Computational analysis to understand the performance difference between two small-molecule acceptors differing in their terminal electron-deficient group

The end groups of small-molecule acceptors strongly affect their properties and performance. In this study, theoretical analysis is performed to determine the reason why two similar molecules differing in their end group show very different performance in organic solar cells. The 1,1-dicyanomethylene-3-indanone-based small-molecule acceptor (DC-IDT2Tz) shows a higher transition dipole moment as compared with the rhodanine-based small acceptor (RD-IDT2Tz). DC-IDT2Tz presents a lower exciton binding energy as compared with RD-IDT2Tz. Moreover, DC-IDT2Tz shows a lower reorganization energy and higher transfer integrals than RD-IDT2Tz. All these theoretical descriptors can explain the reason behind the higher efficiency of DC-IDT2Tz. The studied theoretical parameters can help to verify the performance of organic semiconductors before synthesis. This work will thus be helpful for experimental scientists to screen compounds and select the best one for synthesis. Graphic abstract