Theoretical study of the impact of rear interface passivation on MWT silicon solar cells

In this study we analyze the impact of a rear point contact (RPC) scheme in metal wrap through (MWT) solar cells with passivated base by means of numerical simulations. We adopt a modeling methodology which avoids cpu and memory intensive simulations of the whole true three-dimensional solar cell. The proposed approach exploits simplified three-dimensional simulation in combination to the adoption of calibrated semi-empirical models to account for the RPC scheme in an effective way. The sensitivity of the main figures of merit of the complete MWT cell to geometrical and doping parameters such as substrate thickness, hole size as well as substrate resistivity is discussed. From our simulations we observe that the adoption of a passivated base enhances significantly the conversion efficiency. In particular, we calculate an increase of efficiency up to 1.07%abs1.07%abs with respect to MWT without RPC and up to 1.33%abs1.33%abs with respect to conventional front contact solar cells, depending upon the substrate resistivity and the substrate thickness. The optimum base contact fraction results within the range 3–5 % and it is higher in the case of lower substrate doping or larger holes.