Forty years of the Staebler–Wronski effect

ABSTRACT

This article describes highlights of investigations of the Staebler–Wronski effect (SWE), observed in hydrogenated amorphous silicon since its discovery. Some of the basic characteristics of SWE are discussed along with some solved and unsolved puzzles. Particular emphasis is given to a recent model based on long-range potential fluctuations caused by heterogeneities present in the films. Evidence is reviewed for the presence of several kinds of dangling-bond defects produced by light exposure (hv > 1.3 eV) at different temperatures between 4.2 and 360 K. With exposure at lower temperature the defects become less stable, but they possess larger recombination cross-sections. Voids in the material have been identified as the location for light-induced defects most harmful to the efficiency of solar cells. Ways to eliminate them are discussed. We suggest that progress in this field was delayed by lack of sample sharing among laboratories.

KEYWORDS:

• A-Si:H
• amorphous silicon
• conductivity
• photo-induced effects
• photo-induced metastability

Acknowledgements

This article is in honour of Professor Hellmut Fritzsche, who turned 90 in February, 2017. We thank him for his valuable comments and suggestions on this manuscript. Thanks are also due to our students, colleagues and friends for many fruitful discussions, which helped us clarify many points discussed here. We would like to thanks Professor Pratima Agarwal, Professor Kasturi L. Chopra and Professor Sushil Auluck for the useful comments and discussion. Finally, one of us (SCA) is grateful to Professor Gautam Biswas, Director, IIT, Guwahati, for inviting him to visit his Institute, where most of this article was written.

Disclosure statement

No potential conflict of interest was reported by the authors.