Electronic states of phosphorescent molecules Ir(PPY)3 and PtOEP used in organic light emitting diodes

Photo luminescence (PL) of phosphorescent molecules fac tris (2-phenylpyridine) iridium (Ir(ppy)(3)) and platinum octaethyl porphine (PtOEP) has been studied using films of Ir(ppy)(3) doped in CBP and PtOEP doped in TPD, respectively. A weak emission band is observed at 396 nm in Ir(ppy)(3). Its intensity increases with decreasing temperature from 300 K. This emission is attributed to the singlet emission from (MLCT)-M-1 state. The singlet emission band of PtOEP is observed at 542 nm, which appears below 150 K. The intersystem crossing conversion is estimated to be 98.7% for Ir(ppy)(3). From the excitation spectra for Ir(ppy)(3) emission, we suggest energy transfer from the n = 1 vibrational state of Ir(ppy)(3) to the n = 0 state of CBP host. (c) 2006 Elsevier B.V. All rights reserved.