Hot Charge Transfer States and Charge Generation in Donor Acceptor Blends

TL;DR

This paper presents a model explaining how vibrational modes influence charge transfer and generation in organic donor-acceptor blends, showing that excess driving force can enhance charge yield despite fast recombination.

Contribution

A new model incorporating vibrational relaxation effects explains the relation between exciton splitting driving force and charge yield in organic blends.

Findings

High charge yields are achievable with fast recombination rates.

Vibrational modes play a crucial role in charge transfer efficiency.

Excess driving force can improve charge generation despite rapid recombination.

Abstract

In an organic blend the vibrational normal mode excited by exciton splitting is the same as the one coupled to charge hopping. Excess driving force for exciton splitting can therefore aid charge transfer, if vibrational relaxation is slow compared to charge transfer. A model is developed that takes this into account and hence explains the experimentally observed relation of driving force for exciton splitting and charge yield and that high charge yields can be achieved with the observed fast rates of recombination.