Gate induced modulation of electronic states in monolayer organic field-effect transistor

Abstract

Organic field-effect transistors with ionic liquids have attracted much attention, since the ionic liquids induce an intense electric field at a semiconductor interface, resulting in a high concentration of charge carriers. It is expected that such strong electric fields and highly doped charges induce nontrivial effects on the electronic band structures. Recently, the blue shift of the peak wavelength in photo-absorption spectra for a DNBDT-monolayer transistor was experimentally observed by increasing an ionic-liquid gate voltage, although the origin of the shift is still under debate. Therefore, we investigate the hole-doping and external electric-field effects on the electronic states of the organic semiconducting monolayer within the framework of the density functional theory. The calculated results show that the photo-absorption energy is increased by hole doping while an external field decreases the photo-absorption energy. We demonstrated that the calculations give useful information to understand the origin of the experimentally observed wavelength shift of photo-absorption spectra.