An investigation on the optical parameters of TPD:Alq3 composite thin films

In this work, a broad investigation on the optical parameters of TPD:Alq3 composite thin films is reported. The films are prepared from different solution-processed mixtures and are deposited onto the quartz substrate in order to measure their optical response with UV–Vis–NIR spectrophotometer. Results showed that the non-dispersive refractive index and dielectric constant of TPD was increased from 1.49 to 1.75 and from 2.19 to 2.99 by Alq3 doping, respectively. The optical conductivity of TPD:Alq3 (1:3) composite was seen to be highly improved, reaching the value of 144 S/cm. The Wemple and DiDomenico (WD) model was used to find the band gap ( E g W D ) of the films and results were compared to those deduced from the Tauc's equation ( E g o p t ). It was found that the investigated films obey the single-oscillator model in defining the strength of the optical transitions.