and 2,4-dimethyl-6-8-(pyren-1-yl)pyrrolo [1,2-a]pyrimidine-7-carbonitrole (PCNP)] with cyano groups as the interfacial passivate layer to facilitate energy band matching between the perovskite and the hole transport layer as confirmed by the energy band bending at the perovskite surface. Consequently, we achieved effective charge carrier extraction and suitable bandgap alignment. A detailed comparative analysis of the photophysical and electrical properties among the three molecules elucidated the origin of higher open circuit voltage (1.18 ​V) and improved fill factor (83.15 %) in the solar cell device based on PCN molecule (24.22 %).

Stability of Mixed Lead Halide Perovskite Films Encapsulated in Cyclic Olefin Copolymer at Room and Cryogenic Temperatures.

Lead Mixed Halide Perovskites (LMHPs), CsPbBrI2, have attracted significant interest as promising candidates for wide bandgap absorber layers in tandem solar cells due to their relative stability and red-light emission with a bandgap ∼1.7 eV. However, these materials segregate into Br-rich and I-rich domains upon continuous illumination, affecting their optical properties and compromising the operational stability of devices. Herein, we track the microscopic processes occurring during halide segregation by using combined spectroscopic measurements at room and cryogenic temperatures. We also evaluate a passivation strategy to mitigate the halide migration of Br/I ions in the films by overcoating with cyclic olefin copolymer (COC). Our results explain the correlation between grain size, intensity dependencies, phase segregation, activation energy barrier, and their influence on photoinduced carrier lifetimes. Importantly, COC treatment increases the lifetime charge carriers in mixed halide thin films, improving efficient charge transport in perovskite solar cell applications.

Investigating the Impact of Interfacial Layers on Device Performance of Highly Stable Cs2InBiBr6Based Double Perovskite Solar Cells

AbstractPerovskite solar cells, a third‐generation photovoltaic technology, have recently emerged as a game‐changing innovation. However, lead (Pb) is a toxic heavy metal, and it is crucial to explore lead‐free perovskite solar cells with continuously improving efficiency for long‐term development. Recently, materials researchers have discovered a lead‐free double perovskite solar cell material, Cs2InBiBr6with a small direct bandgap of 1.27 eV and strong thermodynamic and mechanical structural stability. The power conversion efficiency of Cs2InBiBr6‐based perovskite solar cells is not reported yet. To investigate its potential, a solar cell capacitance simulator to analyze the solar cell structure of FTO (Fluorine Doped Tin Oxide)/ETL (Electron Transport Layer)/Cs2InBiBr6/HTL (Hole Transport Layer)/Au, selecting appropriate hole transport materials and electron transmission materials to achieve high efficiency is used. Moreover, this study explores the impact of several factors, including absorber layer thickness, acceptor and donor doping density, and the influence of total defect density of the perovskite and interface layers on the performance of solar cells. Advanced device characterization methods such as Mott‐Schottky analysis are performed to unravel the effect of interfaces on the device performance. The solar cell with the device structure FTO/TiO2/Cs2InBiBr6/Cu2O/Au achieves an outstanding PCE of 23.64% demonstrating the immense potential of Cs2InBiBr6as a lead‐free double perovskite solar cell absorber layer.

Two-dimensional CsPbI3/CsPbBr3 vertical heterostructure: a potential photovoltaic absorber

First-principles methods have been employed here to calculate structural, electronic and optical properties of CsPbI3 and CsPbBr3, in monolayer and heterostructure (HS) (PbI2-CsBr (HS1), CsI-CsBr (HS2), CsI-PbBr2 (HS3) and PbI2-PbBr2 (HS4)) configurations. Imaginary frequencies are absent in phonon dispersion curves of CsPbI3 and CsPbBr3 monolayers which depicts their dynamical stability. Values of interfacial binding energies signifies stability of our simulated heterostructures. The CsPbI3 monolayer, CsPbBr3 monolayer, HS1, HS2, HS3 and HS4 possess direct bandgap of 2.19 eV, 2.73 eV, 2.41 eV, 2.11 eV, 1.88 eV and 2.07 eV, respectively. In the HS3, interface interactions between its constituent monolayers causes substantial decrease in its resultant bandgap which suggests its solar cell applications. Static dielectric constants of all simulated heterostructures are higher when compared to those of pristine monolayers which demonstrates that these heterostructures possess low charge carrier recombination rate. In optical absorption plots of materials, the plot of HS3 displayed a red shift and depicted absorption of a substantial part of visible spectrum. Later on, via Shockley-Queisser limit we have calculated solar cell parameters of all the reported structures. The calculations showed that HS2, HS3 and HS4 showcased enhanced power conversion efficiency compared to CsPbI3 and CsPbBr3 monolayers when utilized as an absorber layer in solar cells.

A-Site Cation Replacement of Hydrazinium Lead Iodide Perovskites by Borane Ammonium Ions: A DFT Calculation.

Organometallic perovskites have become one of the most common multifunctional materials in optoelectronic research fields. This research studies density functional theory calculation on orthorhombic hydrazinium lead iodide (N2 H5 PbI3 ) perovskite by replacing A-site cation with a borane ammonium (BH2 NH3 + ) ion. The perovskite showed a significant structural deformation and an orthorhombic to triclinic phase transition due to A-site ion replacement. The N2 H5 PbI3 perovskite has a band gap of 1.64 eV, suitable for the solar cell absorber layer. The band gap has increased to 2.12 eV after complete A-site ion replacement. All structures showed a high absorption coefficient over 104 cm-1 in the low wavelength region and an increase in refractive index from 2.5 to 2.75 due to ion replacement. All the structures showed high optical conductivity of 1015 s-1 order in the blue wavelength region. These new perovskite structures hold the potential to provide a revolution in optoelectronic research.

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

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

3D and Multimodal X-Ray Microscopy Reveals the Impact of Voids in CIGS Solar Cells.

Small voids in the absorber layer of thin-film solar cells are generally suspected to impair photovoltaic performance. They have been studied on Cu(In,Ga)Se2 cells with conventional laboratory techniques, albeit limited to surface characterization and often affected by sample-preparation artifacts. Here, synchrotron imaging is performed on a fully operational as-deposited solar cell containing a few tens of voids. By measuring operando current and X-ray excited optical luminescence, the local electrical and optical performance in the proximity of the voids are estimated, and via ptychographic tomography, the depth in the absorber of the voids is quantified. Besides, the complex network of material-deficit structures between the absorber and the top electrode is highlighted. Despite certain local impairments, the massive presence of voids in the absorber suggests they only have a limited detrimental impact on performance.

Numerical modeling and performance analysis of a novel Cd-free all-Kesterite tandem solar cell using SCAPS-1D

Tandem solar cells have the potential to surpass conventional single-junction photovoltaics by harnessing a wider range of the solar spectrum and reducing losses caused by thermalization and transmission. This study examines the performance of a kesterite-kesterite tandem solar cell with two different absorber layers in each subcell using SCAPS-1D. The upper subcell comprises CZTS and ACZTS with wider bandgaps, while the lower subcell comprises ACZTSe and CZTSe with narrower bandgaps. The CZTS- and CZTSe-based solar cells were first validated using experimental data to determine the feasibility of the tandem solar cell design. The CZTS-based solar cell was modified by replacing the back contact, adding a Cd-free buffer layer of ZnMnO, and using a SnMnO2 layer as a window layer. The band gap and electron affinity of ZnMnO and SnMnO2 layers were adjusted by changing their manganese contents for optimal conduction band offset. A thin ACZTS layer was also added as a second absorber layer in the CZTS-based solar cell to enhance open circuit voltage. The CZTSe-based solar cell was thereafter modified by including an ACZTSe layer as a second absorber layer and by selecting ZnSe as a buffer layer and optimizing the thicknesses of all layers. Both upper and lower subcells were analyzed for tandem configuration using filtered spectra and current-matching techniques. The thickness of the CZTS layer in the upper subcell was adjusted to achieve current matching; consequently, the proposed tandem cell had an efficiency of ∼24%. These findings provide valuable insights for future advancements in kesterite-kesterite-based tandem solar cells.