A theoretical insight into multiple charge-transfer mechanisms at the P3HT/non-fullerenes interface in organic solar cells

Poly(3-hexylthiophene) (P3HT)-based organic solar cells (OSCs) have been developed in recent years because of easy-production, low-cost and large-area manufacture. However, fewer non-fullerene acceptors with higher power conversion efficiency (PCE) than PC61BM have been explored in P3HT-based OSCs. In this contribution, the excited states were in-depth analyzed towards probing the particularities of superior P3HT/non-fullerene systems. Multiple charge-transfer (CT) mechanisms involving intermolecular electric field (IEF), hot CT states and direct excitation of CT states were found, which suggests more favorable CT pathways exist in these P3HT/non-fullerene interfaces. Accordingly, the calculations on charge-transfer rates of all the investigated donor/acceptor interfaces further verified the positive effect of multiple CT pathways. In addition, the interesting hybrid Frenkel-CT states were firstly found to be relevant with the stronger electrostatic surface potential (ESP) differences on donor and accepto...