title: A fused-ring acceptor unit in d-a copolymers benefits photovoltaic performance.
abstract: Pentacyclic lactam acceptor unit TPTI invented by our group is proved to be a good building block for efficient D-A copolymers used in organic solar cells. Here, two D-A copolymers PBTTPTI and PTTTPTI are developed by copolymerizing TPTI with 2,2'-bithiophene (BT) or thieno[3,2-b]thiophene (TT). PBTTPTI and PTTTPTI exhibit good solubility and strong interchain π-π interaction even in dilute solution. They possess deep HOMO levels (ca. -5.3 eV), partial crystallinity, and good hole mobilities. Blending with PC71 BM, PBTTPTI and PTTTPTI give decent power conversion efficiencies (PCE) up to 6.83% and 5.86%, with outstanding fill factors (FF) of 74.3% and 71.3%, respectively.
authors.affiliation: National Center for Nanoscience and Technology, Beijing, 100190, China.
authors.forename: Chuantian
authors.initials: C
authors.lastname: Zuo
authors.forename: Jiamin
authors.initials: J
authors.lastname: Cao
authors.forename: Liming
authors.initials: L
authors.lastname: Ding
mesh_terms: D037741:Fullerenes / Q000737:chemistry; D007769:Lactams / Q000737:chemistry; D018625:Microscopy, Atomic Force; D011108:Polymers / Q000737:chemistry*; D011789:Quantum Theory; D012993:Solar Energy; D012995:Solubility; D013876:Thiophenes / Q000737:chemistry
chemical_list: D037741:Fullerenes; D007769:Lactams; D011108:Polymers; D013876:Thiophenes