Bauer, Reinhard and Finkenzeller, Walter J. and Bogner, Udo and Thompson, Mark E. and Yersin, Hartmut (2008) Matrix influence on the OLED emitter Ir(btp)(2)(acac) in polymeric host materials - Studies by persistent spectral hole burning. ORGANIC ELECTRONICS, 9 (5). pp. 641-648. ISSN 1566-1199,
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Fundamental photophysical properties of the phosphorescent organometallic complex Ir(btp)(2)(acac) doped in the polymeric matrices PVK, PFO, and PVB, respectively, are investigated. PVK and PFO are frequently used as host materials in organic light emitting diodes (OLEDs). By application of the laser spectroscopic techniques of phosphorescence line narrowing and persistent spectral hole burning - improved by a synchronous scan technique we studied the zero-field splitting (ZFS) of the T-1 state into the substates I, II, and III. Thus, we were able to probe the effects of the local environment of the emitter molecules in the different amorphous matrices. The magnitude of US is determined by the extent of spin-orbit coupling (SOC) of the T-1 state to metal-to-ligand charge transfer (MLCT) states. Only by mixings of MLCT singlets, a short-lived and intense emission of the triplet state to the singlet ground state becomes possible. Thus, sufficiently large ZFS is crucial for favorable luminescence properties of emitter complexes for OLED applications. The analysis of the spectral hole structure resulting from burning provides information about the ZFS values and their statistical (inhomogeneous) distribution in the amorphous matrices. For Ir(btp)(2)(acac), we found a significant value of approximate to 18 cm(-1) for the splitting between the substates II and III for all three matrices. Interestingly, for PVK the width of the US distribution is found to be 14 cm(-1) - almost twice as large as for PFO and PVB. Consequently, for a considerable fraction of Ir(btp)(2)(acac) molecules in PVK, the ZFS is relatively small and thus, the effective SOC is weak. Therefore, it is indicated that a part of the emitter molecules shows a limited OLED performance. (C) 2008 Elsevier B.V. All rights reserved.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | CYCLOMETALATED IRIDIUM COMPLEXES; TRIPLET-STATE; DEVICES; SPECTROSCOPY; RELAXATION; EXCITATION; PERYLENE; EMISSION; DYNAMICS; DIODES; triplet emitter; OLED; persistent spectral hole burning; zero-field splitting; polyvinylbutyral; poly-N-vinylcarbazol; poly(9.9-dioctylfluoren-2,7-diyl); Ir(btp)(2)(acac); phosphorescence line narrowing; metal-to-ligand charge transfer; PVK; PVB; PFO; MLCT; ZFS; spin-orbit coupling; SOC |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry III - Physical Chemistry (Molecular Spectroscopy and Photochemistry) Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry III - Physical Chemistry (Molecular Spectroscopy and Photochemistry) > Prof. Dr. Hartmut Yersin |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 23 Oct 2020 07:09 |
| Last Modified: | 23 Oct 2020 07:09 |
| URI: | https://pred.uni-regensburg.de/id/eprint/30252 |
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