Defect activation and annihilation in CIGS solar cells: an operando x-ray microscopy study
Abstract

The efficiency of thin-film solar cells with a Cu($In1−x$Gax)Se2absorber 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($In1−x$Gax)Se2solar 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 combinedoperandoandin situx-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.

Authors:
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Publication Date:
NSF-PAR ID:
10303266
Journal Name:
Journal of Physics: Energy
Volume:
2
Issue:
2
Page Range or eLocation-ID:
Article No. 025001
ISSN:
2515-7655
Publisher:
IOP Publishing
National Science Foundation
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