Space charge limitation on the response time of organic photodiodes
article
The dynamic response of an organic bulk heterojunction photodiode to small changes in applied bias orlight intensity is investigated as function of the intensity of a constant background illumination by meansof photoimpedance and transient photocurrent measurements. For bias voltages close to the open circuitvoltage wefind that the response timescale with the square root of the light intensity. The results can bequantitatively explained in terms of a space charge limitation on the photocurrent as predicted byGoodman and Rose (J. Appl. Phys.42, 2823 (1971)). The relaxation time of the diode at open circuitcorresponds to the lifetime of the slowest charge carrier in the diode. This relaxation time is determinedby the dielectric constant and the smallest of the two carrier mobilities in the bulk heterojunction. Thisillustrates the importance of balanced carrier mobilities for obtaining diodes with fast response time atlow bias for e.g. imaging arrays.
Topics
TNO Identifier
865856
ISSN
1566-1199
Source
Organic Electronics, 34, pp. 218-222.
Publisher
Elsevier
Pages
218-222
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