Broadband and omnidirectional antireflective film with bioinspired nanocone-grid hybrid structures for enhanced solar energy harvesting

The accelerating development of solar energy conversion technology has raised an urgent demand for high-performance antireflective (AR) materials to enhance photon transmission. However, conventional AR materials are constrained by limited spectral bandwidth and pronounced angular dependence, leading to significant reductions in photon transmission under broadband and wide-angle conditions. Herein, we propose a broadband omnidirectional antireflective (BOAR) film with unique nanocone-grid-like (NCGL) hybrid structures, inspired by dragonfly wings. Optical characterization reveals that the biomimetic NOA61 film with the NCGL structure achieves approximately 96.3% transmittance in the visible spectrum at normal incidence, which is about 3.7% higher than that of the smooth NOA61 film. This transmittance enhancement remains at ∼2.9% within a 30° incidence range, and even at an extreme 75° incidence, the transmittance still reaches ∼78%. The excellent optical performance stems from the continuous, effective refractive index gradient constructed by the NCGL structure, which enables a smooth optical transition from air to the substrate by mitigating interfacial optical discontinuities. Moreover, the biomimetic BOAR film exhibits good environmental stability and mechanical properties. Notably, under AM1.5G simulated solar illumination at 25 °C, the solar panel integrated with the NOA61 film exhibits a 36.6% relative improvement in power conversion efficiency compared to that with the smooth film. In the 350-900 nm spectral range, the structured NOA61 film achieves an average 2.9% enhancement in external quantum efficiency. These results confirm that the NCGL hybrid structure enhances transmittance by suppressing Fresnel reflection, thereby increasing the photon flux into the active layer. This work provides new design principles for developing high-performance optical interfaces in photoelectric and photothermal conversion systems.