Epitaxial wafer equivalent solar cells with overgrown SiO₂ layer and varying doping profile to reduce the influence of defects

Abstract

Epitaxial wafer equivalent solar cells require a reflecting rear side to reach similar efficiencies as wafer based cells. This can be achieved by implementing a SiO 2 layer using the epitaxial lateral overgrowth technique. In this work defect structure and density within the silicon layers are discussed. As defect densities rise towards the SiO 2 layers, solar cells are fabricated with increasing sizes of moderately doped back surface fields to reduce their influence. Thereby, a benefit of 3 % absolute in efficiency is obtained. However, the best cell with an efficiency of 14.1 % is still limited by the reduced crystal quality.Index Terms -crystalline silicon thin film, epitaxial wafer equivalent, epitaxial lateral overgrowth, defect density.