Broadband and omnidirectional highly-transparent coverglasses coated with biomimetic moth-eye nanopatterned polymer films for solar photovoltaic system applications

摘要

Highly-transparent coverglasses coated with broadband and omnidirectional antireflective (AR) moth-eye nanopatterned ultra-violet (UV) curable polymer, i.e., Norland Optical Adhesive (NOA) 63, films are reported. The moth-eye nanopattems on the NOA63 polymer films/glasses are transferred from the silicon molds with conical nanogratings (NGs) using poly-dimethylsiloxane stamps by a soft imprint lithography technique. For the NOA63 NGs/glasses, surface wetting behaviors, UV radiation/thermal effects, and optical properties, together with theoretical analyses using rigorous coupled-wave analysis calculations, are investigated. For a period of 380 nm, the NOA63 NGs/glass exhibits a hydrophobic surface with a water contact angle of similar to 112 degrees. Furthermore, it increases the transmittance of the bare glass over a wide range of wavelengths and incident light angles, showing the higher solar weighted transmittance (T-sw) of similar to 93.2% at an incident angle (theta(i)) of 0 degrees and the larger average T-sw value of similar to 83.6% at theta(i)=10-70 degrees than those (i.e., T-sw similar to 90.1% at theta=0 degrees and average T-sw value of similar to 81.5% at theta(i)=10-70 degrees) of the bare glass in the wavelength range of 350-1800 nm. In addition, it shows a relatively good stability under intense UV radiation and high temperature. By employing the 380 nm-period NG patterned NOA63 films into an AR coating of coverglasses in encapsulated III-V GaInP/GaInAs/Ge triple-junction solar photovoltaic (PV) sub-receiver modules, an enhanced power conversion efficiency (PCE) of 31.33% is obtained mainly due to an increased short-circuit current density (J(sc)) of 14.68 mA/cm(2) compared to reference PV modules with the bare coverglass (i.e., PCE=30.12% and J(sc=) 14.07 mA/cm(2)) at theta(i)=0 degrees. For incident angle-dependent PV module characteristics, it also has more outstanding solar energy conversion properties in a wide theta(i) range of 10-70 degrees. (C) 2014 Elsevier B.V. All rights reserved.