A Wide Band Gap Naphthalene Semiconductor for Thin‐Film Transistors

Abstract

This study reports a new simple organic semiconductor 2,6‐bis(4‐methoxyphenyl)naphthalene (BOPNA) with unprecedentedly large band gap of 3.35 eV and an apparent hole mobility of ≈1 cm2 V–1 s–1 measured in thin‐film organic field‐effect transistors in a saturation regime. This large band gap leads to complete optical transparency in the visible range (>370 nm), very high stability and independence of the device current with illumination conditions; this is in contrasts to the behavior of common organic semiconductors that have the band gap in the visible or near‐IR range of the spectrum. Crystal structure of BOPNA reveals a highly isotropic electronic coupling in two directions of a herringbone‐packing plane. A uniform, nearly single crystalline morphology can be achieved in highly crystalline BOPNA films through a rapid thermal annealing. Temperature‐dependent studies reveal increase of the hole mobility as the temperature is reduced from +25 to –25 °C, suggesting a band‐like transport, followed by a nearly temperature‐independent mobility down to at least –150 °C.