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

摘要

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 urn 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 J_(sr) by 21 % without degrading V_(oc) of the cells. Such textures improve absorption-based J_(sr) up to 45 % with only 90 nm SiN_x as the antireflection and barrier layer; however, the enhancement degrades to ~10 % with 100 nm SiO_x + 90 nm SiN_x as the barrier layer. The absorption-based J_(sr) is abbreviated by J_(sr)(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 wave/ength. This investigation is also relevant to other thin-film solar cell technologies which require evaporating the absorber onto textured substrate/superstrate.