Time-dependent density functional calculations of phosphorescence parameters for fac-tris(2-phenylpyridine) iridium

被引:154
作者
Jansson, Emil [1 ]
Minaev, Boris
Schrader, Sigurd
Agren, Hans
机构
[1] Royal Inst Technol, SE-10691 Stockholm, Sweden
[2] Univ Appl Sci, Tech Fachhsch Wildau, D-15745 Wildau, Germany
关键词
Ir(ppy)(3); phosphorescence; OLED; DFT;
D O I
10.1016/j.chemphys.2007.01.021
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
fac-Tris(2-phenylpyridine) iridium [fac-Ir(PPY)(3)] produces strong phosphorescence and has therefore been used as materials in organic light emitting diodes to overcome the efficiency limit imposed by the formation of triplet excitons. Accounting for this circumstance we present in this paper a theoretical study of phosphorescence in the Ir(PPY)(3) complex. The spin-orbit coupling effects and the radiative lifetime in the high temperature limit (T) are calculated by time-dependent density functional theory using quadratic response technology in order to elucidate the main mechanism of the phosphorescence. It is found that the orbital structure of the T, state has a localized character and that the T1 -> S0 transition is determined mostly by charge transfer from one of the ligands to the metal. At the vertical S-0-T-1 excitation the triplet state is highly delocalized among all three ligands and has a mixed pi pi* and metal-to-ligand charge transfer character. The intensity borrowing from the S-0 to S-5 transitions is mostly responsible for the strong phosphorescence emission from the x and y spin sublevels. Our results concord with the experimental data on temperature and magnetic field dependence of the phosphorescence kinetics. The calculated radiative lifetime in the high temperature limit agrees well with the measured decay times (2 mu s) accounting for negligible non-radiative quenching of the lowest triplet state. (c) 2007 Elsevier B.V. All rights reserved.
引用
收藏
页码:157 / 167
页数:11
相关论文
共 40 条
[1]  
Allen F.H., 1993, CHEM AUTOMAT NEWS, V8, P31
[2]   Excitonic singlet-triplet ratio in a semiconducting organic thin film [J].
Baldo, MA ;
O'Brien, DF ;
Thompson, ME ;
Forrest, SR .
PHYSICAL REVIEW B, 1999, 60 (20) :14422-14428
[3]   Highly efficient phosphorescent emission from organic electroluminescent devices [J].
Baldo, MA ;
O'Brien, DF ;
You, Y ;
Shoustikov, A ;
Sibley, S ;
Thompson, ME ;
Forrest, SR .
NATURE, 1998, 395 (6698) :151-154
[4]   Transient analysis of organic electrophosphorescence: I. Transient analysis of triplet energy transfer [J].
Baldo, MA ;
Forrest, SR .
PHYSICAL REVIEW B, 2000, 62 (16) :10958-10966
[5]   DENSITY-FUNCTIONAL THERMOCHEMISTRY .3. THE ROLE OF EXACT EXCHANGE [J].
BECKE, AD .
JOURNAL OF CHEMICAL PHYSICS, 1993, 98 (07) :5648-5652
[6]   SELF-CONSISTENT MOLECULAR-ORBITAL METHODS .21. SMALL SPLIT-VALENCE BASIS-SETS FOR 1ST-ROW ELEMENTS [J].
BINKLEY, JS ;
POPLE, JA ;
HEHRE, WJ .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1980, 102 (03) :939-947
[7]   Crystal structure of fac-Ir(ppy)3 and emission properties under ambient conditions and at high pressure [J].
Breu, J ;
Stössel, P ;
Schrader, S ;
Starukhin, A ;
Finkenzeller, WJ ;
Yersin, H .
CHEMISTRY OF MATERIALS, 2005, 17 (07) :1745-1752
[8]   Improved quantum efficiency for electroluminescence in semiconducting polymers [J].
Cao, Y ;
Parker, ID ;
Yu, G ;
Zhang, C ;
Heeger, AJ .
NATURE, 1999, 397 (6718) :414-417
[9]   A NEW SYNTHETIC ROUTE TO THE PREPARATION OF A SERIES OF STRONG PHOTOREDUCING AGENTS - FAC TRIS-ORTHO-METALATED COMPLEXES OF IRIDIUM(III) WITH SUBSTITUTED 2-PHENYLPYRIDINES [J].
DEDEIAN, K ;
DJUROVICH, PI ;
GARCES, FO ;
CARLSON, G ;
WATTS, RJ .
INORGANIC CHEMISTRY, 1991, 30 (08) :1685-1687
[10]  
Dunning T. H., 1976, MODERN THEORETICAL C, V2