Design and Synthesis of Heteroleptic Iridium(III) Phosphors for Efficient Organic Light-Emitting Devices

Abstract

The phosphorescent emitters are essential to realize energy-efficient display and lighting panels. The solution processability is of particular interest for large-scale and low-cost production. Here, we present a series of the heteroleptic iridium (Ir) complexes, Ir(ppy)L1, Ir(ppy)L2, and Ir(ppy)L3, using the new ancillary ligands, including 1-(2-chlorophenyl)-5-hydroxy-3-methyl-1H-pyrazole-4-carbaldehyde (L1), 5-hydroxy-3-methyl-1-(p-tolyl)-1H-pyrazole-4-carbaldehyde (L2), and 5-hydroxy-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde (L3). Their photophysical and electrochemical properties were systematically characterized, followed by comparing with those predicted by density functional theory simulations using hybrid functionals. Among the three phosphors synthesized, Ir(ppy)L1 exhibits the highest photoluminescence quantum yield (Φ = 89%), with an exciton lifetime of 0.34 μs. By using 4,4'-bis(carbazole-9-yl)biphenyl as the host material, we demonstrate high current efficiencies of 64 and 40 cd A at 100 cd m in its vacuum-evaporated and solution-processed organic light-emitting devices, respectively, revealing the promise for large-area light sources.

Aggregation Induced Emission (AIE) Properties of Heteroleptic IrIII Complexes With Non‐chromophoric Ligand Effect: Synthesis, Characterization and Photophysical Investigations

“…The Photoluminescence quantum yields ( Φ PL ) for solid state were performed using integrating sphere according to relative method by the following equation …”

“…The complexes were characterized by elemental analysis, FT‐IR, Thermogravimetric Analyzer (TGA), Differential Scanning colorimetry (DSC), mass spectrometry, 1 H‐NMR, 13 C‐NMR and UV‐visible analysis. The 1 H‐NMR spectra of the ligands showed the characteristics of an enolic proton at δ 11.34 – δ 11.44‐ which disappeared during complexation with the Ir III metal ion. FT‐IR spectra of the complexes show band between 1504‐1527cm ‐1 which is assigned to aromatic C=C bond.…”

Highly Efficient and Stable Green Phosphorescent Light‐Emitting Diodes Based on Solution‐Processable Ir(III) Complexes with Electron‐Transporting Ancillary Ligands

“…Ir(CF 3 BNO) 2 ‐pop and Ir(BNO) 2 ‐pop dissolving in toluene exhibited featureless strong PL emission with peaks at 524 and 526 nm, respectively, suggesting that the emission profile of Ir(III) complexes located from 3 MLCT or ligand‐to‐ligand charge‐transfer ( 3 LLCT) state and not from the triplet 3 LC. [ 39 ] In DCM solution, the Ir(CF 3 BNO) 2 ‐pop shows greater positive solvatochromic shift than Ir(BNO) 2 ‐pop perhaps due to presence of strongly electron withdrawing CF 3 group on the main ligand. Additionally, the narrow full width at half maximum values were observed; 67 and 70 nm for Ir(CF 3 BNO) 2 ‐pop and Ir(BNO) 2 ‐pop, respectively.…”

Unusual formation of Ir(III) complexes with non‐symmetrical NacNac ligands: Synthesis, characterization, and evaluation of catalytic activity in transfer hydrogenation reduction reactions

“…10 Additionally, iridium complexes have photophysical properties due to the electron-rich character of the Nac-Nac fragment. [11][12][13][14][15] NacNac-iridium complexes have been widely investigated as photo-sensitizers 16 and as agents of photo-luminescence [17][18][19][20] and red-and near-infrared phosphorescence. Moreover, some of them have been evaluated for anti-cancer [21][22][23][24][25] and anti-bacterial activity.…”