Investigation of Ultrafast Electronic Transfer Process on Organic/Inorganic Heterojunction by Femtosecond Transient Absorption

We detect a relaxation process of excited SQ02 dye in the chlorobenzene solution and an-chor SQ02 on Al₂O₃ and TiO₂ lm, so as to investigate the photophysical properties of pristine SQ02 in the monodisperse system, aggregation state, and the corresponding inter-facial electron transfer process. The experimental data show that the lifetime of SQ02 in the monondisperse system is ~2.0 ns, but that of SQ02 anchored on the Al₂O₃ lm could obviously decrease to ~21 ps. The time of electron transfer from excited SQ02 to TiO₂ lm is estimated to be ~2.6 ps and the yield of electron injection is estimated to be ~89.1%, which matches the incident photon to current e ciency of dye-sensitized solar cell based on SQ02. In addition, some dyes are found to pack on the other dyes anchored on the nanocrystal lm, and their relaxation time could reach ~60 ps. They couldn't participate in the interfacial electron transfer, since they are far away from the TiO₂ interface.