Charge transfer and recombination at conjugated polymer/semiconductor nanoparticle interfaces

摘要

We study the processes of charge transfer and recombination at the interface between semiconductor nanoparticles and conjugated polymers. These processes are crucial in determining the performance of photovoltaic devices based on these materials. Using femtosecond transient absorption we are able to follow the charge separation on picosecond timescales in blends of spherical CdSe nanocrystals with a poly(p-phenylenevinylene) derivative. Charge separation occurs on timescales of greater than 15 ps, indicating that it is limited by the diffusion of excitons to the nanoparticle interface. We also use time-resolved photoluminescence and quasi-steady-state photoinduced absorption measurements to study the vertical structure in films containing conjugated polymers and semiconductor tetrapods. Finally, we demonstrate that use of slow-evaporating solvents allows the formation of fibrilar structures in poly(3-hexylthiophene) films, and that this is correlated with improved performance in photovoltaic devices containing poly(3-hexylthiophene) and CdSe nanorods.