Poly(N-vinylcarbazole) (PVK) deposited by evaporation for light emitting diodes thin films structures

Abstract The sandwich structures have been obtained by deposition of organic thin films on commercial tin oxide. Then the organic films were covered by a thin aluminium film. All the films were deposited by evaporation. The organic component was either a thin (150 nm) poly( N -vinylcarbazole) (PVK) film or a bilayer constituted of a thin PVK layer covered with a 8-hydroxyquinoline, aluminium (Alq 3 ). When PVK is deposited by classical thermal evaporation there is a shortening effect of the chain length, however, the main properties of the vinyl-carbazole molecules are preserved. These films are photoluminescent with blue light emission. The I – V characteristics of the sandwich structures are typical of such organic sample. They exhibit a rectifying behaviour, with a forward polarisation when the SnO 2 electrode is positively biased. They also exhibit electroluminescence. When a single PVK film is used, the signal is quite faint. It is improved when an organic bilayer is used. However, simultaneously there is a red shift of the signal.