Effiziente Triplett-Emitter für Organische Leuchtdioden auf der Basis von Iridium(III)-Komplexen (English shop)

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The development of organic light emitting diodes (OLEDs) as lighting and display elements has been greatly advanced by the use of iridium(III) complexes as emitter materials. The advantages of OLEDs lie above all in their very thin design and their extremely energy-saving mode of operation, as well as in the possibility of manufacturing them over large areas.

This work comprised the synthesis and characterisation of modified Ir(ppy)3 complexes (fac‑tris[2‑(2‑pyridyl‑kN)phenyl]iridium(III)) as well as novel five-membered heterocyclic ring complexes based on fac‑tris(2‑methylthiazol‑4‑yl‑kN)iridium(III) for application in OLEDs. Both homoleptic and heteroleptic complexes of the two substance classes were synthesised and the distribution of the electron density within the complexes was investigated by means of 13C NMR spectroscopy. Conclusions regarding the redox behaviour were drawn from cyclic voltammetry measurements. In addition, variations in the bond lengths and angles of selected complexes were determined by X-ray diffraction.

Against the background of electro-optical applications, attempts to alter the emission wavelength were also a focus of the investigations. The influence of electron-withdrawing and electron-donating substituents at various positions within the ligands was examined experimentally by absorption and emission spectroscopy, both in solution and in an inert matrix. Changes in the optical properties were successfully correlated with calculated emission wavelengths and cyclic voltammetry results, and the influence of the substituents on the positions of the frontier orbital levels HOMO and LUMO was highlighted. Using the novel five-membered heterocyclic ring system as emitter material in an OLED, efficiencies of 39.0 cd × A–1 and 30.6 lm × W–1 respectively were achieved at 500 cd × m2.