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

Abstract

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 UV nanoimprint lithography. A UV-curable acrylated HBP and a hybrid composite of the HBP with silica nanoparticles and 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 around 4% when using 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.Antireflective hardcoats: Synthetic moth eye textures eliminate light reflection in the front encapsulation of solar cells, leading to a 5% photocurrent increase in thin film tandem a-Si:H and µc-Si devices. The sub-micron antireflective textures are optimized using optical simulations and replicated in a low shrinkage and superhard hyperbranched polymer nanocomposite hybrid by means of a UV nanoimprint lithography process.