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The realization of operationally stable blue organic light-emitting diodes is a challenging issue across the field. While device optimization has been a focus to effectively prolong device lifetime, strategies based on molecular engineering of chemical structures, particularly at the subatomic level, remains little. Herein, we explore the effect of targeted deuteration on donor and/or acceptor units of thermally activated delayed fluorescence emitters and investigate the structure-property relationship between intrinsic molecular stability, based on isotopic effect, and device operational stability. We show that the deuteration of the acceptor unit is critical to enhance the photostability of thermally activated delayed fluorescence compounds and hence device lifetime in addition to that of the donor units, which is commonly neglected due to the limited availability and synthetic complexity of deuterated acceptors. Based on these isotopic analogues, we observe a gradual increase in the device operational stability and achieve the long-lifetime time to 90% of the initial luminance of 23.4 h at the luminance of 1000 cd m−2 for thermally activated delayed fluorescence-sensitized organic light-emitting diodes. We anticipate our strategic deuteration approach provides insights and demonstrates the importance on structural modification materials at a subatomic level towards prolonging the device operational stability. Structural engineering at the subatomic level remains little for boosting operational stability of organic light-emitting diodes. Here, authors show that deuteration of acceptor is critical to enhance device stability, which is commonly neglected due to limited availability and synthetic complexity. [ABSTRACT FROM AUTHOR]

Herein, a family of six [3+2+1] coordinated 2‐(2′,4′‐difluorophenyl) pyridine‐based Iridium(III) complexes with intermolecular interactions have been designed to improve their emission properties. These molecular interactions have been regarded as an effective way to suppress non‐radiative decay and enhance the photoluminescence quantum yield (PLQY) of the light‐emitting materials. Specifically, complex 3 functionalized with new −CF3 ligand exhibits PLQY of up to 100%, and the emission peak at ≈485 nm with short excited‐state lifetime down to 1 µs. Therefore, the blue phosphorescent organic light‐emitting diode (OLED) based on complex 3 dopant exhibits excellent performance with a maximum external quantum efficiency of 22.0% and low efficiency roll‐off. Upon increasing the current density to 250 mA cm−2, high brightness value of 53 400 cd m−2 is achieved, which is not attainable with the similar molecular structure that we have reported recently, indicating the importance of the presence of the (CF···H/CN···H) interactions. Given the well‐overlapping of the emission spectra of these Iridium(III) complexes and absorption spectrum of v‐DABNA emitter, complex 3 has been successfully applied as a sensitizer for v‐DABNA‐based OLED, and a maximum current efficiency of 27.13 cd A−1 with high brightness level of up to 10 000 cd m−2 have been achieved. [ABSTRACT FROM AUTHOR]

A new series of blue phosphorescent cyclometalated [3+2+1] coordinated iridium (III) complexes containing 2‐(2′,4′‐difluoropyridyl) pyridine derivatives have been designed and synthesized to investigate their structure–property relationship on the nature of excited states and tune their emission wavelengths from saturated‐blue to sky‐blue region at 437−489 nm. These complexes exhibit high photoluminescent quantum yields (PLQYs) of up to 90% and short excited state lifetime in the range of 2−5 µs in polymethylmethacrylate (PMMA) thin films. Sky‐blue organic light‐emitting diodes (OLEDs) based on such pyridine‐containing [3+2+1] iridium (III) dopants have exhibited maximum external quantum efficiencies (EQEmax) and current efficiency (CE) of 17.3% and 42.3 cd A–1, respectively. To note, very small efficiency roll‐off value from 4.3% to 19.7% is achieved at the luminance level of 1000 cd m–2. The well‐balanced electron and hole injection currents, the short lifetime of excited excitons, and wide recombination zone by leveraging the obtained iridium (III) dopants and exciplex co‐host have greatly decreased the accumulation of triplet excitons at the high luminescence level, leading to dramatically reduced efficiency roll‐off. It is anticipated that this work provides new insights into the design of saturated‐blue‐emitting iridium (III) complexes with reduced efficiency roll‐off in their fabricated OLEDs. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate a novel one‐pot synthetic method towards a series of boron‐doped polycyclic aromatic hydrocarbons (B‐PAHs, 1 a–1 o), including hitherto unknown B‐doped zethrene derivatives, from ortho‐aryl substituted diarylalkynes with high atom efficiency and broad substrate scopes. A reaction mechanism is proposed based on the experimental investigation together with the theoretical calculations, which involves a unique 1,4‐boron migration process. The resultant benchtop‐stable B‐PAHs are thoroughly investigated by X‐ray crystallography, cyclic voltammetry, UV/Vis absorption, and fluorescence spectroscopies. The blue and green organic light‐emitting diode (OLED) devices based on 1 f and 1 k are further fabricated, demonstrating the promising application potential of B‐PAHs in organic optoelectronics. [ABSTRACT FROM AUTHOR]

Phosphorescent dopants are promising candidates for organic light‐emitting diodes (OLEDs). Although it has been established that the out‐coupling efficiency and overall performances of vacuum‐deposited OLEDs can be significantly improved by a horizontal orientation of the dopants, no horizontally oriented gold(III) complexes have been reported to date. Herein, a novel class of tetradentate C^C^N^N ligand‐containing gold(III) complexes with a preferential horizontal orientation successfully generated through a one‐pot reaction is reported. These complexes demonstrate high photoluminescence quantum yields of 70 % and a high horizontal dipole ratio of 0.87 in solid‐state thin films. Green‐emitting OLEDs based on these complexes operate with a maximum external quantum efficiency of 20.6 % with an estimated out‐coupling efficiency of around 30 %. A promising device stability has been achieved in the vacuum‐deposited OLEDs, with operational half‐lifetimes of around 37 500 h at 100 cd m−2. [ABSTRACT FROM AUTHOR]

A new class of brightly blue-green-emitting arylgold(III) complexes has been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of solution-processable and vacuum-deposited organic light-emitting devices (OLEDs). These arylgold(III) complexes can be readily synthesized by reacting the corresponding arylboronic acids with the gold(III) precursor complexes in a one-pot Suzuki-Miyaura coupling reaction. When compared to the structurally related alkynylgold(III) complex, arylgold(III) complexes 1 and 2 exhibit much higher photoluminescence quantum yields in solution state. High photoluminescence quantum yields are also observed in solid-state thin films. More importantly, the solid-state emission spectra show strong resemblance to those in solution, irrespective of the dopant concentration, leading to significant improvement in the color purity of the OLEDs by suppressing any excimer emission resulting from the π-stacking of the tridentate ligand. High performance solution-processable and vacuum-deposited blue-green-emitting OLEDs have also been realized, with maximum external quantum efficiencies of 7.3% and 14.7%, respectively, representing the first demonstration of efficient blue-green-emitting OLEDs based on cyclometalated arylgold(III) complexes. [ABSTRACT FROM AUTHOR]

Blue fluorescent materials are an essential part of commercial OLED displays and lightings. However, the market lacks highly efficient, short-emission wavelength blue fluorescent materials. Herein, two new blue fluorescent materials, SAFPI-3 and SAFPI-2, are developed based on a phenanthroimidazole derivative and spiro fluorene triphenylamine by replacing the substitution sites, which tactfully utilize the spatial configuration of the molecules to achieve higher external quantum efficiency and a shorter emission wavelength at the same time. Furthermore, the versatility of SAFPI-3 and SAFPI-2 can be demonstrated as non-doped emitters for blue OLEDs and as the hosts of yellow phosphorescent OLEDs, which have achieved a high external quantum efficiency of 23.98% with extremely low-efficiency roll-off. [Display omitted] • Two novel blue fluorescent isomers are developed. • SAFPI-3 -based non-doped OLED achieves a high EQE of 4.99% with EL emission peak at 432 nm. • OLED using SAFPI-3 as host obtains high EQE of 23.98% with negligible efficiency roll-off. [ABSTRACT FROM AUTHOR]