From Monomer Sequence to Charge Mobility in Semiconductor Polymers via Model Reduction

A model reduction scheme for polymer semiconductors is presented that can be utilized to compute intra-chain charge-carrier mobility from the monomer sequence. The reduced model can be used in conjunction with any quantum dynamics approach, but it is explored here assuming that transport takes place through incoherent hopping events between states of different degrees of delocalization. The procedure is illustrated by considering 28 realistic polymers for which a quantitative correlation is established between charge localization characteristics and charge mobility. The data set helps in establishing plausible ranges for all the microscopic parameters of the model and it can therefore be used to determine the maximum plausible improvement in mobility. The reduced model is also used to provide some insight on the observation that the highest mobility polymers do not have very broad valence bands: there is indeed a range of the inter-monomer coupling for which this parameter has little effect on the mobility.