Nanostructured encapsulation coverglasses with wide-angle broadband antireflection and self-cleaning properties for III-V multi-junction solar cell applications

We report the effect of nanocone arrays (NCAs) as an antireflection coating (ARC) of encapsulation coverglasses on the device performance of encapsulated III-V InGaP/GaAs/Ge triple-junction (TJ) solar cells. The NCAs were fabricated on the single-side surface of glasses using the gold nanopatterns (i.e., nanoclusters) prepared by the glancing angle deposition technique without additional thermal treatment and the subsequent dry etching. Their wetting behavior and optical properties, together with a theoretical prediction using the rigorous coupled-wave analysis method, were investigated. The NCAs ARC coverglass exhibited a much lower water contact angle (θ_CA) of <5 (i.e., superhydrophilic surface) and higher solar weighted transmittance (SWT) of ~95.9% over a wide wavelength region of 300-1800 nm at normal incidence compared to the bare coverglass (i.e., θ_CA~63 and SWT ~92.8%). The use of the NCAs ARC coverglass in encapsulated III-V InGaP/GaAs/Ge TJ solar cells led to the higher short circuit current density (J_sc) of 14.22 mA/cm² and thus improved the conversion efficiency (η) to 32.07% (cf., J_sc=13.84 mA/cm² and η=30.6% for the cell with the bare coverglass). For incident angle-dependent solar cell characteristics, it also showed a superior solar power conversion property in wide incident light angles of 20-80.