Photophysical Properties and OLED Applications of Phosphorescent Platinum(II) Schiff Base Complexes

Abstract

The syntheses, crystal structures, and detailed investigations of the photophysical properties of phosphorescent platinum(II) Schiff base complexes are presented. All of these complexes exhibit intense absorption bands with lambda(max) in the range 417-546 nm, which are assigned to states of metal-to-ligand charge-transfer ((1)MLCT) (1)[Pt(5d)-->pi*(Schiff base)] character mixed with (1)[lone pair(phenoxide)-->pi*(imine)] charge-transfer character. The platinum(II) Schiff base complexes are thermally stable, with decomposition temperatures up to 495 degrees C, and show emission lambda(max) at 541-649 nm in acetonitrile, with emission quantum yields up to 0.27. Measurements of the emission decay times in the temperature range from 130 to 1.5 K give total zero-field splitting parameters of the emitting triplet state of 14-28 cm(-1). High-performance yellow to red organic light-emitting devices (OLEDs) using these platinum(II) Schiff base complexes have been fabricated with the best efficiency up to 31 cd A(-1) and a device lifetime up to 77 000 h at 500 cd m(-2).

Switching On Luminescence by the Self‐Assembly of a Platinum(II) Complex into Gelating Nanofibers and Electroluminescent Films

“…Nonetheless, our devices perform quite well in comparison to sublimed platinum(II) complexes with N^C^N tridentate ligands (h c,max = 15-40 cd A À1 , L max = 3500-12 100 cd m À2 ) [16] or O^N^N^O Schiff base tetradentate units (h c,max = 1.6-31 cd A À1 , L max = 3000-20 000 cd m À2 ). [17] The efficiency of small-molecule OLEDs is higher owing to a more sophisticated device configuration. However, solution-processable emitters would enable a cost-effective fabrication.…”

Lumineszenz eines Platin(II)‐Komplexes in gelierenden Nanofasern und elektrolumineszierenden Filmen

“…[17] Die Effizienz von OLEDs mit kleinen Molekülen ist wegen ihrer anspruchsvollen Struktur höher, doch würden in Lösung prozessierbare Emitter eine kostengünstigere Herstellung ermöglichen.…”

Application of [Pt(II)(Tetra-Tert-Butylsalophen)] Complex within Organic Devices: Deep Red Emission, Bistable Light-Emitting Diodes and Operational Stability

“…The doping rate of the emissive layer plays a key role in the efficiency and the color emission of devices. It was demonstrated that the device efficiency increased with a concentration of platinum (II) dopant, up to 5 wt % or 6 wt % depending on the platinum(II) complex [16]. By considering a 6 wt % concentration of [Pt] (with Alq3 number density ~10 21 cm −3 [17]) and by assuming that the Ptcomplexes do not aggregate, the number density of Pt-complex is estimated at about 6.10 19 [Pt]/cm 3 and the average distance between neighboring complexes at ~ 3 nm.…”

“…Thereby, the effective distance over which the energy transfers between complexes (estimated at 3 nm) would be higher than the radius of triplet-triplet annihilation (<1 nm through Dexter mechanism) [18][19][20]. Furthermore, the steric hindrance between adjacent molecules induced by the tert-butyl substituents of [Pt] tends to limit the formation of [Pt] aggregates and hence reduces aggregation-induced phosphorescence quenching in thin solid film [15,16]. Consequently, doping rate of [Pt] is fixed at 6 wt % to maximize the performance of the devices.…”

“…Based on C. Che et al research on phosphorescent Pt(II) Schiff Base complexes [16], we synthetized [Pt(II)(tetra-tert-butylsalophen)] named [Pt] (Scheme 1) which is thermally stable (Td = 390 • C). Time-dependent density functional theory (TD-DFT) calculations [15] have been performed in order to assign the different electronic transition of [Pt].…”