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Voltage-Induced Charge Redistribution in Cu(In,Ga)Se <sub/>2</sub> Devices Studied With High-Speed Capacitance–Voltage Profiling
摘要： Devices made from Cu(In,Ga)Se2 (CIGS) solar cell material have been evaluated with high-speed capacitance–voltage pro?ling after stepwise voltage changes. The changes primarily affect near-interface charge at deep acceptors within the CIGS absorber layer and generate temperature-dependent capacitance changes observed in deep-level transient spectroscopy measurements. SCAPS device modeling indicates that the deep acceptor concentration is up to the two orders of magnitude higher than the shallow doping level. High deep acceptor concentrations are found in all materials studied here. The large deep defect levels are high enough to limit minority carrier lifetime and cell ef?ciency.
关键词： CuInx Ga1 ?x Se2 (CIGS),capacitance methods,solar cells
更新于2025-09-23 15:23:52
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Defect activation and annihilation in CIGS solar cells: an operando X-ray microscopy study
摘要： The efficiency of thin-film solar cells with a Cu(In1?xGax)Se2 absorber is limited by nanoscopic inhomogeneities and defects. Traditional characterization methods are challenged by the multi-scale evaluation of the performance at defects that are buried in the device structures. Multi-modal X-ray microscopy offers a unique tool-set to probe the performance in fully assembled solar cells, and to correlate the performance with composition down to the micro- and nanoscale. We applied this approach to the mapping of temperature-dependent recombination for Cu(In1?xGax)Se2 solar cells with different absorber grain sizes, evaluating the same areas from room temperature to 100 ?C. It was found that poor performing areas in the large-grain sample are correlated with a Cu-deficient phase, whereas defects in the small-grain sample are not correlated with the distribution of Cu. In both samples, classes of recombination sites were identified, where defects were activated or annihilated by temperature. More generally, the methodology of combined operando and in-situ X-ray microscopy was established at the physical limit of spatial resolution given by the device itself. As proof-of-principle, the measurement of nanoscopic current generation in a solar cell is demonstrated with applied bias voltage and bias light.
关键词： X-ray beam induced current (XBIC),solar cell,Multi-modal X-ray microscopy,X-ray fluorescence (XRF),Cu(In1?xGax)Se2 (CIGS),X-ray beam induced voltage (XBIV)
更新于2025-09-12 10:27:22
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Modeling Diffusion of Impurities in Molybdenum Thin Films as a Function of Substrate Temperature
摘要： Alkali ions are key to improving the performance of polycrystalline Cu(In,Ga)Se2 (CIGS) solar cells. Typically, a soda–lime glass substrate acts as an intrinsic source for many alkali ions. For these ions to reach the CIGS layer, diffusion through a metallic back contact is necessary. Typically deposited via sputtering, the morphology of this metallic back contact is dependent on multiple including substrate temperature. By deposition parameters, preparing ?lms with varying deposition parameters, and utilizing both, multiple material characterizations (X-ray diffraction, scanning electron microscopy, and secondary ion mass spectrometry) and numerical modeling, we demonstrate here that effective paths of diffusion are just as important as diffusion rate for the alkali ions. As the substrate temperature increases, the mechanism that hinders the ability for alkali ions to diffuse switches effectively from diffusion rate to effective path of diffusion. It is shown that the lack of viable diffusion paths at substrate temperatures above 100 °C becomes the dominant factor for the transport of alkali ions.
关键词： solar cell,impurities,Back contact,modeling,diffusion,molybdenum,Cu(In,Ga)Se2 (CIGS)
更新于2025-09-04 15:30:14