Mobility, recombination kinetics, and solar cell performance

In order to optimize the amorphous silicon solar cell structure for improved stabilized performance it is necessary to understand a great number of material parameters as they exist in the solar cell under operating conditions. Towards the goal of using the solar cells themselves for quantitative defect analysis, the authors show that the short wavelength quantum efficiency measurement is a means to determine the total density of charged and uncharged dangling bonds in the i-layer as a function of light soaking time. The compound effect that dangling bond defects have on solar cell performance, consisting of the redistribution of the electric fields and decreased lifetimes are considered. The magnitude of the short wavelength response can be directly linked to the number of bulk defects in the solar cells. Also it is not possible to directly determine the electron mobility from solar cell characterization due to the diffusive carrier transport found in amorphous materials. Surprisingly, the electron mobility is not expected to be directly linked to the stability of the solar cells.