Correlation between fill factors of amorphous silicon solar cells, and their i layer densities of states as determined by DLTS

Deep-level transient spectroscopy (DLTS), based on short-circuit current transients after repetitive excitation by light, was performed on a-Si:H p-i-n solar cells over the temperature range 90-350 K. The fill factors of these same cells were measured at room temperature (at a light intensity of 0.01 sun to minimize series resistance effects) to obtain a measure of i layer quality. Dangling bond concentrations, N_s, deduced from the DLTS spectra, and changes in N_s caused by light soaking, agree with values commonly reported in the literature. The collection length/i layer thickness ratios deduced from the measured fill factors are found to be inversely related to N_s. However, fill factor is not uniquely determined by N_s-field distortion in the i layer must be taken into account.