Synthesis and Photovoltaic Performance of Anthracene‐Based Small Molecules for Solution‐Processed Organic Solar Cells

Increasing molecular π‐conjugation length generally improves the light‐harvesting ability and enhancing π‐π stacking interactions could improve the charge‐carrier transport ability in small molecules (SMs). Both are beneficial for increasing power conversion efficiencies (PCEs) in organic solar cells. In this work, two linear (A−D) 2 Ar‐type SMs of (DTBT‐TPA) 2 An and (DPP‐TPA) 2 An were designed and synthesized, in which 4,7‐di(thiophen‐2‐yl)benzothiadiazole (DTBT) and diketopyrrolopyrrole (DPP) were selected as electron acceptors (A), triphenylamine (TPA) was used as electron donor (D) and 9,10‐anthracene (An) was used as π‐bridge (Ar group), respectively. For comparison, two D−A‐type SMs of DTBT‐TPA and DPP‐TPA were also prepared without anthracene unit. By systematically comparing their optical and electronic properties, it was found that (A−D) 2 Ar‐type SMs show stronger photo response with higher absorption coefficients than the D−A‐type counterparts. And introducing anthracene unit could slightly lower their HOMOs of the resulting (A−D) 2 Ar‐type SMs. In bulk heterojunction solar cells, PCEs of 1.72% and 1.36% were achieved in (DTBT‐TPA) 2 An and (DPP‐TPA) 2 An based devices without any solvent additive, which are about 1.5 and 1.9 times the corresponding values of the DTBT‐TPA and DPP‐TPA based devices, respectively.