Rausch, A. F. and Homeier, H. H. H. and Djurovich, P. I. and Thompson, M. E. and Yersin, Hartmut (2007) Spin-orbit coupling routes and OLED performance - Studies of blue light emitting Ir(III) and Pt(II) complexes. In: Kafafi, Z. H. and So, F., (eds.) Organic Light Emitting Materials and Devices XI. Proceedings of SPIE, 6655. SPIE, 66550F-1.
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In this study, detailed spectroscopic investigations of the blue emitting compounds Ir(4,6-dFppy)₂(pic) and Pt(4,6-dFppy)(acac) are presented. Due to spin-orbit coupling (SOC) of the emitting triplet state with higher lying singlet states both complexes show an intense phosphorescence and are utilized as emitters in organic light emitting diodes (OLEDs). Distinct differences with respect to important photophysical properties are found for the two compounds.
For example, the (distorted) octahedral Ir(4,6-dFppy)₂(pic) complex exhibits a shorter emission decay time and shows a larger zero-field splitting (ZFS) than the (distorted) square planar Pt(4,6-dFppy)(acac) complex (τ(Ir) = 0.4 μs and τ(Pt) = 3.6 μs of the respective shortest-lifed triplet substate; ΔE(ZFS, Ir) = 67 cm⁻¹, ΔE(ZFS, Pt) = 8 cm⁻¹). This behaviour is connected with the extent of metal-to-ligand charge transfer (MLCT, dπ*) character in the emitting triplet state. High MLCT character usually results in a high emission decay rate and indicates a good suitability as OLED emitter material. Of crucial importance in this respect is the effectiveness of SOC. In this study it is shown that the SOC routes depend on the coordination geometry of the emitter compound. In particular, the couplings can be more effective in (distorted) octahedral than in (distorted) square planar compounds. Hence, the photophysical differences of Ir(4,6-dFppy)₂(pic) compared to Pt(4,6-dFppy)(acac) can be rationalized. Moreover, this investigation shows that the analysis of SOC paths provides general guidelines for the design of efficient emitters for OLED applications.
|Item Type:||Book Section|
|Institutions:||Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry III - Physical Chemistry (Light and Matter) > Prof. Dr. Hartmut Yersin|
|Subjects:||500 Science > 540 Chemistry & allied sciences|
|Refereed:||Yes, this version has been refereed|
|Created at the University of Regensburg:||Partially|
|Owner:||Prof. Dr. Hartmut Yersin|
|Deposited On:||17 Dec 2010 08:09|
|Last Modified:||17 Dec 2010 08:09|