New low bandgap conjugated polymer derived from 2, 7-carbazole and 5, 6-bis(octyloxy)-4, 7-di(thiophen-2-yl) benzothiadiazole: Synthesis and photovoltaic properties

Ping Ding, Cheng Che Chu, Yingping Zou*, Dequan Xiao, Chunyue Pan, Chain-Shu Hsu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

To develop conjugated polymers with low bandgap, deep HOMO level, and good solubility, a new conjugated alternating copolymer PC-DODTBT based on N-9′-heptadecanyl-2,7-carbazole and 5, 6-bis(octyloxy)-4,7-di(thiophen-2- yl)benzothiadiazole was synthesized by Suzuki cross-coupling polymerization reaction. The polymer reveals excellent solubility and thermal stability with the decomposition temperature (5% weight loss) of 327°C. The HOMO level of PC-DODTBT is -5.11 eV, indicating that the polymer has relatively deep HOMO level. The hole mobility of PC-DODTBT as deduced from SCLC method was found to be 2.03 × 10-4 cm2/Versus Polymer solar cells (PSCs) based on the blends of PC-DODTBT and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) with a weight ratio of 1:2.5 were fabricated. Under AM 1.5 (AM, air mass), 100 mW/cm-2 illumination, the devices were found to exhibit an open-circuit voltage (Voc) of 0.73 V, short-circuit current density (Jsc) of 5.63 mA/cm-2, and a power conversion efficiency (PCE) of 1.44%. This photovoltaic performance indicates that the copolymer is promising for polymer solar cells applications.

Original languageEnglish
Pages (from-to)99-107
Number of pages9
JournalJournal of Applied Polymer Science
Volume123
Issue number1
DOIs
StatePublished - 5 Jan 2012

Keywords

  • benzothiadiazole
  • low bandgap
  • poly(2,7-carbazole)
  • polymer solar cells

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