Light emission from the polythiophene derivative/ITO structure under electron beam excitation

Abstract

Light emission of poly [3-(2-benzotriazolo) ethylthiophene] (PBET) at a different electron beam current density has been investigated by the cathodoluminescence (CL) spectroscopy. An electron beam was used to inject directly electrons and holes in the polymer. Under the low electron beam excitation the CL spectra show two peaks centered at 540 and 620 nm . Above some threshold beam current density, we observed an ultraviolet (UV) emission centered at 347 nm , in addition to the characteristic green–orange luminescence of PBET. The relative intensity of these bands was shown to depend on an electron beam current density and temperature. A ratio of the UV/green–orange band intensities increases with an increase of the current density and a decrease of temperature. The highest electron beam excitation used in our experiment at room temperature results in the UV-blue band broadening which is attributed to the charging effect and the structural change in the polythiophene derivate induced by the electron beam excitation. This effect could be used to obtain white light emission from the PBET/ITO structure.