Synthesis, molecular and photovoltaic properties of donor-acceptor conjugated polymers incorporating a new heptacylic indacenodithieno[3,2-b] thiophene arene

Huan Hsuan Chang, Che En Tsai, Yu Ying Lai, De Yang Chiou, So Lin Hsu, Chain-Shu Hsu, Yen-Ju Cheng*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

60 Scopus citations

Abstract

We have developed a new multifused indacenodithieno[3,2-b]thiophene arene (IDTT) unit where the central phenylene is covalently fastened with the two outer thieno[3,2-b]thiophene (TT) rings, forming two cyclopentadiene rings embedded in a heptacyclic structure. This rigid and coplanar IDTT building block was copolymerized with electron-deficient acceptors, 4,7-dibromo-2,1,3- benzothiadiazole (BT), 4,7-dibromo-5,6-difluoro-2,1,3-benzothiadiazole (FBT) and 1,3-dibromo-thieno[3,4-c]pyrrole-4,6-dione (TPD) via Stille polymerization, respectively. Because the higher content of the thienothiophene moieties in the fully coplanar IDTT structure facilitates π-electron delocalization, these new polymers show much improved light-harvesting abilities and enhanced charge mobilities compared to PDITTBT copolymer using hexacyclic diindenothieno[3,2-b] thiophene (DITT) as the donor moieties. The device using PIDTTBT:PC 71BM (1:4, w/w) exhibited a decent power conversion efficiency (PCE) of 3.8%. Meanwhile, the solar cell using PIDTTFBT:PC71BM (1:4 in wt %) blend exhibited a greater Voc value of 0.9 V and a larger J sc of 10.08 mA/cm2, improving the PCE to 4.2%. The enhanced Voc is attributed to the lower-lying of HOMO energy level of PIDTTFBT as a result of fluorine withdrawing effect on the BT unit. A highest PCE of 4.3% was achieved for the device incorporating PIDTTTPD:PC71BM (1:4 in wt %) blend.

Original languageEnglish
Pages (from-to)9282-9291
Number of pages10
JournalMacromolecules
Volume45
Issue number23
DOIs
StatePublished - 11 Dec 2012

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