Hybrid Buffer Layer Research Articles

Hydrothermal synthesis of kesterite CZTSSe nanoparticles for highly efficient thin film

CZTSSe kesterite nanoparticles have been investigated for the efficient. The hydrothermal method has been used to prepare the material. The various characterization like X-ray diffraction (XRD), Raman scattering, Scanning Electron Microscopy (SEM) for (UV–Vis) ultraviolet–visible spectrophotometry and (EDS) energy-dispersive X-ray spectroscopy and of the prepared nano particles have been studied. Furthermore, numerical analysis of the synthesized material has also been investigated to optimize the performance for more characterization at the device level. For the optimization purpose, we have modelled a device structure of the hybrid buffer layer and optimized its physical parameters for the efficient. Theoretical efficiency is found to be 18.46 % for the prepared model. The results of this study show that Cu2ZnSn (S, Se)4 could be used as an absorbent layer for efficient solar cell.

Maximizing the solar output power using hybrid (CdS/ZnSe) buffer for CIGS thin film solar cell

In this work, a hybrid buffer layer (CdS & ZnSe) is placed between the absorber and the window layer in a CIGS (Copper Indium Gallium Selenide) solar cell replacing the commonly used single-layer CdS. The buffer layer plays a crucial role in interface electricity to enhance the performance of the solar cell. Although, CdS is used as a buffer layer in CIGS solar cells, the toxic nature and parasitic absorption due to the narrowband gap (2.4 eV) become issues during its application in devices. To reduce Cd concentration and ameliorate the bandgap issue, the hybrid buffer layer (CdS & ZnSe) is a perfect supplant. In this study, numerical simulation is performed on CIGS-based solar cells comprised of a hybrid buffer layer to enhance the performance by optimizing the physical parameters (thickness, carrier concentration, and defect density) of both absorber and buffer layer using SCAPS-1D software. In the process of optimizing physical parameters, the effect of the mentioned parameters is observed on the solar cell performance. Later, the impact of working temperature is shown in the solar cell performance. Finally, with all those optimized parameters, a comparison has been done between the reference and the proposed structure. The comparison asserts that the proposed structure with a conversion efficiency of 24.55% is outdistancing the reference structure as well as some relative structures from the recent study. The simulation results in this study can be a didactic one in the fabrication of high-efficiency CIGS solar cells

Performance enhancement of Sb2Se3-based solar cell with hybrid buffer layer and MoSe2 as a hole transport material using simulator device

In this work, we first compared the experimental and simulated J-V characteristics of the Sb2Se3-based solar cell without and with a hybrid buffer layer using SCAPS-1D software. The introduction of a second buffer layer reduces the current leakage caused at the front contact of the solar cell and the power conversion efficiency (PCE) increases from 3.75% to 5.18%; and the use of the ternary compound cadmium zinc sulfide (CdZnS), as an alternative electron transport layer (ETL) to the traditional cadmium sulfide (CdS), increases the PCE from 5.18% to 7.13%. Thereafter, different thicknesses of the SnO2/CdZnS hybrid buffer layer were simulated, and the optimization resulted in a value of 50 nm, with thicknesses of 10 nm and 40 nm for the SnO2 and CdZnS layers respectively. Furthermore, the optimization of the Sb2Se3 absorber allows to obtain a bulk defect density of 1011 cm−3 and a carrier capture cross section of 10–14 cm2. Finally, the low doping problem of the absorber is solved by forming a MoSe2 layer at the Sb2Se3/Mo interface. MoSe2 acts as a hole transport material (HTM) and is used for high mobility of charge carriers within it; moreover, its presence improves the performance of the Sb2Se3-based solar cell and a PCE of 18.77% (JSC = 34.37 mA/cm2, VOC = 660 mV, FF = 82.78%) is obtained. Our simulation results also show that the n-i-p configuration of the Sb2Se3-based solar cell is more stable.

Promising Cd-free double buffer layer in CZTSSe thin film solar cells

Zn(O,S) film is widely used as a Cd-free buffer layer for kesterite thin film solar cells due to its low-cost and eco-friendly characteristics. However, the low carrier concentration and conductivity of Zn(O,S) will deteriorate the device performance. In this work, an additional buffer layer of In2S3 is introduced to modify the properties of the Zn(O,S) layer as well as the CZTSSe layer via a post-annealing treatment. The carrier concentrations of both the Zn(O,S) and CZTSSe layers are increased, which facilitates the carrier separation and increases the open circuit voltage (VOC). It is also found that ammonia etching treatment can remove the contamination and reduce the interface defects, and there is an increase of the surface roughness of the In2S3 layer, which works as an antireflection layer. Consequently, the efficiency of the CZTSSe solar cells is improved by 24% after the annealing and etching treatments. Simulation and experimental results show that a large band offset of the In2S3 layer and defect energy levels in the Zn(O,S) layer are the main properties limiting the fill factor and efficiency of these CZTSSe devices. This study affords a new perspective for the carrier concentration enhancement of the absorber and buffer layers by In-doping, and it also indicates that In2S3/Zn(O,S) is a promising Cd-free hybrid buffer layer for high-efficiency kesterite solar cells.

Contribution to sustainable and environmental friendly non-toxic CZTS solar cell with an innovative hybrid buffer layer

Due to non-toxicity and earth abundancy of raw materials, CZTS grabbing the attention of researchers to make it highly efficient and cost-effective solar cell harvesting. Thin-film CZTS based solar cell of higher efficiency reported with conventional CdS layer. Toxicity of Cd influences to reduce the thickness of the CdS buffer layer without compromising with the efficiency. The present paper deals with CdS/In2S3 and CdS/ZnS hybrid buffer layer which is more efficient than the solar cell using only the CdS buffer layer. The reduced thickness of the CdS layer in CZTS/CdS/In2S3/ZnO: Al and CZTS/CdS/ZnS/ZnO: Al structures have been optimized by using SCAPS-1D simulation software. This study reveals that there is an enhancement in the performance of solar cells from η = 15.68% with CdS to η = 16.52% with CdS/In2S3 and η = 15.81% with CdS/ZnS hybrid buffer layer. Variation in PV parameters with a variation of the thickness of the buffer and absorber layer has been optimized. The acceptor density of CZTS/CdS/In2S3 and CZTS/CdS/ZnS was varied and results have been optimized. A numerical study of both structures on the photovoltaic performance of CZTS solar cells has been done by using SCAPS-1D simulation software.

Improving cathode/Li6.4La3Zr1.4Ta0.6O12 electrolyte interface with a hybrid PVDF-HFP-based buffer layer for solid lithium battery

Solid-state lithium battery is considered as a promising solution to improve safety performance. However, huge interfacial resistance and polarization between cathode and solid electrolyte are still big challenges for further application. In this study, an improved cathode/Li6.4La3Zr1.4Ta0.6O12 garnet electrolyte interface with low resistance and reduced polarization is successfully constructed by introduced a Li6.4La3Zr1.4Ta0.6O12-C added hybrid PVDF-HFP-based buffer layer. The hybrid buffer layer provides ionic and electronic transport pathways simultaneously at the interface. With the improved interface, the LiFePO4 cathode in the solid-state battery using LLZTO electrolyte displays an increased Li+ diffusion coefficient of 3.42 × 10−12 cm2 s−1 and low charge transfer resistance of 345.2 Ω at 1st cycle. The LFP solid-state battery reaches an initial capacity of 152.2 mA h g−1 and, in particular, displays an outstanding cycle performance with a retention of 84.6% over 200 cycles at 0.5 C and an average columbic efficiency of 99.5%.

Hybrid chemical bath deposition-CdS/sputter-Zn(O,S) alternative buffer for Cu2ZnSn(S,Se)4 based solar cells

To replace the conventionally used CdS buffers in Cu2ZnSn(S,Se)4 (CZTSSe) based thin-film solar cells, sputtered Zn(O,S) buffer layers have been investigated. Zn(O,S) layers with three different [O]/([O] + [S]) ratios (0.4, 0.7, and 0.8)—and a combination of Zn(O,S) and CdS (“hybrid buffer layer”) were studied. In comparison to the CdS reference, the external quantum efficiency (EQE) of the Zn(O,S)-buffered devices increases in the short- and long-wavelength regions of the spectrum. However, the average EQE ranges below that of the CdS reference, and the devices show a low open-circuit voltage (VOC). By adding a very thin CdS layer (5 nm) between the absorber and the Zn(O,S) buffer, the VOC loss is completely avoided. Using thicker intermediate CdS layers result in a further device improvement, with VOC values above those of the CdS reference. X-ray photoelectron spectroscopy (XPS) measurements suggest that the thin CdS layer prevents damage to the absorber surface during the sputter deposition of the Zn(O,S) buffer. With the hybrid buffer configuration, a record VOC deficit, i.e., a minimum difference between bandgap energy Eg (divided by the elementary charge q) and VOC (Eg/q – VOC) of 519 mV could be obtained, i.e., the lowest value reported for kesterite solar cells to date. Thus, the hybrid buffer configuration is a promising approach to overcome one of the main bottlenecks of kesterite-based solar cells, while simultaneously also reducing the amount of cadmium needed in the device.

Organic/Inorganic Hybrid Buffer in InGaZnO Transistors under Repetitive Bending Stress for High Electrical and Mechanical Stability.

We investigated the influence of the multilayered hybrid buffer consisting of Al2O3/PA (polyacrylic) organic layer/Al2O3 on the electrical and mechanical properties of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs). The multilayered organic/inorganic hybrid buffer has multiple beneficial effects on the flexible TFTs under repetitive bending stress. First, compared to the PA or Al2O3 single-layered buffer, the multilayered hybrid buffer showed an improved WVTR value of 1.1 × 10-4 g/m2 day. Even after 40,000 bending cycles, the WVTR value of the hybrid buffer increased only by 17%, while the WVTR value of the Al2O3 layer doubled after cyclical bending stress. We also confirmed that the hybrid buffer has advantages in mechanical durability of the TFT layers because of the change in the position of the neutral plane and the strain reduction effect by the PA organic layer. When we fabricate a top-gate a-IGZO TFT with the hybrid buffer layer (HB TFT), the device shows Vth = 0.74 V, μFE = 14.4 cm2/V·s, a subthreshold slope of 0.27 V/dec, and hysteresis of 0.21 V, which are superior to that of TFTs fabricated on an Al2O3 single-layer buffer (IB TFT). From the X-ray photoelectron spectroscopy and elastic recoil detection analysis, the difference in the electrical performance of TFTs could be explained by hydrogen-related molecules. After annealing at 270 °C, the amounts of hydrogen found in the a-IGZO layer for the IB, HB, and OB TFTs were 3.57 × 1021, 5.77 × 1021, and 7.34 × 1021 atoms/cm3, respectively. A top-gate bottom-contact structured a-IGZO TFT fabricated on the PA layer (OB TFT) showed a gate dielectric breakdown because of excessively high hydrogen content and high nonbonding oxygen content. On the other hand, HB TFTs showed better positive bias stability because of the higher hydrogen concentration, as hydrogen (when not excessive) is beneficial in passivating electron traps. Finally, we conducted 60,000 repetitive bending cycles on IB TFTs and HB TFTs with various bending radii down to 1.5 mm. The HB TFT shows improved mechanical durability and exhibits less electrical degradation during and after repetitive bending stress, compared to the IB TFT.

Efficiency Improvement of CZTSe Solar Cell with Ag Doped Zno/Cds Buffer Layer, using Scaps Simulation Programme

Compound semiconductor CZTSe is a popular absorber layer for thin film solar cells. Instead of single semiconductor buffer layer, a hybrid buffer layer is used with CZTSe absorber layer. To reduce further usage of toxic materials(CdS) and simultaneously to increase the solar cell efficiency, Ag doped buffer layer was proposed and a numerical studies were performed using SCAPS 1-D simulation programme. Also the thickness and the carrier density of the different layers in the solar cell were optimized to achieve the above goals. After the simulation process, the toxic materials usage was reduced by 62% and the efficiency was increased from 12.24% to 12.69%

Thickness optimization of CdS/ZnO hybrid buffer layer in CZTSe thin film solar cells using SCAPS simulation program

In CZTSe thin film solar cell, CZTSe/CdS as absorber/buffer layer has been used and ZnO is used as a window layer. CdS as buffer layer have high efficiency but it is toxic due to cadmium. So to reduce the cadmium usage, a hybrid buffer layer of ZnO/CdS is proposed and the numerical study has been performed using SCAPS-1D simulator. The thickness of ZnO/CdS buffer layer has been optimized at ZnO-15 nm/CdS-65 nm, for maximum solar cell efficiency. The solar cell with hybrid buffer layer of ZnO/CdS exhibits more efficiency compared to the solar cell using only CdS or only ZnO as buffer layers. The solar cell efficiency variation with temperature has been studied for CdS, ZnO and CdS/ZnO buffer layer and observed that the variations are almost same for all the three layers.

P‐13.4: Enhancement of top emission white organic light‐emitting diodes with a buffer layer

The top‐emitting white organic light‐emitting diodes (TE‐WOLEDs) containing transparent cathode with various structures of buffer layers were developed. The HATCN effectively protects the underlying organic layers from plasma damage during deposition by sputtering, and the optimized thickness was determined by the UV—Vis absorption spectroscopy. The device with 23 nm HATCN showed higher luminance than other devices. A simple and effective method to determine the buffer layer thickness was discovered. The device using the hybrid buffer layer (HATCN /Mg : Ag) showed the lower voltage and longer lifetime than single buffer layer. The reason is that the hybrid buffer layer have excellent contact and plasma protection performance.

Conduction band offset engineering in wide-bandgap Ag(In,Ga)Se2 solar cells by hybrid buffer layer

Ag(In,Ga)Se2 (AIGS) is one of the promising candidates for the top cell absorber in the tandem structure. However, the conversion efficiency of AIGS solar cells is still lower than that required for the top cell. In this study, to improve the conversion efficiency of AIGS solar cells, we controlled the conduction band offset (CBO) at the buffer layer/ZnO and buffer layer/AIGS interfaces. The reduction in interface recombination at the CdS buffer layer/AIGS interface was achieved by introducing a ZnS(O,OH) buffer layer instead of a CdS buffer layer, although the fill factor (FF) decreased markedly because the CBO at the ZnS(O,OH)/ZnO interface prevented the electron flow under a forward bias. We found that the introduction of a CdS/ZnS(O,OH) hybrid buffer layer is efficient in controlling the CBO at both the buffer layer/AIGS and buffer layer/ZnO interfaces and improving the solar cell conversion efficiency.

Low-Cd CIGS Solar Cells Made With a Hybrid CdS/Zn(O,S) Buffer Layer

In Cu(In,Ga)Se2 (CIGS) solar cells, CdS and Zn(O,S) buffer layers were compared with a hybrid buffer layer consisting of thin CdS followed Zn(O,S). We explore the physics of this hybrid layer that combines the standard (Cd) approach with the alternative (Zn) approach in the pursuit to unlock further potential for CIGS technology. CdS buffer development has shown optimal interface properties, whereas Zn(O,S) buffer development has shown increased photocurrent. Although a totally Cd-free solar module is more marketable, the retention of a small amount of Cd can be beneficial to achieve optimum junction properties. As long as the amount of Cd is reduced to less than 0.01% by weight, the presence of Cd does not violate the hazardous substance restrictions of the European Union (EU). We estimate the amount of Cd allowed in the EU for CIGS on both glass and stainless steel substrates, and we show that reducing Cd becomes increasingly important as substrate weights decrease. This hybrid buffer layer had reduced Cd content and a wider space charge region, while achieving equal or better solar cell performance than buffer layers of either CdS or Zn(O,S) alone.

A Cd-reduced hybrid buffer layer of CdS/Zn(O,S) for environmentally friendly CIGS solar cells

For the fabrication of high efficiency Cu(In,Ga)Se2 (CIGS) solar cells, a Cd-reduced hybrid CdS/Zn(O,S) is used as the buffer layer.

Employing inorganic/organic hybrid interface layer to improve electron transfer for inverted polymer solar cells

The performance of inverted polymer solar cells (PSCs) was enhanced by introducing TiOx and poly(9,9-dioctylfluorenyl-2,7-diyl) (PFD) as a hybrid buffer layer. Surface morphology and work function measurement demonstrated that PFD interlayer eliminated the defects and traps from TiOx surface and acted as an efficient charge transport matrix, resulting in enhanced electron mobility and reduced interface resistance. Therefore, the employment of TiOx/PFD composite layer improved to extract electron from active layer to ITO electrode and dramatically increased device efficiency from 5.717% to 7.272%, accounting for a 27.2% increase. The achieved high device efficiency, low-cost materials, and solution processes of TiOx/PFD layer provide a promising candidate for realizing high performance photovoltaic devices.

All-solution processed double-decked PEDOT:PSS/V2O5 nanowires as buffer layer of high performance polymer photovoltaic cells

In this study, a high performance organic–inorganic polymer photovoltaic device with double-decked anode buffer layer sandwiched between indium tin oxide (ITO) and the photoactive layer is reported. The double-decked buffer layer is fabricated by coating vanadium oxide (V2O5) nanowire on top of the PEDOT:PSS layer and the reported device has the structure of ITO/PEDOT:PSS/V2O5/P3HT:PCBM/Al. The power conversion efficiency (PCE) of polymer photovoltaic cells with the hybrid buffer layer is improved by 14.10% compared to the polymer photovoltaic cell commonly employed PEDOT:PSS hole transporting material; and PCE of this proposed polymer photovoltaic cell is improved by 30.40% compared with the polymer photovoltaic cell employed V2O5 powder as buffer layer. The improvement of PCE is mainly caused by the elevation of short circuit current density (Jsc) instead of the open circuit voltage (Voc). Experimental results show that layer of V2O5 nanowires cannot only block electron from wrong directions efficiently, but also increase incident light paths in the hybrid buffer layers due to refraction and reflection. And pseudo texturing effects of V2O5 nanowires which result in higher photon absorptivity of the photoactive layer make polymer photovoltaic cells with this double-decked buffer layer outperform that with buffer layers constructed by either PEDOT:PSS or V2O5 nanowires only.

P‐128: High‐Efficiency Hybrid Buffer Layer in Inverted Top‐Emitting Organic Light‐Emitting Diodes

A hybrid buffer layer with superior plasma protection ability and high injection efficiency was developed. The hybrid buffer layer composed by dual‐layered structure of HATCN/MoO3 enhances hole‐injection efficiency and protects organic layers under the top electrode. This hybrid buffer layers improve the electric characteristics of inverted top‐emitting organic light‐emitting diodes.

High-performance hybrid buffer layer using 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile/molybdenum oxide in inverted top-emitting organic light-emitting diodes.

A high-performance 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HATCN)/molybdenum oxide (MoO3) hybrid buffer layer with high hole-injection efficiency and superior plasma resistance under the sputtering process was developed. The HATCN enhances the hole-injection efficiency, and the MoO3 effectively protects the underlying organic layers from plasma damage during deposition by sputtering. This improves the characteristics of inverted top-emitting organic light-emitting diodes using a top transparent conductive oxide electrode. The device using the hybrid buffer layer showed the highest electroluminescence characteristics among devices with other buffer layers. The high hole-injection efficiency of HATCN was shown by the J-F curve of hole-only devices, and the plasma protection performance of MoO3 was shown by atomic force microscope surface morphology images of the buffer layer film after O2 plasma treatment.

Improving Efficiency by Hybrid TiO2 Nanorods with 1,10-Phenanthroline as A Cathode Buffer Layer for Inverted Organic Solar Cells

We reported a significant improvement in the efficiency of organic solar cells by introducing hybrid TiO2:1,10-phenanthroline as a cathode buffer layer. The devices based on polymer thieno[3,4-b]thiophene/benzodithiophene:[6,6]-phenyl C71-butyric acid methyl ester (PTB7:PC71BM) with hybrid buffer layer exhibited an average power conversion efficiency (PCE) as high as 8.02%, accounting for 20.8% enhancement compared with the TiO2 based devices. The cathode modification function of this hybrid material could also be extended to the poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) system. We anticipate that this study will stimulate further research on hybrid materials to achieve more efficient charge collection and device performance.

Enhanced carrier mobility and photon-harvesting property by introducing Au nano-particles in bulk heterojunction photovoltaic cells

In this study, polymer solar cells (PSCs) doped with Au nanoparticles (Au NPs) were successfully fabricated to maximize the photon-harvesting properties on the photoactive layer. In addition, a conductivity-enhanced hybrid buffer layer was introduced to improve the photon absorption properties and effectively separate the generated charges by adding Au NPs and dimethylsulfoxide (DMSO) to the PH 500 as a buffer layer. The PSC performance was optimized with a 88% improvement over the conventional PSCs (photoactive area: 225mm2, power conversion efficiency (PCE): 3.2%) by the introduction to the buffer layer of Au NPs and DMSO at 10wt% and 1.0wt%, respectively, and with 15wt% Au NP doping in the photoactive layer. The internal resistance was decreased due to the increased photocurrent caused by the localized surface plasmon resonance (LSPR) effect of the Au NPs in the photoactive layer and by the improvement of carrier mobility induced by the DMSO doping of the buffer layer. As a result, the series resistance (RS) deceased from 42.3 to 19.7Ωcm2 while the shunt resistance (RSH) increased from 339 to 487Ωcm2.