Electron Transfer Kinetics of a Series of Bilayer Triphenylamine–Oligothiophene–Perylenemonoimide Sensitizers for Dye-Sensitized NiO

5 years ago

Electron Transfer Kinetics of a Series of Bilayer Triphenylamine–Oligothiophene–Perylenemonoimide Sensitizers for Dye-Sensitized NiO

Mingfu He, Shane M. Polen, Yiying Wu, Christopher M. Hadad, Kevin A. Click, Yongze Yu

A series of triphenylamine (TPA)–oligothiophene–perylenemonoimide (PMI) molecules, denoted as the BH dyes, which mimic membrane lipid bilayers to enable stable operation of dye-sensitized NiO photocathodes under extremely acidic (pH = 0) conditions, have been recently reported for solar hydrogen production. In this work, we systematically study the photophysical properties of the BH series molecules with various lengths of π-linkers in solution via density functional theory (DFT) calculations and time-resolved spectroscopic techniques. When dissolved in DMF, the molecules undergo ultrafast intramolecular charge transfer within 1 ps upon photoexciation. The charge-separated state then recombines within tens of picoseconds. The electron transfer kinetics of dye-sensitized mesoporous NiO photocathodes exhibit both fast and slow charge recombination processes (70 ps and 4.5 μs, respectively, for BH4). The effect of various lengths of π-linkers is modeled with a spatial attenuation factor of 0.20 Å^–1 with a longer spatial separation of charge recombination centers, giving rise to a slower recombination rate between the reduced dye species and NiO surface.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b07859

DOI: 10.1021/acs.jpcc.7b07859