Staebler-Wronski effect light-induced defects

Illumination of solar cells causes a reduction of efficiency and fill factor, as a result of light-induced creation of defects (Staebler-Wronski effect. Section 1.1.2.5). This reduction is halted after several hundred hours of illumination. The reduction is correlated with solar cell thickness. A large intrinsic layer thickness leads to a large reduction of efficiency and fill factor compared to a small intrinsic layer thickness. The solar cell properties can be completely recovered by annealing at about 150°C. The open circuit voltage and short circuit current decrease only slightly. 

In the original studies of the S-W effect on undoped and doped a-Si H films, the principal characteristics of the S-W effect and the presence of metastable defects in a-Si H were established (Staebler and Wronski, 1977 Wronski, 1978 Staebler and Wronski, 1980). It was found that the large light-induced conductivity changes are a bulk phenomenon that occurs between what may be considered a thermally stable state A and a new metastable conductivity state B. State A is perfectly reproducible and is independent of previous exposures to light. It is obtained after the a-Si H film is annealed (in the dark) at temperatures above 150 C and then cooled to room temperature. The annealing time required for state A depends on the... 

---