Abstract

Studies on concentrated light influence do not take into account the effect of the heating and this proves to be harmful on photovoltaic parameters. The main purpose of this work is to study the effects of light concentration and the heating caused by this concentration on intrinsic properties and carrier density profile. A thermal model of the PV cell is proposed. By applying the power balance at the steady-state, the PV cell thermal equation is determined. The resolution of this equation leads to temperature profile which shows a rapid increase with light concentration. The mobility  and diffusion  coefficients of electrons increase to reach their maxima, respectively  at C=6,77 Suns where temperature is T=430,92 K and  at C= 12,59 Suns where temperature is T=508,24; before decreasing. However, for the holes these parameters decrease slowly with concentration increase. Silicon gap energy decreases while electrons intrinsic density increases with increasing concentration. The variations of these parameters are explained on one hand by their dependence on temperature but also by temperature profile with concentration. An electrical model of the PV cell under variable concentration is also proposed and from which the carrier’s density is determined. It emerges that the carrier density increases significantly with concentration ratio. This fact is explained by the photo-generation increase with concentration. And also, by thermal generation increase linked to temperature increases with concentration increase. Results also show that carriers density is greater in the rear side compared to the zone near the junction in opposite to authors who did not take into account temperature effect and who showed that carriers density is greater at the illuminated face.

Key words: Temperature profile, concentrated light PV cell, intrinsic density, gap energy, carriers density profile.