title: Naphthalenediimide-alt-Fused Thiophene D-A Copolymers for the Application as Acceptor in All-Polymer Solar Cells.
abstract: Three n-type alternating D-A copolymers based on a naphthalenediimide (NDI) acceptor (A) unit and three different donor (D) units with varied electron-donating strength including thiophene (P(NDI-T)), thieno[3,2-b]thiophene (P(NDI-TT)), and thieno[3,2-b;4,5-b]dithiophene (P(NDI-TDT)), were synthesized, for the application as acceptor materials in all-polymer solar cells (all-PSCs). The effect of the donor units of thiophene, thienothiophene (TT) and thienodithiophene (TDT) on the physicochemical and photovoltaic properties of the n-type D-A copolymers was systematically investigated. It was found that the absorption spectrum is red-shifted and the energy band gap (Eg) is reduced for the NDI-based D-A copolymers with increasing number of thiophene rings in the thiophene or fused thiophene donor units. All-PSCs were fabricated with the medium band gap conjugated polymer J51 (Egof ca 1.9 eV) as polymer donor and the n-type D-A copolymers as acceptor. The power conversion efficiency reached 2.59 %, 3.70 % and 5.10 % for the all-PSCs with P(NDI-T), P(NDI-TT), and P(NDI-TDT) as acceptor, respectively. The results indicate that a larger conjugated fused molecular plane with more thiophene rings as donor units in the NDI-based D-A copolymers is beneficial to reduce the band gap, broaden the absorption and enhance the photovoltaic performance of n-type D-A copolymer acceptors.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.|School of Chemical & Biological Engineering, Department of Chemistry&Chemical Engineering, University of Science&Technology Beijing, Beijing, 100083, China.
authors.forename: Lingwei
authors.initials: L
authors.lastname: Xue
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Yankang
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China. zgzhangwhu@iccas.ac.cn.
authors.forename: Zhi-Guo
authors.initials: ZG
authors.lastname: Zhang
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Gao
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Haijun
authors.initials: H
authors.lastname: Bin
authors.affiliation: School of Chemical & Biological Engineering, Department of Chemistry&Chemical Engineering, University of Science&Technology Beijing, Beijing, 100083, China. yxyang@ustb.edu.cn.
authors.forename: YunXu
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China. liyf@iccas.ac.cn.|University of Chinese Academy of Sciences, Beijing, 100049, China. liyf@iccas.ac.cn.
authors.forename: Yongfang
authors.initials: Y
authors.lastname: Li
keywords: all-polymer solar cells; donor-acceptor systems; fused thiophene; n-type conjugated polymers; naphthalenediimide-based D-A copolymers