Fully Non‐Fused Organic Photovoltaic Systems Based on a Pyrazine‐Functionalized Polymer Donor

Comprehensive Summary

Solution‐processable organic photovoltaic (OPV) cells show promise for industrialization; however, high‐performance polymer donors often rely on costly fused‐ring structures. Here, we propose a novel polymer donor, 4T‐Pz, which is a low‐cost, fully non‐fused donor featuring a pyrazine‐based structure. Benefiting from the energy‐level modulation induced by pyrazine units and enhanced backbone planarity, 4T‐Pz exhibits a deep HOMO level (–5.38 eV), pronounced solution‐state pre‐aggregation, and favorable molecular packing behavior, thereby facilitating efficient charge generation and transport. When blended with two non‐fused acceptors, A4T‐16 and TBT‐26, to form fully non‐fused active layers, the optimized OPV cells deliver power conversion efficiencies of 14.2% and 12.7%, respectively. The 4T‐Pz:A4T‐16 system shows superior performance due to lower energy loss, weaker trap‐assisted recombination, a uniform fibrous film morphology, and compact face‐on π–π stacking, which favors charge transport. Cost analysis confirms competitiveness of 4T‐Pz, with materials‐only cost (MOC) of 11.63 USD·g ^–1 , far lower than that of fused‐ring analogs. This work demonstrates the promise of pyrazine‐based fully non‐fused polymer donor in balancing performance and cost, and provides a viable materials‐design route toward scalable, high‐efficiency OPVs.