Hydrogenated amorphous silicon (a-Si:H) films were deposited at high growth rates by increasing the rf power density in a (SiH4+H2) discharge, while powder formation due to gas phase polymerization was controlled by heating the cathode together with the anode. A combination of Raman scattering, infrared absorption, and small angle x-ray scattering experiments was used to study the short-range order and microstructure of films deposited in different (dusty or otherwise) plasma conditions. The results were correlated with initial and light-soaked photoresponse to demonstrate that films with more microstructure and less short-range order were generally poorer.

Using a combination of infrared absorption and small-angle x-ray scattering on hydrogenated amorphous silicon alloy films and efficiency measurements of solar cells with intrinsic layers prepared under nominally identical conditions to those for the deposition of the films, we observe a correlation between microstructure in the films and solar cell performance. With increasing microvoid density, both the initial and light-degraded performance of solar cells are found to deteriorate.

We have used small-angle X-ray scattering (SAXS) and Doppler-broadening measurements of positron-annihilation radiation to study changes in the microvoid distribution in PECVD a-Si:H films during annealing. From a comparison of data on deuterium diffusion with information obtained from SAXS we conclude that changes, during annealing, in the dispersive character of deuterium diffusion are likely to be caused by void formation through clustering of smaller structural defects.