ORIGIN OF THE OPTICAL GAP DEPENDENCE OF A-SIGE SOLAR-CELL STABILITY

The effect of the optical gap (E-opt) on the thermal recovery behavior s of a-SiGe solar cells was systematically investigated. It was found that the time constant and the activation energy required for the ther mal annealing of metastable defects do not strongly depend on E-opt. T he independence of the activation energy from E-opt suggests that the variation of E-opt causes little energy difference in the trap depth o f hydrogen, which should diffuse to remove metastable defects during n etwork relaxation by annealing. It was also shown that the degradation ratio for narrower E-opt cells exhibits greater temperature dependenc e after prolonged light soaking. This tendency was analytically attrib uted to the E-opt dependence of the light-induced defect creation proc ess and the E-opt independence of the thermally induced annealing proc ess. (C) 1998 American Institute of Physics. [S0021-8979(98)03519-1]