Theory and experiment on the surface-photovoltage diffusion-length measurement as applied to amorphous silicon

The collection-efficiency theory for low-mobility solar cells proposed by Reichman has been adapted to the analysis of the surface-photovoltage experiment in amorphous silicon. From measurement of the apparent diffusion length at low- and high-bias light intensity the ambipolar diffusion length and space-charge width can be obtained. In order to fit experimental observations to the theory it was necessary to assume that the positive space-charge density in the surface barrier increases with the light level. This was independently confirmed by capacitance measurements.