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HL: Halbleiterphysik
HL 56: Photovoltaik I
HL 56.5: Talk
Tuesday, March 8, 2005, 16:00–16:15, TU P-N202
Amorphous silicon solar cells under different illumination levels — •A. Al Tarabsheh, M. B. Schubert, and J. H. Werner — Institut für Physikalische Elektronik, Uni-Stuttgart, Pfaffenwaldring 47, 705 69 Stuttgart
The use of hydrogenated amorphous silicon-based (a-Si:H) solar cells in consumer products, and their potential for clothing-integrated photovoltaics (ipv) motivate us to study their performance under different illumination levels. In this work, we analyse the current/voltage (I/V) characteristics of a-Si:H solar cells as a function of the illumination intensity Φ. We start with the most simple equivalent circuit model of a real solar cell, with incorporating series and parallel resistances. Our measurements yield in an illumination-intensity dependent parallel resistance Rp(Φ) rather than a constant one. The decrease in Rp with Φ follows a power law, which we explain by the photoconductivity of parallel resistances that are distributed over the whole solar cell area. The dependence of Rp on Φ deteriorates the solar cell fill factor FF and conversion efficiency at high illumination levels. Therefore the implicit relation between FF and open-circuit voltage, which is generally valid for ideal solar cells, does not hold for our cells.