Dithienocarbazole-based ladder-type heptacyclic arenes with silicon, carbon, and nitrogen bridges: Synthesis, molecular properties, field-effect transistors, and photovoltaic applications

Jhong Sian Wu, Yen Ju Cheng, Tai Yen Lin, Chih Yu Chang, Peng I. Shih, Chain Shu Hsu

Research output: Contribution to journalArticlepeer-review

84 Citations (Scopus)

Abstract

A new class of ladder-type dithienosilolo-carbazole (DTSC), dithienopyrrolo-carbazole (DTPC), and dithienocyclopenta-carbazole (DTCC) units is developed in which two outer thiophene subunits are covalently fastened to the central 2,7-carbazole cores by silicon, nitrogen, and carbon bridges, respectively. The heptacyclic multifused monomers are polymerized with the benzothiadiazole (BT) acceptor by palladium-catalyzed cross-coupling to afford three alternating donor-acceptor copolymers poly(dithienosilolo-carbazole-alt- benzothiadiazole) (PDTSCBT), poly(dithienocyclopenta-carbazole-alt- benzothiadiazole) (PDTCCBT), and poly(dithienopyrrolo-carbazole-alt- benzothiadiazole) (PDTPCBT). The silole units in DTSC possess electron-accepting ability that lowers the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of PDTSCBT, whereas stronger electron-donating ability of the pyrrole moiety in DTPC increases the HOMO and LUMO energy levels of PDTPCBT. The optical bandgaps (E g opt) deduced from the absorption edges of thin film spectra are in the following order: PDTSCBT (1.83 eV) > PDTCCBT (1.64 eV) > PDTPCBT (1.50 eV). This result indicated that the donor strength of the heptacyclic arenes is in the order: DTPC > DTCC > DTSC. The devices based on PDTSCBT and PDTCCBT exhibited high hole mobilities of 0.073 and 0.110 cm 2 V -1 s -1, respectively, which are among the highest performance from the OFET devices based on the amorphous donor-acceptor copolymers. The bulk heterojunction photovoltaic device using PDTSCBT as the p-type material delivered a promising efficiency of 5.2% with an enhanced open circuit voltage, V oc, of 0.82 V.

Original languageEnglish
Pages (from-to)1711-1722
Number of pages12
JournalAdvanced Functional Materials
Volume22
Issue number8
DOIs
Publication statusPublished - Apr 24 2012
Externally publishedYes

Keywords

  • field-effect transistors
  • ladder-type structures
  • polymer solar cells

ASJC Scopus subject areas

  • Biomaterials
  • Electrochemistry
  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

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