Microwave-assisted synthesis of colloidal ZnO nanocrystals and their utilization in improving polymer light emitting diodes efficiency.

Graphical abstract Highlights • Original facile microwave-assisted synthesis of Zinc oxide nanoparticles is reported. • Prepared ZnO nanoparticles form stable colloidal dispersions in toluene. • Solution of MEH-PPV polymer and ZnO nanodispersions mix without agglomeration. • Polymer LEDs with MEH-PPV/ZnO nanocomposite active layer were successfully prepared. • The PLEDs with MEH-PPV/ZnO layer exhibited high electroluminescence at low voltage. Abstract Zinc oxide nanoparticles were synthesized via microwave-assisted reactions from a zinc acetate dihydrate. The reactions were performed in diethylene glycol (DEG) at 220 °C and 250 °C while using oleic acid as the surfactant. The ZnO precipitates obtained were washed with methanol and dried or kept as colloidal solutions redispersed in toluene. The size of the nanoparticles ranged from ca. 5 to 12 nm and they could be modified by the concentration of Zn precursor. Different morphologies due to the function of oleic acid concentration were observed. The resulting ZnO nanocolloids were mixed with the poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) polymer to obtain MEH-PPV/ZnO nanocomposites. The nanocomposite layers exhibited optoelectronic properties which were found to be beneficial for being applied as the active layer in the polymer light emitting diodes. The intensity of the electroluminescence of the prepared PLED devices was enhanced by one order of magnitude keeping all other parameters constant and powered as the same operation voltage. As additional step the effect of active layer thickness on optoelectronic performance of PLED devices was investigated as well. [ABSTRACT FROM AUTHOR]