Biomimetic Conical Microhole Architecture Enabling 18.4%-Efficient Silicon Solar Cells with Superior Durability

Three-dimensional structured silicon solar cells have demonstrated remarkable potential for enhanced light absorption, yet their practical implementation remains limited by mechanical fragility. While microwire architectures offer superior optical properties through effective light scattering and radial junction formation, their high aspect ratio creates significant mechanical stress at the wire-substrate interface, leading to structural failure under physical strain. Here, we present conically etched microhole arrays (CEMA) that fundamentally address this challenge by inverting the conventional microwire concept while maintaining its optical and electrical advantages. Through rigorous coupled-wave analysis simulations, we optimize the geometric parameters of these inverted structures, demonstrating that controlled hole tapering significantly reduces surface reflection while preserving carrier collection efficiency. We develop a specialized fabrication process combining deep reactive ion etching with diffusion-limited wet chemical etching, enabling precise control over both hole geometry and surface morphology. The resulting honeycomb-like architecture exhibits exceptional mechanical stability under stress testing, while maintaining weighted average reflectance below 5% across the solar spectrum. This structural advantage, combined with efficient carrier collection through radial junctions, enables devices achieving 40 48 mA/cm² short-circuit current density and 599 mV open-circuit voltage. The optimized CEMA solar cells demonstrate 18.4% power conversion efficiency─the highest reported for microhole-based silicon solar cells, providing a practical pathway toward mechanically robust high-efficiency photovoltaics.