The development of organic semiconductors is of key importance in order to improve the performance of organic solar cells (OSCs). Three indenothiophene (IT)-containing small molecules (IT3T, ITFBT and IT2FBT) were designed and synthesized for small molecule OSCs. The thermal, optical, and electrochemical properties of the molecules were investigated. The optical bandgaps of the three small molecules are ranged from 1.80 to 2.20 eV depending on different terminal groups flanked on the IT. We study the photovoltaic performances of the three molecules by fabricating OSCs with PC₇₁BM as an electron acceptor. Among the three molecules, ITFBF exhibited the best power conversion efficiency of 4.57% with a high open circuit voltage (V_OC) of 0.98 V. We also briefly discuss structure–property guidelines for small molecules used for OSCs. The results demonstrate that IT-based small molecules are promising for small molecule OSCs with large V_OCs.