High-mobility low-bandgap conjugated copolymers based on indacenodithiophene and thiadiazolo[3,4-c]pyridine units for thin film transistor and photovoltaic applications

Ying Sun, Shang Chieh Chien, Hin Lap Yip, Yong Zhang, Kung Shih Chen, David F. Zeigler, Fang-Chung Chen, Baoping Lin*, Alex K.Y. Jen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

90 Scopus citations

Abstract

Two new semiconducting polymers based on indacenodithiophene and thiadiazolo[3,4-c]pyridine units were synthesized via Stille coupling polymerization. The polymers, PIDTPyT and PIDTDTPyT, exhibited main absorption bands in the range of 550-800 nm while their absorption maxima were located at around 700 nm in films. With two additional thiophene spacers, PIDTDTPyT showed a broader absorption band but a 20 nm blue-shifted maximum peak compared to that of PIDTPyT. Both of the polymers possess low bandgaps (∼1.6 eV) and deep energy levels for both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). Organic field-effect transistors (OFETs) device measurements indicate that PIDTPyT and PIDTDTPyT have high hole carrier mobilities of 0.066 and 0.045 cm2 V-1 s -1, respectively, with the on/off ratio on the order of 10 6. Bulk heterojunction photovoltaic devices consisting of the copolymers and PC71BM gave power conversion efficiencies (PCE) as high as 3.91% with broadband photo-response in the range of 300-800 nm. The relationships between the photovoltaic performance and film morphology, energy levels, hole mobilities are discussed.

Original languageEnglish
Pages (from-to)13247-13255
Number of pages9
JournalJournal of Materials Chemistry
Volume21
Issue number35
DOIs
StatePublished - 21 Sep 2011

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