Carrier conduction mechanism for Phosphorescent materials doped organic semiconductor

The mobility of charge carriers has been investigated in the pristine and phosphorescent material doped 4,4 ,4 -tris N-carbazolyl triphenylamine TCTA using time-of-flight photoconductivity technique. Doping phosphorescent material fac-tris 2-phenylpyridine iridium Ir ppy 3 increases the electron mobility whereas the hole mobility decreases to the order of 10−4–10−6 cm2 /V s measured at room temperature with different bias voltages. The analysis of field and temperature dependences of the mobility agrees well with the Gaussian disorder model. The calculated positional disorders for TCTA, Ir ppy 3-doped TCTA, and tris 1-phenylisoquinoline iridium Ir piq 3 -doped TCTAare 0.12, 2.05, and 1.62 for hole, respectively; 3.89 for electron in only Ir ppy 3-doped TCTA. The ambipolar transport for holes and electrons is possible by doping TCTA with Ir ppy 3 green dopant whereas only hole transport with reduced mobility is achieved for Ir piq 3 red dopant