Enhanced photoluminescence characteristics in Mg doped Alq3: An insight into doping mechanism

Abstract

The present paper deals with the investigations on the effect of Mg doping on the structural and photophysical properties of Alq3 thin films. Mg doped Alq3 powders, with varying Mg concentrations, are synthesized using co-precipitation method and their thin films are deposited using vacuum evaporation method. These films are subjected to different analytical analyses to study the effect of Mg doping on the structural and photophysical properties of Alq3. It has been observed that Mg is attached at the central part of the Alq3 molecules making bonds with Al, N and O atoms. In this process, Mg atoms transfer electrons to Alq3 molecules and increases the electron density in its highest occupied molecular orbital (HOMO). Increased HOMO electron density in Mg doped Alq3 results in the improvement in its photoluminescence characteristics. Highest photoluminescent characteristics are observed for Mg doped Alq3 having 1.5 % (by mole) Mg which shows almost 2-fold enhancement in photoluminescence quantum efficiency (PLQY) and 3-fold enhancement in radiative decay rate. The results obtained in this work suggest that Mg doped Alq3 films may be integrated in high performing organic light emitting devices.