Bioinspired Broadband Omnidirectional Anti-Reflective Coatings by Scalable Dip-Coating Process for Efficient Solar Energy Collection

The interface reflection loss severely constrains the light-harvesting efficiency in solar technologies. Conventional anti-reflective coatings face limitations such as narrow wavelength, angular dependence, and complicated fabrication process. Here, we propose an omnidirectional light-harvesting biomimetic design based on refractive index tunable core-shell particles. The carboxyl groups-containing polymers aggregate into nanocluster as the core and tetraethyl orthosilicate hydrolyzes into SiO₂ shell. The gradient refractive index of core-shell particles can be achieved by regulating the composition of core and shell, as well as the pH value during the hydrolysis process. The broadband omnidirectional anti-reflection (BOAR) coating can be prepared by a scalable dip-coating process, providing flexibility for the adaptation of different substrates. The BOAR coating has an average transmittance of over 80% across a broad spectral range of 300–2500 nm and a wide incidence angle range of 0 °- 85 °. Compared to bare cells, the solar cells with BOAR coating show a 2.5 mA cm⁻² increase in short–circuit current density and an improvement in power conversion efficiency from 10.8% to 11.8%. Our work provides a scalable approach that integrates broadband angular stability, omnidirectional performance, and ambient temperature processability, making it suitable for applications in photovoltaic modules, solar energy collectors, and optical devices.