Highly Efficient and Long‐Range Charge‐Transfer Complex Emission Between Two Blue Phosphorescent Emitters for White Organic Light‐Emitting Diodes

Abstract

Herein, the authors report on charge-transfer (CT) complex emission-based organic light-emitting diodes (OLEDs), which emit light by electric field-induced intermolecular CT complex formation in the light-emitting layer. Two phosphorescent materials are chosen to have energy level offset for the CT complex formation. This process generates the CT complex, which efficiently emits only in the electroluminescent device by electric-field-induced complex formation. A phenylpyridine-ligand-based Ir compound and phenylimidazole-based Ir compounds are selected as the CT complex-forming materials, and the CT complex exhibits yellow emission under an electric field. Moreover, the doping of the two compounds in the host material produces white OLEDs, exhibiting both blue emission and yellow emission at a quantum efficiency of 13.7%. In particular, the color of the CT complex device can be tuned by the content of each material in the emitting layer. As an initial result, the quantum efficiency is acceptable, and further material development would enhance the quantum efficiency of the CT complex OLEDs. This light-emitting device can be used in various applications, e.g., a mono-color or a white-color light-emitting diode.

Blue Iridium (III) Phosphorescent OLEDs with High Brightness Over 10 000 cd m−2 and Ultralow Efficiency Roll‐Off

“…However, complexes 4 and 6 exhibited a red-shifted emission and complex 3 showed a vibronic-structural emission spectra, indicating that the polarity of the solvent and the molecular packing styles in the solid condition may also affect the emissive state and in turn the emission spectra. [38,43,49,50] Specifically, complexes 3 and 6 exhibit almost unity internal quantum efficiency with short excited state lifetime value down to 1 µs in the 10 wt% doping in co-host (mCBP: B4PymPm = 1:1) thin-film, indicating a high k r of up to 10 6 s −1 (see Figure 2d and Table 2), highly comparable to the most advanced iridium(III), [51][52][53][54][55] platinum(II), [56][57][58] and TADF-gold(III) emitters. [59][60][61] Such observations suggested that the short-excited state properties of the complexes are also beneficial to reduce the annihilation process due to the rapid radiative decay.…”

Theoretical investigation of the influence of heterocycles on the radiative and non-radiative decay processes of iridium(iii) complexes

“…White OLEDs could be constructed by doping these Ir( iii ) complexes into the host material, which exhibited both blue emission and yellow emission with a quantum efficiency of 13.7%. 22 Strassner et al synthesized and characterized cyclometalated arylthiazole-based iridium( iii ) phosphorescent emitters and their emission behavior revealed emission maxima at 495 ± 5 nm. 23 Idris et al investigated the photophysical and electrochemical properties of N-heterocyclic carbene complexes of iridium( iii ) (Ir(C ^ C:) 3 (C^C: = N -phenyl, N -methyl-pyrazinoimidazol-2-yl(pmpz), N , N -di- p -tolyl-pyrazinoimidazol-2-yl (tpz))), namely, fac -Ir(pmpz) 3 and fac -Ir(tpz) 3 .…”

Selective Gain in a Periodic Array of Nano-organic Light-Emitting Diodes

“…Organic light-emitting diodes (OLEDs) have attracted extensive research interests due to their applications in efficient full-color displays, , solid-state lighting, − and liquid-crystal display backlighting sources. − OLEDs have multifold advantages, such as excellent flexibility, positive luminescence, simple preparation process, large-area devices, and a large variety of material availability. − Although efficient OLEDs have been reported for a large variety of organic semiconductors and structural designs, and optically pumped microcavity lasers have been achieved with low thresholds, − electrically pumped organic lasers have not been officially reported. Reasons may include the lower injection current than the threshold required by the lasing actions, and the designed structures cannot supply sufficiently high efficiency of optical confinement and optical gain.…”