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 C-60 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.