The physical behaviour of an n+p silicon solar cell in concentrated sunlight

Abstract

The performance of a simple n + p silicon solar cell at various illumination levels is analysed by a modified form of the Gummel and De Mari numerical algorithms. Effects of high doping, such as bandgap narrowing together with the correction to density of states are included. The effective recombination life time of the charge carriers due to both Shockley-Read-Hall recombination via traps and Auger recombination is taken into account. The base acceptor doping concentration is 10 16 cm −3. The light concentration is varied from 1 to 200 AM1. The physical mechanisms of the device at various levels of illumination are discussed by determining the cell parameters, namely, saturation current density, short circuit current density, ideality factor and fill factor. The ideality factor which is close to 1 at low illumination suggests that the cell is controlled by diffusion-recombination processes. The high value of the ideality factor, which is very much greater than 1 but less than 2, at high-illumination is attributed to high-injection effect. The efficiency reaches a maximum around 100 AM1 and starts falling beyond that. This fall is due to the high-injection and the voltage drop in the base layer. The fill factor starts falling at high-illumination.