Optical characteristics of PtOEP and Ir(ppy)3 triplet-exciton materials for organic electroluminescence devices

Abstract Absorption and magnetic circular dichroism spectra of PtOEP and Ir(ppy)3 films evaporated on fused silica substrate are studied at 13–320 K. The characteristics of absorption bands related with the spin triplet and singlet states are clarified. The energy states of the absorption bands are identified, e.g. relatively weak absorption bands at 485 and 452 nm of Ir(ppy)3 are attributed to the metal-to-ligand charge-transfer spin triplet state (3MLCT). Photoluminescence (PL) and electroluminescence (EL) spectra of PtOEP and Ir(ppy)3 organic EL devices with a multi-layer are also investigated, where PtOEP and Ir(ppy)3 molecules are doped in CBP host. In the PtOEP EL device, an additional emission band is observed at 542 nm in the PL and EL spectra, which is due to a hot level of thermally populated triplet state in PtOEP.