Bio-inspired surface structures promote optical transmittance and hydrophobicity in cellulose-based films for self-cleaning perovskite solar cells

Developing suitable light management layers can improve the lifetime and efficiency of solar cells and other optoelectronics. Here, a bioinspired approach to produce all-biobased films with high anisotropic light scattering and superhydrophobicity is presented as a route toward sustainable light management layers for photovoltaics. The multifunctional films are achieved by replicating leek leaves onto cellulose acetate, producing hierarchical surface structures. The free-standing films show a transmittance of ≈94% and a haze of ≈54% at the wavelength of 550 nm. Moreover, anisotropic advancing contact angles of up to 160° and 156° in cross directions are achieved through tailoring a carnauba wax coating. Using the replica as the light management layer on perovskite solar cells improved the power conversion efficiency by 6 ± 0.3%. Meanwhile, the surface water repellency facilitates self-cleaning, ensuring maximum incident light over time by tackling dirt accumulation. Furthermore, the method can be potentially employed to fabricate substrates from virtually any leaf or patterned surface as the initial replication template.