Directly Cross‐Linked Conjugated Polymer Donor Enables Efficient Polymer Solar Cells with Extraordinary Mechanical Robustness

Abstract

AbstractA cross‐linking strategy can result in a three‐dimensional network of interconnected chains for the copolymers, thereby improving their mechanical performance. In this work, a series of cross‐linked conjugated copolymers, named PC2, PC5, and PC8, constructed with different ratios of monomers are designed and synthesized. For comparison, a random linear copolymer, PR2 is also synthesized based on the similar monomers. When blended with Y6 acceptor, the cross‐linked polymers PC2, PC5, and PC8‐based polymer solar cells (PSCs) achieve superior power conversion efficiencies (PCEs) of 17.58%, 17.02%, and 16.12%, respectively, which are higher than that (15.84%) of the random copolymer PR2‐based devices. Moreover, the PCE of PC2:Y6‐based flexible PSC retains ≈88% of the initial efficiency value after 2000 bending cycles, overwhelming the PR2:Y6‐based device with the remaining 12.8% of the initial PCE. These results demonstrate that the cross‐linking strategy is a feasible and facile approach to developing high‐performance polymer donors for the fabrication of flexible PSCs.