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[Formula: see text] [Formula: see text]m-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 (Si3N4) 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[Formula: see text] [Formula: see text]m achieves a global average absorptance of 68.27%, while introducing a secondary shallow groove yields a pronounced broadband enhancement. The optimal 1–0.2[Formula: see text] [Formula: see text]m composite V-groove reaches a spectrally averaged absorptance of 78.31% and delivers a short-circuit current density ([Formula: see text] of 34.80[Formula: see text]mA[Formula: see text] [Formula: see text]cm[Formula: see text] with open-circuit voltage ([Formula: see text] [Formula: see text]V and fill factor (FF) [Formula: see text] 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 high-efficiency ultra-thin c-Si photovoltaics enabled by scalable V-groove light-trapping structures.