Azo-compound-aggregate Induced Photocarrier Generation in Layered Organic Photoreceptors

概要

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The extrinsic photocarrier generation between an azo compound and a carrier transport molecule was investigated using aggregate and non-aggregate azo compounds in order to elucidate the high yield of photocarriers based on aggregation. The differences between the two systems were compared in terms of geminate-pair formation and dissociation efficiencies. The efficiencies of charge separation for generation of geminate pairs, which are independent of an electric field, do not vary significantly. Charge separation occurs via a fixed energy state which appears due to relaxation from a higher excited state of the photoexcited azo compound. This suggests that charge separation occurs between the two closest neighboring molecules. However, the efficiencies of geminate pair dissociation into free carriers are quite different; the electric field dependence of the photocarrier generation efficiency of the system containing a non-aggregated azo compound is much larger than that containing an aggregated one. According to the Onsager theory, the geminate hole-electron distance for dissociation is estimated to be 26 Å for the former system and 140 Å for the latter system. It is concluded that the primary geminate pair, the two closest neighboring molecules, relaxes to a looser condition in terms of distance based on the aggregation.
Publication Office, Japanese Journal of Applied Physics, Faculty of Science, University of Tokyoの論文
1997-06-15