Efficient Buffer Layer Research Articles

A Deep Analysis and Enhancing Photovoltaic Performance Above 31% with New Inorganic RbPbI3‐Based Perovskite Solar Cells via DFT and SCAPS‐1D

AbstractThe inimitable structural, electronic, and optical properties of inorganic cubic rubidium‐lead‐halide perovskite have obtained significant attention. In this research, novel rubidium‐lead‐iodide (RbPbI3)‐based perovskite solar cells incorporating Tin Sulfide (SnS2) is investigated as an efficient buffer layer, utilizing both Density Functional Theory (DFT) calculations and SCAPS‐1D simulator. Primarily, DFT is used to compute the bandgap, partial density of states (PDOS), and optical properties of the RbPbI3 absorber, which are then applied in the SCAPS‐1D simulator. An optimized Al/FTO/SnS2/RbPbI3/Au device is systematically studied. Additionally, the effect of various influencing factors are investigated such as layer bulk defect density, interface defect density, doping concentration, and thickness. The highest power conversion efficiency (PCE) of 31.11% is achieved for the SnS2 Electron Transport Layer (ETL), with a JSC of 32.47 mA cm−2, VOC of 1.10 V, and FF of 87.14% for the Al/FTO/SnS2/RbPbI3/Au structure. Characteristics of quantum efficiency (QE) are also analyzed. Therefore, SnS2 ETL demonstrates the robust potential for utilization in high‐performance photovoltaic cells based on RbPbI3 perovskite.

Sputtering Deposited and Energy Band Matched ZnSnN2 Buffer Layers for Highly Efficient Cd‐Free Cu2ZnSnS4 Solar Cells

AbstractKesterite Cu2ZnSnS4 (CZTS) solar cells with CdS buffer layers have the problem of toxicity and cliff‐like energy band diagram disfavoring higher photoelectric conversion efficiency (PCE (%)). The preparation method for ZnSnO buffer layers which enable Cd‐free CZTS solar cells to reach the certified PCE (%) of 11.4 is limited to atomic layer deposition and sputtering deposition severely reduces PCE (%). Here, it is showed that sputtering deposited ZnSnN2 is an efficient buffer layer for Cd‐free CZTS solar cell, and without antireflection coating or additional passivation layers its champion PCE (%) has reached 10.00 which is comparable to the certified value. No buried junction and current blocking behavior are observed in the CZTS\ZnSnN2 junctions. Elemental inter‐diffusion is observed at the interface between CZTS and ZnSnN2. Most importantly, the energy band of ZnSnN2 is well‐matched with that of CZTS. The former straddles the latter. The conduction band offset is spike‐like with the conduction band of ZnSnN2 higher than that of CZTS, which effectively suppresses interface recombination and results in PCE (%) comparable to the certified value.

Li3BO3-Li3PO4 Composites for Efficient Buffer Layer of Sulphide-Based All-Solid-State Batteries

All-solid-state batteries (ASSBs) based on sulphide electrolytes are promising next-generation energy storage systems because they are expected to have improved safety, increased volumetric energy density, and a wide operating temperature range. However, side reactions at the cathode/electrolyte interface deteriorate the electrochemical performance and limit the commercialization of ASSBs. Surface coating of the cathode is an efficient approach for overcoming this issue. In this study, new Li3BO3 (LBO)-Li3PO4 (LPO) composites were applied as coating materials for high-Ni cathodes (NCM). PO4-based materials (such as LPO) have been used as coating layers because of their good chemical stability in sulphide electrolytes. However, the ionic conductivity of LPO is slightly insufficient compared to those of generally used ternary oxides. The addition of LBO could compensate for the low ionic conductivity of LPO and may provide better protection against sulphide electrolytes owing to the effect of LBO, which has been used as a good coating material. As expected, the LBO-LPO composites (LBPO) NCM exhibited superior discharge capacity, rate capability, and cyclic performance compared to the pristine and LPO-coated NCMs. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS) analyses confirmed that the LBPO coating on the cathodes successfully suppressed the byproduct formation and an undesirable interfacial layer, which are attributed to interfacial side reactions. This result clearly shows the potential of the LBPO coating as an excellent buffer layer to stabilise the oxide cathode/sulphide electrolyte interface.

Mechanism and principle of doping: realizing of silver incorporation in CdS thin film via doping concentration effect.

A high-quality buffer layer serves as one of the most significant issues that influences the efficiency of solar cells. Doping in semiconductors is an important strategy that can be used to control the reaction growth. In this study, the influence of Ag doping on the morphological, optical and electrical properties of CdS thin films have been obtained. Herein, we propose the mechanism of CdS film formation with and without Ag ions, and we found that changes in the reaction of preparing CdS by the chemical bath deposition (CBD) method cause a shift in the geometric composition of the CdS film. XRD showed that the position of peaks in the doped films are displaced to wider angles, indicating a drop in the crystal lattice constant. The optical analysis confirmed direct transition with an optical energy gap between 2.10 and 2.43 eV. The morphological studies show conglomerates with inhomogeneously distributed spherical grains with an increase of the Ag ratio. The electrical data revealed that the annealed Ag-doped CdS with 5% Ag has the highest carrier concentration (3.28 × 1015 cm-3) and the lowest resistivity (45.2 Ω cm). According to the results, the optimal Ag ratio was obtained at Ag 5%, which encourages the usage of CdS in this ratio as an efficient buffer layer on photovoltaic devices.

Boosting Potassium Storage by Integration Advantageous of Defect Engineering and Spatial Confinement: A Case Study of Sb2 Se3.

The potassium ion batteries (KIBs) based on conversion/alloying reaction mechanisms show high theoretical capacity. However, their applications are hampered by the poor cyclability resulting from the inherent large volume variations and the sluggish kinetics during K+ repeated insertion/extraction process. Herein, taken Sb2 Se3 as a model material, by rational design, nickel doped-carbon coated Sb2 Se3 nanorods (denoted as (Sb0.99 Ni0.01 )2 Se3 @C) are prepared through combined strategies of the conductive encapsulation and crystal structure modification. The carbon coating acts as an efficient buffer layer that maintains superior structural stability upon cycling. The introduction of Ni atoms can enhance electrical conductivity, leading to outstanding rate performance, which are confirmed by density functional theory calculation. The (Sb0.99 Ni0.01 )2 Se3 @C displays excellent reversible capacity (410mAhg-1 at 0.1Ag-1 after 100 cycles) and unprecedented rate capability (140mAhg-1 at 10Ag-1 ). Furthermore, KFeHCF//(Sb0.99 Ni0.01 )2 Se3 @C full cell exhibits a high specific capacity (408mAhg-1 at 0.1Ag-1 ), superior rate capability (260mAhg-1 at 2Ag-1 ). This work can open up a new avenue for the design of stable conversion/alloying-based anodes for high energy density KIBs.

Enhanced physicochemical properties of ZnTe thin films as potential buffer layer in solar cell applications

The Cd-based solar cells possess rear contact problem in superstrate device architecture, which may be eliminated by inserting a suitable buffer layer of zinc telluride (ZnTe) films of appropriate thickness between CdTe absorber and Cu/Au metal contacts. The present work meticulously reports the influence of annealing on the physicochemical properties of ZnTe thin films where ZnTe films were grown employing electron beam thermal evaporation technique and subsequently annealed for 1 h in air ambient and vacuum in 100–300 °C temperature range with an interval of 100 °C. Structural analysis reveals that as-grown and air/vacuum annealed ZnTe films have (111) preferred reflection with zinc blende structure of cubic phase (except 300 °C air annealed films) and grain size is boosted from 22 to 40 nm with annealing. The direct optical energy band gap is estimated in range of 2.25–2.84 eV and 2.65–2.87 eV for air and vacuum annealing, respectively. The contacts between the film surface and the TCO layer showed ohmic behavior as revealed by the I–V characteristics. The EDS results confirmed ZnTe thin film deposition and FESEM micrographs of air annealed films demonstrated the grain growth. The AFM images of vacuum annealed films showed hill-like topographies where hill density and RMS surface roughness reduced with annealing. The findings warrant that 100 °C air annealed ZnTe thin films could be employed as an efficient buffer layer and rear contact material to the Cd-based solar cell devices.

Air‐Stable Solar Cells with 0.7 V Open‐Circuit Voltage Using Selenized Antimony Sulfide Absorbers Prepared by Hydrazine‐Free Solution Method

Antimony chalcogenide is a promising absorber material for photovoltaic (PV) cells because of its tunable band gap, strong optical absorption, earth‐abundant, and nontoxic constituents. Here, a novel hydrazine‐free approach for fabricating antimony chalcogenide films prepared via spray pyrolysis deposition with further selenylation, as well as high performance solar cells are reported. The fabricated antimony chalcogenide solar cells exhibits remarkably high open‐circuit voltage (VOC) comparing with that of Sb2Se3 and Sb2S3 devices. The distribution of Se during the selenylation process via refering to the Fick's second law is discussed. The results show that the selenized absorber has tremendously improved absorbance for visible light and a cascade‐type energy level from surface to bulk, resulting in an ideal energy level matching for p‐n junction. By introducing an efficient buffer layer, the detrimental short‐circuit is avoided by reducing the cracks. Finally, 4.57% of the power conversion efficiency (PCE) of the solar cell is achieved. Furthermore, a module with a large‐scale active area of 21 cm2 is successfully fabricated, which shows a PCE of 3.19%, and a VOC of 3.42 V. The present work suggests that the antimony chalcogenide solar cells are promising for industrial application.

Cationic Interdiffusion at the SOFC Electrolyte/Cathode Interface in La2Mo2O9/La0.8Sr0.2MnO3‐δ

AbstractIn this work cation diffusion between a La2Mo2O9 (LM) ionic conductor and the conventional Solid Oxide Fuel Cell (SOFC) cathode material La0.8Sr0.2MnO3‐δ (LSM), was probed using secondary ion mass spectrometry (SIMS), and diffusion coefficients of Sr, Mo and Mn cations within both materials evaluated. Diffusion coefficients extracted from samples with a Sr solution deposited on the LM pellets and from a Mo solution deposited on LSM pellets were found to be orders of magnitude higher than the cross‐diffusion through the interface between two dense pellets in direct contact. These differences may be due to uncertainty in determining the interface position, or to a real dependence on the source of the diffusing cation. In the most favorable case, that of pellets in direct contact, extrapolation of diffusion coefficients down to a typical SOFC operating temperature, 800 °C, show that Mo diffusion in LSM (diffusion coefficient ∼ 10−14 cm2.s−1) is much higher than Sr or Mn diffusion in LM, and incompatible with use in a SOFC device, unless an efficient buffer layer is used.

Enhancing efficiency of perovskite solar cells using a thin buffer layer

A perovskite solar cell was fabricated; the active layer was treated with a solvent and a thin buffer layer was inserted. Methylbenzene treatment caused large agglomeration in the MAPbI3 active layer in the perovskite solar cell, reducing the series resistance (Rs). 1,3,5-Tris(N-phenylbenzimidazol-2-yl)benzene (TPBi) formed an efficient buffer layer, which enhances the performance of the device by improving interfacial contact between cathode and hole blocking layer and by preventing transportation of the holes to the cathode. The perovskite solar cell herein had an open circuit voltage (Voc) of 0.90 V, a short circuit current density (Jsc) of 13.44 mA/cm2, a fill factor (F.F.) of 64.69%, and a power conversion efficiency (PCE) of 7.81% under simulated AM1.5G illumination of 100 mW/cm2.

High-Performance Polymer Solar Cells Realized by Regulating the Surface Properties of PEDOT:PSS Interlayer from Ionic Liquids.

Significant efforts have been dedicated to the interface engineering of organic photovoltaic device, suggesting that the performance and aging of the device are not only dependent on the active layer, but also governed by the interface with electrodes. In this work, controllable interfacial dipole and conductivity have been achieved in ionic liquids (ILs) modified poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). We conclude that an appropriate interfacial conductivity is as essential as the suitable work function for an efficient buffer layer. Through forming favorable dipoles for hole transportation and reducing the film resistance by [HOEMIm][HSO4] treatment, an averaged performance of 8.64% is obtained for OPVs based on PTB7:PC71BM bulk heterojunction with improved stability. However, the improvement of performance is inconspicuous for OPVs based on PTB7-Th:PC71BM bulk heterojunction due to the incompetent energy level of high concentration ILs-modified PEDOT:PSS. The enhanced in-plane conductivity will reduce shunt resistance, and produce a fake high short-circuit current density (Jsc) with a lower fill factor. We point out that the Jsc can be improved by decreasing series resistance; meanwhile, the accompanying reduced shunt resistance has an unfavorable effect on device performance.

Curvature Management in Buffer Layer for Device Quality GaN Growth on Si (111)

ABSTRACTAn efficient buffer layer scheme has been designed to address the issue of curvature management during metalorganic chemical vapour deposition growth of GaN on Si (111) substrate. This is necessary to prevent cracking of the grown layer during post-growth cooling down from growth temperature to room temperature and to achieve an allowable bow (<40 μm) in the wafer for carrying out lithographic processes. To meet both these ends simultaneously, the stress evolution in the buffer layers was observed carefully. The reduction in precursor flow during the buffer layer growth provided better control over curvature evolution in the growing buffer layers. This has enabled the growth of a suitable high electron mobility transistor (HEMT) stack on 2" Si (111) substrate of 300 μm thickness with a bow as low as 11.4 μm, having a two-dimensional electron gas (2DEG) of mobility, carrier concentration, and sheet resistance values 1510 cm2/V–s, 0.96 × 1013/cm2, and 444 Ω/□, respectively. Another variation of similar technique resulted in a bow of 23.4 μm with 2DEG mobility, carrier concentration, and sheet resistance values 1960 cm2/V–s, 0.98 × 1013/cm2, and 325 Ω/□, respectively.

ZnS buffer layer for Cu2ZnSn(SSe)4 monograin layer solar cell

Copper zinc tin sulfo-selenide Cu2ZnSn(SSe)4 (CZTSSe) is a low-cost alternative semiconductor material that can be used as an absorber in solar cells. CdS deposited by chemical bath deposition (CBD) is the most efficient buffer layer for Cu2ZnSn(SSe)4 and Cu(InGa)(SSe)2 (CIGS) solar cells. However, there is a strong demand for the development of a Cd-free buffer layer due to the toxicity of Cd and its associated concerns with respect to the disposal and long term safety of Cd containing solar modules. In this work, we report for the first time, the successful use of a ZnS buffer layer for CZTSSe monograin solar cell that shows similar functionality level as a CdS buffer layer. ZnS buffer layer was deposited onto CZTSSe absorber layer by employing a scalable non-vacuum CBD method. The effect of morphology, thickness, as well as chemical composition of the ZnS buffer layer on the efficiency of the CZTSSe solar cell was investigated, and the best CZTSSe monograin solar cell had an efficiency of 4.50 (±0.16)%. External quantum efficiency (EQE) showed higher transmission in the blue light region for the ZnS buffer compared to CdS. Increased number of ZnS layers decreased the EQE signal in 400–800nm regions, resulting in decreased J–V parameters, suggesting a single layer of 10–25nm ZnS as a most efficient alternative buffer for CZTSSe.

Greatly Reduced Processing Temperature for a Solution‐Processed NiOx Buffer Layer in Polymer Solar Cells

By application of thermal annealing and UV ozone simultaneously, a solution‐processed NiOx film can achieve a work function of approximately –5.1 eV at a temperature below 150 °C, which allows the processing of NiOx that is compatible with fabrication of polymer solar cells (PSCs) on plastic substrates. The low processing temperature, which is greatly reduced from 250–400 °C to 150 °C, is attributed to the high concentration of NiOOH species on the film surface. This concentration will result in a large surface dipole and lead to increased work function. The pretreated NiOx is demonstrated to be an efficient buffer layer in PSCs based on polymers with different highest occupied molecular orbital energy levels. Compared with conventional poly(3,4‐ethylenedioxy‐thiophene):poly(styrenesulfonate)‐buffered PSCs, the NiOx‐buffered PSCs achieve similar or improved device performance as well as enhanced device stability.

Giant changes in magnetic and magnetoresistive properties of CoFe/Cu multilayers at subnanosized variations in the thickness of the chromium buffer layer

The article discusses the magnetic and magnetoresistive properties of the [Co90Fe10/Cu]n multilayers prepared by magnetron sputtering as a function of the type of the substrate and the material and thickness of a buffer layer (Co90Fe10, Cu, Cr, Fe). The multilayers with a chromium buffer layer exhibit a sharp transition from low-coercive to high-coercive state at low variations in the thickness of the chromium layer (from 15 to 20 A). It has been demonstrated that the revealed sudden change in the hysteresis properties of the multilayers with a Cr buffer layer is accompanied by structural changes in the Cu and Co90Fe10 layers, characterized by the disappearance of the 〈111〉 texture at tCr > 20 A. It has been found that the most efficient buffer layer, which at room temperature ensures a threefold increase in the magnetoresistance at a minimum increase in hysteresis, is the Co90Fe10 (15 A) layer. It has been established that the substrate type ((100)Si, \((10\bar 12)\) Al2O3, glass) does not exert a significant effect on the magnetoresistive properties of the multilayers studied.

Effects of Amorphous Carbon Films on the Performance of Porous Silicon Electroluminescence

ABSTRACTEfficient electroluminescence (EL) is obtained at low operating voltages (&lt;3 V) from n+-type silicon- electrochemically oxidized thin nanocrystalline porous silicon (PS)-amorphous carbon-Indium tin oxide (ITO) junctions. The effects of a few nanometer thick amorphous carbon film between PS and ITO on the EL characteristics have been investigated. The carbon film enhances the stability. The EL efficiency is improved due to a reduction of current density and an increase in EL intensity. In addition, the reproducibility from device to device is very much improved by the carbon film. The enhancement in stability should originate from the capping of PS by the carbon film and the high chemical stability of carbon and Si-C bonds, which should prevent PS oxidation. The carbon film acts as an efficient buffer layer between PS and ITO, resulting in enhanced mechanical, electrical and chemical stability of the top contact and providing high reproducibility. The thin carbon film has only positive effects on all the EL characteristics. This is a very important step towards application.