Superhard, Antireflective Texturized Coatings Based on Hyperbranched Polymer Composite Hybrids for Thin-Film Solar Cell Encapsulation

In this study, we demonstrate by simulation and experiment the antireflective (AR) performance of hyperbranched polymer (HBP) nanocomposites textures replicated from a moth-eye pattern using ultraviolet (UV) nanoimprint lithography. A UV-curable acrylated HBP and a hybrid composite of the HBP with silica nanoparticles with an organometal precursor were used. Using effective medium theory (EMT) simulations, optimal patterns were found to be arrays of paraboloids with stable AR performance over a large range of geometries. A good agreement was found between the simulated and measured optical behavior of such AR arrays with a normal reflectance within the visible range of approximately 4% for the use of a glass substrate. The photocurrent of AR-coated a-Si:H solar cells was found to be 2% higher than the reference value of an uncoated cell whereas, for AR-coated tandem thin film Si cells, the increase was 3% for the top a-Si:H cell and 2% for the bottom microcrystalline Si cell.