Diketopyrrolopyrrole-basedsmallmolecules with simple structure for high VOC organic photovoltaics

Abstract

A series of simple structured smallmoleculesbased on diketopyrrolopyrrole (DPP) are synthesized and their photovoltaic properties are investigated in terms of the type of electron donating unit. By introducing a donor unit with different electron-donating power such as thiophene (T) and phenylene (Ph), into A?D?A type smallmolecule, the frontier orbital energy levels of smallmolecules can effectively be tuned. The smallmolecule with a weak donor unit of Ph, Ph(TDPP)2 exhibits a power conversion efficiency of 4.01% with a remarkably high open circuit voltage of 0.93 V when it is blended with [6,6]-phenyl-C71-butyric acid methyl ester as an active layer material in bulk heterojunction solar cells.