Open-circuit voltage increase dynamics in high and low deposition rate polymorphous silicon solar cells

The dynamics of the open-circuit voltage (V _OC) of polymorphous silicon (pm-Si:H) solar cells deposited at high and low rates (8 and 1.5 Å/s, HR and LR) and containing lightly or heavily doped p-layers (LD or HD) are compared through in situ, variable intensity measurements during light-soaking (LS). The V _OC's of the LR cells show an increase with LS, regardless of doping level, whereas the HR cells show decreasing V _OC's. This result is in contrast to the changes predicted by the dark diode characteristics, which predict increasing V _OC for all the devices. The device measurements are compared to the analogous measurements on co-deposited coplanar p-i layer stacks to determine whether the V _OC dynamics can be linked to changes in the p-layer doping efficiency during LS. The changes to the macroscopic electrical behaviour of the cell under varying light conditions are modelled using a simple, three parameter function, and are compared to results from a detailed, numerical modelling tool, AFORS-HET.