Rigidity‐Enhanced Narrowband Iridium(III) Complexes with Finely‐Optimized Emission Spectra for Efficient Pure‐Red Electroluminescence

Abstract

Attaining phosphorescent materials with narrowband emission is crucial for advancing wide‐color‐gamut organic light‐emitting diode (OLED). Herein, a rigid modification strategy is introduced for iridium(III) complexes to achieve the narrowband red emission with negligible 0–1 peak. By introducing the rigid indolo[3,2,1‐jk]carbazole (ICz) into the cyclometalated ligand, Ir(III) complexes, ICziq‐Ir and ICzqz‐Ir, exhibit pure red phosphorescence with emission peaks at 608 and 613 nm and full widths at half‐maximum (FWHMs) of 37 and 38 nm (0.12 and 0.13 eV) in toluene, respectively. Furthermore, the specific site modification of ICzqz‐Ir greatly suppresses the high‐frequency vibration of the structure, resulting in the narrowband photoluminescent spectrum close to the Gaussian distribution with superior color purity. The OLEDs utilizing ICziq‐Ir and ICzqz‐Ir demonstrate maximum external quantum efficiencies of 21.4 and 17.8% as well as mild efficiency roll‐off. Remarkably, the electroluminescence spectra exhibit similar narrowband red emission with FWHMs of 37 and 43 nm and CIE coordinates of (0.65, 0.35) and (0.66, 0.34), attesting to the excellent color purity of the phosphorescent OLEDs.

Efficient narrowband yellow organic light-emitting diodes based on iridium(iii) complexes with the rigid indolo[3,2,1-jk]carbazole unit

“…This narrowing can also be observed in the PL spectra measured at 77 K in DCM, as the destabilization of 3 MLCT excited states and significant suppression of molecular vibrations lead to an increase of 3 LC components. 25 As a consequence, narrower FWHMs of 24 and 31 nm are shown by the enhancement of the main peak and the weakening of the shoulder one.…”

“…2). The intense absorption bands between 330 and 400 nm can be assigned to π–π* and n–π* transitions of the ligand centered ( 1 LC) states originating from cyclometalated ligands, 25 while the weak absorption bands between 400 and 500 nm correspond to spin-allowed 1 MLCT, spin-forbidden 3 MLCT and 3 LC transitions, arising from the strong spin–orbital coupling (SOC) effect of the transition metal iridium. 32,33 The absorption peaks of the Ir( iii ) complexes remain essentially unchanged as the solvent polarity increases (Fig.…”

“…17–21 In our previous work, we incorporated the planar and rigid aromatic indolo[3,2,1- jk ]carbazole (ICz) unit into Ir( iii ) complexes, and the corresponding OLEDs exhibited good performances with external quantum efficiencies (EQEs) of over 20% and full width at half maximum (FWHM) bands below 50 nm. 22–25 These results indicate incorporating rigid ICz units can contribute to the structural rigidity and increase the proportion of 3 LC transitions, thereby achieving narrow emissions.…”

High-performance solution-deposited ambipolar Ir(iii) complex phosphors with aggregation-induced phosphorescence enhancement behavior based on an N–PO resonant variation skeleton

“…Zheng and co-workers successively reported a series of carbazole-based Ir( iii ) complexes based on fused carbazole units. 48–50 Their optimal vacuum-deposition OLED can give EL efficiencies with η ext of 31.3%, η L of 103.8 cd A −1 and η P of 98.8 lm W −1 , respectively. However, most of their optimal vacuum-deposition OLEDs give EQEs less than 26%.…”

Three-Charge (0, −1, −2) Ligand-Based Binuclear and Mononuclear Deep-Red Phosphorescent Iridium Complexes Bearing Benzo[d]oxazole-2-Thiol Ligand

“…Phosphorescent metal iridium complexes have been widely used as ideal luminescent materials in organic light-emitting diodes (OLEDs), − biological imaging, − solar cells, − and photocatalysts , due to their stable octahedral geometry, excellent optical properties, and rich adjustable chemical structures. For classical phosphorescent iridium complexes with three monoanionic (−1, −1, −1) ligands, such as typical green-emitting materials fac -Ir­(ppy) 3 and Ir­(ppy) 2 acac (Scheme a), a nonluminescent chloro-bridged binuclear complex intermediate is usually formed during their synthetic reaction, and then a luminescent mononuclear complex is further formed (Scheme a).…”