Small Molecules with Asymmetric 4-Alkyl-8-alkoxybenzo[1,2-b:4,5-b ']dithiophene as the Central Unit for High-Performance Solar Cells with High Fill Factors

Guo, YQ (Guo, Yuan-Qiang)^[ 1,2 ] ; Wang, YC (Wang, Yunchuang)^[ 1,2 ] ; Song, LC (Song, Li-Cheng)^[ 1,2 ] ; Liu, F (Liu, Feng); Wan, XJ (Wan, Xiangjian)^[ 1,2 ] ; Zhang, HT (Zhang, Hongtao)^[ 1,2 ] ; Chen, YS (Chen, Yongsheng)^[ 1,2,3 ]

CHEMISTRY OF MATERIALS, 2017, 29(8): 3694-3703

DOI: 10.1021/acs.chemmater.7b00642

 WOS:000400233100040

Abstract

A small molecule named DRBDTCO based on benzo[1,2-b:4,5-b']dithiophene (BDT) with an asymmetric side chain and its dimer, dDRBDTCO, with the octamethylene connector were designed and synthesized as donor materials for solution-processed bulk heterojunction solar cells. The optimized power conversion efficiency of a DRBDTCO-based device was 8.18% under AM 1.5 G irradiation (100 mW cm(-2)), which is higher than that of its dDRBDTCO-based device. Both molecule based devices exhibited high fill factors of >73%, which are attributed to their optimized morphologies with a feature size of 15-20 nm, highly efficient charge collection, less bimolecular recombination, and well-balanced charge transport properties. The results demonstrate that the asymmetric BDT unit could be a promising building block for donor materials with high efficiencies and high fill factors.