Optimal Design and Photoelectric Performance Investigation of Composite V-Groove Light-Trapping Structures for Ultrathin Crystalline Silicon Solar Cells

Ultra-thin crystalline silicon (c-Si) solar cells suffer from insufficient absorption, making effective light-trapping architectures essential for high efficiency at micrometer-scale thickness. Here, we propose and optimize a multi-scale (composite) V-groove surface texture for a 1-μm-thick c-Si absorber and evaluate its photoelectric performance using fully coupled finite-element optoelectronic simulations in COMSOL, combining Maxwell-equation optical modeling with drift.diffusion carrier transport. The anti-reflection/passivation layer (Si 3 N 4 ) thickness is first optimized, and V-groove geometries are then systematically scanned to maximize AM1.5G spectrum-weighted absorption. A single V-groove depth of 1.0 μm achieves a global average absorptance of 68.27%, while introducing a secondary shallow groove yields a pronounced broadband enhancement. The optimal 1-0.2 μm composite V-groove reaches a spectrally averaged absorptance of 78.31% and delivers a short-circuit current density (J sc ) of 34.80 mA·cm −2 with open-circuit voltage (V oc ) = 0.5779 V and fill factor (FF) = 79.47%, resulting in a power conversion efficiency of 15.98%, substantially exceeding the planar reference (8.69%). Field and carrier analyses indicate that the composite texture increases optical path length via multi-reflection interference and resonance-assisted coupling, enhancing generation while maintaining favorable electrical quality. These results provide practical design guidelines for highefficiency ultra-thin c-Si photovoltaics enabled by scalable V-groove light-trapping structures.