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Syntheses of Biaxially Extended Octithiophene‐Based Conjugated Copolymers for High‐Open‐Circuit‐Voltage Photovoltaic‐Cell Applications
Author(s) -
Wu HungChin,
Lai YiCang,
Chiu YuCheng,
Lee WenYa,
Chen WenChang
Publication year - 2014
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201300765
Subject(s) - moiety , conjugated system , thiophene , polymer , materials science , stille reaction , open circuit voltage , copolymer , polymer chemistry , homo/lumo , polymer solar cell , coupling reaction , photochemistry , chemistry , organic chemistry , molecule , voltage , catalysis , physics , quantum mechanics , composite material
Novel biaxially extended octithiophene (8T)‐based conjugated polymers are successfully synthesized using Stille coupling reactions of the branched octithiophene moiety with selenophene (P8TSe), thiophene (P8TT), and thieno[3,2‐b]thiophene (P8TTT). The 8T moiety can significantly lower the highest occupied molecular orbital (HOMO) level and leads to an enhanced open‐circuit voltage because of the branched conformation. The power conversion efficiencies (PCE) of the polymer/[6,6]‐phenyl‐C71‐butyric acid methyl ester PC 71 BM photovoltaic cells are in the range of 1.28–2.30%. In particular, the P8TTT‐based device processed from an o ‐dichlorobenzene/1,8‐diiodoctane mixed solvent shows the best PCE among the studied polymers (2.81%), demonstrating that 8T‐based polymers with a low HOMO level can emerge as promising candidates for organic device applications.