Microstructure of evaporated organic photovoltaics with novel non-fullerene acceptors

Polymer-based organic photovoltaic (OPV) systems have increased their power conversion efficiency from 12% to 18% by replacing fullerene derivates with non-fullerene acceptors (NFAs), reducing voltage losses and allowing for greater absorption in these systems while retaining good charge transport. Similarly well-performing NFAs for evaporated small molecules, a technology that is commercially scalable, have been scarce, but we recently received our first such NFAs from collaborators. We seek to use Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) to study the crystalline make-up of the active blend as the substrate temperature during growth is varied, a key way of influencing the blend's microstructure. By coupling microstructural data with optical data and device performance, we will identify key structure-property relationships to better understand the interplay between these aspects of OPVs, improve the device performance, and guide the development of future OPV materials.