Bias-induced instability in an intrinsic hydrogenated amorphous silicon layer for thin-film solar cells

In this article we present a mechanism for creating metastable defects in intrinsic hydrogenated amorphous silicon (a-Si:H) layers by changing the flow-rate ratio of SiH₄ and H₂. This is an important cardinal property that restricts the performance of both solar cells and thin-film transistors (TFT). Light or electrical bias results in generation of metastable dangling bonds. We evaluated the gas flow-rate ratio dependence of current decrease before and after application of electrical bias stress. Furthermore, we produced an a-Si:H TFT for comparison with a single-layer a-Si:H. Intrinsic layers deposited by SiH₄ to H₂ flow-rate ratios of 1:3 exhibited greater resistance to stress. In a-Si:H single layer experiment, we got a similar result, samples with SiH₄ and H₂ flow-rate ratios of 1:3 exhibited less decrease in current after application of electrical bias stress. These results will facilitate fabrication of more-stable a- Si:H thin film p-i-n solar cells.