Atomic structure of defect responsible for light-induced efficiency loss in silicon solar cells in warmer climates

Abstract

Light-induced degradation of Si solar cells when deployed in warmer climates can cause up to a ∼10% relative degradation in efficiency, but the atomic structure of the defect responsible for this degradation remains elusive. Herein, using electron paramagnetic resonance, we show that the defect responsible for light- and elevated-temperature-induced degradation (LeTID) is likely an Si dangling bond within an extended defect such as a vacancy agglomerate, with H atoms in its vicinity and likely O nearby. Our atomistic-level insights suggest that the defect responsible for LeTID can be mitigated by targeted engineering of the intrinsic defect populations by optimizing annealing routines prior to or during device fabrication and by controlling the amount of H injected in the Si bulk during cell processing. Mitigating LeTID through detailed knowledge of its atomic structure can help preserve the long-term efficiency of gigawatts of future worldwide installations of solar based on crystalline Si.