Homojunction and heterojunction silicon solar cells deposited by low temperature-high frequency plasma enhanced chemical vapour deposition

Plasma enhanced chemical vapour deposition (PECVD) is widely used to deposit materials on a variety of substrates at low temperature. However, examples of epitaxial growth on silicon with this technique are scarce. In this paper, we present homojunction silicon solar cells, epitaxially grown by PECVD, and muc-Si/a-Si:H/c-Si heterojunctions deposited with the same technique, manufactured by a completely low temperature process. All cells incorporate an intrinsic buffer layer, whose deposition conditions were varied. It is shown that the best V-oc is obtained when the intrinsic layer is deposited under two extreme conditions, i.e. zero or very high (99.4%) hydrogen dilution of the gas mixture, resulting in a totally amorphous or epitaxial i-layer, respectively. Intermediate conditions result in V-oc degradation. Efficiencies as high as 13.7% were obtained in planar devices that include an amorphous i-layer, and 13.1% in homojunction devices. (C) 2002 Elsevier Science B.V. All rights reserved.