Nanovoid-driven light management in emerging c-Si solar technologies

Diffuse (directional-hemispherical) and angular transmittance are critical figures of merit for wave-optical light-trapping, yet have never been available directly from finite-difference time-domain (FDTD) calculations. We introduce an FDTD post-processing formalism capable of returning absolute diffuse, direct and total transmittance together with complete angle-resolved distributions, grounded in in-house open-source package coded for seamless integration with optimization workflows and for independent verification. The reliability of this method is demonstrated by simulating three canonical crystalline-silicon architectures: a planar reference, periodic micrometric upright pyramids and novel photonic nanovoids. From the resulting angular power maps we extract the silicon critical angle and quantify the portion of incident light retained by total internal reflection in each design, thereby establishing a rigorous link between optical scattering and carrier-generation potential. The wavelength-scaled nanovoid coating sustains broadband diffusion, converting incoming solar radiation into scattering angles that maximize optical path length. By providing a standard-compliant, parameter-driven route to diffuse and angular transmittance, the proposed formalism eliminates laboratory integrating-sphere measurements from the design loop and compresses development cycles from weeks to hours. Beyond photovoltaic modules, this architecture-agnostic framework is readily extensible to ASTM- or ISO-based standards and other photonic systems, enabling a truly simulate-to-specification paradigm for large-scale manufacturing and rapid materials discovery.