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

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) AlO_x films are widely used to passivate edge defects arising from CTM loss in c-Si 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 AlO_x 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 AlO_x 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%, a 0.22% increase. Further elemental analysis confirmed the subsurface passivation effects, including 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.