Compatibility of glass textures with E-beam evaporated polycrystalline silicon thin-film solar cells

Abstract

For polycrystalline silicon thin films on glass, E-beam evaporation capable of high-rate deposition of amorphous silicon (a-Si) film precursor up to 1 μm/minute is a potentially low-cost solution to replace the main stream a-Si deposition method—plasma enhanced chemical vapour deposition (PECVD). Due to weak absorption of near infrared light and a target of 2 μm Si absorber thickness, glass substrate texturing as a general way of light trapping is vital to make E-beam evaporation commercially viable. As a result, the compatibility of e-beam evaporation with glass textures becomes essential. In this paper, glass textures with feature size ranging from ∼200 nm to ∼1.5 micron and root-mean-square roughness (Rms) ranging from ∼10 nm to 200 nm are prepared and their compatibility with e-beam evaporation is investigated. This work indicates that e-beam evaporation is only compatible with small smooth submicron sized textures, which enhances Jsc by 21 % without degrading Voc of the cells. Such textures improve absorption-based Jsc up to 45 % with only 90 nm SiNx as the antireflection and barrier layer; however, the enhancement degrades to ∼10 % with 100 nm SiOx+90 nm SiNx as the barrier layer. The absorption-based Jsc is abbreviated by Jsc(A), which is deduced by integrating the multiplication product of the measured absorption and the AM1.5G spectrum in the wavelength range 300–1050 nm assuming unity internal quantum efficiency at each wavelength.