Ester-Functionalized Poly(thiophene vinylene) with Controlled Molecular Weights for High-Performance Intrinsically-Stretchable Organic Solar Cells

Poly(thiophene vinylene)s (PTVs) are a promising type of polymer donors (PDs) for organic solar cells (OSCs) owing to their advantages of simple chemical structures and straightforward synthesis. However, the structural rigidity of PTVs results in the formation of thin films with inadequate mechanical properties for application in intrinsically stretchable (IS)-OSCs. In this work, we prepare a new ester-functionalized PTV with controlled molecular weights (MWs) (PETTCVT-X, X = L, M, and H) and demonstrate efficient and mechanically durable IS-OSCs. The crystallinity of the PTVs increases gradually with increasing MW, yielding enhanced hole mobility and suppressed charge recombination of the OSCs. Moreover, both the mechanical stretchability and electrical properties of the PTVs are improved notably with increasing MW. Consequently, rigid-OSCs featuring a PTV with the highest MW (PETTCVT-H) exhibit the highest PCE (15.3%) and crack-onset strain (COS, 8.3%) among the series, compared to lower values for the low- (PETTCVT-L, PCE = 9.7% and COS = 1.2%) and medium-MW counterparts (PETTCVT-M, PCE = 12.5% and COS = 4.3%)-based OSCs. Accordingly, the IS-OSCs utilizing PETTCVT-H present the highest initial PCE (10.1%) and stretchability (strain at PCE80% (retaining 80% of the initial PCE) = 16%). This work leverages the use of PTV for high-performance IS-OSCs.