Electron transfer and geminate pair dissociation processes in layered photoreceptors containing azo compounds

Minoru Umeda

doi:10.1117/12.328162

23 October 1998 Electron transfer and geminate pair dissociation processes in layered photoreceptors containing azo compounds

Minoru Umeda

Author Affiliations +

Proceedings Volume 3471, Xerographic Photoreceptors and Organic Photorefractive Materials IV; (1998) https://doi.org/10.1117/12.328162
Event: SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, 1998, San Diego, CA, United States

Abstract

Photoinduced electron transfer (ET) and geminate hole- electron pair dissociation are the most essential processes for carrier photogeneration in organic materials In azo- compound-based layered photoreceptors, carrier photogeneration is sensitized by hole transport material (HTM) incorporation. We have investigated these two processes to elucidate the highly sensitizing mechanism. First, the photoinduced ET efficiency and overall quantum efficiency were measured and compared for the layered photoreceptor and carrier generation layer. The result that the HTM enhances the photoinduced ET implies that the HTM works, catalytically to diminish the activation energy. Although such extrinsic ET takes place independently of an electric field, the subsequent geminate pair dissociation depends on an electric field. Next, the energy gap dependence of the ET was investigated employing more than 50 photoreceptors to vary the energy gap over a wide range. The efficiency measured was plotted against the energy gap, in which the inverted region was not observed. This result was explained by the small change in ET activation energy even when the energy gap is large, which is a feature of charge separation. The Marcus inverted region reported for titanyl- phthalocyanine-based photoreceptors was compared with the azo-based system. Finally, the dissociation process of geminate pairs on azo and HTM was investigated and compared employing five azo compounds. The result that the dissociation efficiency strongly depends on the azo compound revealed that the reaction consists of azo + azo yields azo + azo. The dissociation efficiency exhibited da strong relationship with the polarizability of photoexcited azo compound. It is concluded that the strong polarizability azo compound enhances geminate pair dissociation.

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Minoru Umeda "Electron transfer and geminate pair dissociation processes in layered photoreceptors containing azo compounds", Proc. SPIE 3471, Xerographic Photoreceptors and Organic Photorefractive Materials IV, (23 October 1998); https://doi.org/10.1117/12.328162

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