Fabrication and optical characterization of hybrid antireflective structures with zinc oxide nanorods/micro pyramidal silicon for photovoltaic applications

We investigated the hybrid antireflective (AR) structures with zinc oxide nanorods (ZnO NRs) grown on micro pyramidal silicon (MP-Si) structures. The MP-Si structures were fabricated by a simple and cost-effective anisotropic wet chemical etching technique under different ratios between potassium hydroxide (KOH) and isopropyl alcohol (IPA). For the MP-Si structures etched at 10:9 vol% of KOH and IPA, the relatively low average reflectance (R-avg) value of 14.5% was obtained in the wavelength range of 300-1100 nm. Its solar weighted reflectance (SWR) value was also estimated to be 12.6% in the wavelength range of 400-1100 nm. The ZnO NRs were hydrothermally grown on the MP-Si structures at various solution concentrations. For the ZnO NRs (25 mM)/MP-Si, the R-avg and SWR values were further decreased to 3.6% and 3.8%, respectively. The omnidirectional AR behavior was also observed in the wide incident angle range of 20-70 degrees. The hybrid ZnO NRs/MP-Si AR structures revealed a superhydrophilic surface with water contact angles of < 5 degrees. (C) 2016 Optical Society of America