%0 Journal Article
%T Optical Absorption Enhancement in Amorphous Silicon Films and Solar Cell Precursors Using the Aluminum-Induced Glass Texturing Method
%A Nasim Sahraei
%A Selvaraj Venkataraj
%A Premachandran Vayalakkara
%A Armin G. Aberle
%J International Journal of Photoenergy
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/842891
%X One of the key issues of thin-film silicon solar cells is their limited optical absorptance due to the thin absorber layer and the low absorption coefficient for near-infrared wavelengths. Texturing of one or more interfaces in the layered structure of these cells is an important technique to scatter light and enhance the optical pathlength. This in turn enhances the optical absorption of the solar radiation in the absorber layer and improves the solar cell efficiency. In this paper we investigate the effects of textured glass superstrate surfaces on the optical absorptance of intrinsic a-Si:H films and a-Si:H p-i-n thin-film solar cell precursors deposited onto them. The silicon-facing surface of the glass sheets was textured with the aluminium-induced glass texturing method (AIT method). Absorption in both intrinsic silicon films and solar cell precursor structures is found to increase strongly due to the textured glass superstrate. The increased absorption due to the AIT glass opens up the possibility to reduce the absorber layer thickness of a-Si:H solar cells. 1. Introduction Thin-film solar cells have potential for low-cost photovoltaic (PV) electricity generation due to inherent advantages such as reduced semiconductor material consumption and the ability to deposit thin films over large areas. However, the thin nature of the absorber limits the optical absorption of the cells. Hydrogenated amorphous silicon (a-Si:H) has a very high optical absorption coefficient for photons with energy larger than the bandgap, enabling absorber layer thicknesses of well below 500£¿nm for such solar cells. However, light-induced degradation (Staebler-Wronski effect) is a known phenomenon that degrades the efficiency of a-Si:H solar cells when exposed to sunlight. To minimize the light-induced degradation effect, absorber layer thicknesses of less than 250£¿nm are required, which demands excellent light trapping in the structure [1]. To overcome the problem of low optical absorption, various techniques have been tested in the past and reported in the literature to enhance the absorption in these cells, whereby light trapping in thin-film silicon solar cells has been used as early as 1974 [2]. Textured surfaces are known to scatter the light passing through thin-film solar cells, thereby increasing the optical pathlength in the cells and hence the overall absorptance. Advanced optical modeling predicts that light trapping methods, such as texturing the superstrate of thin-film solar cells, can maintain high photocurrents in very thin a-Si:H solar cells [3].
%U http://www.hindawi.com/journals/ijp/2014/842891/