In this paper, in contrast with previously reported approaches, we suggest exploiting a microcavity effect using nanoparticles to improve the optical efficiency of organic light-emitting diodes (OLED). The method to input the nanoparticles inside the OLED device is simple and cost effective by virtue of employing a solution process using a spin coating fabrication method. Titanium dioxide (TiO2) nanoparticles were used to improve the reflection by its high refractive index. In tandem with optimized heights of the organic layers, the increased light reflectance improved the optical efficiency of the OLED device via the microcavity effect. In order to prove that the enhancement of the optical efficiency was due to an enhanced microcavity effect caused by TiO2 nanoparticles, a microcavity simulation was conducted. The electrial characteristics were not affected by the nanoparticles and a clear pixel image was maintained. The results in this paper show that a nanoparticle based microcavity effect can be exploited to enhance the optical efficiency of OLEDs.