losses due to a suitable Δ E T (≤0.3 eV) between the respective host and guest. Employing as few as possible components in the emitting system of WOLEDs is a means to reduce the energy losses through the simplifi ed exciton-formation and energy-transfer processes. For achieving this, appropriate multifunctional emitter molecules are needed combined with a smart device design strategy.A few effi cient phosphorescent OLEDs (PhOLEDs) have been reported based on phosphorescent hosts. [ 7a,d ] These nofl uorescent-host emitting systems are promising to simplify/optimize the electrophosphorescent process. [ 7 ] However, until now, integrating such an advanced doping model into the construction of the WOLEDs has not yet been achieved. In this work, three emitting complexes originating from our group: bis(2-(2-hydroxyphenyl)-pyridine)beryllium (Bepp 2 , λ max ≈ 450 nm), [ 8 ] bis(4,6-di-fl uorophenyl)pyridinato-N , C 2′ iridium (III) N , N ′-diisopropyl-carbazol-9-yl-amidine (FPPCA, λ max ≈ 500 nm), and bis (7,8-benzoquinolinato)[ 9 ] which could provide essential colors of blue (B), green (G), and orangered (OR), respectively, for white light, were well organized for realizing a simplifi ed WOLED composed of two adjacent G-OR (FPPCA:BZQPG) and B-G (Bepp 2 :FPPCA) emitting layers (EMLs). In this strategy, phosphorescent (P) molecule FPPCA was distributed through both EMLs and showed an unprecedented multifunctional property by playing four key roles: (i) the charge-transporting host, (ii) the green emitting host, (iii) the sensitizer for the dopant P molecule BZQPG in the G-OR layer, and (iv) the green dopant emitter in the B-G layer. This new method endowed the device with the advantage of a reduced number of constituent components and EMLs, which allows for a simplifi ed fabrication processes and effectively reduces structural heterogeneity. Furthermore, careful manipulation for the well-matched FPPCA:BZQPG combination utilizes all the electrically generated excitons in the phosphor-phosphor type (PPT) G-OR layer, where the bipolar character of FPPCA results in a wide emission zone to enhance carrier and exciton utilization, thereby dominating the high electrophosphorescent effi ciency. Meanwhile, the fl uorescent (F) molecule Bepp 2 is used to generate blue singlet emission in the B-G layer and served as a host for sensitizing green emission, thereby achieving the broad white EL spectrum. An optimal management of B-G and G-OR layers aiming at balanced charge injection together with simultaneous effi cient charge/exciton confi nement, ensured this three-color device possesses stable and high EL performance White organic light-emitting diodes (OLEDs) are a very promising technology for next-generation solid-state lighting. [ 1 ] High-quality illumination sources require white OLEDs (WOLEDs) with a high color-rendering index (CRI) of >80. [ 1c ] Although some two-color WOLEDs produced by an orange or yellow emitter complemented with a blue emitter, exhibit impressive electroluminescence (EL) effi ciency, they ha...

A novel organosilane compound Si(PPI)2 with good carrier-transport ability has been used as an efficient host for high-performance fluorescent pure-blue and phosphorescent green/red OLEDs.

The pursuit of ideal narrowband yellow multiple resonance (MR) emitters is hampered by the mutual constraints of effective spectral redshift and maintaining a small full width at half maximum (FWHM) value. Here, a novel multiple fusion molecular design strategy is reported to break this trade‐off. Compared with the selected narrowband parent core, the specific multiple MR effects in target molecules can simultaneously extend the π‐conjugation length, increase the rigidity of the structure, and reduce the vibrational frequency. Proof‐of‐the‐concept emitters BN‐DICz and DBN‐ICz show bright yellowish green to yellow emissions in dilute toluene solutions with peaks at 533–542 nm and extremely small FWHMs of ≤20 nm. Notably, BN‐DICz‐based electroluminescent device exhibits excellent efficiencies of 37.4%, 136.6 cd A−1, and 119.2 lm W−1 with an FWHM of merely 23 nm, representing the best performance for yellow MR organic light‐emitting diodes.

A novel macrocycle of B/N-doped calix-[4]arene (C-BN) was synthesized by a one-shot double boronation. Owing to the structural tension and electron-donating properties of the nitrogen atoms in the macrocycle, reaction selectively proceeds between the adjacent benzene rings outside the macrocycle. C-BN shows a highly centrosymmetric structure with two multiple resonance (MR) fragments bridged by tertiary amine groups at the 1,3 positions of the benzene ring. Benefiting from the large intermolecular distance (> 4.6 Å) between adjacent MR-emitting cores, C-BN also exhibits excellent narrowband emitting features against aggregation-induced quenching and spectrum broadening. Optimized organic light-emitting diode devices based on C-BN exhibit high maximum external quantum efficiencies of 24.7-26.6 % and small full width at half maximums of 25-28 nm over a wide doping range of 1-12 wt %.