Investigation of a-Si:H p-i-n Solar Cell Degradation

Based on measured characteristics of degraded p-i-n structures, simulations of degraded structures were performed using our numerical simulator ASPIN in order to fit and explain pronounced hump-shaped voltage-dependent internal collection efficiency (ICE) characteristics under weak short-wavelength illumination. Agreement with measured hump-shaped ICE characteristics was obtained only if in addition to the introduction of light-induced dangling bond defect states, their capture cross-sections were also increased, in particular capture crosssection for the charged defect states. This causes a change in occupancy of defect states at the p-i interface and front part of the i-layer under forward bias. Consequently, it increases the electric field in the front part of the cell, which results in recovery of the ICE.