A novel chlorinated small molecule donor for efficient binary and ternary all-small-molecule organic solar cells

Abstract

A new acceptor-donor-acceptor (A-D-A) type small molecule donor named BTEHR-CT has been developed, taking the chlorothienyl-substituted benzodithiophene (BDT) as the central unit and 3-(2-ethylhexyl)rhodanine as the terminal group. BTEHR-CT shows a low-lying highest occupied molecular orbital (HOMO) level of −5.56 eV and the suitable molecular aggregation benefiting from the introduction of chlorine atoms, which contributes to achieving excellent photovoltaic performances. Based on an efficient non-fullerene acceptor F–2Cl, the optimized binary device exhibits a high power conversion efficiency (PCE) of 11.13% with an open-circuit voltage ( V oc ) of 0.946 V, short-circuit current densities ( J sc ) of 17.05 mA cm −2 and FF of 0.690. With the incorporation of PC 71 BM, the ternary blend film based on BTEHR-CT:F–2Cl:PC 71 BM (weight ratio of 1:0.8:0.2) shows a fibrous morphology with suitable domain size and favorable phase separation after solvent vapor annealing (SVA) treatment, leading to a superior J sc of 18.53 mA cm −2 and fill factor (FF) of 0.692, thus a higher PCE of 12.05%. To our best knowledge, the PCEs of 11.13% and 12.05% are among the highest values reported to date for non-Y series acceptors based binary and ternary all-small-molecule organic solar cells (ASM-OSCs), respectively. The results indicate that the combination of careful molecular design and suitable morphology control is an effective strategy to achieve high performances for ASM-OSCs. • A new chlorinated small molecule donor named BTEHR-CT was designed and synthesized. • BTEHR-CT exhibits excellent optical and electrochemical properties. • The binary ASM-OSCs based on BTEHR-CT:F–2Cl gave a high PCE of 11.13%. • BTEHR-CT based ternary ASM-OSCs showed a higher PCE of 12.05% with the incorporation of PC 71 BM. • The PCEs are among the highest values reported to date for non-Y series acceptors based ASM-OSCs.