Leitl, Markus J. and Krylova, Valentina A. and Djurovich, Peter I. and Thompson, Mark E. and Yersin, Hartmut (2014) Phosphorescence versus Thermally Activated Delayed Fluorescence. Controlling Singlet-Triplet Splitting in Brightly Emitting and Sublimable Cu(I) Compounds. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136 (45). pp. 16032-16038. ISSN 0002-7863,
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Photophysical properties of two highly emissive three-coordinate Cu(I) complexes, (IPr)Cu(py(2)-BMe2) (1) and (Bzl-3,5Me)Cu(py(2)-BMe2) (2), with two different N-heterocyclic (NHC) ligands were investigated in detail (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; Bzl-3,5Me = 1,3-bis(3,5-dimethylphenyl)-1H-benzo[d]imidazol-2-ylidene; py2-BMe2 = di(2-pyridyl)dimethylborate). The compounds exhibit remarkably high emission quantum yields of more than 70% in the powder phase. Despite similar chemical structures of both complexes, only compound 1 exhibits thermally activated delayed blue fluorescence (TADF), whereas compound 2 shows a pure, yellow phosphorescence. This behavior is related to the torsion angles between the two ligands. Changing this angle has a huge impact on the energy splitting between the first excited singlet state S1 and triplet state T1 and therefore on the TADF properties. In addition, it was found that, in both compounds, spinorbit coupling (SOC) is particularly effective compared to other Cu(I) complexes. This is reflected in short emission decay times of the triplet states of only 34 mu s (1) and 21 mu s (2), respectively, as well as in the zero-field splittings of the triplet states amounting to 4 cm(1) (0.5 meV) for 1 and 5 cm(1) (0.6 meV) for 2. Accordingly, at ambient temperature, compound 1 exhibits two radiative decay paths which are thermally equilibrated: one via the S-1 state as TADF path (62%) and one via the T1 state as phosphorescence path (38%). Thus, if this material is applied in an organic light-emitting diode, the generated excitons are harvested mainly in the singlet state, but to a significant portion also in the triplet state. This novel mechanism based on two separate radiative decay paths reduces the overall emission decay time distinctly.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | COPPER(I) COMPLEXES; ELECTROLUMINESCENT DEVICES; PHOTOPHYSICAL PROPERTIES; OLED APPLICATIONS; EMISSION; LUMINESCENCE; LIGANDS; DIODES; EMITTERS; EFFICIENCY; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | 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: | 07 Aug 2019 13:14 |
| Last Modified: | 07 Aug 2019 13:14 |
| URI: | https://pred.uni-regensburg.de/id/eprint/9209 |
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