Interfacial exciplex electroluminescence between diamine derivatives with starburst molecular structure and tris(acetylacetonato)-(mono-phenothroline) thulium

The authors demonstrate the interfacial exciplex electroluminescence (EL) between tris(acetylacetonato)-(mono-phenothroline) thulium [Tm(AcA)3phen] and two diamine derivatives with starburst molecular structure- 4,4′,4″-tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA) and 4,4′,4″-tris[3-methyl-pheny(phenyl)-amino]triphenyl-amine (m-MTDATA), both of which have the same ionization potential (IP) (approximately 5.1 eV). When the Tm-complex and the two diamine derivatives are respectively used as the electron accepter and donors, the two EL devices exhibit different exciplex emissions, which verifies our previously reported opinion regarding the effect of the different substitutes on exciplex emission [W.M. Su, W.L. Li, Q. Xin, Z.S. Su, B. Chu, D.F. Bi, H. He, J.H. Niu, Appl. Phys. Lett. 91 (2007) 043508]. When the mixture of the two diamine derivatives is used as a donor, a white EL device with the Commission International de l’Eclairage (CIE) coordinates of (0.277, 0.323) is achieved. The exciplex formation mechanisms of the devices with the two different donors are discussed.