期刊
SOLAR ENERGY MATERIALS AND SOLAR CELLS
卷 91, 期 5, 页码 390-393出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.solmat.2006.10.020
关键词
organic photovoltaics; impedance spectroscopy; doping; kink; model
The current-voltage characteristic and the performance of organic bulk-heterojunction solar cells are very sensitive to small variations in the production steps or environmental influences. In our experiments, we found a large variation of the short-circuit current, which does not correspond to the device thickness as one might expect. The fill factor of some devices is below 25% under illumination, while the best devices have a fill factor of about 70%. Electrical impedance spectroscopy can provide information about the conductivity of different regions within the device. In earlier measurements, it was observed that devices with a thick absorber layer might consist of a conductive bulk region and a very poorly conductive depletion region at the metal contact. Using a standard semiconductor device model, it is shown in this paper that this reduces the charge collection efficiency under short-circuit conditions, as there is no electrical field in the bulk region, supporting the charge separation. For devices with the low fill factor, a thin-current limiting layer under forward bias can be identified by electrical impedance spectroscopy and is suggestive of a corroded metal contact. (c) 2006 Elsevier B.V. All rights reserved.
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