Electroluminescence and photoluminescence in CdSe/poly (p-phenylene vinylene) composite films

Thin films are prepared from water-soluble precursor of poly (p-phenylene vinylene) (pre-PPV) and CdSe nano-colloidal particles using a self-assembly deposition method. The pre-PPV is converted to PPV by heating of the whole film structure. Stable elctroluminescence is obtained from an ITO//PEI/(PPV/CdSe)*20//Al device with a turn on voltage below 5 V. In electroluminescence only the emission of the particles is seen. The current voltage curves show inversion symmetry but light emission is observed only under forward bias. The broad emission spectra are related to exciton trapping at the particle surface, which is confirmed by temperature dependent measurements of photoluminescence.