Isomerically Pure Anthradithiophene Derivatives

Pentacene shows good hole-transporting properties, but it is unstable toward oxidation due to its inherent high HOMO-level. This instability causes variability of device-performance and also limits long-term use of devices. Anthradithiophene also shows good hole-transporting properties, and is more stable toward oxidation because of its lower HOMO-level compared with pentacene. Anthradithiophene derivatives have been reported as mixtures of syn- and anti- isomers according to the direction of the thiophene moiety, and the effect of each isomer in device performance is not clear.

Tokito and Mamada have reported the synthesis and properties of isometrically-pure syn- and anti-2,8-dimethylanthradithiophenes (DMADTs).¹⁾ Both isomers (anti-DMADT and syn-DMADT) show similar optical properties and energy levels, but the more symmetric anti-DMADT (μ = 0.41 cm²/Vs) shows five times superior hole-mobility compared with syn-DMADT (μ = 0.084 cm²/Vs). This result clearly shows the importance of using the single isomer in device-fabrication.

TCI developed new synthetic approach to provide high pure anti-DMADT (1) and syn-DMADT (2) with no isomer contamination.