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Efficient solution-processible yellow/orange emissive phosphors are highly required in solution-processed phosphorescent organic light-emitting diodes ( s -PhOLEDs). With respect to phenyl pyridine (ppy)-type Ir(III) complexes, 2-(9,9-diethylfluoren-2-yl)pyridine (Flpy)-type Ir(III) complexes have huge potential in yellow/orange s -PhOLEDs due to their extended conjugation and excellent solubility in common organic solvents. Herein, a new series of phosphorescent Ir(III) complexes, i.e. Ir(Flpy) 2 pic-N O, Ir(Flpy-CF 3 ) 2 pic-N O, Ir(Flpy-CF 3 ) 2 dbm and Ir(Flpy-CF 3 ) 2 acac, based on Flpy main ligand and picolinic N-oxide (pic-N O), acetylacetone (acac), and dibenzoyl methane (dbm) ancillary ligands are synthesized. The photophysical, electrochemical, and electroluminescent (EL) properties of these phosphorescent Ir(III) complexes are investigated in details. By introducing the CF 3 group in Flpy ligand and varying the ancillary ligands, the emission spectra of these phosphorescent complexes are tuned in a large range with EL emission peaks from 544 nm to 588 nm. The s -PhOLEDs employing these phosphors show promising EL performance with maximum external quantum efficiency (EQE) from 15.4% to 23.7% and high power efficiency from 61.9 l m W −1 to 80.4 l m W −1 . These highly efficient phosphorescent Ir(III) complexes may serve as ideal chromaticity components in solution-processed full-color displays and lighting devices. [ABSTRACT FROM AUTHOR]

The exploitation of soluble and efficient deep-red phosphorescent emitters is of paramount importance for solution-processed organic light-emitting diodes (OLEDs) applied in both high-quality RGB displays and high color-rendering-index (CRI) solid-state lighting source. In this work, a new deep-red heteroleptic iridium(III) complex, i.e. bis[2,5-di(4-hexylthiophen-2-yl)pyridine][acetylacetonate]iridium(III) [Ir(ht-5ht-py) 2 (acac)], has been synthesized and successfully used to fabricate solution-processed saturated red and white organic light-emitting diodes (WOLEDs). The long alkyl side-chains of Ir(ht-5ht-py) 2 (acac) render its excellent solubility in common organic solvents and good compatibility with common host materials. The solution-processed red OLED based on Ir(ht-5ht-py) 2 (acac) exhibited a decent external quantum efficiency of 8.2% and a power efficiency of 6.5 lm/W, with satisfactory Commission International de L’Eclairage (CIE) coordinates of (0.68, 0.31) for saturated red emission. Furthermore, the prepared multiple-phosphors-doped WOLED with Ir(ht-5ht-py) 2 (acac) as the red emitter showed an excellent high color rendering index (CRI) value of 89 as well as low color-correlated temperature (CCT) of 2331 K, which can meet the call for physiologically-friendly indoor illumination. [ABSTRACT FROM AUTHOR]

Highlights: [•] Phase separation in solution-processed OLEDs is restrained by adjusting processing solvent. [•] The solution-processed emissive layer is denser than the vacuum-evaporated counterpart. [•] Efficient solution-processed blue OLEDs with halogen-free solvent are achieved with power efficiency of 15.6lm/W. [Copyright &y& Elsevier]

The optical waveguide effect limits strongly the light out-coupling efficiency in organic light-emitting diodes (OLEDs). Patterning the transparent ITO anode on the substrate is a potential way to weaken the optical waveguide effect and enhance the light-emitting efficiency of OLEDs. Herein, the one-dimensional (1D) and two-dimensional (2D) periodic patterned ITO/glass substrates have been successfully fabricated by using the holographic lithography technology and used to fabricate highly efficient OLEDs. The periodic micro-structured ITO layer could manipulate the total internal reflection at the organic/ITO interfaces and enhance the scattering effect so as to improve the light out-coupling efficiency. The effect of different micro-structured ITO layers on the light-emitting efficiency was investigated in a kind of orange phosphorescent OLEDs based on the m-MTDATA:Ir(Flpy-CF 3) 3 /TmPyPB emissive layer. The orange OLEDs employing the 1D grating and 2D lattice patterned ITO/glass substrates show the external quantum efficiencies (EQEs) of 25.12% and 29.61%, respectively. The orange OLEDs fabricated with the 2D hole patterned ITO glass substrate demonstrate the best light-emitting performance with a current efficiency of 100.55 cd A−1, an EQE of 31.39% and a power efficiency of 121.50 lm W−1, respectively. The 1D grating and 2D patterned ITO microstructures have been successfully fabricated with the holographic lithography. The phosphorescent OLEDs employing the periodic patterned ITO/glass substrate improve the light out-coupling leading to signigicantly increased light-emitting efficiency. A power efficiency of 121.50 lm W−1 is achieved for yellow phosphorescent OLEDs employing the 2D hole-patterned ITO/glass substrate. Image 1 • The 1D and 2D patterned ITO/glass substrate via holographic lithography enhances the outcoupling of emitted light from the device structure. • The light-emitting efficiencies are greatly increased by using the patterned ITO/glass substrate. • A power efficiency of 121.50 lm W−1 and an external quantum efficiency of 31.39% are achieved for yellow phosphorescent OLEDs employing the 2D hole-patterned ITO/glass substrate. [ABSTRACT FROM AUTHOR]