Polymer Acceptor with Hydrogen-Bonding Functionality for Efficient and Mechanically Robust Ternary Organic Solar Cells

Organic solar cells (OSCs) with a high power conversion efficiency (PCE) and excellent stretchability are required for applications in wearable devices. However, the use of rigid and highly crystalline small-molecule acceptors (SMAs) limits the mechanical robustness of OSCs. To overcome this limitation, a stretchable and conjugated polymer acceptor (PA, N2200-ThyDap) was synthesized and introduced as the third component to the benchmark polymer donor (PD):SMA system PM6:Y6-BO. N2200-ThyDap was designed to incorporate hydrogen bonding into the N2200 PA backbone using thymine (Thy) and diaminopyrazine (Dap) units, and the neat film shows excellent stretchability (crack onset strain (COS) = 28.2%) compared to the PA of similar molecular weight without hydrogen bonding (N2200, COS = 1.5%). The N2200-ThyDap-incorporated ternary system (PM6:Y6-BO:N2200-ThyDap) exhibits a higher PCE (16.4%) than the reference binary (PM6:Y6-BO, PCE = 15.4%) and N2200-incorporated control ternary system (PCE = 14.7%). The PM6:Y6-BO:N2200-ThyDap ternary blend film achieves a higher stretchability (COS = 4.8%) than the PM6:Y6-BO binary (COS = 2.1%) and PM6:Y6-BO:N2200 ternary (COS = 2.4%) films. It is likely that a stronger intermolecular interaction enabled by N2200-ThyDap leads to higher photovoltaic performance and improved stretchability.