Alternating and diblock donor-acceptor conjugated polymers based on diindeno[1,2-b:2′,1′-d]thiophene structure: Synthesis, characterization, and photovoltaic applications

Chiu Hsiang Chen, Yen-Ju Cheng*, Martin Dubosc, Chao Hsiang Hsieh, Cheng Che Chu, Chain-Shu Hsu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Pentacyclic diindeno[1,2-b:2′,1′-d]thiophene (DIDT) unit is a rigid and coplanar conjugated molecule. To the best of our knowledge, this attractive molecule has never been incorporated into a polymer and thus its application in polymer solar cells has never been explored. For the first time, we report the detailed synthesis of the tetra-alkylated DIDT molecule leading to its dibromo- and diboronic ester derivatives, which are the key monomers for preparation of DIDT-based polymers. Two donor-acceptor alternating polymers, poly(diindenothiophene-alt-benzothiadiazole) PDIDTBT and poly(diindenothiophene- alt-dithienylbenzothiadiazole) PDIDTDTBT, were synthesized by using Suzuki polymerization. Copolymer PTDIDTTBT was also prepared by using Stille polymerization. Although PTDIDTTBT is prepared through a manner of random polymerization, we found that the different reactivities of the dibromo-monomers lead to the resulting polymer having a block copolymer arrangement. With the higher structural regularity, PTDIDTTBT, symbolized as (thiophene-alt-DIDT) 0.5-block-(thiophene-alt-BT)0.5, shows the higher degree of crystallization, stronger π-π stacking, and broader absorption spectrum in the solid state, as compared to its alternating PDIDTDTBT analogue. Bulk heterojunction photovoltaic cells based on ITO/PEDOT:PSS/polymer:PC 71BM/Ca/Al configuration were fabricated and characterized. PDIDTDTBT/PC71BM and PTDIDTTBT/PC71BM systems exhibited promising power-conversion efficiencies (PCEs) of 1.65 % and 2.00 %, respectively. Owing to the complementary absorption spectra, as well as the compatible structures of PDIDTDTBT and PTDIDTTBT, the PCE of the device based on the ternary blend PDIDTDTBT/PTDIDTTBT/PC71BM was further improved to 2.40 %.

Original languageEnglish
Pages (from-to)2483-2492
Number of pages10
JournalChemistry - An Asian Journal
Volume5
Issue number12
DOIs
StatePublished - 3 Dec 2010

Keywords

  • copolymerization
  • donor-acceptor systems
  • photovoltaics
  • polymers
  • solar cells

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