title: Donor-acceptor-type copolymers based on a naphtho[1,2-c:5,6-c]bis(1,2,5-thiadiazole) scaffold for high-efficiency polymer solar cells.
abstract: Four donor-acceptor-type low-bandgap conjugated polymers based on a naphtho[1,2-c:5,6-c]bis(1,2,5-thiadiazole) (NT) acceptor and different donors bridged by a bithiophene spacer have been synthesized through Suzuki or Stille polymerization reactions. Fluorene (F), carbazole (Cz), alkylidene fluorene (AF), and benzodithiophene (BDT) were selected as the donor units to produce a series of new conjugated polymers. Owing to the different electron-donating ability of the donor units, the energy levels, absorption spectra, bandgaps, and carrier mobilities of the resulting polymers were systematically tuned. Bulk-heterojunction-type polymer solar cells based on the new polymers and [6,6]-phenyl-C61 -butyric acid methyl ester (PC61 BM) or [6,6]-phenyl-C71 -butyric acid methyl ester (PC71 BM) were investigated and all of the devices exhibited good photovoltaic performance, with power-conversion efficiencies (PCEs) over 3 %. The best device performance was achieved by PF-C12NT, with an open-circuit voltage (Voc ) of 0.87 V, a short-circuit current density (Jsc ) of 12.19 mA cm(-2) , a fill factor (FF) of 61.36 %, and a PCE of 6.51 % under simulated sunlight (100 mW cm(-2) , AM 1.5G).
authors.affiliation: Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640 (P. R. China).
authors.forename: Li-Qian
authors.initials: LQ
authors.lastname: Liu
authors.forename: Gui-Chuan
authors.initials: GC
authors.lastname: Zhang
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Sheng
authors.initials: S
authors.lastname: Dong
authors.forename: Ming
authors.initials: M
authors.lastname: Wang
authors.forename: Yu-Guang
authors.initials: YG
authors.lastname: Ma
authors.forename: Hin-Lap
authors.initials: HL
authors.lastname: Yip
authors.forename: Fei
authors.initials: F
authors.lastname: Huang
keywords: donor-acceptor systems; molecular electronics; polymers; semiconductors; solar cells