A solution-processed bis-tridentate iridium(iii) complex-cored dendrimer for green OLEDs

Abstract

We report a solution-processable dendronised bis-tridentate iridium(iii) complex composed of a bis(imidazolyl)phenyl ligand with a first-generation biphenyl dendron containing t-butyl surface groups and a 2-pyrazolyl-6-phenylpyridine co-ligand.

Novel Ir(III) Complexes with NHC-Based Ancillary Ligands for Efficient Nondoped OLEDs

“…Moreover, devices N1 and N2 realize good EL efficiencies with a maximum PE of 20.8 and 27.8 lm W –1 , a CE of 16.6 and 24.3 cd A –1 , and an external quantum efficiency (EQE) of 4.9 and 7.2%. N3 achieves the highest EL efficiency among N1 – N3 with a maximum PE of 30.7 lm W –1 , a maximum CE of 27.0 cd A –1 , and an EQE of 8.0%, which are equivalent to previously reported Ir­(III) complex-based outstanding nondoped OLEDs, as listed in Table S4. − Compared to the PE of the nondoped OLED employing tBu-Ir-FTZ , a maximum PE of N3 magnifies 1.9-folds. These results indicate that selecting NHC units functionalized with electron-deficient units as ancillary ligands is crucial to accomplishing eminent EL efficiency.…”

Blue Light-Emitting Cyclometalated Spirofluorenexanthene Imidazolylidene Platinum(II) Complexes

“…Typically, such materials possess several advantages, which lead to innovations, especially in the area of electronic devices like lighting, screens, or sensors. , Luminescent metal complexes are well-established emitters for organic light-emitting diodes (OLEDs), taking advantage of the heavy-metal atom-induced spin–orbit coupling (SOC) effect . In the past decade, large libraries of iridium­(III) − and platinum­(II) − complexes with tridentate − and tetradentate ligands − were synthesized and investigated with respect to their photophysical properties. Meanwhile, purely organic emitters have overcome quantum efficiency limitations due to spin statistics utilizing specific molecular design strategies, separating the highest occupied molecular orbitals (HOMOs) from the lowest unoccupied molecular orbitals (LUMOs).…”

Effect of dendrimer generation and surface groups on the optoelectronic properties of green emitting bis-tridentate iridium(iii) complexes designed for OLEDs

“…We are only aware of one report at this time where a bis-tridentate iridium( iii ) complex has been dendronised leading to a solution processable light-emitting material. 24 In that report, a green emissive dendrimer composed of three first-generation biphenyl-based dendrons with t -butyl surface groups attached to one of the tridentate ligands had a PLQY of around 70% in solution, which decreased to 22% in neat film. Evidence for the decrease in the film PLQY being due to intermolecular interactions of the emissive cores in the solid state was provided by the observation that when the dendrimer was blended into tris[4-carbazoyl-9-ylphenyl]amine (TCTA) the PLQY increased to near the value in the solution.…”

“…34 and hence 1 , 2 , 3 and 4 had M̄ v values (based on M̄ n ) of 1482, 2365, 2760 and 3937. Using M̄ v and a combination of the Hester–Mitchell equation and Mark-Houwink relationship, 24 dendrimers 2 , 2 , 3 and 4 were calculated to have hydrodynamic radii in tetrahydrofuran of 8 Å, 11 Å, 12 Å, and 14 Å, respectively. There are two trends to note from these radii, first, the second-generation dendrimers are larger than the first-generation materials, and second, the dendrimers with the 2-ethylhexyloxy groups are larger than their equivalent generation with t -butyl surface groups.…”