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Hybridized local and charge‐transfer (HLCT) with the utilization of both singlet and triplet excitons through the "hot excitons" channel have great application potential in highly efficient blue organic light‐emitting diodes (OLEDs). The proportion of charge‐transfer (CT) and locally excited (LE) components in the relevant singlet and triplet states makes a big difference for the high‐lying reverse intersystem crossing process. Herein, three novel donor (D)‐acceptor (A) type HLCT materials, 7‐([1,1′‐biphenyl]‐4‐yl(9,9‐dimethyl‐9H‐fluoren‐2‐yl)amino)‐3‐phenyl‐1H‐isochromen‐1‐one (pPh‐7P), 7‐([1,1′‐biphenyl]‐4‐yl(9,9‐dimethyl‐9H‐fluoren‐2‐yl)amino)‐3‐methyl‐1H‐isochromen‐1‐one (pPh‐7M), and 6‐([1,1′‐biphenyl]‐4‐yl(9,9‐dimethyl‐9H‐fluoren‐2‐yl)amino)‐3‐methyl‐1H‐isochromen‐1‐one (pPh‐6M), were rationally designed and synthesized with diphenylamine derivative as donor and oxygen heterocyclic coumarin moiety as acceptors. The proportions of CT and LE components were fine controlled by changing the connection site of diphenylamine derivative at C6/C7‐position and the substituent at C3‐position of coumarin moiety. The HLCT characteristics of pPh‐7P, pPh‐7M, and pPh‐6M were systematically demonstrated through photophysical properties and density functional theory calculations. The solution‐processed doped OLEDs based on pPh‐6M exhibited deep‐blue electroluminescence with the maximum emission wavelength of 446 nm, maximum luminance of 8755 cd m−2, maximum current efficiency of 5.83 cd A−1, and maximum external quantum efficiency of 6.54 %. The results reveal that pPh‐6M with dominant 1LE and 3CT components has better OLED performance. [ABSTRACT FROM AUTHOR]

CsPbBr3 quantum dots (QDs) prepared through traditional hot‐injection and room temperature reprecipitation methods are usually hexahedral (nanoplate/cube) and green‐emitting. These methods severely obstruct the development of blue perovskite‐based light‐emitting diodes (PeLEDs) because the resultant QDs always suffer unachievable morphology regulation. Here, highly efficient blue‐emitting rhombic dodecahedron CsPbBr3 QDs (CsPbBr3 <12> QDs) are obtained by regulating morphological transformation for the first time through a novel and facile sequential post‐treatment strategy. Hydrobromide (‐NH3+) with stronger adsorption energy promotes the morphology transform of QDs from nanoplate to cube by substituting oleylamine in the first step. Then, polar solvent vapor eliminates PbX64− and led to the (112) crystal plane of the cube QDs being exposed, which is effectively stabilized by ‐NH3+ to realize morphology transition from cube to the dodecahedron. Highly efficient 12‐faceted dodecahedrons are endowed with significantly enhanced photoluminescence quantum yield of 89.8% at 476 nm as well as uniform size distribution and mono‐dispersity. The target blue PeLEDs achieve the maximum external quantum efficiency of 6.6% (480 nm) and excellent spectrum stability. This study provides a new strategy to prepare blue‐emitting CsPbBr3 <12> QDs by delicate control toward the growth and polyhedron process of crystal. [ABSTRACT FROM AUTHOR]

The crystal form of semiconductor materials is keenly correlated with the photosensitivity of optoelectronic devices. Thus, understanding the crystal form-dependent photosensitivity mechanism is critical. In this work, the microemulsion phase transfer method was adopted to prepare α- and β-titanylphthalocyanine (TiOPc NPs) with an average diameter of 35 nm. The photosensitivity (E1/2) of α-TiOPc NPs was 2.73 times better than that of β-TiOPc NPs, which was characterized by photoconductors under the same measurement conditions. DFT was performed to explain the relationship between crystal form and photosensitivity by systematically calculating the charge transfer integrals for all possible dimers in the two different crystal forms. The hole and electron reorganization energies of TiOPc were respectively calculated to be 53.5 and 271.5 meV, revealing TiOPc to be a typical p-type semiconductor. The calculated total hole transfer mobility (μ+) ratio (2.83) of α- to β-TiOPc was almost identical to the experimental E1/2 ratio (2.73) and the calculated photogeneration quantum efficiency (ηe-h) ratio (2.23). In addition, the optimum hole transfer routes in the crystal of α- and β-TiOPc were all along with the [1 0 0] crystal orientation, which was determined by the calculated μ+. A high charge transfer mobility leads to a high photosensitive TiOPc crystal. Consequently, these results indicate that the selected theoretical calculation method is reasonable for indirectly explaining the relationship between crystal form and photosensitivity. The TiOPc molecular solid-state arrangements, namely, the crystal forms of TiOPc, have a strong influence on the charge transport behavior, which in turn, affects its photosensitivity. [ABSTRACT FROM AUTHOR]

High performance with color stability and simplified device structure with uncomplicated fabrication processes are research focuses in white organic light-emitting diodes (WOLEDs). But it is not easy to simultaneously combine these characteristics into WOLEDs. Herein, efficient and color-stable WOLEDs with double light-emitting layer are constructed. The double light-emitting layer structure is composed of a red-green (RG) emitting light which originate from incomplete energy transfer from the host of tris-(8-hydroxyquinolinato)aluminum (Alq3) to guest of 4-(Dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)−4 H -pyran (DCJTB), and a blue-green emitting light from ( E )-9-(4-(2-(anthracen-9-yl)vinyl)phenyl)-10-(naphthalen-1-yl)anthracene (APEAn1N). In these WOLEDs, the different doping concentrations of DCJTB in Alq3 were optimized. Finally, a WOLEDs with relatively simple preparation was obtained with a maximum brightness of 9296 cd m −2 , maximum current efficiency (CE) of 10.17 cd A −1 , maximum power efficiency (PE) of 5.80 lm W −1 , maximum external quantum efficiency (EQE) of 4.09%, Commission Internationale de L'Eclairage (CIE) coordinate of (0.41, 0.46) and color rendering index (CRI) of 75 (85), respectively. And the chromaticity coordinate is stable at (0.41, 0.46) with increasing operation voltage. These results reveal that the fluorescent WOLEDs possess simplified fabrication, low cost, relatively high efficiency, acceptable CRI and stable color, simultaneously. [ABSTRACT FROM AUTHOR]

[Display omitted] • T5DP36 with one-dimensional transport channel deserved super carrier mobility. • One-dimensional transport channel was firstly constructed in CHTL (T5DP36:V-CBP). • One-dimensional transport channels in CHTL are formed by π-π interaction of T5DP36. • The carrier mobility of CHTL was boosted from 6.6 × 10−5 to 2.16 × 10−3 cm2V−1s−1. • The EQE of blue QLED has increased from 10.03% to 18.16%, which is the cutting edge. Quantum dot light-emitting diodes (QLEDs) emerged as very competitive candidates for next generation display and lighting applications. Cross-linked hole transport materials (HTMs) permit the flourish of solution-processed QLEDs. Whereas, unbalanced charge injection and energy level mismatch happened to cross-linked HTMs severely suppress the efficiency of blue QLEDs, which limits the full-color display application. Here, discoid molecules with self-assembly behavior were firstly proposed to construct one-dimensional transport channels in cross-linked hole transport layer (HTL) to advance the carrier transport property of the target composite HTL (CHTL). Compared with CHTLs prepared from amorphous and disordered crystalline discoid molecules, the carrier mobility of CHTL (T5DP36: V-CBP) with one-dimensional transport channels was signally boosted by two orders of magnitude from 6.6 × 10−5 to 2.16 × 10−3 cm2 V−1 s−1. The relevant blue QLED was qualified with notably enhanced external quantum efficiency of 18.16 %, deep blue emission with Commission International de I'Eclaiiage of (0.14, 0.04) and extended T 50 lifetime from 177 to 417 h under 100 cd m−2. This is at a cutting edge of deep blue light and eligible for high-end display applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Indium tin oxide was hybrid modified with MoO 3 and self-assembled monolayer. • Self-assembled monolayer was used to adjust oxygen vacancies in MoO 3. • Solution-processed hole transport layer-free OLED achieved EQE max of 18.18% Compared with current vacuum-deposited multilayer organic light-emitting diodes (OLEDs), solution-processed simplified-structured OLEDs are more appealing by merits of low costs and promising potentials in large-area OLEDs. Nevertheless, it remains challenging due to intermixing between adjacent organic layers. Herein, indium tin oxide (ITO) surface was deposited with molybdenum trioxide (MoO 3) and then modified with self-assembled monolayer (SAM) of pentafluorobenzyl phosphonic acid. The SAM modification process made the MoO x film rich in oxygen vacancies, which ensured effective hole injection from the hybrid modified ITO directly to the emitting layer. This strategy facilitates HTL-free OLEDs and then completely avoids interlayer intermixing. Using the hybrid modified ITO as anode, HTL-free solution-processed green phosphorescent OLED was prepared and achieved a maximum current efficiency of 63.24 cd A−1 and a maximum external quantum efficiency of 18.18%. Meanwhile, preferable operational stability than standard multilayer OLEDs was obtained. For red phosphorescent OLED, a maximum external quantum efficiency of 17.49% was achieved. This work proposed a new way of adjusting cation valence to improve hole injection, contributing to solution-processed OLED fabrication. [ABSTRACT FROM AUTHOR]

Since the inter-layer mutual solubility is an obstacle to the development of solution-processed OLED, cross-linking is considered to be the best method to obtain solvent resistance. Vinyl is the most widely reported crosslinking group, but a problem raised that crosslinking usually need a high temperature. Here, two vinyl-crosslinked hole transporting materials, 3,3'-(1,3,4-oxadiazole-2,5-diyl)bis (N -phenyl- N -(4-vinylphenyl)aniline) (OXZ-VPAN), 3,3'-(4-phenyl-4 H -1,2,4-triazole-3,5-diyl)bis (N -phenyl- N -(4-vinylphenyl)aniline) (TRZ-VPAN) were designed and synthesized. The introduction of pentaerythritol tetra(3-mercaptopropionate) (PETMP) and vinyl groups by thiol-ene reaction to reduce the crosslinking temperature. As a result, crosslinking can be achieved at 120 °C with the solvent resistance higher than 99%. The surface morphology of the films before and after crosslinking were characterized by atomic force microscope, and it was found that the roughness of the film was improved after dopped with PETMP. The solution-processed green phosphorescent OLEDs devices based on the obtained HTM exhibit excellent performance. Maximum current efficiency of 57.1 cd A−1 and external quantum efficiency of 16.0% (Ir (mppy) 3) are obtained when OXZ-VPAN served as HTL. This low temperature feasible cross-linking process to prepare HTLs promotes the development solution-processed OLEDs. [Display omitted] • Two cross-linked hole transport material of D-A-D structure was synthesized. •The cross-linking temperature was lowed to 120 °C by introducing PETMP. •The solution-processed PHOLED achieved CE max of 57.1 cd A−1. [ABSTRACT FROM AUTHOR]

• QD films based on modified Poly-TPD exhibited higher PL intensity and lower fluorescence quenching properties. • Reduced defects density at the interface between QD films and Poly-TPD modified with diamine molecules. • QLEDs exhibited a distinctly enhancement in EQE from 4.93 to 8.90%. Inorganic perovskite quantum dots (QDs) have emerged as promising materials for light-emitting devices by merits of their high photoluminescence quantum yield (PLQY), narrow full width at half-maximum and tunable emission spectrum. However, fluorescence quenching and trap-mediated nonradiative recombination between hole transport layer (HTL) and QD films are prejudicial to the performance of perovskite-QDs-based light-emitting devices (QLEDs). Here, HTL was modified with diamine molecules (1,4-butanediamine (4-DA), 1,8-octyldiamine (8-DA) and 1,11-aminoundecylamine (11-DA)) through a simple self-assembly method. QD films based on modified poly[ N , N ′-bis(4-butylphenyl)- N , N ′-bis(phenyl)-benzidine] (Poly-TPD) exhibited higher PL intensity and lower fluorescence quenching properties. Meanwhile, diamine molecules do favor to the flatness of Poly-TPD film and contribute to the smoothness of QD films. Moreover, the exciton quenching and the density of defects at the interface between HTL and QD films were effectively reduced. Particularly, QLEDs based on HTL modified with 8-DA was endowed with a maximum luminance of 78634 cd/m2, a peak current efficiency of 30.77 cd/A, a maximum external quantum efficiency of 8.90% and T 50 of 16.8 min when the initial brightness is about 1000 cd/m2. [ABSTRACT FROM AUTHOR]

• Two vinyl-based cross-linkable hole transporting materials are synthesized. • Cross-linking temperature is markedly lowered by doping photoinitiator. • Hole mobility is also enhanced by doping photoinitiator. • The highest external quantum efficiencies are 15.5% (green) and 15.0% (red). Recently, developing insoluble cross-linkable functional layers plays a vital role for solution-processed organic light emitting diodes (OLEDs). Here, two vinyl-based cross-linkable hole transporting materials V-TPAVTPD and V-TPAVCBP are designed and synthesized. Additionally, cationic photoinitiator 4-octyloxydiphenyliodonium hexafluoroantimonate (OPPI) is first introduced to chemically induce vinyl-based photo cross-linking process, aiming at lowering cross-linking temperature and enhancing hole mobility. As a result, cross-linking can occur at expressly low temperature of 120 °C with >95% solvent resistance. Moreover, hole mobility is markedly enhanced with the value higher than 10−3 cm2 V−1 s−1. When applying hole transporting layers (HTLs) to solution-processed green and red phosphorescent OLEDs, devices exhibit excellent properties. Particularly, the maximum current efficiency of 54.0 cd A−1 (green), 9.8 cd A−1 (red) and external quantum efficiency of 15.5% (green), 15.0% (red) are obtained when OPPI doped V-TPAVCBP serves as HTL. This low temperature feasible cross-linking process to prepare HTLs with preferable hole mobility promotes the development of OLEDs. [ABSTRACT FROM AUTHOR]