N-type conjugated materials based on 2-vinyl-4,5-dicyanoimidazoles and their use in solar cells

The synthesis and characterization of a novel class of n-type conjugated materials based on the Heck reaction of 2-vinyl-4,5-dicyanonimidazole, called vinazene, which can be used in solar cells, were analyzed. Vinazene derivatives V-DP, V-F, V-BT, and V-TBT were synthesized from the Heck coupling in DMF using bis(tri-t-butylphosphine)-palladium (O) [Pd[P(t-Bu)3]2] as catalyst, and dicyclohexylmethylamine (Cy2NMe) as base/HBr scavenger. The thermal properties of the materials was analyzed by DSC and TGA and it was noticed that all the materials melt above 205°C and have relatively high thermal stability under N2. Cyclic voltammetry (CV) and the UV-vis absorption band edge were used to estimate the ionization (HOMO) electron affinity (LUMO), and band gap of the vinazene materials. Result shows that organic solar cells using P3HT as donor and V-BT as electron acceptor display high external quantum efficiencies.