Mobility-lifetime product and interface property in amorphous silicon solar cells

Abstract

The mobility-lifetime products ( μτ) and interface property have been examined through the photovoltaic studies in actual hydrogenated amorphous silicon (a–Si:H) p–i–n junction solar cells. A small amount of boron atoms included in a–Si:H enhances the μτ products of both electrons and holes up to the order of 10−7 cm2/V, which corresponds to the carrier diffusion length in excess of 5000 Å. The doped window layer possessing inferior photoelectric property works as the recombination region for photocarriers generated in the active i layer, and practically dominates the interface property together with the surface recombination velocity S0 at the electrode/doped layer interface. The S0 at the SnO2/p a–Si:H interface is estimated to be about 3×102 cm/s with an assumption of the electron mobility at 0.1 cm2/Vs. Prolonged light exposure causes a reversible change of the μτ products in every layer composing the p–i–n junction. These experimental results are discussed in connection with photovoltaic performances.