Understanding the Role of Solvent Additives in Organic Photovoltaic Blends

At Sheffield, organic solar cells (OSCs) have been made using a new class of materials called non-fullerene acceptors (NFAs) producing high efficiency devices (9-11%) in polymer blends. For OSCs containing ITIC, a NFA, the inclusion of solvent additives (e.g. 1,8-diioodocatane (DIO)) in the blend solution increases efficiency at a detriment to stability. This is not observed in OSCs containing PCBM, a more traditional material. SANS measurements at ISIS will allow us to probe the morphological stability of blend films by characterising the phase separation length scale between blend components. We also plan to do NR at D17, ILL on similar samples to study the vertical composition profiles of the blend films. SANS and NR will link the bulk morphology of the blends to device performance, helping us achieve high efficiency OSCs with real-world stability.