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Reactive Mechanism of Cu2ZnSnSe4 Thin Films Prepared by Reactive Annealing of the Cu/Zn Metal Layer in a SnSex + Se Atmosphere
摘要： Cu2ZnSnSe4 (CZTSe) thin films were prepared by a two-step process with the electrodeposition of a Cu/Zn metallic stack precursor followed by a reactive anneal under a Se + Sn containing atmosphere. We investigate the effect of the Sex and SnSex (x = 1,2) partial pressures and annealing temperature on the morphological, structural, and elemental distribution of the CZTSe thin films. Line scanning energy dispersive spectroscopy (EDS) measurements show the presence of a Zn-rich secondary phase at the back-absorber region of the CZTSe thin films processed with higher SnSex partial pressure and lower annealing temperatures. The Zn-rich phase can be reduced by lowering the SnSex partial pressure and by increasing the annealing temperature. A very thin MoSe2 film between the CZTSe and Mo interface is confirmed by X-ray diffraction (XRD) and grazing incidence X-ray diffraction (GIXRD) measurements. These measurements indicate a strong dependence of these process variations in secondary phase formation and accumulation. A possible reaction mechanism of CZTSe thin films was presented. In a preliminary optimization of both the SnSex partial pressure and the reactive annealing process, a solar cell with 7.26% efficiency has been fabricated.
关键词： Sex and SnSex (x = 1,2) partial pressures,annealing temperature,metallic stack precursor,Cu2ZnSnSe4 (CZTSe),electrodeposition
更新于2025-11-14 15:15:56
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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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Fabrication and Characterization of Cu2ZnSnSe4 Thin-Film Solar Cells using a Single-Stage Co-Evaporation Method: Effects of Film Growth Temperatures on Device Performances
摘要： Kesterite-structured Cu2ZnSnSe4 (CZTSe) is considered as one of the Earth-abundant and non-toxic photovoltaic materials. CZTSe films have been prepared using a single-step co-evaporation method at a relatively low temperature (i.e., below 500 °C). Due to the volatile nature of tin-selenide, the control over substrate temperature (i.e., growth temperature) is very important in terms of the deposition of high-quality CZTSe films. In this regard, the effects of growth temperatures on the CZTSe film morphology were investigated. The suitable temperature range to deposit CZTSe films with Cu-poor and Zn-rich compositions was 380–480 °C. As the temperature increased, the surface roughness of the CZTSe film decreased, which could improve p/n junction properties and associated device performances. Particularly, according to capacitance-voltage (C-V) and derived-level capacitance profiling (DLCP) measurements, the density of interfacial defects of CZTSe film grown at 480 °C showed the lowest value, of the order of ~3 × 1015 cm?3. Regardless of applied growth temperatures, the formation of a MoSe2 layer was rarely observed, since the growth temperature was not high enough to have a reaction between Mo back contact layers and CZTSe absorber layers. As a result, the photovoltaic (PV) device with CZTSe film grown at 480 °C yielded the best power conversion efficiency of 6.47%. It is evident that the control over film growth temperature is a critical factor for obtaining high-quality CZTSe film prepared by one-step process.
关键词： kesterite structure,earth-abundant,growth temperature,CZTSe
更新于2025-09-23 15:21:01
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Developing highly crystalline, single-phase and copper-poor Cu2ZnSnSe4 nanoparticles for solar cell application
摘要： In this study, we report the synthesis of Cu(Zn,Sn)Se2 (CZTSe) nanoparticles by hot-injection method for application to the absorber layer in solar cells. The composition of elements in the CZTSe nanoparticles depends mainly on the injection speed of the Se precursor. By controlling the injection speed, we obtained complete single-phase CZTSe nanoparticles with high crystallinity and copper-poor composition. The nanoparticle diameter mainly ranged from ~ 7 nm to 18 nm. The obtained CZTSe nanoparticles were used to fabricate a light absorber layer in the CZTSe solar cells. The cell exhibited performance, with short-circuit current density of ~ 30.8 mA/cm2, open-circuit voltage of 0.39 V, ?ll factor of 0.47 and conversion ef?ciency of 5.8%.
关键词： Hot-injection method,Single phase,CZTSe nanoparticles,Copper-poor composition
更新于2025-09-23 15:19:57
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Effects of Annealing on Characteristics of Cu2ZnSnSe4/CH3NH3PbI3/ZnS/IZO Nanostructures for Enhanced Photovoltaic Solar Cells
摘要： This paper presents new photovoltaic solar cells with Cu2ZnSnSe4/CH3NH3PbI3(MAPbI3)/ZnS/IZO/Ag nanostructures on bi-layer Mo/FTO (fluorine-doped tin oxide) glass-substrates. The hole-transporting layer, active absorber layer, electron-transporting layer, transparent-conductive oxide layer, and top electrode-metal contact layer, were made of Cu2ZnSnSe4, MAPbI3 perovskite, zincsulfide, indium-doped zinc oxide, and silver, respectively. The active absorber MAPbI3 perovskite film was deposited on Cu2ZnSnSe4 hole-transporting layer that has been annealed at different temperatures. TheseCu2ZnSnSe4 filmsexhibitedthe morphology with increased crystal grain sizesand reduced pinholes, following the increased annealing temperature. When the perovskitefilm thickness was designed at 700 nm, the Cu2ZnSnSe4 hole-transporting layer was 160 nm, and the IZO (indium-zinc oxide) at 100 nm, and annealed at 650°C, the experimental results showed significant improvements in the solar cell characteristics. The open-circuit voltage was increased to 1.1 V, the short-circuit current was improved to 20.8 mA/cm2, and the device fill factor was elevated to 76.3%. In addition, the device power-conversion efficiency has been improved to 17.4%. The output power Pmax was as good as 1.74 mW and the device series-resistance was 17.1 ?.
关键词： IZO,hole-transporting material,perovskite,CZTSe,magnetron sputtering
更新于2025-09-23 15:19:57
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Over 10% Efficient Pure CZTSe Solar Cell Fabricated by Electrodeposition with Ge Doping
摘要： The fabrication of kesterite CZTSe solar cells with electrodeposition method provides an attractive approach for the low-cost and environmental-friendly energy supply, yet the highest conversion efficiency for such solar cells (around 9%) still far away from the highest efficiency of Cu-based kesterite solar cells. Here a 10.54% efficiency CZTSe solar cell (0.28 cm2 active sized area, without anti-reflection layer) is reported through introducing electrodeposited Cu-Ge alloy layer at the bottom of metal precursor. It is found that the presence of Ge element within the bottom of the film can promote downwards diffusion of Sn element. Consequently, the distribution of Sn is relatively homogeneous during annealing process, thus the formation of undesirable defect clusters is inhibited and the band alignment of CdS/CZTSe interface is optimized. As a result, the conversion efficiency of CZTSe thin film solar cells is increased from 6.74% to 10.54%, which is the highest efficiency reported for electrochemically fabricated CZTSe solar cells.
关键词： Cu-Ge alloy,solar cell,electrodeposition,CZTSe
更新于2025-09-23 15:19:57
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Nano-scale sulfurization of the Cu <sub/>2</sub> ZnSnSe <sub/>4</sub> crystal surface for photovoltaic applications
摘要： The objective of this study was to find an effective method to improve VOC without JSC loss for Cu2ZnSnSe4 (CZTSe) monograin layer solar cells. Sulfurization of the surface of the kesterite absorber layer may lead to enhanced device efficiency via band gap widening at the surface. Surface sulfurization was carried out in two steps: a CdS layer was first deposited onto the CZTSe crystals by a chemical solution deposition method, and then the CdS-coated CZTSe was annealed at elevated temperature in evacuated quartz ampoules. The thickness of the sulfurized surface of CZTSe crystals was varied by adjusting the thickness of the CdS layer (from 100 nm to 200 nm) and by modifying the temperature of the annealing process from 400 to 700 °C for 60 min. SEM, EDX and Raman analysis showed that the CdS layer still existed on the surface of CZTSe crystals after annealing at 400 °C. After annealing at higher temperatures, the CdS layer disappeared and a new surface layer was formed. Annealing at 570 °C resulted in secondary phases on the surface, which are probably caused by decomposition reactions on the CZTSe crystal surface. Annealing at 700 °C formed a well-crystallized Cu2ZnSn(S, Se)4 thin layer on the surface of the CZTSe crystals, which was confirmed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The Raman peak located at 331 cm?1 provides strong evidence that a wider band gap Cu2ZnSn(S, Se)4 surface layer is formed after the sulfurization while the CdS peak at 308 cm?1 has disappeared. Compositional profiles of EDX and XPS showed that S is located in the surface layer, but Cd has diffused into the bulk of the crystal and acts as a dopant. The content of S in Cu2ZnSn(S, Se)4 depended on the CdS layer thickness.
关键词： CZTSe,band gap engineering,sulfurization,solar cells,photovoltaic applications
更新于2025-09-16 10:30:52
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Engineering of effective back-contact barrier of CZTSe: Nanoscale Ge solar cells – MoSe2 defects implication
摘要： Using temperature-dependent measurements and device modeling, we systematically study the e?ective back-contact barrier of CZTSe devices to improve the property of the back-contact interface. By comparing with CZTSe devices with various nanoscale Ge con?gurations, CZTSe nanoscale Ge bi-layers devices show the improved power conversion e?ciency by 1.1%. DC magnetron sputtering is used to fabricate CZTSe: nanolayer Ge devices. Critical device parameters are characterized to understand the impact of nanoscale Ge ?lms on the back-contact device characteristics. Based on empirical results, modeling is performed for the in?uence of MoSe2 defects on the e?ective back-contact barrier. Analysis of experimental results of Ge bi-layers devices with the improved back-contact barrier makes a good agreement with modeling and Sentaurus TCAD simulation at the 95% con?dence-level. The conversion e?ciency of CZTSe: nanoscale Ge bi-layers devices is improved up to 8.3%.
关键词： Schottky barrier,Thin ?lm solar cells,CZTSe,Kesterite,Back-contact,Ge nanolayer
更新于2025-09-12 10:27:22
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Germanium substitution effect on the property and performance of Cu2ZnSnSe4 thin films and its solar cell having absorber layer made by sputtering with single metallic target plus selenization
摘要： We report on the germanium substitution effect on the Cu2ZnSnSe4 solar cell performance with absorber layer prepared by sputtering with a single metallic target plus further selenization. We synthesized the Cu2Zn(Sn1-xGex)Se films with the [Ge]/([Ge] + [Sn]) percentages of 0%, 5%, 10%, 15%, and 20% when different x ratios were 0, 0.05, 0.1, 0.15, and 0.2. Defect chemistry was studied by measuring the structural, electrical, and optical properties of CZTGSe as a function of dopant concentration. The enhanced device performance was shown with the increased Ge content to CZTSe. The solar cell was fabricated with a stack structure of Ag/ITO/ZnO/CdS/CZTGSe/Mo/SLG. The efficiencies of CZTGSe films at the Ge percentages of 0%, 5%, 10%, 15%, and 20% were 1.90, 2.35, 3.32, 4.64, and 4.24%, respectively. The further improvement in conversion efficiency of 7.23% was achieved by incorporating a NaF layer between the Mo bottom electrode and CZTGSe absorber to form a Mo-NaF bilayer.
关键词： Germanium,CZTSe,Semiconductor,Doping,Films
更新于2025-09-12 10:27:22
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Modified Stack Layer for a Two-Step Process for High Efficiency CZTSe Solar Cell
摘要： For kesterite Cu2ZnSnSe4 (CZTSe) solar cells, the CZTSe absorber is usually fabricated using a two-step process, in which the CZTSe absorber is made by using post-selenization of a sputtered metal stack ?lm. In the post-selenized CZTSe ?lm, a rough surface, voids, and small-grained structures at bottom near the Mo back contact are frequently observed. To avoid these inferior features, we designed and fabricated a new modi?ed stack layer that showed compact and larger grains with no voids and with small-grain-free near the bottom side. Several measurements, such as X-ray di?raction, Raman spectroscopy, photoluminescence, and time-resolved photoluminescence measurements, showed that the selenized ?lm from the newly designed stack layer had high crystal quality. With the fabricated absorber, we made two types of CZTSe solar cells, one with a CdS bu?er and the other with a (Zn,Sn)O bu?er. The (Zn,Sn)O- bu?ered CZTSe solar cell showed a power conversion e?ciency of 8.31%, which is comparable to the 8.84% of the CdS-bu?ered CZTSe solar cell. Our results indicates that the CZTSe solar cells made by using our newly designed stack layer and a (Zn,Sn)O bu?er are promising for high-e?ciency Cd-free CZTSe solar cells.
关键词： Film growth,Stack layer,CZTSe,Solar cell
更新于2025-09-12 10:27:22