Polyaniline-fumed silica (PANI-SiO2) nanocomposites were synthesized through in-situ chemical oxidative polymerization of the aniline in the presence of SiO2 nanoparticles by using ammonium peroxydisulphate (APS) as an oxidant. The resulting PANI-SiO2 nanocomposites with different SiO2 contents were characterized using FT-IR, XRD, FE-SEM and UV-vis techniques. The influence of SiO2 contents on the sheet resistance of the nanocomposite was investigated by four-point probe system. The optical properties of poly [2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) in toluene solution studied by UV-vis and photoluminescence (PL) measurements at room temperature. For the first time, the application of the prepared PANI-SiO2 nanocomposites as a hole-injection layer (HIL) of electroluminescent (EL) devices was examined and the device performance (e.g., turn-on voltage and current density-voltage (J-V) characteristics) was investigated. The Fowler-Nordheim (FN) field-emission tunneling model was used to explain the J-V characteristics of the fabricated devices. The hole-injection barrier height (phi) values for the devices were obtained and reported. (C) 2015 Elsevier Ltd. All rights reserved.