Photovoltaic properties and high efficiency of preferentially doped polysilicon solar cells

Abstract

Making use of new solutions for the photocurrent and dark current, developed earlier, the photovoltaic properties of a preferentially doped n + p solar cell are examined taking into consideration Shockley-Read-Hall recombination, Auger recombination and heavy doping effects. Numerical calculations have been carried out for the analysis of the effects of the doping concentration, grain size, preferential doping penetration depth along the grain boundaries, and grain boundary recombination velocity on the photovoltaic parameters of the cell. The results reveal that, in order to obtain a high cell efficiency, the emitter doping level should not exceed 5 × 10 19 cm −3 and the base must be doped at an optimum level. It is found that the optimum base doping depends on the grain width and grain boundary recombination velocity and is practically unchanged with preferential doping. The results also show that a conversion efficiency exceeding 20% under AM1 conditions is obtained, when the grain is preferentially doped, and when the grain boundaries and the top and back contact surface are passivated.