Molecular design strategy for realizing vectorial electron transfer in photoelectrodes

Abstract

Vectorial electron transfer is essential for developing ideal artificial photosystems. Conventional photosensitizers with only strong electronic coupling, as used in photovoltaics, cannot achieve vectorial electron transfer because of their rapid charge recombination. Herein, we present a design strategy for integrating strong (∼600 cm−1) and relatively weak (310 cm−1) electronic coupling in a single molecule to realize vectorial electron transfer in dye-sensitized solar cells. Four sensitizers with donor-acceptor-π-spacer and anchoring group configurations are developed, and the electronic coupling in these sensitizers is controlled by the π-spacers of varying steric hindrances. Transient-absorption spectroscopies reveal the occurrence of vectorial electron transfer in the designed sensitizer by suppressing charge recombination via weakened electronic coupling between the acceptor and π-spacer and the efficient charge injection via strong electronic coupling between the donor and acceptor. The optimization of electronic coupling in the sensitizers improves the photovoltaic performances, achieving a power-conversion efficiency of 10.8%.