MRS Proceedings

Articles

Characterization of the Bulk Recombination in Hydrogenated Amorphous Silicon Solar Cells

2004 MRS Spring Meeting.

J. Denga1, J.M. Pearcea1, V. Vlahosa1, R.W. Collinsa1 and C.R. Wronskia1

a1 Center for Thin Film Devices, the Pennsylvania State University, University Park, PA 16802

ABSTRACT

Dark forward bias current, JD-V, characteristics offer a probe for characterizing carrier recombination and the defect states in the intrinsic layers of hydrogenated amorphous silicon (a-Si:H) solar cells. Detailed studies were carried out on such characteristics for the cells with optimized p/i interfaces and high quality i-layers in which the current transport is bulk recombination dominated. It was found that the diode quality factor n is not a constant with bias voltages as has been generally considered. Instead, it can be best described through the bias dependent differential diode quality factors, n(V) = [kT/q]−1[d(lnJD)/dV]−1, whose magnitude and shape reflect the gap state distribution in the corresponding bulk i-layers. The n(V) characteristics obtained on cell structures with both hydrogen diluted and undiluted i-layers have been utilized in characterizing the differences in the distribution of defect states in the two i-layers both in annealed state as well as after creating light induced defects. In the characterization of the Staebler-Wronski Effect (SWE) using JD-V characteristics, a newphenomenon is observed – relaxation of light induced defect states created by 1 sun illumination at 25°C, which is also found in the follow-on studies on the photo-conductivities of corresponding thin films.

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