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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] • 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]

• 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]