Amorphous silicon solar cells deposited at high growth rate

Abstract

A series of investigations was performed to improve stabilized efficiency of hydrogenated amorphous silicon (a-Si:H) solar cells deposited at a high growth rate of 15–20 Å/s by the plasma-enhanced chemical vapor deposition method. The deterioration of film stability accompanied by an increase of deposition rate was found to be closely correlated with the increase of Si–H 2 bond hydrogen content in the deposited film. Plasma diagnosis results by quadrupole mass spectrometry and optical emission spectroscopy showed that reduction of electron temperature of plasma can effectively suppress the formation of higher-order silane-related species in the plasma and can improve film stability. According to the guiding principles deduced from the plasma diagnosis, we successfully improved the stability of cell performance and obtained a considerably improved stabilized efficiency of 8.2% at a high rate of 20 Å/s. Key issues for improving stabilized efficiency of high growth-rate a-Si:H solar cells, by making the best use of plasma diagnostic techniques, are presented and discussed.