A Twisted Thieno[3,4‐b]thiophene‐Based Electron Acceptor Featuring a 14‐π‐Electron Indenoindene Core for High‐Performance Organic Photovoltaics

• DOI: 10.1002/adma.201704510
• Publication Date: 2017-10-06T14:06:39Z
• Authors: Sheng jie Xu; Zichun Zhou; Wuyue Liu; Zhongbo Zhang; Feng Liu; Hongping Yan; Xiaozhang Zhu
• Keywords: Electron acceptor; Acceptor; HOMO/LUMO

With an indenoindene core, a new thieno[3,4-b]thiophene-based small-molecule electron acceptor, 2,2'-((2Z,2'Z)-((6,6'-(5,5,10,10-tetrakis(2-ethylhexyl)-5,10-dihydroindeno[2,1-a]indene-2,7-diyl)bis(2-octylthieno[3,4-b]thiophene-6,4-diyl))bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (NITI), is successfully designed and synthesized. Compared with 12-π-electron fluorene, carbon-bridged biphenylene axial symmetry, indenoindene, E-stilbene centrosymmetry, shows elongated π-conjugation 14 π-electrons one more sp3 carbon bridge, which may increase the tunability of electronic structure film morphology. Despite its twisted molecular framework, NITI low optical bandgap 1.49 eV in thin high molar extinction coefficient 1.90 × 105 m-1 cm-1 solution. By matching large-bandgap polymer donor, extraordinary power conversion efficiency 12.74% achieved, among best performance so far reported for fullerene-free organic photovoltaics inspiring design acceptors.