Carbazole based electroluminescent devices obtained by vacuum evaporation

Abstract Transparent conductive oxide (SnO 2 )/organic layers/aluminum thin film sandwich structures have been obtained by vacuum evaporation. The organic component was either a thin carbazole film or a bilayer. In that case, the carbazole film was deposited on a thin insulating polymer film. The polymer used was the poly(tetrabromo- p -phenylenediselenide) (PBrPDSe). Photoluminescence measurements have shown that the carbazole thin films emit blue light. The I – V measurements have shown that the structures exhibit diode characteristics. The forward direction is obtained when the TCO is positively biased. However, the reproducibility of the results obtained with a single carbazole layer is poor. It appears that the stability of the sample is improved when a thin PBrPDSe film (50 nm) is introduced between the carbazole and the SnO 2 . The polymer film avoids short circuit effect. In that case, the turn-on voltage of the diode is about 3 V, when the thickness of the carbazole film is around 250 nm and the electroluminescence appears at a voltage of about 4 V.