Facile synthesis of bis-dicyanovinylidene-end-capped push-pull molecules as panchromatic absorbers

A new π-conjugated building block containing bis-dicyanovinylidene as an end-capping group has been explored for the development of n-type organic semiconductors. This building block can be easily obtained from commercialized 2,3-thiophenedicarboxaldehyde and introduced into a π-conjugated system in high-yield. By using indaceno[1,2-b:5,6-b']dithiophene (IDT) as the core moiety, an A-π-D-π-A molecule with up to 8 cyano-groups (DH8CN) was firstly synthesized and employed as an electron-accepting material in bulk-heterojunction organic solar cells. Preliminary organic cell fabrication gave a 1.1% power conversion efficiency with PTB7-Th and DH8CN as active layer, show the potential of this bis-dicyanovinylidene group in organic photovoltaics.