Share Email Print

Proceedings Paper

Spin-orbit coupling routes and OLED performance: studies of blue-light emitting Ir(III) and Pt (II) complexes
Author(s): Andreas F. Rausch; Herbert Homeier; Peter I. Djurovich; Mark E. Thompson; Hartmut Yersin
Format Member Price Non-Member Price
PDF $17.00 $21.00

Paper Abstract

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; Δ(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.

Paper Details

Date Published: 26 October 2007
PDF: 16 pages
Proc. SPIE 6655, Organic Light Emitting Materials and Devices XI, 66550F (26 October 2007); doi: 10.1117/12.731225
Show Author Affiliations
Andreas F. Rausch, Univ. Regensburg (Germany)
Herbert Homeier, Univ. Regensburg (Germany)
Peter I. Djurovich, Univ. of Southern California (United States)
Mark E. Thompson, Univ. of Southern California (United States)
Hartmut Yersin, Univ. Regensburg (Germany)

Published in SPIE Proceedings Vol. 6655:
Organic Light Emitting Materials and Devices XI
Zakya H. Kafafi; Franky So, Editor(s)

© SPIE. Terms of Use
Back to Top