Enhancing efficiency and stability of organic solar cells through a simplified four-step synthesis of fully non-fused ring electron acceptor

Design and synthesis of superior cost-effective non-fullerene acceptors (NFAs) are still big challenges for facilitating the commercialization of organic solar cells (OSCs), yet to be realized. Herein, two medium bandgap fully non-fused ring electron acceptors (NFREAs, medium bandgap, i.e., 1.3–1.8 eV), namely PTR-2Cl and PTR-4Cl are synthesized with only four steps by using intramolecular noncovalent interaction central core, structured alkyl side chain orientation linking units and flanking with different electron-withdrawing end group. Among them, PTR-4Cl exhibits increased average electrostatic potential (ESP) difference with polymer donor, enhanced crystallinity and compact π-π stacking compared with the control molecule PTR-2Cl. As a result, the PTR-4Cl-based OSC achieved an impressive power conversion efficiency (PCE) of 14.72%, with a much higher open-circuit voltage (V_oc) of 0.953 V and significantly improved fill factor (FF) of 0.758, demonstrating one of the best acceptor material in the top-performing fully NFREA-based OSCs with both high PCE and V_oc. Notably, PTR-4Cl-based cells maintain a good T₈₀ lifetime of its initial PCE after over 936 h under a continuous thermal annealing treatment and over 1300 h T₈₀ lifetime without encapsulation. This work provides a cost-effective design strategy for NFREAs on obtaining high V_oc, efficient exciton dissociation, and ordered molecular packing and thus high-efficiency and stable OSCs.