Electron-transfer process in layered photoreceptors containing azo compounds

Photoinduced electron transfer (ET) is the most essential process for carri er photogeneration in organic optoelectronic devices, In azo compound-based layered photoreceptors, carrier photogeneration is sensitized by hole tran sport material (HTM) incorporation. We investigated this process to elucida te the highly sensitizing mechanism. First, the photoinduced ET efficiency and overall quantum efficiency were measured and compared for the layered p hotoreceptor and the carrier generation layer. The result that the HTM enha nces the photoinduced ET implies that the HTM works catalytically to dimini sh the activation energy. Although such extrinsic ET takes place independen tly of an electric field, the subsequent geminate pair dissociation depends on the electric field. Next, the energy-gap dependence of the ET was inves tigated by employing more than 50 photoreceptors to vary the energy gap ove r a wide range. The measured efficiency was plotted against the energy gap, in which an inverted region was not observed.