Unveiling crystalline silicon edge subsurface passivation impact on photovoltaics via three-dimensional spatially resolved micro-photoelectrical mapping

Abstract Employing half-cut thermal-laser-separation (TLS)-induced crystalline silicon (c-Si) wafers in high-efficiency solar cells is indispensable to mitigate cell-to-module (CTM) efficiency loss, which incurs unnecessary electrical loss due to the associated extra wafer edge. Atomic layer deposition (ALD) AlOx films are widely used to passivate edge defects arising from CTM loss in c-Si photovoltaic (PV) modules. However, the inferior spatial resolution and the absence of depth perception inherent in current photoelectric characterization technologies fail to disclose the passivation properties of AlOx films fabricated by diverse ALD processes, hindering further development to address edge electrical defects. Here, a high spatial resolution (up to ~ 0.3 μm) three-dimensional multi-laser integration system was developed to investigate the impact of TLS-induced edge recombination on c-Si solar cells. The results show that sequential ALD AlOx films offer superior passivation, especially for subsurface defects. The process improved the power conversion efficiency of a large-scale PV module (2278 mm × 1134 mm) from 22.95% to 23.17%, an increase of 0.22%. Further elemental analysis confirmed the subsurface passivation effects, including the enhanced hydrogen diffusion and an enlarged surface electric field. This work provides critical insights into edge defects in industrial c-Si solar cells, guiding the optimization of ALD-based edge passivation.