Synthesis and characterization of pyrido[3,4-b]pyrazine-based low-bandgap copolymers for bulk heterojunction solar cells

Mao Chuan Yuan, Mao Yuan Chiu, Chien Ming Chiang, Kung-Hwa Wei*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

82 Scopus citations

Abstract

We have used Stille polycondensation to prepare a series of low-bandgap copolymers, P1-P4, by conjugating the electron-accepting pyrido[3,4-b]pyrazine (PP) moieties with the electron-rich benzo[1,2-b:3,4-b′]dithiophene (BDT) or cyclopentadithiophene (CPDT) units. P1 and P3 are based on PP and BDT units while P2 and P4 are based on PP and CPDT units. All of these polymers exhibited excellent thermal stability and sufficient energy offsets for efficient charge transfer and dissociation, as determined through thermogravimetric analyses and cyclic voltammetry, respectively. The bandgaps of the polymers could be tuned in the range 1.46-1.60 eV by using the two different donors, which have different electron-donating abilities. The three-component copolymers, P3 and P4, incorporating the thiophene and bithiophene segments, respectively, absorbed broadly, covering the solar spectrum from 350 to 800 nm. The morphologies of the blends of P3 and P4 with [6,6]-phenyl-C70-butyric acid methyl ester (PC70BM) were more homogeneous than those of P1 and P2; in addition, devices incorporating the P3 and P4 blends exhibited superior performance. The best device performance resulted from an active layer containing the P4:PC 70BM blend; the short-circuit current was 10.85 mA cm-2 and the power conversion efficiency was 3.15%.

Original languageEnglish
Pages (from-to)6270-6277
Number of pages8
JournalMacromolecules
Volume43
Issue number15
DOIs
StatePublished - 10 Aug 2010

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