Accelerating ultrafast processes in hydrogen-bonded complexes under pressure

Abstract

Acceleration of ultrafast processes is vital in hydrogen-bonded coumarin–methanol complexes for improving the photoelectric conversion efficiency of dye-sensitized solar cells (DSSCs). The traditional methods expedite ultrafast processes individually related to electron injection in DSSCs, namely, internal conversion (IC) or intermolecular charge transfer (inter-CT), by adjusting molecular topologies. We introduce pressure as an external drive to realize the acceleration of both processes simultaneously without changing the configuration. In the definite hydrogen-bonded complexes, the acceleration of IC and inter-CT processes is visualized by in situ high-pressure femtosecond transient absorption spectroscopy. In liquid-phase methanol, the IC and inter-CT processes are actuated effectively from 150.20 to 59.21 fs and 93.95 to 29.05 ps, respectively. The quickening of both processes is attributed to the enhancement of intermolecular hydrogen bonds under pressure. After the pressure-induced methanol phase transition, the rates of IC and inter-CT processes at 3.67 GPa are increased by 36.42% and 80.55% compared to at 1.00 atm. Our study results open an enlightening avenue for boosting the photoelectric conversion efficiency of DSSCs.