IMX Talks - Modelling Charge Transport at the Atomic Scale in Organic Semiconductors

Charge transport is ubiquitous in the operation of organic-based electronic devices such as solar cells or field-effect transistors. A central quantity that has to be maximized is the charge carrier mobility, currently much lower than in silicon-based devices. In this context, I will review some of our works illustrating that theory can prove very useful here by shedding light on the molecular parameters controlling the efficiency of charge transport, in particular the electronic couplings between adjacent molecules and the charge reorganization energy. Other key ingredients that will be discussed are the energetic disorder in the HOMO/LUMO levels and the spatial and time distribution in electronic couplings. Disorder plays indeed a major role and can be static in nature when resulting from structural defects or dynamics when induced by thermal fluctuations. We will illustrate that such thermal effects can be grasped from molecular dynamics simulations by extracting snapshots along the trajectory and by tracking the time evolution of relevant parameters. On the basis of these considerations, we will finally define some general guidelines to design organic semiconductors with high mobility values.