Non-toxic Buffer Research Articles

Opto-electrical study of 4T perovskite-chalcogenide tandem solar cell with the addition of quasi-2D perovskite as capping layer of 3D perovskite layer

This study presents a four-terminal (4T) perovskite-chalcogenide tandem solar cell (TSC) that includes quasi-2D perovskite material in the top sub-cell in order to provide a stable structure, and the bottom sub-cell contains Zn(O,S,OH) material to provide a nontoxic buffer layer. First, a reference TSC with a total power conversion efficiency (PCE) of 26.48% is modeled, using MAPbI3 and CIGSSe as 3D perovskite and chalcogenide absorber layers (ALs), respectively. Next, two structures are designed to produce a stable SC using the Ruddlesden Popper (RP) quasi-2D perovskite materials, which have the chemical formula BA2MAm−1PbmI3m+1, m = 2–5. The initial structure uses quasi-2D perovskites in place of the 3D perovskite AL. According to the results, BA2MAPb2I7 represents the maximum PCE of 16.00%, 10.48% less than previously. This is caused by quasi-2D materials’ high Eg and low carrier mobility. In the second structure, 3D perovskite AL is capped with the quasi-2D perovskites. In terms of attaining maximum PCE, the optimal TSC is found for BA2MA3Pb4I13 with a PCE of 25.80%. Compared to the initial structure, this one’s PCE increased by 61.25%. In order to boost PCE, a 80 nm-thick anti-reflection (AR) layer is added to the second structure, and the PCE increased to 27.48%. Therefore, the final TSC is proposed as a 4T quasi-2D/3D perovskite-chalcogenide TSC that is stable, and has nontoxic buffer layer, with 3.78% more PCE than the reference structure.

Efficiency improvement of antimony selenide solar cells based on S-doped SnO2 buffer layer

Antimony Selenide (Sb2Se3) exhibits potential as a solar energy material owing to its optimal bandgap, lack of toxicity, and abundance of earth abundant elements. Currently, cadmium sulfide (CdS) serves as the predominant buffer layer for Sb2Se3 solar cells. However, the use of CdS hinders environmentally friendly advancement due to the toxic properties of the element cadmium. Hence, the quest for non-toxic buffer layers poses a significant challenge to the further advancement of Sb2Se3 solar cells. In prior research, tin oxide (SnO2) has been explored as a buffer layer. Nonetheless, the efficiency of SnO2/Sb2Se3 solar cells was hampered by the rough surface of SnO2 films and the poor crystallinity of Sb2Se3 films. In this investigation, we enhanced device efficiency by improving the uniformity of the SnO2 surface and enhancing the crystallinity of Sb2Se3 through spin-coating sulfur (S) onto the SnO2 film. Detailed examinations were conducted on the structure, optical, and electrical properties of the respective SnO2 and Sb2Se3 thin films. Ultimately, an efficiency of 3.38% was achieved using the spin-coated S:SnO2 film, marking an 85% enhancement compared to the baseline device.

Enhanced Efficiency of Thin‐Film Solar Cells via Cation‐Substituted Kesterite Absorber Layers and Nontoxic Buffers: A Numerical Study

Herein, the 1D Solar Cell Capacitance Simulator software is used to perform numerical analysis of thin‐film solar cells with Cu2ZnSnS4, Cu2BaSnS4, Cu2FeSnS4, and Cu2MnSnS4 absorber layers. The main goal is to investigate the impact of parameters, such as absorber layer thickness, acceptor density, buffer layer, bandgap, and donor density, on the efficiency of these solar cells. The absorber layer investigation entails varying the thickness and the acceptor density to evaluate their influence on the efficiency of the solar cell. A new zinc oxide sulfide (Zn(O,S)) buffer layer is also introduced instead of the conventional cadmium sulfide (CdS) buffer layer. The Zn(O,S) bandgap and its donor density, which are investigated in terms of how they affect the efficiency of the solar cells, have been varied. The optimal values for the thickness of the absorber layer, acceptor density, and the bandgap of the buffer layer are calculated. Subsequently, the donor density is evaluated to find any potential defects that may affect the efficiency of the solar cell. These results confirm that Zn(O,S) can be utilized as a buffer layer. This study concludes that Cu2ZnSnS4, Cu2BaSnS4, and Cu2MnSnS4 absorber layers have superior efficiency in comparison with Cu2FeSnS4.

Scalable CIGS Solar Cells Employing a New Device Design of Nontoxic Buffer Layer and Microgrid Electrode.

The efficiency of copper indium gallium selenide (CIGS) solar cells that use transparent conductive oxide (TCO) as the top electrode decreases significantly as the device area increases owing to the poor electrical properties of TCO. Therefore, high-efficiency, large-area CIGS solar cells require the development of a novel top electrode with high transmittance and conductivity. In this study, a microgrid/TCO hybrid electrode is designed to minimize the optical and resistive losses that may occur in the top electrode of a CIGS solar cell. In addition, the buffer layer of the CIGS solar cells is changed from the conventional CdS buffer to a dry-processed wide-band gap ZnMgO (ZMO) buffer, resulting in increased device efficiency by minimizing parasitic absorption in the short-wavelength region. By optimizing the combination of ZMO buffer and the microgrid/TCO hybrid electrode, a device efficiency of up to 20.5% (with antireflection layers) is achieved over a small device area of 5 mm × 5 mm (total area). Moreover, CIGS solar cells with an increased device area of up to 20 mm × 70 mm (total area) exhibit an efficiency of up to 19.7% (with antireflection layers) when a microgrid/TCO hybrid electrode is applied. Thus, this study demonstrates the potential for high-efficiency, large-area CIGS solar cells with novel microgrid electrodes.

Highly efficient emerging Ag2BaTiSe4 solar cells using a new class of alkaline earth metal-based chalcogenide buffers alternative to CdS

Cu2ZnSn(S,Se)4 is a non-toxic, earth-abundant photovoltaic absorber. However, its efficiency is limited by a large open circuit voltage (VOC) deficit occurring due to its antisite defects and improper band alignment with toxic CdS buffer. Therefore, finding an absorber and non-toxic buffers that reduce VOC deficit is crucial. Herein, for the first time, Ag2BaTiSe4 is proposed as an alternative absorber using SCAPS-1D wherein a new class of alkaline earth metal chalcogenide such as MgS, CaS, SrS, and BaS is applied as buffers, and their characteristics are compared with CdS to identify their potential and suitability. The buffer and absorber properties are elucidated by tuning their thickness, carrier concentration, and defect density. Interestingly, optimization of the buffer’s carrier concentration suppressed the barrier height and accumulation of charge carriers at the absorber/buffer interface, leading to efficiencies of 18.81%, 17.17%, 20.6%, 20.85%, 20.08% in MgS, CaS, SrS, BaS, and CdS-based solar cells respectively. Upon optimizing Ag2BaTiSe4, MoSe2, and interface defects maximum efficiency of > 28% is achieved with less VOC loss (~ 0.3 V) in all solar cells at absorber’s thickness, carrier concentration, and defect density of 1 µm, 1018 cm−3, 1015 cm−3 respectively, underscoring the promising nature of Ag2BaTiSe4 absorber and new alkaline earth metal chalcogenide buffers in photovoltaics.

A qualitative Design and optimization of CIGS-based Solar Cells with Sn2S3 Back Surface Field: A plan for achieving 21.83 % efficiency

Conventional Copper Indium Gallium Di Selenide (CIGS)-based solar cells are more efficient than second-generation technology based on hydrogenated amorphous silicon (a-Si: H) or cadmium telluride (CdTe). So, herein the photovoltaic (PV) performance of CIGS-based solar cells has been investigated numerically using SCAPS-1D solar simulator with different buffer layer and less expensive tin sulfide (Sn2S3) back-surface field (BSF). At first, three buffer layer such as cadmium sulfide (CdS), zinc selenide (ZnSe) and indium-doped zinc sulfide ZnS:In have been simulated with CIGS absorber without BSF due to optimized and non-toxic buffer. Then the optimized structure of Al/FTO/ZnS:In/CIGS/Ni is modified to become Al/FTO/ZnS:In/CIGS/Sn2S3/Ni by adding a Sn2S3 BSF to enhanced efficiency. The detailed analysis have been investigated is the influence of physical properties of each absorber and buffer on photovoltaic parameters including layer thickness, carrier doping concentration, bulk defect density, interface defect density. This study emphasizes investigating the reasons for the actual devices' poor performance and illustrates how each device's might vary open-circuit voltage (VOC), short-circuit current density (JSC), fill factor (FF), power conversion efficiency (PCE), and quantum efficiency (QE). The optimized structure offers outstanding power conversion efficiency (PCE) of 21.83 % with only 0.80 μm thick CIGS absorber. The proposed CIGS-based solar cell performs better than the previously reported conventional designs while also reducing CIGS thickness and cost.

Modeling of Copper Zinc Tin Sulfide Solar Cells with Various Buffers Using SCAPS‐1D

Recently, researchers have shown a strong interest in research on quaternary semiconductor copper zinc tin sulfide (CZTS) photovoltaic cells. These cells have a high absorption coefficient, a direct bandgap, and excellent electrical properties. However, the toxicity of cadmium (Cd) in the cadmium sulfide (CdS) buffer layer in standard CZTS solar cells, can generate severe environmental contamination that is hazardous to humans. As a result, building a Cd‐free CZTS solar cell is critical. Meanwhile, given that the peak power conversion efficiency of CZTS solar cells stands at a modest 11%, this study is dedicated to identifying an optimal approach for replacing the environmentally hazardous CdS layers to enhance overall efficiency. SCAPS‐1D is a one‐dimensional solar cell simulation program commonly used to examine proposed solar cells without building them. This study highlights the performance of CZTS with various nontoxic buffer layers, as well as the key results obtained through numerical research with SCAPS‐1D.

Simulation of antimony chalcogenide thin film solar cell with high-efficiency

Second generation solar cell (TFPV) have captured the attention of the majority of the research community in the energy sector due to dramatic enhancement in its efficiency. Copper Indium Gallium Selenide (CIGS) and Cadmium Telluride (CdTe) have been extensively investigated as light absorbing layer for thin film solar cells since last few years. However, limitations such as low abundance and toxicity of these materials precluded them from being used further in thin film solar cell technology. In this research work, we utilized photovoltaic materials like Sb2Se3 and Sb2S3 to examine the solar cell efficiency by one dimensional solar simulator (SCAPS-1D). A structural device is modelled for optimizing absorber layer thickness, and thus the solar cell efficiency, using various non-toxic buffer layers like CdS, ZnO, In2S3, ZnS, and ZnSe with the thickness of 40 nm. The modelled structure with optimized thickness (2 μm&2.5 μm) resulted in higher efficiency (∼22 %) antimony chalcogenide thin film solar cells.

N-type SnS2 thin films spray-coated from transparent molecular ink as a non-toxic buffer layer for solar photovoltaics

This paper reports the effect of solvent evaporation temperature on spray-coated tin disulfide (SnS2) thin films from molecular ink. Thiourea and tin chloride were the key chemical reagents used for the synthesis of SnS2 transparent ink under atmospheric conditions. The structural and compositional properties of SnS2 thin films revealed formation of pristine hexagonal SnS2. The films are smooth, homogeneous resulting in band gaps ranging from 2 to 2.22 eV suited for a Cd-free alternative buffer layer for Cu-based multicomponent solar cells. Thermoelectric power measurement showed that tin disulfide films exhibit n-type conductivity. Activation energy estimated from temperature variation of electrical conductivity measurement varied from 40 to 90 mV. Our results suggest that ink-processed SnS2 can be used as a potential alternative for opto-electronic devices such as thin film solar cell and photodetector devices.

Simple and Economical Extraction of Viral RNA and Storage at Ambient Temperature.

ABSTRACTRNA extraction is essential for the molecular detection of common viral pathogens. However, available extraction methods and the need for ultra-cold storage limit molecular testing in resource-constrained settings. Herein, we describe the development of an economical RNA Extraction and Storage (RNAES) protocol that eliminates requirements for instrumentation, expensive materials, and preserved cold chain. Through an iterative process, we optimized viral lysis and RNA binding to and elution from glass fiber membranes included in simple RNAES packets. Efficient viral lysis was achieved with a nontoxic buffer containing sucrose, KCl, proteinase K, and carrier RNA. Viral RNA binding to glass fiber membranes was concentration dependent across seven orders of magnitude (4.0–10.0 log10 copies/μL) and significantly increased with an acidic arginine binding buffer. For the clinical evaluation, 36 dengue virus (DENV)-positive serum samples were extracted in duplicate with the optimized RNAES protocol and once in an EMAG instrument (bioMérieux). DENV RNA was successfully extracted from 71/72 replicates (98.6%) in the RNAES protocol, and real-time RT-PCR cycle threshold (CT) values correlated between extraction methods. DENV RNA, extracted from clinical samples, was stable when stored on dried RNAES membranes at ambient temperature for up to 35 days, with median eluate RNA concentration decreasing by 0.18 and 0.29 log10 copies/μL between day 0 and days 7 and 35, respectively. At a cost of $0.08/sample, RNAES packets address key limitations to available protocols and may increase capacity for molecular detection of RNA viruses.IMPORTANCE RNA extraction methods and ultra-cold storage requirements limit molecular testing for common viruses. We developed a simple, flexible, and economical method that simultaneously addresses these limitations. At $0.08/sample, the new RNA Extraction and Storage (RNAES) protocol successfully extracted viral RNA from acute-phase sera and provided stable, ambient-temperature RNA storage for 35 days. Using this approach, we expect to improve RNA virus detection and outbreak response in resource-constrained settings.

The effect of ZnS buffer layer on Cu2SnS3 (CTS) thin film solar cells performance: Numerical approach

The aim of this paper is to optimize a new structure of Cu2SnS3 (CTS) thin-film based solar cells by using the one-dimensional solar cell capacitance simulator (SCAPS 1D). We proposed ZnS as a non-toxic buffer layer and ITO as a window layer, neither of which has been reported with a CTS absorber layer. The effects of various parameters that affect CTS thin-film solar cell performance, such as thickness of the absorber layer, carrier concentration, band gap, and temperature, are investigated. The generation and recombination rates in both structures, Mo/CTS/ZnS/ITO and Mo/CTS/CdS/ITO, are studied. The results reveal that solar cell performance is enhanced within the range of 5e+16–2e+17 cm−3 of carrier concentration and 1.3–1.5 eV of band gap of CdS. The recombination rate at the CTS/ZnS interface is significantly lower compared to the CTS/CdS interface, indicating good conduction band alignment between the CTS absorber and ZnS buffer. Under the optimum parameters, power conversion efficiency (PCE) of CTS-based solar cells was boosted from 16.53% to 17.05% when ZnS was used as a buffer layer instead of CdS.

Effect of alternative buffer layers for SnS based solar cells: Numerical analysis using SCAPS-1D

In this work, the numerical simulation of SnS thin films based solar cells with different nontoxic buffer layers in comparison to the toxic CdS buffer layer, using the solar cell capacitance simulator (SCAPS-1D) has been done. This is a preliminary study for the purpose of opening the experimental way to make solar cells based SnS thin films with non-toxic tampon layers, and also consists of the earth-abundant elements. The results of this study show that the use of alternate layers such as SnS2 and In2S3 causes an improvement in the performance of SnS thin films based solar cells.

Cubic Silicon Carbide (3C–SiC) as a buffer layer for high efficiency and highly stable CdTe solar cell

Cubic Silicon Carbide (3C–SiC) is a potential material for use in photovoltaics for its significant advancement in growth in terms of crystal quality and domain size. Hence, 3C–SiC has been introduced here as an alternative non-toxic buffer layer for heterojunction CdTe solar cell. The solar cell is designed for the study consisted of multi-junction semiconductor layers such as p-CdTe/n-3C–SiC/n-SnO2. Device modeling of the novel CdTe solar cell including the thickness and doping concentration of the novel buffer layer 3C–SiC are investigated and optimized using SCAPS-1D software. Also, the defect density in the buffer layer is studied to see the tolerance of the proposed device structure. The working temperature and incident light intensity are also varied to deduce the effect of environmental conditions on efficient PV operation.

Citrate-Citric Acid RNA Isolation (CiAR) for Fast, Low-Cost, and Reliable RNA Extraction from Multiple Plant Species and Tissues.

RNA isolation is routinely carried out in many laboratories for different downstream applications. Although protocols for this can vary between labs depending on the specific plant species and tissues under study and the preferences of their researchers, these protocols usually include the use of volatile organic and toxic chemicals. As an alternative, several companies offer less hazardous RNA extraction kits, but these kits significantly increase the cost per sample and are thus not affordable for every lab, especially when a large number of samples is to be processed. We have previously described a fast and efficient method for RNA isolation from plant vegetative tissues that requires only two home-made, simple, inexpensive, and nontoxic buffers. Both buffers have low concentrations of citric acid and its sodium salt. The first buffer also contains a detergent to help with nucleic acid solubilization while keeping RNases inactive. The second buffer has sodium chloride at high molarity to separate protein from nucleic acids. RNA is precipitated, and contaminating DNA can then be optionally removed. Here, we describe and expand on this approach, which we call the citrate-citric acid RNA isolation, or CiAR, method. We provide a detailed description of the protocol, describe a modification to make it compatible with non-vegetative tissues, and compile and extend the number of species and tissues to which it can be applied. © 2021 Wiley Periodicals LLC.

Zn(O,S) Buffer Layer for in Situ Hydrothermal Sb2S3 Planar Solar Cells.

Hydrothermal deposition is emerging as a highly potential route for antimony-based solar cells, in which the Sb2(S,Se)3 is typically in situ grown on a common toxic CdS buffer layer. The narrow band gap of CdS causes a considerable absorption in the short-wavelength region and then lowers the current density of the device. Herein, TiO2 is first evaluated as an alternative Cd-free buffer layer for hydrothermally derived Sb2S3 solar cells. But it suffers from a severely inhomogeneous Sb2S3 coverage, which is effectively eliminated by inserting a Zn(O,S) layer. The surface atom of sulfur in Zn(O,S) uniquely provides a chemical bridge to enable the quasi-epitaxial deposition of Sb2S3 thin film, confirming by both morphology and binding energy analysis using DFT. Then the results of the first-principles calculations also show that Zn(O,S)/Sb2S3 has a more stable structure than TiO2/Sb2S3. The resultant perfect Zn(O,S)/Sb2S3 junction, with a suitable band alignment and excellent interface contact, delivers a remarkably enhanced JSC and VOC for Sb2S3 solar cells. The device efficiency with the TiO2/Zn(O,S) buffer layer boosts from 0.54% to 3.70% compared with the counterpart of TiO2, which has a champion efficiency of Cd-free Sb2S3 solar cells with a structure of ITO/TiO2/Zn(O,S)/Sb2S3/Carbon/Ag by in situ hydrothermal deposition. This work provides a guideline for the hydrothermal deposition of antimony-based films upon a nontoxic buffer layer.

Impact of RbF post deposition treatment on CdS/CIGSe and Zn(O,S)/CIGSe interfaces – A comparative HAXPES study

In conventional Cu(In,Ga)Se2 (CIGSe) solar cells a chemical bath deposited CdS thin film is used as a buffer layer. However, it is desired to replace CdS due to the toxicity of cadmium and the rather narrow bandgap energy of CdS. Zn(O,S) is considered to be one of the most attractive candidates as an alternative, non-toxic buffer layer with a larger bandgap. This paper aims to compare the properties of the CdS/CIGSe and the Zn(O,S)/CIGSe interfaces depending on the absorber composition and the application of an RbF post deposition treatment (PDT). Synchrotron-based hard X-ray photoelectron spectroscopy revealed a strong correlation of Cd diffusion and concentration of VCu in CIGSe before the PDT. Additionally, the RbF-PDT enhanced the Cd diffusion into the CIGSe. On the other hand, it was found that Zn atoms are not as easily incorporated into the CIGSe as Cd atoms. As a result, we consider the formation of donor-like ZnCu+ defects at the interface to be less likely than the formation of CdCu+ defects. Moreover, we observed that the Zn(O,S)/CIGSe interface is less sensitive to changes of the CIGSe composition and to the RbF-PDT compared to the CdS/CIGSe interface.

Comparative study of the CZTS, CuSbS2 and CuSbSe2 solar photovoltaic cell with an earth-abundant non-toxic buffer layer

In the present article, modeling outcomes of novel and third-generation heterojunctions (3G) thin-film solar cells (TFSCs): quaternary semiconductor compound CZTS and ternary semiconductor compound CuSbS2 and CuSbSe2 have been presented. Solar cells have been studied and analysed to investigate optimized structure with good efficiency. CuSbS2 and CuSbSe2 are promising earth-abundant photovoltaic absorber materials which are chemically simpler than the widely studied Cu2ZnSnS4. However, CuSbS2 and CuSbSe2 photovoltaic (PV) devices currently have relatively low efficiency and poor reproducibility, often due to suboptimal material quality and insufficient optoelectronic properties. To overcome these concerns, we carried out numerical analysis using the Solar Cell Capacitance Simulator-1 dimensional software (SCAPS-1D). The band alignment and several parameters such as thickness and doping concentration have been investigated. Further C-V, C-f and J-V characteristics are also studied to compare and optimize the performance of CZTS, CuSbS2 and CuSbSe2 solar cell. Understanding the constraints imposed by the CZTS, CuSbS2, and CuSbSe2 absorber layers could help this technology to overcome the lower efficiency barrier.

Numerical modeling for earth-abundant highly efficient solar photovoltaic cell of non-toxic buffer layer

Abstract Solar photovoltaic cell research is always fascinating due to its clean, green nature. Cu2ZnSnS4Se4(CZTSSe)-based solar cells show fruitful performance in the field of power generation models based on sunlight. To improve the efficiency of CZTSSe-based solar cells, overall optimization remains an obstacle. Both thickness and bandgap of the absorber layer and the buffer layer have been optimized. Additionally, the contour plot of thickness vs. bandgap and bandgap vs. bandgap are further analyzed for overall optimization. Using the optimal values of the buffer layer based CZTSSe solar photovoltaic cell the efficiency has been observed as 24.8%. This earth's abundant, non-toxic buffer layer of CZTSSe solar photovoltaic cells could prove to be highly efficient CZTSSe based solar photovoltaic cells experimentally in the future.

CZTS solar cell with non-toxic buffer layer: A study on the sulphurization temperature and absorber layer thickness

Cu2ZnSnS4 solar cell has been fabricated with a non-toxic buffer layer and Al doped ZnO transparent conducting layer. A detailed material study on each layer of the solar cell has been carried out independently. The precursor films prepared by spin coating were sulphurized at different temperatures to optimize the conditions to obtain phase pure CZTS films. X-ray diffraction, Raman spectroscopy and rietveld refinement studies confirmed the phase purity of the film sulphurized at 500 °C. The optimum CZTS properties like band gap of 1.45 eV, high absorption coefficient ~2 × 105 cm−1 and dense surface morphology were obtained for films sulphurized at 500 °C. Carrier concentration, mobility and resistivity of these films were ~1 × 1019 cm−3, 0.23 cm2 V−1 s−1 and 2.7 Ωcm, respectively. The efficiency measurements of the cells with device structure SLG/Mo/CZTS/ZnS/AZO/Ag were carried out using absorber films with three different thicknesses. The optimized CZTS absorber layer with thickness of ~1.8 µm exhibited solar cell conversion efficiency of 3.02% for an active area of 0.21 cm2 withopen-circuit voltageof 0.38 V,short-circuitcurrent density of 17.19 mA/cm2 and fill factor of 46%.

Efficiency improvement of flexible Sb2Se3 solar cells with non-toxic buffer layer via interface engineering

Thin film Sb2Se3 solar cells have gained a worldwide attention as a highly potential Earth-abundant photovoltaic technology. While Sb2Se3 solar cells are typically fabricated in superstrate structure, substrate configuration devices offer versatility in substrate material choice particularly important for flexible devices. However, all substrate type Sb2Se3 solar cells use CdS as a buffer layer synthesized by chemical bath deposition method, during which Sb2Se3 surface is degraded limiting solar cell performance. Additionally, contamination layer has been reported to exist on Sb2Se3 surface after deposition under low vacuum conditions. In this study, we demonstrate a facile strategy to improve Sb2Se3 solar cell power conversion efficiency (PCE) by replacing CdS with In2S3 and applying a two-step treatment involving chemical etching and subsequent annealing. We show that a combined treatment which first removes the contamination layer and then passivates interface defects improves PCE more than three-fold, from 1.6% to 5.35%. Effective passivation of interface defects is ascribed to the formation of thin crystalline Sb2O3 layer on Sb2Se3 absorber surface after the treatment. In conclusion, optimized two-step treatment offers a simple and effective way to improve PCE and replacement of toxic CdS with In2S3 demonstrates new device design options towards flexible and non-toxic Sb2Se3 solar cells.