Journal of Energy Chemistry, 2019, vol 37pp. 58-65
Small molecule ladder-type heteroarenes IHBT-2F is designed and synthesized with strong electron-donating and molecular packing properties, where the central unit, fused thienobenzene-thienothiphene (IHBT), is attached with the strong electron-deficient 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (2FIC) as the end group. The counterpart IDBT-2F with indancenodibenzothiophene (IDBT) mainchain is sythesized for comparison, in which thieno[3,2-b]thiophene (TT) core of IHBT is replaced by benzene core. Relative to benzene-core IDBT-2F, TT-core IHBT-2F shows a much higher highest occupied molecular orbital energy level (IHBT-2F: − 5.46 eV; IDBT-2F: –5.72 eV) and significantly redshifted absorption, due to the π-donor capability of the sulfur atom, the larger π-conjugation and stronger intermolecular π–π stacking. The as-cast organic solar cells (OSCs) based on blends of PTB7-Th donor and IHBT-2F acceptor without additional treatments exhibit power conversion efficiencies (PCEs) as high as 8.74%, which is much higher than that of PTB7-Th: IDBT-2F (6.73%).