An electron deficient dicyanovinylene-ladder-type pentaphenylene derivative for n-type organic field effect transistors

Abstract

A bridged pentaphenylene derivative functionalized with dicyanovinylene units LPP(C(CN)₂)₂ has been designed, synthesized and characterized. The optical and electrochemical properties have been carefully studied through a combined experimental and theoretical approach and compared with those of two pentaphenylene derivatives bearing methylenes (LPP) or carbonyl (LPP(O)₂) on the bridgeheads. LPP(C(CN)₂)₂ which possesses a very low LUMO level, ca. −4.02 eV, has been successfully used as an active layer in n-channel OFETs using the epoxy based photoresist SU-8 as a gate insulator. LPP(C(CN)₂)₂ based n-channel OFETs show low voltage functioning (low gate–source and drain–source voltages), high ratio between the on and the off currents (2 × 10⁵), interesting subthreshold swing (S = 1) and excellent stability under electrical stress and in a nitrogen atmosphere. More importantly, we have also shown that LPP(C(CN)₂)₂ based n-channel OFETs present an excellent environmental stability. This work is to the best of our knowledge the first report on bridged pentaphenylene-based semiconductors in n-type OFETs and highlights the potential of such type of material to provide air stable OFETs.