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Molybdenum incorporated Cu1.69ZnSnS4 kesterite photovoltaic devices with bilayer microstructure and tunable optical-electronic properties
摘要： Molybdenum (Mo) incorporated Cu1.69ZnSnS4 (CZTS) absorber has been deposited onto Mo-coated soda lime glass (SLG) by co-sputtering of Mo and non-stoichiometric quaternary compound targets. After sulfurization at 600 °C, Mo incorporation into CZTS was confirmed by X-ray diffraction (XRD) and secondary ion mass spectrometry (SIMS). From the observed shifts for the (1 1 2) and (2 2 0) peaks, both lattice parameters a and c of the CZTS unit cell were found to decrease with increasing Mo incorporation suggesting cationic substitution by Mo. The Mo incorporated CZTS has a bilayer microstructure in which the lower sub-layer adjacent to the substrate has a smaller grain size and higher porosity than the upper sub-layer. The lower sub-layer is also richer in Mo and has a graded Mo profile. Sheet resistance measurements on Mo incorporated CZTS films deposited on SLG and on quartz show resistivity that decreases with the amount of Mo in CZTS and Mo acts as an acceptor dopant. The energy band gap of CZTS on SLG increases from 1.38 eV to about 1.68 eV as a result of Mo incorporation and the absorbance of Mo incorporated CZTS is increased for wavelengths shorter than 600 nm. When Mo is co-deposited at the optimized DC sputtering power of 10 W, Mo incorporated CZTS/CdS solar cells attain a maximum power conversion efficiency (PCE) of 5.49% versus 1.63% for the reference device under 1 Sun AM 1.5 illumination. Device efficiency enhancement is due to back surface field, increased carrier concentration and reduced band tailing.
关键词： Kesterite solar cell,porosity,Molybdenum,Bilayer microstructure,Co-sputtering
更新于2025-09-11 14:15:04
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Solution-processed method for high-performance Cu2ZnSn(S,Se)4 thin film solar cells and its characteristics
摘要： Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) has attracted much attention as an ideal absorber material for thin film solar cells. Solution deposition methods provide a crucial approach for lowering the fabricating price of CZTSSe based photovoltaic devices. Here, a low-cost and robust ethanol/thioglycolic acid/1-butylamine ternary solutions method was developed to fabricate the CZTSSe solar cells. Characterization was performed using XRD, Raman, and C–V, which showed that the material fabricated by this method expressed high-phase purity, suitable carrier concentration, and large depletion width, and those features are vital to high efficiency photovoltaic devices. Hence, based on this high quality CZTSSe absorbed layer, photovoltaic device with a power conversion efficiency (PCE) as high as 9.71% was achieved. The PCE can be further enhanced through passivating with alkali metal and optimizing the device fabrication conditions, making this method much promising for lowering the manufacturing cost of kesterite solar cells. Additionally, this approach is full of application prospect for other burgeoning photovoltaic absorber materials which could dramatically reduce the cost of solar electricity.
关键词： Thin film,CZTSSe,Kesterite,Solution process,Solar cells
更新于2025-09-11 14:15:04
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Wide band-gap Cu <sub/>2</sub> SrSnS <sub/>4</sub> solar cells from oxide precursors
摘要： Recent progress in the efficiency of Cu2ZnSnS4 (CZTS) solar cells has been relatively slow due to severe bulk band tailing issues that have proven difficult to resolve. Band tails in CZTS are caused by defect-related potential fluctuations, as diagnosed by the large shift between the CZTS band gap and its photoluminescence (PL) peak. In this work, we demonstrate that the PL-band gap shift can be decreased roughly by a factor of 5 when Zn is replaced by the heavier cation Sr. The resulting Cu2SrSnS4 compound is of considerable interest for photovoltaics due to its sharp band edges and suitable band gap (1.95-1.98 eV) for a top absorber in tandem cells. Trigonal CSTS thin films are synthesized in this work by sulfurization of strongly Cu-poor co-sputtered Cu2SrSnO4 precursors. The first functioning CSTS solar cells are demonstrated, even though the very high conduction band of CSTS implies that the typical CdS/ZnO electron contact of CZTS solar cells must be redesigned to avoid large voltage losses.
关键词： tail states,tandem solar cell,sputtering,wide band-gap absorber,Kesterite,cation substitution,potential fluctuations
更新于2025-09-11 14:15:04
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Cross-Section Analysis of the Composition of Sprayed Cu <sub/>2</sub> ZnSnS <sub/>4</sub> Thin Films by XPS, EDS, and Multi-Wavelength Raman Spectroscopy
摘要： A detailed cross-section analysis of the chemical composition of sprayed Cu2ZnSnS4 thin films is presented. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy (with near-IR, visible, and UV-lasers) are used to demonstrate that while CZTS effectively forms within the bulk of the film, there is some degree of element segregation, formation of undesirable secondary phases, and the presence of a disordered kesterite structure across the film. Different penetration depths of the excitation signals correspond to the many different surface sensitive techniques employed in this work. XPS results reveal that the surface of Cu4ZnSnS4 (CZTS) films presents a high concentration of tin and zinc and a low sulfur concentration, while being highly depleted in copper. EDS, XRD, and infrared Raman spectroscopy confirm that the composition of as-sprayed and sulfurized films is close to stoichiometric Cu2ZnSnS4. Resonant UV-Raman spectroscopy helps to identify secondary phases located at the external surface of sprayed and sulfurized CZTS films (mainly ZnS, ZnO), while VIS-Raman spectroscopy helps to identify a disordered kesterite structure close to the surface. Secondary phases need to be chemically etched when aiming at incorporating kesterite films obtained by spray pyrolysis into photovoltaic devices.
关键词： multi-wavelength Raman spectroscopy,X-ray photoelectron spectroscopy,spray pyrolysis,thin films,kesterite
更新于2025-09-10 09:29:36