Boosting the efficiency and stability of polymer solar cells using poly(3-hexylthiophene)-based all-conjugated diblock copolymers containing pentafluorophenyl groups

Herein, we have developed a new poly(3-hexylthiophene) (P3HT)-based diblock copolymeric additive bearing pentafluorophenyl side groups, poly(3-hexylthiophene)-b-poly(3-(6-pentafluorophenyl-hexyloxy)thiophene) (P3HT-b-P3FPHT), to boost the efficiency and stability of P3HT:PC₆₁BM bulk-heterojunction polymer solar cells. By doping a certain amount of P3HT-b-P3FPHT, a better miscibility of P3HT with PC₆₁BM can be acquired, forming a nanoscale bicontinuous interpenetrating network for efficient exciton dissociation. Meanwhile, the crystalline and ordered packing of P3HT chains can also be enhanced by doping P3HT-b-P3FPHT, which is benefit for efficient charge carrier transport. On this basis, the power conversion efficiency (PCE) of P3HT:PC₆₁BM-based solar cells is improved mainly due to the increase of short circuit current density (J_sc) and fill factor (FF). More interestingly, induced by the supramolecular interaction between the pentafluorophenyl groups of P3FPHT blocks and the C₆₀ cores of PC₆₁BM, the severe aggregations of PC₆₁BM molecules in the prolonged thermal annealing can be effectively suppressed, leading to the significantly improved thermal stability of the morphology and photovoltaic performance. These findings indicate that utilization of P3HT-based diblock copolymeric additives bearing pentafluorophenyl side groups is an effective and practical strategy to improve the performance and thermal stability of P3HT:PC₆₁BM polymer solar cells.