Design, preparation, and durability of TiO2/SiO2 and ZrO2/SiO2 double-layer antireflective coatings in crystalline silicon solar modules

This paper reports the use of a combination of numerical calculations and experimental work to establish the optimum photovoltaic transmittance (T-pv) and durability of the quarter wave, the quarter-half wave, and the non-quarter wave double-layer TiO2-SiO2 and ZrO2-SiO2 antireflective coatings (ARCs) on solar glass towards practical photovoltaic applications. Numerical calculations based on 4 x 4 propagation matrix method indicated that the non-quarter wave double-layer ARCs exhibited higher T-pv values than those of the quarter wave and the quarter-half wave ARCs. Such calculated values are in good agreement with the experimental T-pv values. For examples, the Tpv values for the non-quarter wave double-layer TiO2-SiO2 and ZrO2-SiO2 ARCs prepared by sol gel reached 94.4 +/- 0.1% and 94.3 +/- 0.1%, respectively. In terms of the coating durability, the non-quarter wave double-layer coatings with a dense and thicker TiO2 or ZrO2 barrier layer on solar glass exhibited less than 1% reduction in T-pv after 96 h highly-accelerated temperature and humidity stress test (HAST), as compared with the standard single-layer porous SiO2 used in industry which tested in the same HAST conditions to be greater than (15.4%) after 48 h. Single crystalline Si modules encapsulated by the non-quarter wave TiO2-SiO2 or ZrO2-SiO2 AR-coated glass are more durable, with only less than 10% degradation in efficiency after 48 h HAST, as compared with Si modules encapsulated by single-layer porous SiO2 AR-coated glass which have signification loss in efficiency (circa. 21.8%). (C) 2012 Elsevier Ltd. All rights reserved.