High quality factor microcavity OLED employing metal-free electrically active Bragg mirrors

A Fabry-Perot microcavity with a high quality Q-factor is an excellent tool to finely tune and narrow the emission spectrum of embedded organic dyes, leading also to a modification of the radiative emission rate (Purcell effect). For a real application of these properties in light emitting diodes and lasers, high Q-factors should be also provided in electrically-driven organic microcavities, that is still a challenge when organic materials are employed. Metallic contacts can be safely deposited onto organic layers, although they result in strong absorption losses. In this work, we successfully integrated an Organic LED architecture within specifically tailored metal-free electrically active Bragg mirrors, finely optimized to achieve simultaneously high reflectivity and good electrical properties. The resulting electroluminescent microcavity showed a Q-factor of more than 200 (emission linewidth of 2.7 nm at a peak wavelength of 555 nm) and a clear proof of the occurrence of Purcell effect leading to a decrease of exciton radiative lifetime by a factor above 6. Finally, we analysed the parameters that still limit the Q-factor of our architecture, paving the way for future improvements. The proposed approach can be exploited for the fabrication of novel monochromatic organic light sources for telecommunications or biological sensing and it represents an important step towards the realization of electrically driven organic lasers.