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Study of (AgxCu1a??x)2ZnSn(S,Se)4 monograins synthesized by molten salt method for solar cell applications
摘要： The open circuit voltage (VOC) deficit of Cu2ZnSn(S,Se)4 (CZTSSe) kesterite solar cells is higher than that of the closely related Cu(InGa)Se2 solar cells. One of the most promising strategies to overcome the large VOC deficit of kesterite solar cells is by reducing the recombination losses through appropriate cation substitution. In fact, replacing totally or partially Zn or Cu by an element with larger covalent radius one can significantly reduce the concentration of I–II antisite defects in the bulk. In this study, an investigation of the impact of partial substitution of Cu by Ag in CZTSSe solid solution monograins is presented. A detailed photoluminescence study is conducted on Ag-incorporated CZTSSe monograins and a radiative recombination model is proposed. The composition and structural quality of the monograins in dependence of the added Ag amount are characterized using Energy Dispersive X-ray Spectroscopy and X-Ray Diffraction method, respectively. The Ag-incorporated CZTSSe monograin solar cells are characterized by temperature dependent current-voltage and electron beam induced current methods. It was found, that low Ag contents (x ≤ 0.02) in CZTSSe lead to higher solar cell device efficiencies.
关键词： Copper zinc tin sulfur selenide,Monograins,Electron beam induced current,Photoluminescence,Kesterite,Cations substituation
更新于2025-11-21 10:59:37
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Band Alignment of the CdS/Cu <sub/>2</sub> Zn(Sn <sub/>1-x</sub> Ge <sub/>x</sub> )Se <sub/>4</sub> Heterointerface and Electronic Properties at the Cu <sub/>2</sub> Zn(Sn <sub/>1-x</sub> Ge <sub/>x</sub> )Se <sub/>4</sub> surface: x = 0, 0.2, 0.4
摘要： The surface electronic properties of the light absorber and band alignment at the p/n heterointerface are key issues for high performance heterojunction solar cells. We investigated the band alignment of the heterointerface between cadmium sulfide (CdS) and Ge incorporated Cu2ZnSnSe4 (CZTGSe), with Ge/(Ge+Sn) ratios (x) between 0 and 0.4, by X-ray photoelectron, ultra-violet, and inversed photoemission spectroscopies (XPS, UPS, and IPES, respectively). In particular, we used interface-induced band bending in order to determine the conduction-band offset (CBO) and valence-band offset (VBO), which were calculated from the core-level shifts of each element in both the CdS overlayer and the CZTGSe bottom layer. Moreover, the surface electronic properties of CZTGSe were also investigated by laser-irradiated XPS. The CBO at the CdS/CZTGSe heterointerface decreased linearly, from +0.36 to +0.20 eV, as x was increased from 0 to 0.4; in contrast, the VBO at the CdS/CZTGSe heterointerface was independent of Ge content. Both UPS and IPES revealed that the Fermi level at the CZTGSe surface is located near the center of the bandgap. The hole concentration at the CZTGSe surface was of the order of 1011 cm-3, which is much smaller than that of the bulk (~1016 cm-3). We discuss the differences in hole deficiencies near the surface and in the bulk on the basis of laser-irradiated XPS, and conclude that hole deficiencies are due to defects distributed near the surface with densities that are lower than in the bulk, and the Fermi level is not pinned at the CZTGSe surface.
关键词： Solar cell,Kesterite,IPES,XPS,Band alignment,CZTGS,UPS
更新于2025-09-23 15:23:52
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Voids in Kesterites and the Influence of Lamellae Preparation by Focused Ion Beam for Transmission Electron Microscopy Analyses
摘要： Kesterite solar cells based on Cu2 ZnSnS4 and Cu2 ZnSnSe4 (CZTSe) are potential future candidates to be used in thin-film solar cells. The technology still has to be developed to a great extent and for this to happen, high levels of confidence in the characterization methods are required, so that improvements can be made on solid interpretations. In this study, we show that the interpretations of one of the most used characterization techniques in kesterites, scanning transmission electron microscopy (STEM), might be affected by its specimen preparation when using focused ion beam (FIB). Using complementary measurements based on scanning electron microscopy and Raman scattering spectroscopy, compelling evidence shows that secondary phases of ZnSe mixed in the bulk of CZTSe are the likely cause of the appearance of voids in STEM lamellae. Sputtering simulations support this interpretation by showing that Zn in a ZnSe matrix is preferentially sputtered compared with any metal atom in a CZTSe matrix.
关键词： Cu2 ZnSn(S, Se)4 (CZTSSe),thin-film solar cells,transmission electron microscopy (TEM),focused ion beam (FIB),kesterite
更新于2025-09-23 15:22:29
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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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Current-voltage and capacitance study of light-induced metastabilities in CuZnSnSSe thin-film solar cells
摘要： White, red and blue light-induced metastabilities in Cu2ZnSnS4(Se4) solar cells were investigated by temperature dependent current-voltage measurements, drive level capacitance profiling, impedance and thermal admittance spectroscopy. A set of devices were studied where white and blue light soaking at room temperature led to degradation of the device performance, while after red light soaking the solar cell efficiency did not change. We observed a significant effect of light soaking on capacitance data measured in both low and high-temperature ranges for these devices. In particular, the net doping concentration extracted from drive-level capacitance profiling substantially increased after light soaking treatments. Low and high-temperature capacitance steps observed in the reference capacitance-frequency spectra were assigned to Fermi level pinning and bulk defects, correspondingly. Light soaking with different-wavelength light led to a shift of both steps toward the high-frequency range, and hence a decrease in the thermal admittance activation energies. A low-frequency “inductive” loop was detected in the impedance spectra after light soaking, regardless of wavelength. It was proposed that the appearance of the “inductive” loop is due to the formation of a negative electric field at the highly defected CdS/Cu2ZnSnS4(Se4) hetero-interface. This result also leads us to conclude that such electric field is responsible for the metastable behaviour of these devices at room temperature, while the low temperature metastable changes might have a different origin. We also discuss the methodology for electrical characterization of the metastable solar cells in detail.
关键词： impedance spectroscopy,metastability,kesterite solar cells,electrical characterization
更新于2025-09-23 15:19:57
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Reaction Pathway for Efficient CZTSe Solar Cells from Alloyed Cu-Sn Precursor via a Cu-Rich Selenization Stage
摘要： A detailed reaction pathway for efficient CZTSe solar cells from alloyed Cu-Sn precursor via a Cu-rich selenization stage is presented. The study focuses on the selenization of stacked elemental metallic layers (Cu-Sn-Zn), a commonly reported approach in kesterite Cu2ZnSnSe4 (CZTSe) processing. The high volatility of binary selenides, such as SnSe2-x, at necessary annealing temperatures (500 – 550 °C) makes this reaction pathway prone to Sn loss, which challenges the control of the composition and quality of the grown material. The present work reports an approach based on stacked elemental and alloyed precursors, discussing the benefits of using a Zn/Cu-Sn/Zn configuration. The absence of non-alloyed elemental Sn helps in suppressing the formation and subsequent evaporation of SnSe2-x phases, preventing Sn loss from the film during selenization. This reaction pathway involves a process scheme which i) starts with the growth of CZTSe in a Cu-rich environment, ii) includes a shift of the composition by supply of SnSe2-x vapor, and iii) terminates in the Cu-poor regime, leading to device efficiencies above 10%. This composition shift in the presented process appears similar to the final stage of the commonly known CIGSe three-stage co-evaporation.
关键词： Reaction pathway,Selenization,Kesterite,Alloying
更新于2025-09-23 15:19:57
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Growth and Characterization of Cu2Zn1a??xFexSnS4 Thin Films for Photovoltaic Applications
摘要： Photovoltaics is a promising technology to produce sustainable energy, thanks to the high amount of energy emitted by the sun. One way of having solar cells with low production costs is to apply thin-film technology and with earth-abundant raw materials. A keen interest is arising in kesterite compounds, which are chalcogenides composed of abundant and non-toxic elements. They have already achieved excellent performance at the laboratory level. Here, we report the synthesis and characterization of mixed chalcogenides based on copper, zinc, iron, and tin. Solutions have been studied with different zinc and iron ratios. The distortion of the elementary cell of kesterite increases with the addition of iron until a phase transition to stannite occurs. The process of synthesis and deposition proposed herein is cheap and straightforward, based on the sol-gel technique. These thin films are particularly attractive for use in cheap and easily processable solar cells. The synthesized layers have been characterized by X-ray diffraction, UV-Vis absorption, and Raman, X-ray photoelectron, and energy-dispersive X-ray spectroscopy measurements.
关键词： chalcogenide solar cells,iron chalcogenide,sustainable energy,kesterite,stannite
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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Influence of Zn excess on compositional, structural and vibrational properties of Cu2ZnSn0.5Ge0.5Se4 thin films and their effect on solar cell efficiency
摘要： The effect of Zn content on compositional, structural and vibrational properties of Cu2ZnSn1-xGexSe4 (CZTGSe, x ~ 0.5) thin films is studied. Kesterite layer is deposited by co-evaporation onto 5 × 5 cm2 Mo/SLG substrate followed by a thermal treatment at maximum temperature of 480 °C, obtaining areas with different composition and morphology which are due to the sample position in the co-evaporation system and to the non-uniform temperature distribution across the substrate. Kesterite layers with higher Zn amounts are characterized by lower Cu and Ge contents; however, a uniform Ge distribution through the absorber layer is detected in all cases. The excess Zn concentration leads to the formation of ZnSe secondary phase on the surface and in the bulk of the absorber as determined by Raman spectroscopy. When higher Ge content and no ZnSe are present in the absorber layer, a compact structure is formed with larger grain size of kesterite. This effect could explain the higher Voc of the solar cell. The Zn content does not affect the bandgap energy significantly (Eg near 1.3 eV), although the observed effect of Zn excess in CZTGSe results in a decreased device performance from 6.4 to 4.2%. This investigation reveals the importance of the control of the off-stoichiometric CZTGSe composition during the deposition process to enhance solar cells properties.
关键词： Solar cells,Ge,ZnSe,Kesterite
更新于2025-09-19 17:13:59
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Sputtered ZnSnO buffer layers for kesterite solar cells
摘要： Replacing the CdS buffer layer with a ZnSnO one in Cu2ZnSnS4-based solar cells allows both to improve the device performances and to avoid using toxic Cd. Additionally, using a sputtered buffer layer is a major asset for solar cells fabricated by physical vapor deposition processes. In this study, ZnSnO layers are deposited by sputtering of a single metal-oxide target. Structural and optical properties of the layers deposited on Si or glass are first described. The possibility of modifying the ZnSnO metallic composition by adjusting the deposition power is demonstrated. Attempts to improve the optoelectronic properties of the ZnSnO layers with Ar:O2 or Ar:SF6 reactive sputtering are shown as well. These ZnSnO buffer layers are transferred in Mo/CZTS/ZnSnO/ZnO:Al solar cells. After post-deposition thermal treatment and optimization of the deposition condition (notably with the use of Ar:O2 or Ar:SF6 reactive sputtering), a solar cells with a power conversion efficiency of 5.2% is demonstrated. It is 0.6% absolute higher than the reference solar cell with a CdS buffer layer. To avoid absorber damaging and achieve high performances, deposition power must be as low as possible. A two stages sputtering process is used to conciliate both the absorber surface preservation and a reasonable deposition time. Last, photovoltaic properties of optimized CZTS- and CZTSe-based solar cells with ZnSnO buffer layers are compared.
关键词： Cu2ZnSnS4,ZnSnO buffer layer,Cd-free devices,sputtering,reactive sputtering,Kesterite solar cells
更新于2025-09-19 17:13:59