Vibration Correlation Function Investigation on the Phosphorescence Quantum Efficiency and Spectrum for Blue Phosphorescent Ir(III) Complex
Received date: 2013-01-22
Online published: 2013-03-26
Supported by
Project supported by the National Natural Science Foundation of China (Nos. 21290190, 91233105) and the Ministry of Science and Technology of China through 973 Program (Nos. 2009CB623600, 2013CB834703).
A challenging issue for white organic light-emitting diodes is to improve the luminescence efficiency and stability for blue phosphorescence materials. In order to deeper understand the relationship between molecular structure and luminescence quantum efficiency, we apply our recently developed correlation function method coupled with density functional theory calculation to investigate the photophysical properties of fac-tris(2-(4,6-difluorophenyl)pyridyl iridium (fac-Ir(F2ppy)3), including phosphorescence emission spectra, radiative and nonradiative decay rates, and excited-state decay lifetime at different temperatures. All the calculated results can well reproduce the available experimental measurements. We further analyze the relevance of molecular parameters governing the photophysical processes. We found out that in fac-Ir(F2ppy)3: (1) when compared with the archetypal green fac-Ir(ppy)3, the introduction of F atoms can enlarge the energy gap between the excited triplet T1 and the ground state S0 resulting in blue-shift. This does not introduce extra reorganization energies in the excited-state relaxation process. So the blue phosphorescent fac-Ir(F2ppy)3 can exhibit high luminescence efficiency; (2) the main channels for nonradiatively dissipating the electronic excited-state energy are found to be the stretching vibrations of carbon and carbon bonds, such as C(5)—C(46) linking the fluorophenyl and pyridyl rings, C(43)—C(44) and C(42)—C(47) of pyridyl ring, and C(3)—C(6) of fluorophenyl ring in L1 ligand. This points out the direction for further increasing the light-emitting efficiency through suppressing these motions.
Shi Qinghua , Peng Qian , Sun Shaorui , Shuai Zhigang . Vibration Correlation Function Investigation on the Phosphorescence Quantum Efficiency and Spectrum for Blue Phosphorescent Ir(III) Complex[J]. Acta Chimica Sinica, 2013 , 71(06) : 884 -891 . DOI: 10.6023/A13010113
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