Toward High Efficiency Polymer Solar Cells: Rearranging the Backbone Units into a Readily Accessible Random Tetrapolymer

摘要

Two donor-acceptor (D-A) conjugated polymers composed of the same ratio of 5-fluorobenzothiadiazole and thiophene subunits are synthesized through different routes, providing a precisely regioregular (2TRR) and a random (2TRA) polymer structures. Detailed structural analyses indicate that the backbone of regioregular 2TRR has only one donor segment of bithiophene, while the backbone of random 2TRA consists of three different donor segments: thiophene, bithiophene, and terthiophene (in a ratio of 0.16:0.68:0.16). Synergetic contributions from these segments allow the "tetrapolymer" 2TRA to achieve more favorable film morphology and a higher hole-mobility relative to 2TRR. Consequently, the random polymer 2TRA achieves a substantially higher power conversion efficiency (8.8%) than the regioregular polymer 2TRR (5.1%). Notably, the "tetrapolymer" 2TRA is readily synthesized from two monomers, rather than through complex conventional preparation required for similar multipolymers. These findings provide a novel route toward the design and synthesis of multipolymeric materials and demonstrate their potential advantages in high-performance organic electronic applications.