Exploiting Photo- and Electroluminescence Properties of FIrpic Organic Crystals

Abstract

In this work, we investigate the optical and structural properties of the well-known triplet emitter bis(4',6'-difluorophenylpyridinato)-iridium(III) picolinate (FIrpic), showing that its ability to pack in two different ordered crystal structures promotes attractive photophysical properties that are useful for solid-state lighting applications. This approach allows the detrimental effects of the nonradiative pathways on the luminescence performance in highly concentrated organic active materials to be weakened. The remarkable electro-optical behavior of sky-blue phosphorescent organic light-emitting diodes incorporating crystal domains of FIrpic, dispersed into an appropriate matrix as an active layer, has also been reported as well as the X-ray diffraction, nuclear magnetic resonance, electro-ionization mass spectrometry, and scanning electron microscopy analyses of the crystalline samples. We consider this result as a crucial starting point for further research aimed at the use of a crystal triplet emitter in optoelectronic devices to overcome the long-standing issue of luminescence self-quenching.

Nanostructuring Iridium Complexes into Crystalline Phosphorescent Nanoparticles: Structural Characterization, Photophysics, and Biological Applications

“…As far as the nanostructures are concerned, in the case of FI-Nps and PPY-Nps the aggregation induces both a change in the relative intensity of the vibronic peaks and the appearance of a broad shoulder extending to lower energy (Figure A,B). The presence of a lower-energy band has been recently reported for highly doped FI films, and it was ascribed to the interaction between nearby cyclometalating ligands in the FI crystalline domains of the films . A similar scenario can be proposed for these highly crystalline nanoparticles, further corroborating the hypothesis that the observed changes in the emission properties are due to stronger intermolecular interactions present in the tightly packed core of the nanoparticles.…”

“…In particular, FI-Nps and PPY-Nps appear to have a higher propensity to form highly ordered nanocrystals than MDQ-Nps which displays only one narrow reflection peak at 11.5° (2-theta) in the diffraction pattern. The comparison with diffraction data previously reported for FIrpic polymorphs confirms that FIrpic nanoparticles reproducibly crystallize in the monoclinic form of methanol solvate crystals, well-known to be stable also in the absence of solvent molecules . This evidence provided us further information about the structural organization of the molecules within the nanoparticle, suggesting that π–π stacking interactions among the phenylpyridine moieties play an important role in driving the assembly and stabilizing the nanostructure.…”

Unusual dual-emissive heteroleptic iridium complexes incorporating TADF cyclometalating ligands

“…Cationic cyclometalated Ir complexes with pendant ligands that show dual emission from ligand-centred (LC) and interligand charge transfer (ILCT) states have been synthesised and shown to function as sensors for biomolecules. 11 An iridium complex containing a dibenzoylmethane ancillary ligand has been reported to exhibit different emission spectra from two distinct polymorphs, related to the difference in π-stacking interactions in the solid state. 12 Iridium complexes have also been incorporated into polymer chains containing other emissive materials of different colours.…”

“…The target heteroleptic picolinate iridium complexes 2-6 were then synthesised (Scheme 1, Scheme 2) via the standard method. 26,27 Reaction of the ligands (7)(8)(9)(10)(11) with IrCl3•3H2O gave yellow precipitates presumed to be the intermediate μdichloro-bridged dimers. Picolinic acid was added and the solution heated to 110-130 ⁰C.…”

Ambient-Processed, Additive-Assisted CsPbBr3 Perovskite Light-Emitting Diodes with Colloidal NiOx Nanoparticles for Efficient Hole Transporting

“…Furthermore, Device-ND achieved the low light threshold voltage V T of 2.4 V, high luminance maximum (L max ) of 4456 cd/m 2 , and high current efficiency of 2.9 cd/A by adopting the NiO x NPs and the additive-assisted EML that gave a better hole transporting and high radiative recombination rate, respectively. It can be clearly observed that the threshold of the minority carrier (holes) injection Coatings 2020, 10, 336 6 of 8 at 2.4 V and the onset of majority carrier (electrons) injection at~2.3 V matched pretty well, which suggests that those negative effects such as Auger recombination (trions) and improper shift of exciton recombination zone can therefore be prevented [29,30]. Overall, compared with Device-PA, Device-ND had roughly 17-and 94-fold increased L max and η CE , respectively.…”