Charge Transfer States at Organic Heterojunctions

We will resolve key questions involving ground state integer charge transfer (ICT) and photo-induced charge transfer states (CTS) at organic donor:acceptor (D:A) heterojunctions common in organic electronics, in particular organic photovoltaic (OPV) cells.

Our goals are: (i)  Determine the orientation dependence of energy level alignment (ELA) at non-fullerene acceptor:donor polymer interfaces, (ii) Reveal the origin of CTS dissociation in absence of driving force at D:A heterojunctions, (iii) Obtain a precise description on how degree and vertical extension of intermixing at D:A heterojunctions affect ELA and CTS dissociation, (iv) Explore the optimal vertical D:A concentration gradient for so-called p-i-n OPV structures and (v) Probe the effect of spatial separation and permittivity on ground state ICT and ambipolar charge transport for D:A interfaces.

To achieve these goals, we will utilize Langmuir-Blodgett and Langmuir-Schaefer deposition techniques to fabricate well-defined polymer and large molecule organic semiconductor films with monolayer-by-monolayer control of material composition (both vertical and in-layer) and molecular orientation (face-on / edge-on).

Such precise control is unattainable by other deposition methods of solution-processed materials, so our project will set a new standard for the field. The work will be carried out over 4-years by a PhD student and assisted by senior researchers, internal and external.