Surface passivation of high efficiency silicon solar cells

Theroretically and experimentally determined design guides for reducing significantly recombination at the emitter and rear surfaces of full-area AI-BSF and oxide passivated bifacial cells are given. The impact of emitter thickness and surface dopant concentration on emitter saturation current and solar cell efficiency is outlined. A modified emitter structure (locally deep diffused below the metal contacts) is predicted to have superior performance Measured V"oc"-values reveal the potential of deep emitter cells to achieve efficiencies above 20% in spite of high metallisation factors. Emperimentally we find strong dependence of passivation quality on oxide thickness and base doping concentration. The BSF quality of a diffused aluminum layer decreases strongly with increasing drive-in time. For SiO2-passivated rear surfaces of bifacial cells measurements of the dependence of the surface recombination velocity on the excess concentration are presented.