Beschreibung:
Stretchable organic solar cells are promising wearable power generators. Here, we synthesize a series of bithienyl-benzodithiophene- alt -fluorobenzotriazole copolymer (PBZ-2Si) with siloxane-terminated side chains, and compare with J52 analogues to investigate side chain effects on the photovoltaic and mechanical properties. When different molecular weight ( M n ) of PBZ-2Si, denoted as PBZ-2Si L , PBZ-2Si M and PBZ-2Si H , blended with the N2200 acceptor, the PBZ-2Si M based all-polymer solar cell (all-PSC) shows an improved PCE of 7.01% as compared to that of J52 (5.30%). The improved PCE of PBZ-2Si M is attributed to the enhanced molecule aggregation, balanced charge transport and optimal film morphology induced by siloxane side chains. Notably, the PBZ-2Si M :N2200 blend film shows a significantly improved stretchability of 38.4% compared to 19.5% of J52 reference, because the plasticizing effect that extended soft siloxane side chains enlarge interchain distance of polymer backbones and increase the chain rotational free volume. Further increasing M n enhances polymer chain entanglements and boosts the stretchability up to 50.7%, known as the highest stretchability reported to date. Moreover, the PBZ-2Si M -based stretchable OSC showed a high PCE of 6.0% and maintained over 80% of its initial PCE at 50% enormous strain, outperforming the J52 reference. Therefore, our work provides practical guidelines for developing highly efficient and stretchable all-PSC