Effects of prolonged illumination on the properties of hydrogenated amorphous silicon

In the last few years, light-induced changes have been observed in many of the properties of hydrogenated amorphous silicon (a-Si:H). This article reviews the light-induced effects in properties such as conductivity, photoconductivity, photoluminescence, electron spin density, density of gap states, diffusion length, optical absorption and photovoltaic performance. Some of the experimental results indicate that more than one type of metastable center is operative in a-Si:H. We discuss several proposed models for these centers and also suggest some new models.