Spin mixed charge transfer states of iridium complex Ir(ppy)3: transient absorption and time-resolved photoluminescence

Mohan Singh Mehata; Yang Yang; Zong-Jing Qu; Jun-Sheng Chen; Feng-Jiao Zhao; Ke-Li Han

doi:10.1039/C5RA01404B

Spin mixed charge transfer states of iridium complex Ir(ppy)₃: transient absorption and time-resolved photoluminescence†

Mohan Singh Mehata,*^ab Yang Yang,^a Zong-Jing Qu,^a Jun-Sheng Chen,^a Feng-Jiao Zhao^a and Ke-Li Han*^a

* Corresponding authors

^a State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics (DICP), Chinese Academy of Sciences, Dalian 116023, China
E-mail: msmehata@gmail.com, klhan@dicp.ac.cn

^b Laser-Spectroscopy Laboratory, Department of Applied Physics, Delhi Technological University, Bawana Road, Delhi 110042, India

Abstract

Nanosecond transient absorption and time-resolved spectroscopic techniques were applied to study an organometallic phosphorescent emitter Ir(ppy)₃ complex, tris[2-phenylpyridinato-C²,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 (³MLCT) states produced from a non-equilibrium ¹MLCT state following fast intersystem crossing (ISC), whereas the ¹MLCT 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.

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Article information

DOI: https://doi.org/10.1039/C5RA01404B
Article type: Communication
Submitted: 23 Jan 2015
Accepted: 07 Apr 2015
First published: 13 Apr 2015

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RSC Adv., 2015,5, 34094-34099

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Spin mixed charge transfer states of iridium complex Ir(ppy)₃: transient absorption and time-resolved photoluminescence

M. S. Mehata, Y. Yang, Z. Qu, J. Chen, F. Zhao and K. Han, RSC Adv., 2015, 5, 34094 DOI: 10.1039/C5RA01404B

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