Effect of optical gap on the stability of a-SiGe solar cells

Abstract

The light-induced degradation and thermal recovery behaviors of a-SiGe single-junction solar cells with i-layers having various optical gaps ( E opt) have been investigated. The narrower E opt cells show slower degradation under light-soaking than the wider E opt cells. However, they recover by thermal annealing at 150°C as fast as the wider E opt cells. The results indicate that the light-induced defect creation processes are suppressed in the narrower E opt materials, but the thermally induced process does not depend on E opt. From a comparison among several samples, the E opt dependence of the light-induced processes is attributable to the difference of E opt itself, i.e., the band-to-band recombination energy, rather than to the difference of the compositions.