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In this report, we investigate the effects of a strong electron-donating group on the electron injection and recombination processes of diketopyrrolopyrrole (DPP)-sensitized TiO2 films by comparing the dynamics of triphenylamine donor-installed DPP_A and donor-absent DPP_R dyes. We show that the electron-donating group enhances the intramolecular charge transfer (ICT) characteristics of DPP_A, as demonstrated by a significant spectral redshift in the steady-state measurement of DPP_A compared to that of DPP_R. By comparing the ultrafast transient behaviors of the dye-coated films through femtosecond transient absorption (fs-TA) measurements, we provide insight into the high efficiency of DPP_A: most of the electrons from DPP_A are injected into the conduction band of TiO2 within the time resolution of TA (
Michael Graetzel, Shaik Mohammed Zakeeruddin, Felix Thomas Eickemeyer
Michael Graetzel, Jacques-Edouard Moser, Etienne Christophe Socie, George Cameron Fish, Aaron Tomas Terpstra