Effect of the optical gap on the temperature dependence of a-SiGe solar cell stability

The effect of the optical gap (E(opt)) on the thermal recovery behavior of a-SiGe solar cells and on the temperature dependence of the cell stability was systematically investigated. It was found that the time constant and activation energy of thermal recovery do not depend on E(opt). The independence of the activation energy from E(opt) suggests that the variation of E(opt) causes little energetic difference in the trap depth for hydrogen moving to remove defects during annealing. The steady-state defect density of the narrower E(opt) alloy is also considered to exhibit a greater temperature dependence than that of the wider E(opt) alloy, because of the E(opt) dependence of the light-induced creation of defects and the independence of thermal-induced annealing. (C) 1998 Elsevier Science B.V. All rights reserved.