title: Impact of constitution of the terthiophene-vinylene conjugated side chain on the optical and photovoltaic properties of two-dimensional polythiophenes.
abstract: The effects of the spatial arrangement of the conjugated side chains of two-dimensional polymers on their optical, electrochemical, molecular-packing, and photovoltaic characteristics were investigated. Accordingly, novel polythiophenes with horizontally (PBTTTV-h) and vertically (PBTTTV-v) grafted terthiophene–vinylene (TTV) conjugated side chains were synthesized that display two and one UV-vis peaks, respectively; the difference is due to the different constitutions of the conjugated side-chains. Because the spatial arrangement affects the molecular self-assembly, PBTTTV-h shows stronger crystallinity than PBTTTV-v, which enhances the charge mobility in devices. Moreover, PBTTTV-h has a lower HOMO energy level (−5.49 eV) than PBTTTV-v (−5.40 eV). Bulk heterojunction solar cells fabricated from PBTTTV-h/PC71BM and PBTTTV-v/PC71BM exhibit power conversion efficiencies of 4.75% and 4.00%, respectively, and Voc values of 800 and 730 mV, respectively, under AM1.5G illumination (100 mW cm(−2)). Thus, the architecture of the TTV conjugated side chains affects the optical, electrochemical, and photovoltaic properties; this study provides more ideas for improving 2-D conjugated polymers for semiconductor devices.
authors.affiliation: Institute of Polymer Science and Engineering, National Taiwan University, 10617 Taipei, Taiwan. ycchiu@ntu.edu.tw chingih@ntu.edu.tw leewang@ntu.edu.tw.
authors.forename: Chuen-Yo
authors.initials: CY
authors.lastname: Hsiow
authors.forename: Rathinam
authors.initials: R
authors.lastname: Raja
authors.forename: Chun-Yao
authors.initials: CY
authors.lastname: Wang
authors.forename: Yu-Hsiang
authors.initials: YH
authors.lastname: Lin
authors.forename: Yu-Wen
authors.initials: YW
authors.lastname: Yang
authors.forename: Yen-Ju
authors.initials: YJ
authors.lastname: Hsieh
authors.forename: Syang-Peng
authors.initials: SP
authors.lastname: Rwei
authors.forename: Wen-Yen
authors.initials: WY
authors.lastname: Chiu
authors.forename: Ching-I
authors.initials: CI
authors.lastname: Huang
authors.forename: Leeyih
authors.initials: L
authors.lastname: Wang