Search

High-efficiency narrowband near-ultraviolet (NUV) organic light-emitting diodes with high color purity have currently encountered great challenges. Here, using butyl (Bu) and cyanogen (CN) substituted strategy in the simplest polycyclic aromatic hydrocarbons of indolocarbazole (ICz), two simple emitters of BuICz and BuICzCN were demonstrated. This simple strategy was observed to enable both emitters to realize NUV emission at 380–381 nm with a small full width at half maximum (FWHM) of 21–23 nm and high photoluminescent quantum efficiency of 50%–59% in toluene solution. Furthermore, the BuICzCN doped devices exhibited a slightly blueshifted narrowband NUV electroluminescence at 388 nm with a small FWHM of 32.3 nm but a higher external quantum efficiency of 3.92% in comparison with the BuICz doped devices. This work provides a path to realize high-performance narrow-band NUV emission. [ABSTRACT FROM AUTHOR]

The correlation between molecular packing structure and its room-temperature phosphorescence (RTP), hence rational promotion of the intensity, remains unclear. We herein present racemism enhanced RTP chiral chromophores by 2,2-bis-(diphenylphosphino)-1,1-napthalene (rac-BINAP) in comparison to its chiral counterparts. The result shows that rac-BINAP in crystal with denser density, consistent with a long standing Wallach's rule, exhibits deeper red RTP at 680 nm than that of the chiral counterparts. The cross packing between alternative R- and S- forms in rac-BINAP crystal significantly retards the bimolecular quenching pathway, triplet-triplet annihilation (TTA), and hence suppresses the non-radiative pathway, boosting the RTP intensity. The result extends the Wallach's rule to the fundamental difference in chiral-photophysics. In electroluminescence, rac-BINAP exhibits more balanced fluorescence versus phosphorescence intensity by comparison with that of photoluminescence, rendering a white-light emission. The result paves an avenue en route for white-light organic light emitting diodes via full exploitation of intrinsic fluorescence and phosphorescence. Room temperature phosphorescence (RTP) is a topic which is currently widely studied, but a study on the correlation between types of molecular solid and RTP properties is lacking. Here the authors show that RTP is enhanced in the racemic form of axial chiral molecules due to its denser R- and S- cross packing arrangement. [ABSTRACT FROM AUTHOR]

Abstract: A novel near-infrared-emitting binuclear platinum complex of (piq)2Pt2(μ-C8OXT)2 was synthesized and characterized, in which piq is 1-phenylisoquinolinato and C8OXT is a bridging ancillary ligand of 5-(4-octyloxyphenyl)-1,3,4-oxadiazole)-2-thiol. Its optophysical, electrochemical and electroluminescent characteristics were primary studied. This binuclear platinum complex exhibited an intense UV absorption at about 493nm from the metal–metal-to-ligand charge transfer transition and a bright near-infrared emission at 721nm in chloromethane. Using (piq)2Pt2(μ-C8OXT)2 as a single dopant, its single-emissive-layer polymer light-emitting devices presented a high-efficiency near-infrared emission peaked at 702nm with the maximum external quantum efficiency of 6.3% at 7.6mAcm−2. This work provides an efficient approach to realize high-efficiency near-infrared emission by binuclear platinum complexes. [Copyright &y& Elsevier]

Nitrogen-containing polycyclic aromatic hydrocarbons (PAHs) have exhibited a great potential in deep-blue emission of organic light-emitting diodes (OLEDs), but efficient narrowband emission remains an enormous challenge with excellent color purity and high external quantum efficiency (EQE s) contemporaneously. Herein, two novel deep-blue-emitting diindolophenazine derivatives of OCzN and MCzN were obtained, in which a carbazole was respectively grafted in ortho - and meta -position of phenazine. It is found that the comparatively weak intramolecular charge transfer (ICT) state and rigid fused-ring structure of diindolophenazine can prominently reduce the molecular vibration relaxation, resulting in a comparatively narrow emission spectrum. And the attached carbazole at different grafted position plays an important role in color regulation. As a result, the OCzN- and MCzN-doped devices display deep-blue electroluminescence at 418 nm and 432 nm with CIE coordinates of (0.18, 0.08) and (0.16, 0.09), high color purity, as well as narrow full-width-at-half-maximums (FWHM) of 41 nm and 51 nm, respectively, which is commendably complied with CIEy about 0.08 of the National Television Standards Committee (NTSC) standard. More importantly, the eminent EQE s as high as 6.87% and 6.09% are obtained in the fluorophores-doped OLEDs using mCP as host, respectively. This is a first representation to realize high-efficiency and narrow-band deep-blue emission by PAH fluorophores with dual ortho- positioned N -atoms. Two narrow-band deep-blue-emitting diindolophenazine derivatives of OCzN and MCzN are obtained with a grafted carbazole. An eminent EQE of 6.87% is exhibited in the OCzN-doped mCP devices at 418 nm with a CIEy coordinates of 0.08. [Display omitted] • OCzN and MCzN were obtained with diindolophenazine and a grafted carbazole respectively in 12 and 13 position. • The effect of carbazole and diindolophenazine on photoelectronic properties for both emitters is primarily studied. • Deep-blue emission peaked at 415/428 nm with narrow FWHM of 45/50 nm is observed in their mCP-hosted films. • The OCzN doped mCP devices display a higher EQE of 6.87% at 418 nm with narrow FWHM of 41 nm. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) luminescent materials based on transition metal complexes have made great progress in recent years. However, there are few reports on pure NIR-emitting iridium complexes with rigid coordinated core and their organic light-emitting devices with an emission peak more than 800 nm. Herein, we designed and synthesized a NIR-emitting iridium (III) complex based on an enlarging rigid coordinated core of tribenzo[ a , c ] phenazine (TPz), namely ( t BuTPA-TPz) 2 Ir(acac), in which di(tert -butyl) triphenylamine ( t BuTPA) is used as a peripheral shield and appended in TPz. The effect of the enlarging rigid coordinated core and peripheral shields on the emissive property was primarily studied. A significantly red-shifted photoluminescent emission peak from 710 nm to 860 nm was exhibited in this iridium complex by enlarging rigid coordinated core from dibenzo[ a , c ]phenazine to TPz in dichloromethane. Furthermore, a pure NIR electroluminescence peaked at 852 nm with a shoulder at 952 nm was observed in the ( t BuTPA-TPz) 2 Ir(acac)-doped polymer light-emitting diodes. An increasing external quantum efficiency of 0.079% and radiant emittance of 879 mW Sr−1m−2 were obtained in the optimized devices. This study provides a feasible strategy to develop pure NIR-emitting iridium complexes with an emissive peak more than 800 nm by enlarging rigid coordinated core. An Ir(III) complex ( t BuTPA-TPz) 2 Ir(acac) is designed and synthesized with tribenzo[a,c] phenazine (TPz) coordination core and di(tert -butyl)triphenylamine ( t BuTPA) peripheral shield. Significantly red-shifted NIR emission at 852 nm is observed for this Ir(III) complex by enlarging rigid coordinated core. An increasing EQE of 0.079% is obtained in the optimized doped PLEDs. [Display omitted] • ( t BuTPA-TPz) 2 Ir(acac) is prepared with tribenzo[ a , c ]phenazine (TPz) and di(tert- butyl)triphenylamine ( t BuTPA). • Effect of TPz coordinated core and t BuTPA peripheral shield on photoelectronic properties of Ir(III) complex is studied. • Pure NIR-EL emission peaked at 852 nm is observed in the PLEDs using ( t BuTPA-TPz) 2 Ir(acac) as dopant. • NIR-emission is well managed from 708 nm to 852 nm for Ir(III) complex by enlarging rigid coordinated core. • An increasing EQE of 0.079% is obtained in the optimized ( t BuTPA-TPz) 2 Ir(acac) -doped PLEDs made by solution process. [ABSTRACT FROM AUTHOR]