Time-dependent density functional theory study of the al complexes with aromatic ligands for blue organic light-emitting diodes

Abstract

Aluminum(III) complexes with 8-hydroxyquinoline have attracted much attention because of their potential application in organic light emitting diodes (OLEDs) as green and blue emitting materials with the subtle effect of the substitution on the fluorescence and electroluminescent (EL) properties. The photoluminescence of aluminum(III) complexes [(tri(2',2-dihydroxybiphenyl) aluminum(III)] have been studied as efficient fluorescence emitting materials [17]. In this paper, geometric and electronic properties of several Al complexes are studied to find the ligand effect related to the intensities of their absorptions and emissions using computational methods. In order to find a new highly efficient blue emitting materials, we have designed new Al complexes with aromatic ligands, [4,5-phenanthrenediol, 3,3'-dihydroxy-2,2'-binaphthalene, 2-(2'-phenol)-2-naphthol, and 1-(2'-phenol)-2-naphthol]. The geometry optimizations of the ground and the lowest excited electronic states were determined using HF/3-21G(d) and configuration interaction with single excitations (CIS) method. The vertical and adiabatic transition energies were calculated using time-dependent density functional theory (TD-DFT) with B1LYP/6-31G(d). As a result, we propose new blue fluorescent Al complexes of high luminescence efficiency.