High open-circuit voltage solution-processed organic solar cells based on a star-shaped small molecule end-capped with a new rhodanine derivative

摘要

A new star-shaped small molecule named TCNR3TTPA,with a triphenylamine(TPA)unit as the central building block and2-(1,1-dicyanomethylene)-3-octyl rhodanine(CNR)as the end-capped group,has been designed and synthesized.TCNR3TTPA showed a deep highest occupied molecular orbital(HOMO)energy level( 5.60 e V)and broad absorption.The solution-processed bulk heterojunction(BHJ)solar cells based on TCNR3TTPA:PC61BM(1:1,w/w)exhibited a high open-circuit voltage(Voc)of 0.99 V,a short-circuit current density(Jsc)of 5.76 m A/cm2,and a power conversion efficiency(PCE)of 2.50%under the illumination of AM 1.5 G,100 m W/cm2.The high Voc is ascribed to the strong electron-with-drawing ability of the end-capped 2-(1,1-dicyanomethylene)-3-octyl rhodanine group.These results demonstrated that the Voc of small-molecule organic solar cells could be increased by introducing a strong electron-withdrawing end-capped block,and that this is an effective strategy to design high-performance small molecules for organic solar cells.