Thin-film monocrystalline-silicon solar cells based on a seed layer approach with 11% efficiency

Solar modules made from thin-film crystalline-silicon layers of high quality on glass substrates could lower the price of photovoltaic electricity substantially. Almost half of the price of wafer-based silicon solar modules is currently due to the cost of the silicon wafers themselves. Using crystalline-silicon thin-film as the active material would substantially reduce the silicon consumption while still ensuring a high cell-efficiency potential and a stable cell performance. One way to create a crystalline-silicon thin film on glass is by using a seed layer approach in which a thin crystalline-silicon layer is first created on a non-silicon substrate, followed by epitaxial thickening of this layer. In this paper, we present new solar cell results obtained on 10-micron thick monocrystalline-silicon layers, made by epitaxial thickening of thin seed layers on transparent glass-ceramic substrates. We used thin (001)-oriented silicon single-crystal seed layers on glass-ceramic substrates provided by Corning Inc. that are made by a process based on anodic bonding and implant-induced separation. Epitaxial thickening of these seed layers was realized in an atmospheric-pressure chemical vapor deposition system. Simple solar cell structures in substrate configuration were made from the epitaxial mono-silicon layers. The Si surface was plasma-textured to reduce the front-side reflection. No other light trapping features were incorporated. Efficiencies of up to 11% were reached with Voc values above 600 mV indicating the good electronic quality of the material. We believe that by further optimizing the material quality and by integrating an efficient light trapping scheme, the efficiency potential of these single-crystal silicon thin films on glass-ceramics should be higher than 15%.