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Strain Mapping of CdTe Grains in Photovoltaic Devices
摘要： Strain within grains and at grain boundaries (GBs) in polycrystalline thin-film absorber layers limits the overall performance because of higher defect concentrations and band fluctuations. However, the nanoscale strain distribution in operational devices is not easily accessible using standard methods. X-ray nanodiffraction offers the unique possibility to evaluate the strain or lattice spacing at nanoscale resolution. Furthermore, the combination of nanodiffraction with additional techniques in the framework of multimodal scanning X-ray microscopy enables the direct correlation of the strain with material and device parameters such as the elemental distribution or local performance. This approach is applied for the investigation of the strain distribution in CdTe grains in fully operational photovoltaic solar cells. It is found that the lattice spacing in the (111) direction remains fairly constant in the grain cores but systematically decreases at the GBs. The lower strain at GBs is accompanied by an increase of the total tilt. These observations are both compatible with the inhomogeneous incorporation of smaller atoms into the lattice, and local stress induced by neighboring grains.
关键词： X-ray microscopy,nanodiffraction,X-ray diffraction (XRD),solar cells,multimodal,CdTe,X-ray,strain,X-ray fluorescence (XRF),photovoltaic,X-ray beam induced current (XBIC)
更新于2025-09-19 17:13:59
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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