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

Abstract

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 (theta(CA)) of < 5 degrees (i.e., superhydrophilic surface) and higher solar weighted transmittance (SWT) of similar to 95.9% over a wide wavelength region of 300-1800 nm at normal incidence compared to the bare coverglass (i.e., theta(CA)similar to 63 degrees and SWT similar to 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/cm(2) and thus improved the conversion efficiency (eta) to 32.07% (cf., J(SC) = 13.84 mA/cm(2) and eta = 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 degrees. (C) 2013 Elsevier B.V. All rights reserved.