Gradient refractive index-based broadband antireflective coatings and application in silicon solar modules

Gradient refractive index-based broadband antireflective coatings (ARCs) could potentially improve solar power production by reducing the amount of sunlight reflected from the surface of photovoltaic (PV) modules. In this study, refractive index tunable hybrid SiO2 sols with refractive indices from 1.20 to 1.44 were prepared by adjusting different volume ratios and pH values and mixing acid-catalyzed SiO2 with base-catalyzed SiO2. Based on Essential Macleod simulation, five-layer graded refractive index broadband ARCs (FGBA) (n = 1.10–1.44) were prepared using hybrid sols derived from the sol-gel method as the building blocks. The morphological and structural characteristics of each coating layer were systematically investigated with different characterization methods. The average transmittance of the glass substrate coated with FGBA reached 97.57% (380–1800 nm), much higher than that of soda-lime glass (88.49%), and exhibited excellent broadband transmittance enhancement performance. The hardness performance of FGBA reached 5H, and the water contact angle of the surface at annealed 400 °C was 149°. The FGBA exhibited excellent durability performance in thermal cycling tests and abrasion tests. According to the external quantum efficiency test and I-V and P-V curve results, the short-circuit current density gain was 4.83% and the photoelectric conversion efficiency gain was 5.81% for the mini-silicon cell solar modules dipped with FGBA, compared to the undipped modules. This indicates positive prospects for application in outdoor PV plants. Meanwhile, it proves that ARCs are essential components of PV modules and could provide additional solar gains.