Spin mixed charge transfer states of iridium complex Ir(ppy)3: transient absorption and time-resolved photoluminescenceElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ra01404b

• Main Authors: Mehata, Mohan Singh, Yang, Yang, Qu, Zong-Jing, Chen, Jun-Sheng, Zhao, Feng-Jiao, Han, Ke-Li
• Format: Article
• Language: English
• ISSN: 2046-2069
• DOI: 10.1039/c5ra01404b

Nanosecond transient absorption and time-resolved spectroscopic techniques were applied to study an organometallic phosphorescent emitter Ir(ppy) 3 complex, tris[2-phenylpyridinato-C 2 ,N] iridium( iii ) dissolved in tetrahydrofuran (THF) under degassed conditions at ambient temperature. Transient absorption curves obtained at a pump pulse of 355 nm and at a probe wavelength of 430-600 nm show positive and negative signals, indicating triplet-triplet (T-T) absorption and triplet-singlet (T-S) emission. Tri-exponential global fitted transient absorption curves and time-resolved photoluminescence (PL) decays demonstrated the presence of four close low lying triplet states, of which, two emit green PL with a lifetime of 210 ns and 1.71 μs. The emitting states are spin mixed metal-to-ligand charge transfer ( 3 MLCT) states produced from a non-equilibrium 1 MLCT state following fast intersystem crossing (ISC), whereas the 1 MLCT state is produced directly and indirectly depending on the excitation wavelength. Moreover, the electronic structures for the ground state and low-lying excited states of Ir(ppy) 3 were studied using quantum chemistry calculations. Transient absorption and time-resolved PL together with quantum chemistry calculations demonstrated the existence of multiple low-lying metal-to-ligand charge transfer states of Ir(ppy) 3 .