Improving operational stability for organic light-emitting diode (OLED) is a hotspot in scientific research. It is proposed that silicon (Si) and germanium (Ge) can exhibit hyperconjugation effects and participate in conjugated systems, thereby stabilizing molecules' excited and polarized states. Herein, the importance of incorporating Si and Ge in multi-resonance thermally activated delayed fluorescence emitters is revealed to improve their luminescence efficiency and intrinsic stability. Computational studies show that introducing Si and Ge atoms can strengthen the C-Si and C-Ge bonds due to the hyperconjugation effect, resulting in higher bond dissociation energies and molecular photostability. With the efficient spin-vibronic coupling and spin-orbital coupling, the flexible conformations of the emitters facilitate the spin-flip processes by enriching the characters and density of their excited states. A maximum external quantum efficiency of 30.0% for BN-Ge-based blue-emitting OLEDs, with (Commission Internationale de l'Eclairage) CIEy <= 0.18 is realized. In particular, the LT90 at 1000 cd m-2 of 48.3 and 7.1 h is achieved for BN-Si-based and BN-Ge-based OLEDs, respectively, using the developed deuterated SiCzCz-d15 and SiTriCz2-d16 as the hole-transporting and host materials. It is anticipated that the study will provide insights into the design of group IV element-containing multiple-resonance thermally activated delayed fluorescent emitters for optoelectronics applications.

The limited proton transfer kinetics within organic positive electrodes restricts the proton storage capacity and hinders achieving high energy density in aqueous zinc-organic batteries. Herein, we obtain superharmonic motion of proton by crosslinking short hydrogen-bonds network within the positive electrode matrix to achieve fast proton transfer. Specifically, the pyrazino[2, 3-g]quinoxaline-5, 10-dione owing strong electrostatic and hydrogen-bond interactions with hydrogen ions is synthesized, which could attract concentrated hydronium and trigger local proton enrichment. Spatially confined water-hydronium domains are therefore formed to generate short hydrogen bonds around pyrazino[2, 3-g]quinoxaline-5, 10-dione molecules. Moreover, the 4,4'-diaminodiphenylamine and polytetrafluoroethylene binder exhibits a mutual affinity with pyrazino[2, 3-g]quinoxaline-5, 10-dione due to the strong hydrogen-bond interactions of them, which reduce the intermolecular distance within positive electrode and construct a highly interconnected state of water-hydronium domains, thereby establishing the short hydrogen bonds network throughout the electrode matrix. The rapid proton transport through short hydrogen bonds consequently reduces the polarization of aqueous zinc-organic batteries (1.47 × 10-3 S cm-1). As a result, the composite positive electrode delivers specific energy of 400 Wh kg-1 at 0.1 A g-1.

AbstractThe realization of highly operationally stable blue organic light‐emitting diodes (OLEDs) is a challenge in both academia and industry. This paper describes the development of anthracene–dibenzofuran host materials, 2‐(10‐(naphthalen‐1‐yl)anthracen‐9‐yl)naphtho[2,3‐b]benzofuran (Host 1) and 2‐(10‐([1,1′‐biphenyl]‐2‐yl)anthracen‐9‐yl)naphtho[2,3‐b]benzofuran (Host 2), namely for use in the emissive layer of an OLED stack. A multiple‐resonance thermally activated delayed serves as the blue fluorescence emitter and exhibits an initial luminance of 1000 cd m−2 and long operational stability (i.e., time to decay to 90% of initial luminance) of 249 h. Furthermore, a deep‐blue OLED with an optimized top‐emitting architecture with a high current efficiency of 154.3 cd A−1, is fabricated and calibrated to a Commission International de l’Éclairage y chromaticity coordinate of 0.048. Moreover, the emission spectrum of this OLED has a narrowband peak at 476 nm with a full width at half maximum (FWHM) of 16 nm. This work provides valuable insights into the design of anthracene‐based host materials and highlights the importance of host optimization in improving the operational stability of OLEDs.

Achieving both high efficiency and high stability in blue thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs) is challenging for practical displays and lighting. Here, we have successfully developed a series of sky-blue to pure-blue emitting donor-acceptor (D-A) type TADF materials featuring a four-coordinated boron with 2,2 '-(pyridine-2,6-diyl)diphenolate (dppy) ligands, i.e.1-8. Synergistic engineering of substituents on the phenyl bridge as well as the electronic properties and the attached positions of heteroatom N-donors not only enables fine-tuning of the emission colors, but also modulates the nature and energies of their triplet excited states that are important for the reverse intersystem crossing (RISC). Particularly for the compound with two methyl substituents on the phenyl bridge (compound 8), RISC is significantly facilitated through the vibronic coupling of the energetically close-lying triplet charge transfer (3CT) and the triplet local excited (3LE) states, when compared to analogue 7. Efficient sky-blue to pure-blue OLEDs with electroluminescence peaks (lambda EL) at 460-492 nm have been obtained, in which ca. five-fold higher external quantum efficiencies (EQEs) of 18.9% have been demonstrated by 8 than that by 7. Moreover, ca. thirty times longer device operational half-lifetimes (LT50) of 9113 hours for 8 than that for 7 as well as satisfactory LT50 reaching 26 643 hours for 6 at an initial luminance of 100 cd m-2 have also been demonstrated. To the best of our knowledge, these results represent one of the best high-performance blue OLEDs based on tetracoordinated boron TADF emitters. Moreover, the design strategy presented here has provided an attractive strategy for enhancing the device performance of blue TADF-OLEDs. A series of sky-blue to pure-blue fluoroboron thermally activated delayed fluorescence (TADF) emitters has been designed and synthesized. Their TADF efficiencies are manipulated through pi-bridge engineering and N-donor modulation.

The exploration of heavy atom effect in organic semiconductors for organic light-emitting diode (OLED) applications has attracted much attention recently. While such effect has been extensively investigated in those incorporated with selenium, copper, silver and gold, there are only few studies on the role of germanium (Ge) on the luminescence and structural properties of emitters. Herein, we reveal the importance of the incorporation of Ge in multi-resonance thermally activated delayed fluorescence emitters that show improved luminescence properties than its carbon and silicon counterparts. We present the distinct single crystal structures of the two conformers of the organogermane emitter that co-exist in the solid state. We describe their conformational changes from open to folded geometries upon thermal stimulation under vacuum, as supported by variable-temperature single crystal diffraction analysis and theoretical calculations. From molecular dynamics simulations, we show that the folded form prevents a close proximity to the sensitizer in solid-state packing, thereby reducing Dexter energy transfer and facilitating efficient Förster energy transfer. Together with the spin-vibronic coupling and heavy atom effect, organogermane emitter shows an accelerated spin-flip process than its carbon and silicon counterparts. Based on the Ge emitter, we achieve a blue emission peaking at 479 nm with a narrow spectral full-width-at-half-maximum of 25 nm and a maximum external quantum efficiency of 38.4%. More importantly, we report the LT90 (90% of the initial luminance at 1000 cd m-2) of 2.2 h for Ge-based OLEDs, unlocking the full potential of organogermane emitters for operationally stable OLEDs. We anticipate our study provides insights into the design of organogermane compounds for optoelectronics applications.

Multiple-resonance thermally activated delayed fluorescence (MR-TADF) emitters have garnered significant attention in recent years due to their remarkable properties, such as high luminescent quantum yield, robustness, and their compliance with the Broadcast Television 2020 standard for the new generation of ultrahigh-definition. Despite these advancements, the operational lifetimes of organic light-emitting diodes (OLEDs) relying on MR-TADF emitters still fall short for practical application. It is believed that the enhancement of the intrinsic molecular stability of tBu-DABNA, a fundamental backbone of MR-TADF emitters, holds great promise to be a universal strategy for all MR-TADF emitters improving the operational lifetimes of OLEDs. Herein, the design and synthesis of targeted deuteration are reported on donor and/or backbone of MR-TADF emitters, where the structure-property relationship between intrinsic molecular stability upon isotopic effect and device operational stability are examined. The isotopic analogs show a gradual increase in the device operational stability and achieve long-lifetime LT80 (80% of the initial luminance of 1000 cd m-2) of 24.3 h for TADF-sensitized fluorescence OLED, representing a sevenfold enhancement when compared with the undeuterated counterpart. This strategic deuteration approach underlines the importance of structural modification on materials toward device operational stability. Recent research has focused on enhancing the operational lifetimes of organic light-emitting diodes (OLEDs) utilizing multiple-resonance thermally activated delayed fluorescence (MR-TADF) emitters. By strategically deuterating the fundamental backbone (NBN) of MR-TADF emitters, a sevenfold increase in device operational stability is achieved, demonstrating the significance of the deuterated effect for improving OLED performance. image

Recent research on anthracene-based hydrocarbon (PNA) as the emissive layer host found that deuteration mediated the formation of these adduct species, presumably quenchers, and thus improved the device lifetime. Meanwhile, studies on deuterium in PNA host materials with stepwise deuteration are scarce. In this work, we report a systematic study of isotopic effects through independent deuteration of the phenyl or/and the dibenzofuran unit on a series of PNA materials polyaromatic dibenzofuran (PAF, PAF-d(5), PAF-d(7) and PAF-d(12)). We fabricated fluorescent OLED based on this triplet-triplet up-conversion active host materials for conventional MR-TADF emitter. A short-lived excited delayed lifetime of less than 2 mu s has been observed in their electroluminescence decay studies. In addition, LT80 of up to 12.7 h has been observed in PAF-d(12) at the brightness of 1000 cd m(-2), corresponding to a 4-fold enhancement of OLED stability compared to the non-deuterated counterpart. We hope the current research can provide insights for further device improvement.

Correction for ‘Saturated-blue-emitting [3+2+1] coordinated iridium( iii ) complexes for vacuum-deposited organic light-emitting devices’ by Meng Zhang et al. , J. Mater. Chem. C , 2022, 10 , 14616–14625, https://doi.org/10.1039/D2TC02829H.

The white organic light-emitting diode has become as a new class of emerging solid-state lighting sources due to its advantage of warm, pure white light emission, flexible lighting, and environmentally friendly indoor lighting. Here, we report three rationally designed cyclometalated [3 + 2+1] iridium(III) complexes that emit white emission simultaneously from phosphorescent blue and yellow in the solid-state thin film. The blue GaN-based solid-state white light-emitting diodes with iridium(III) complexes as a color converter show a color rendering index of 84.4 and International Commission on Illumination (CIE) coordinates of (0.30, 0.33). In addition, the vac-uum-deposited organic light-emitting diode device exhibits a low turn-on voltage of 3.0 V and a maximum luminance (Lmax) of 335 cd m-2 with CIE coordinate of (0.31, 0.33), reaching standard naturally warm white light.

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 −CF 3 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.

A high-valent manganese(IV)-hydroxo porphyrin π-cation radical complex, [Mn(IV)(OH)(Porp+•)(X)]+, was synthesized and characterized spectroscopically. The Mn porphyrin intermediate was highly reactive in alkane hydroxylation and oxygen atom transfer reactions. More importantly, the Mn porphyrin intermediate reacted with water at a fast rate, resulting in the dioxygen evolution. To the best of our knowledge, we report the first manganese Cpd I model compound bearing a porphyrin π-cation radical ligand with a high reactivity in oxidation reactions, including water oxidation.

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.

The molecular design of various heterocycles incorporated into photochromic diarylethenes plays an important role in diversifying functionality. Herein, we report the design, synthesis, and structural characterization of photochromic benzo-[b]-germole-fused diarylethenes. Photochromic behaviors including clean conversion between the open and the photogenerated closed forms under ambient conditions over multiple photoswitching cycles with insignificant loss of photochemical reactivity, thermal irreversibility with negligible backward reaction of the photogenerated closed form back to the open form even at 100 C-o, and satisfactory and comparable photochromic quantum yields for the forward and backward photoswitching processes are observed. This work demonstrates the employment of a rarely explored germole ring with weak aromaticity as a versatile building block for the ethene bridge of the photochromic diarylethene, which is the first of its kind to construct photochromic materials for potential applications, further expanding the diversity of the heterocycle-fused diarylethene-based system with interesting photocontrolled functions.

It was previously found that (MnO)-O-IV species with neutral ligands perform C-H activation reactions through an "excited state reactivity" (ESR), where a valence electron in the (MnO)-O-IV moiety is spontaneously excited to a higher orbital to create a more potent reactant. We extend this to a (MnO)-O-IV compound with a negatively charged ligand ([Mn-IV(O)(DPAQ)](+)), which we investigate with density functional theory. It is found that ESR are indeed preferable even in this case, and that the ligand charge may only have an indirect effect on ESR. Instead, ligand rigidity is proposed to affect the ESR rate more directly. In addition, an example of a new beta-electron transfer pathway was found, where three key orbitals mix to deliver the incoming electron to its final orbital position. This study supports the notion that ESR may be more common in C-H activation reactions of (MnO)-O-IV compounds than what is so far known.

A series of platinum(II) calix[4]arene-based molecular tweezers was synthesized. The studies of the host–guest association with a charge-neutral cyclometalated platinum(II) complex showed a drastic color change and the turning on of near-infrared emission resulting from Pt⋅⋅⋅Pt and π–π interactions. Control of the host–guest assembly process by varying the solvent composition can lead to a change from discrete host and guest molecules to high-ordered host–guest oligomers with the formation of sheet-like nanostructures, demonstrating a rare example of three-state supramolecular host–guest system with high solubility in solvents of diverse polarity. The change in host–guest assembly behaviors could be probed by drastic color changes from yellow to orange to green. The present study provides insights into the systematic design of solvent-responsive molecular materials using molecular tweezers-directed host–guest assembly, with potential applications in colorimetric sensing of changes in the micro-environment.

Photochromic materials have drawn growing attention because using light as a stimulus has been regarded as a convenient and environmental-friendly way to control properties of smart materials. While photoresponsive systems that are capable of showing multiple-state photochromism are attractive, the development of materials with such capabilities has remained a challenging task. Here we show that a benzo[ b ]phosphole thieno[3,2 ‑b ]phosphole-containing alkynylgold(I) complex features multiple photoinduced color changes, in which the gold(I) metal center plays an important role in separating two photoactive units that leads to the suppression of intramolecular quenching processes of the excited states. More importantly, the exclusive photochemical reactivity of the thieno[3,2 ‑b ]phosphole moiety of the gold(I) complex can be initiated upon photoirradiation of visible light. Stepwise photochromism of the gold(I) complex has been made possible, offering an effective strategy for the construction of multiple-state photochromic materials with multiple photocontrolled states to enhance the storage capacity of potential optical memory devices.

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 (EQE max ) 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.

Decanuclear and pentanuclear gold(I) sulfido complexes of phenanthrene- and dibenzothiophene-based diphosphine ligands were synthesized and characterized. Unprecedented stimuli-induced reversible transformation between decanuclear and pentanuclear gold(I) sulfido complexes was observed, which could be readily monitored by NMR and UV-vis absorption spectroscopy in solution. Remarkably, the decanuclear gold(I) sulfido complex (Au10-LPh) was found to show a highly reversible transformation process, which is stable for over 10 successive cycles in solution. The stimuli-induced reversible transformation behavior of the gold(I) sulfido complexes was found to depend on the P-P bite distance of the bidentate phosphine ligands.

The saturated-blue phosphorescent OLEDs based on the [3+2+1] coordinated iridium( iii ) complexes bearing the phenyl-3H-imidazo[4,5- b ]pyridine-based (C^C) bidentate ligands, demonstrating an EQE of 11.2% and CIE ( x , y ) coordinates of (0.16, 0.07).

Switch on of TADF can be achieved by tuning the excited state energy levels via ligand manipulation of the carbazolylgold(iii) C^C^N complexes. The resulting OLEDs show maximum EQEs of over 11% and efficiency roll-offs of down to less than 1%.