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UV-ozone induced surface passivation to enhance the performance of Cu2ZnSnS4 solar cells
摘要： Interface property has been considered one of the most critical factors affecting the performance of semiconductor devices. In this work, we demonstrate an efficient surface passivation for the interface between Cu2ZnSnS4 (CZTS) and CdS buffer layer by using UV-ozone treatment at room temperature. The passivation led to a significant enhancement of short circuit current density (Jsc) of the device from 11.70 mA/cm2 to 18.34 mA/cm2 and thus efficiency of the CZTS solar cells from 3.18% to 5.55%. The study of surface chemistry has revealed that the UV-ozone exposure led to formation of a Sn–O rich surface on CZTS, which passivates the dangling bonds and forms an ultra-thin energy barrier layer at the interface of CZTS/CdS. The barrier is considered to be responsible for the reduction of non-radiative recombination loss in the solar cells as confirmed by photoluminescence (PL) measurement. The elongated lifetime of minority carriers in the CZTS solar cells by time-resolved PL has further verified the interface passivation effect induced by UV-ozone treatment. This work provides a fast, simple yet very effective approach for surface passivation of CZTS film to boost the performance of CZTS solar cells.
关键词： CZTS solar cell,UV-Ozone treatment,Interface modification,Surface passivation
更新于2025-11-21 11:01:37
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Visible light active CZTS sensitized CdS/TiO2 tandem photoanode for highly efficient photoelectrochemical hydrogen generation
摘要： A tandem photoanode consisting of Cu2ZnSnS4 (CZTS) nanoparticles layer over CdS/TiO2 heterostructure thin film on FTO substrate has been fabricated for photoelectrochemical hydrogen generation. CdS thin film has been deposited by chemical bath deposition over the spin-coated TiO2 thin film, which is followed by the deposition of CZTS nanoparticles layer by spray coating technique resulting in a CZTS/CdS/TiO2/FTO photoanode. The coating of CZTS nanoparticles layer over CdS/TiO2 films resulted in the tandem structure of different band level positions, which enhances the optical absorption in the visible region and also leads to higher separation of the photogenerated charge carriers. A substantial enhancement (39 times) in the PEC activity has been demonstrated for the CZTS/CdS/TiO2/FTO photoanode as compared to TiO2/FTO photoanode, which is due to cascade band gap from 3.2 eV to 1.7 eV and formation of heterojunction at interfaces. The enhancement in the charge transport properties of CZTS/CdS/TiO2/FTO photoanode has been confirmed from the electrochemical impedance spectroscopy (EIS) measurement. The EIS results confirm that the CZTS/CdS/TiO2/FTO photoanode exhibited lowest charge transfer resistance (Rct = 302 Ω/cm2) as compared to CdS/TiO2 (Rct = 615 Ω/cm2) and TiO2 (Rct = 1700 Ω/cm2) photoanode. A mechanism depicting the enhanced the performance of photoelectrochemical (PEC) CZTS/CdS/TiO2/FTO photoanode has been proposed.
关键词： EIS,Hydrothermal,PEC,Hydrogen generation,CZTS nanoparticles
更新于2025-10-22 19:40:53
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One-Step Electrodeposition of CuZnSn Metal Alloy Precursor Film Followed by the Synthesis of Cu2ZnSnS4 and Cu2ZnSnSe4 Light Absorber Films and Heterojunction Devices
摘要： CuZnSn metallic alloy precursor films were electrodeposited on Mo substrate from a Zn-rich bath solution yielding low deposition rates. The precursor films were converted to photovoltaic absorber films of Cu2ZnSnS4 and Cu2ZnSnSe4 by sulfurization and selenization processes. X-ray diffraction, Raman spectroscopy and photocurrent spectroscopy techniques were utilized for the identification of films. The surface morphology, uniformity and compactness of the films were examined by scanning electron microscopy. The precursor and absorber films had a uniform and compact structure. The precursor films were composed from the Cu3Sn, Cu6Sn5 and Cu5Zn8 phases and their grain size varied tightly with the cathode potential. The conversion of precursor films to Cu2ZnSnS4 and Cu2ZnSnSe4 were verified from the results of their X-ray diffraction, Raman shifts, and optical transition energies. To assess the device quality of the absorber films, CdS/Cu2ZnSnS4 and CdS/Cu2ZnSnSe4 heterojunction diodes were fabricated and their device parameters were determined. The diodes showed relatively good ideality factor of 1.3-1.9, current rectification factor of ~120, and reverse biased saturation current of ~30-60 μA/cm2. Photocurrent spectroscopy was utilized to evaluate the band gap energy and other optical transition energies of the absorber films from the short-circuit photocurrent of the diodes.
关键词： electrodeposition,CZTS,CZTSe,photocurrent,Raman
更新于2025-09-23 15:23:52
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Impact of sulphurization environment on formation of $$\hbox {Cu}_{2}\hbox {ZnSnS}_{4}$$ Cu 2 ZnSnS 4 films using electron beam evaporated stacked metallic precursors
摘要： The superiority of copper zinc tin sulphide (Cu2ZnSnS4; CZTS) over the existing absorber layer materials is inevitable owing to its cheap, non-toxic and earth abundant constituents with high absorption coefficient value. In the present study, CZTS films are prepared by sulphurizing electron beam deposited precursors of glass/Cu/Zn/Sn/Cu and glass/Cu/Sn/Zn/Cu stacking sequences in two different environments i.e., elemental S powder and 5% H2S + N2 gas at different ramping rates. The effect of sulphurization environment and sulphurization ramping rate on the formation of CZTS is investigated using X-ray diffraction and Raman spectroscopy. The morphology and composition of the films are analysed respectively using field emission gun scanning electron microscopy and energy dispersive X-ray spectroscopy. It is observed that films prepared in elemental S powder at a low ramping rate exhibit better crystallinity with less impurity phases. The presence of ZnS is observed in all the films, while the presence of SnS is observed in films prepared with H2S gas alone, thus concluding that sulphurization in the presence of elemental S powder at a low ramping rate is highly favourable for CZTS film formation. CZTS films with minor ZnS impurity with a bandgap of 1.48 eV is successfully fabricated by using a glass/Cu/Zn/Sn/Cu precursor stack.
关键词： ramping rate,Electron beam evaporation,CZTS
更新于2025-09-23 15:22:29
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Nanoscale charge transport and local surface potential distribution to probe defect passivation in Ag doped Cu2ZnSnS4 absorbing layer
摘要： The performance of earth abundant Cu2ZnSnS4 (CZTS) material is limited by high deficit of open circuit voltage (VOC) which is mainly due to the easy formation of CuZn antisite defects. Suppression of CuZn defects is thus inevitably required for further developments in CZTS based solar cells. We studied systematic increase of Ag doping in CZTS thin film and investigated the nanoscale electrical properties using kelvin probe force microscopy (KPFM) and current sensing atomic force microscopy (CAFM) to probe CuZn defects. Crystallographic analysis indicated the successful partial substitution of Cu+ ions by large size Ag+ ions. The considerable decrease in grain boundary potential from 66.50 ± 5.44 mV to 13.50 ± 2.61 mV with Ag doping, suggesting the substantial decrease in CuZn defects. Consequently, CAFM measurement confirms the remarkable increment in minority carrier current with Ag doping and their local mobility in CZTS layer. Finally, the lower persistent photoconductivity (PPC) and fast decay response of photogenerated carriers for Ag doped CZTS photodetector further validate our results. This study provides a fresh approach of controlling deleterious CuZn defects in CZTS by tuning Ag content that may guide researchers to develop next generation high performance CZTS based solar cells.
关键词： nanoscale surface potential and current,CZTS solar cells,Ag doped CZTS,defects,photodetector
更新于2025-09-23 15:21:01
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CZTS solar cells and the possibility of increasing VOC using evaporated Al2O3 at the CZTS/CdS interface
摘要： We report the effect of an ultra-thin Al2O3 layer (down to 3 nm) as interface passivation strategy for the improvement of the performance of Cu2ZnSnS4/CdS based solar cells. After an initial optimization, the Al2O3 deposited by thermal evaporation is proved to improve the properties of the p-n junction. The fabricated devices showed an increment in Voc depending on the composition of the absorber, and an improvement in fill factor (FF) apparently related to the insulation of possible shunt-paths. Also, the impact on other optoelectronic parameters is discussed.
关键词： Al2O3,Interface passivation,Thermally evaporation,Cu2ZnSnS4 (CZTS)
更新于2025-09-23 15:19:57
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Successes and Challenges Associated with Solution Processing of Kesterite Cu2ZnSnS4 Solar Cells on Titanium Substrates
摘要： Roll-to-roll (R2R) processing of solution-based Cu2ZnSn(S,Se)4 (CZT(S,Se)) solar cells on flexible metal foil is an attractive way to achieve cost-effective manufacturing of photovoltaics. In this work we report the first successful fabrication of solution-processed CZTS devices on a variety of titanium substrates with up to 2.88% power conversion efficiency (PCE) collected on flexible 75 μm Ti foil. A comparative study of device performance and properties is presented aiming to address key processing challenges. First, we show that a rapid transfer of heat through the titanium substrates is responsible for the accelerated crystallisation of kesterite films characterised with small grain size, a high density of grain boundaries and numerous pore sites near the Mo/CZTS interface which affect charge transport and enhance recombination in devices. Following this, we demonstrate the occurrence of metal ion diffusion induced by the high temperature treatment required for the sulfurization of the CZTS stack: Ti4+ ions are observed to migrate upwards to the Mo/CZTS interface whilst Cu1+ and Zn2+ ions diffuse through the Mo layer into the Ti substrate. Finally, residual stress data confirm the good adhesion of stacked materials throughout the sequential solution process. These findings are evidenced by combining electron imaging observations, elemental depth profiles generated by secondary ion mass spectrometry, and x-ray residual stress analysis of the Ti substrate.
关键词： SIMS,titanium,CZTS,solar cell,stress
更新于2025-09-23 15:19:57
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Understanding the effect of the carbon on the photovoltaic properties of the Cu2ZnSnS4
摘要： In this work, crystalline structure, formation energy, electronic, optical and current-voltage properties of Cu2ZnSnS4 (CZTS) with the presence of carbon (C) impurity at various sites is studied using the first-principles density functional theory (DFT) based on the generalized gradient approximation (GGA). Here, we considered possible four substitutional configurations of carbon doped CZTS supercells: Cu by C (Ccu), Cu by Zn (Czn), Sn by C (Csn) and S by C (CS). It was found that the presence of C leads to the formation of localized polarons which have dual functionality; (i) cause an increase in the scattering-limited mobility which reduces the transport efficiency, (ii) create deep acceptor level which acts as a recombination center allowing the scattering of the generated charges carriers. An enhancement in the photo-absorption is observed due to an increase in the density of states at the valence bands after the incorporation of C. This results in the efficiency enhancement by 8%. In addition, the presence of C reduces the transport efficiency and improves the photogeneration efficiency of CZTS in solar cell applications.
关键词： Carbon doped CZTS,Localized polaron,DFT,Optical properties,Solar cell,Electronic structure
更新于2025-09-23 15:19:57
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Growth of Cu<sub>2</sub>ZnSnS<sub>4</sub> (CZTS) thin films using short sulfurization periods
摘要： In this study CZTS thin films were grown by a two-stage process that involved sequential sputter deposition of metallic Cu, Zn, and Sn layers on Mo coated glass substrates followed by RTP annealing at 530 and 560 °C for various dwell times (1, 60, and 180 sec). CZTS thin films obtained by reaction at different sulfurization temperatures and reaction times were characterized employing XRD, Raman spectroscopy, SEM, EDX, and photoluminescence. It showed that extension of the sulfurization time provides better crystalline quality except for the CZTS560-60 thin film. SEM surface microstructure of the films displayed non-uniform, dense, and polycrystalline structure. The optical band gap of the films as determined by photoluminescence was found to be about 1.36-1.38 eV. It was observed that it is possible to obtain Cu-poor and Zn-rich CZTS thin films with short dwell time of reactions. XRD pattern and Raman spectra of the films showed formation of kesterite CZTS structure and some secondary phases such as CuS, SnS, SnS2. The full-width-at-half-maximum (FWHM) values extracted from the (112) diffraction peaks of the CZTS thin films.
关键词： Sulfurization time,Cu2ZnSnS4 (CZTS),Two-stage method,Sputtering,Sulfurization temperature,Kesterite
更新于2025-09-19 17:15:36
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An improvement on the conversion efficiency of Si/CZTS solar cells by LSPR effect of embedded plasmonic Au nanoparticles
摘要： In this work, Au/Si/CZTS/Ag and Au/Si/plasmonic-CZTS/Ag solar cells have been produced using PLD technique. These CZTS solar cells have been produced based on p-type CZTS ultrathin films at different thicknesses of 61 nm, 112 nm and 210 nm which were grown on an n-type Si wafer. Morphologic and crystalline structures as well as optical characteristics of CZTS ultrathin films have been investigated by courtesy of AFM, XRD and UV–vis spectra. J-V characteristics of CZTS solar cells have been obtained under AM 1.5 solar radiation of 80 mW/cm2. It has been observed that Jsc, Voc and η values of CZTS solar cells increase as thickness of CZTS ultrathin films are diagnosed to an optimum thickness. But, CZTS ultrathin films at thickness of 61 nm and 112 nm have low absorption rate and it was observed that absorption rate of CZTS ultrathin films increase dramatically in visible and NIR regions after Au plasmonic nanoparticles were embedded in these CZTS ultrathin films. Furthermore, Jsc and η values of plasmonic CZTS solar cells increase and that increase can be attributed to the transfer of electrons from the plasmonic Au NPs to the conduction band of CZTS semiconductor, the photon absorption of CZTS ultrathin films from visible to NIR region in the wide spectral region, and the increase in the path length of light through in CZTS semiconductor by photon scattering of Au nanoparticles.
关键词： Ultrathin film,CZTS,Au,LSPR,PLD,Efficiency
更新于2025-09-19 17:13:59