Synthesis and characterization of novel low-bandgap triphenylamine-based conjugated polymers with main-chain donors and pendent acceptors for organic photovoltaics

摘要

A series of novel low-bandgap triphenylamine-based conjugated polymers (PCAZCN, PPTZCN, and PDTPCN) consisting of different electron-rich donor main chains (N-alkyl-2,7-carbazole, phenothiazine, and cyclopentadithinopyrol, respectively) as well as cyano- and dicyano-vinyl electron-acceptor pendants were synthesized and developed for polymer solar cell applications. The polymers covered broad absorption spectra of 400-800 nm with narrow optical bandgaps ranging 1.66-1.72 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels of the polymers measured by cyclic voltammetry were found in the range of -5.12 to -5.32 V and -3.45 to -3.55 eV, respectively. Under 100 mW/cm~2 of AM 1.5 white-light illumination, bulk heterojunction photovoltaic devices composing of an active layer of electron-donor polymers (PCAZCN, PPTZCN, and PDTPCN) blended with electron-acceptor [6,6]-phenyl-C_(61)-butyric acid methyl ester or [6,6]-phenyl-C_(71)-butyric acid methyl ester (PC_(71)BM) in different weight ratios were investigated. The photovoltaic device containing donor PCAZCN and acceptor PC_(71)BM in 1:2 weight ratio showed the highest power conversion efficiency of 1.28%, with V_(oc) = 0.81 V, J_(sc) = 4.93 mA/cm~2, and fill factor = 32.1%.