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HL: Fachverband Halbleiterphysik

HL 1: Perovskite and Photovoltaics I (joint session HL/KFM)

HL 1.4: Vortrag

Montag, 17. März 2025, 10:15–10:30, H13

Recombination at grain boundaries in Cd(Te,Se) thin films in comparison with other photovoltaic absorber layers — •Luka Blazevic¹, Sebastian Weitz¹, Elisa Artegiani², Alessandro Romeo², and Daniel Abou-Ras¹ — ¹Helmholtz-Zentrum Berlin, Germany — ²Universita di Verona, Italy

The role of grain boundaries on the device performance is of concern for all polycrystalline absorbers in photovoltaic solar cells. In the present work, recombination velocities s_GB at grain boundaries in Cd(Te,Se) thin-film absorbers were determined from cathodoluminescence (CL) intensity distributions, which were acquired together with electron backscatter diffraction (EBSD) and energy-dispersive X-ray spectroscopy (EDXS) maps. The resulting s_GB values exhibited ranges over several orders of magnitude (10¹−10³ cm/s). These wide value ranges are in good agreement with those obtained on other photovoltaic absorber materials (multicrystalline Si, Cu(In,Ga)Se2, Cu2ZnSn(S,Se)4). The present work suggests a model comprising the enhanced, nonradiative Shockley-Read-Hall recombination at grain boundaries as well as the upward/downward band bending (± several 10 meV) at these planar defects. This model can reproduce successfully the experimental s_GB values from various photovoltaic absorber materials and provides also ranges for the effective defect densities as well as their capture cross-sections at the grain boundaries. It will be shown that typical losses in the open-circuit voltage of the corresponding solar cells due to grain-boundary recombination in the absorbers are few 10 mV.

Keywords: CdTe; solar cells; grain boundaries; recombination; electron microscopy