Improved Light Absorption of GaInP/GaAs/Ge Solar Cell Modules With Micro/Nanoengineered Coverglasses

We report on advanced types of coverglasses, which include the hierarchical micro- and subwavelength-structured surfaces for improved absorption efficiency of photovoltaic modules. Prism-shaped microstructures (PSMSs) help eliminate the optical shading caused by the metal grid of solar cells. The subwavelength structures (SWSs) with a tapered shape behave as a refractive index matching layer to reduce the surface reflection at the interface of air and coverglass. The geometries of the PSMSs and SWSs were designed by ray-tracing and the rigorous coupled-wave analysis method simulations, respectively, which provided the design guidelines. The PSMSs and SWSs were fabricated by a simple two-step process consisting of an isotropic wet etching process with hydrofluoric acid solution using a SiNx mask and a self-masked dry etching process, respectively. A hybrid patterned coverglass incorporating the PSMSs with SWSs were mounted on GaInP/(In)GaAs/Ge triple-junction solar cells with a precise alignment process. The measured power conversion efficiency of the subreceiver module with the patterned glass reached 32.97% for 1 sun, which is 11.19% higher compared with a subreceiver module with a flat coverglass.