The Influence of the Si-H₂ Bond on the Light-Induced Effect in a-Si Films and a-Si Solar Cells

Abstract

The influence of the Si-H2 bond on light-induced degradation and the thermal recovery of a-Si films and a-Si solar cells were studied. The influence of the Si-H2 bond on light-induced degradation depends on the impurity content in a-Si films, and light-induced degradation can be reduced by decreasing the Si-H2 bond density in a-Si films with impurity content of 1018 cm-3. The activation energy of the thermal recovery process was about 1.0 eV, and it did not depend on the Si-H2 bond density. However, an irreversible phenomenon was observed in film properties and solar cell characteristics with high Si-H2 bond density. It is thought that the structural flexibility of the Si-H2 bond is related to this irreversible phenomenon.

Fabrication of hydrogenated amorphous silicon films exibiting higher stability against light soaking

“…At maximum d ms , we obtained the lowest hydrogen concentration (Si-H ¼ 4 at.%, Si-H 2 < 1 · 10 20 cm À3 ) at the substrate temperature of 250°C. As has been suggested by earlier works, low C SiH 2 films should degrade less [2][3][4][5]. It was indeed confirmed in the triode-deposited films, where excellent stability against light soaking was observed in their spin densities as well as the fill-factors of their related Schottky diodes [8].…”

“…Those films are expected to show higher stability against light soaking because of their low Si-H 2 densities [2][3][4][5], and indeed, we observed excellent stability in the fill-factors (FF) of their related Schottky diodes [8]. While the initial FFs are the same in the triode and diode cases ($54%), their stable values are: triode ¼ 52% and diode ¼ 47%, respectively.…”

“…It has been reported that light-induced degradation of a-Si:H correlates with hydrogen concentration, especially with Si-H 2 bond density (C SiH 2 ) [2][3][4][5]. Although a detailed microscopic model for explaining this correlation is not revealed yet, the dependence is observed in films prepared under a wide range of fabrication conditions.…”

Improving the photoresponse spectra of BaSi2 layers by capping with hydrogenated amorphous Si layers prepared by radio-frequency hydrogen plasma

“…In sample G, however, both Si-H and Si-H 2 bonds did not exist, meaning that T S = 80 • C is not sufficient to form Si-H bonds. It was reported by Nakamura et al, 28 that the Si-H 2 bonds are responsible for light-induced degradation of a-Si solar cells. On the basis of these results, we chose the PD method rather than the CD method and went forward to the next experiment.…”

Integration of Expanding Thermal Plasma deposited Hydrogenated Amorphous Silicon in Solar Cells

“…1], decreasing the defect density from 10 20 cm -3 for unhydrogenated a-Si to 10 16 cm -3 for a-Si:H. R* is correlated to the Staebler-Wronski Effect (SWE) [e.g. 56,57], showing a more significant SWE when R* is larger. The hydrogen concentration of ETP material deposited at 7 nm/s decreases with increasing deposition temperature and is lower than 10% above 300ºC.…”