Ultrafast study of charge generation and device performance of a silole-doped fluorene-mixed layer for blue-sensitive organic photoconductive devices



Because color-selective organic photoconductive devices are required for image-sensing applications, high external quantum efficiency (EQE) is necessary. In our previous work, silole derivatives have been used to improve the device performance. In this study, we investigate the carrier kinetics of silole-derivative-doped organic photoconductive devices with a fluorene polymer used as an active layer by measuring the transient absorption spectrum. Transient absorption characteristics show that the silole-induced absorption change corresponds to a negative polaron of the excited fluorene polymer being formed via hole transfer from the silole derivative, and efficient hole transfer is realized by doping with the silole derivative. In addition, peak device performance was also achieved when the doping concentration of the silole derivatives are around 50 wt%. This result can be explained by the high dislocation density of electron–hole pair in individually migration electrons and holes owing to the silole doping in the fluorene polymer.