An extended ´collection length model´ for the description of keV electron induced degradation and thermal recovery of p-i-n solar cells

The results of kiloelectronvolt-electron degradation a and annealing experiments obtained on a-Si:H-based p-i-n solar cells are interpreted using models developed earlier for the degradation of a-Si:H films and are placed in the framework of an extended collection length model. The strong degradation of the short-circuit current and fill factor due to considerable kiloelectronvolt-electron irradiation can be explained quantitatively. This makes possible a crucial test of the validity of the mathematical models for the kiloelectronvolt-electron-induced effects developed so far. It is shown that the major part of these reversible changes can be attributed to bulk effects: interface properties do not have to be considered. Furthermore, the results of a detailed investigation of the thermal recovery of electron-degraded solar cells can be explained consistently. Some unresolved issues are discussed, and experiments to resolve these questions are proposed.