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 angstrom/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). 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 preducted 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 coplanat 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 comapred to results from a detailed, numerical modelling tool, AFORS-HET. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim