Artificial inverted compound eye structured polymer films with light-harvesting and self-cleaning functions for encapsulated III-V solar cell applications

We report the artificial inverted compound eye structured (ICESs) polydimethylsiloxane (PDMS) films with light-harvesting and self-cleaning functions for the enhancement of solar power generation in encapsulated III-V gallium arsenide (GaAs) single-junction solar cells. The ICESs PDMS films are fabricated by facile, simple, and cost-effective soft lithography using sapphire master molds with the CESs consisting of hierarchical nanotextures/periodic microgratings prepared by thermally dewetted gold nanopatterning and subsequent dry etching processes. By attaching the ICESs PDMS film with a hydrophobic surface (i.e., water contact angle (_CA) of ∼121°) to the coverglass, the total and diffuse transmittances of the coverglass are simultaneously increased over a wide wavelength range of 350-900 nm, exhibiting higher solar weighted transmittance (SWT) of ∼94.3% and average haze ratio (H_avg) of ∼67.6% than those of the bare coverglass (i.e., _CA ≈ 32°, SWT ≈ 90.2%, and H_avg ≈ 4.1%, respectively). The resulting encapsulated III-V GaAs single-junction solar cells with the ICESs PDMS/coverglass show an enhanced power conversion efficiency (PCE) of 24.3% compared to the encapsulated solar cell with the bare coverglass (i.e., PCE = 22.96%) due to the increased short circuit current density from 26 to 27.64 mA cm^-2, indicating the PCE increment percentage of ∼5.8%. Moreover, it also exhibits superior device performance at varying angles of incident light. For the long-term self-cleaning effect on the device efficiency, there is no significant variation in the PCE after approximately one month, indicating a low PCE drop percentage of ∼1.4%.