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Developing highly efficient red/near‐infrared (NIR) thermally activated delayed fluorescence (TADF) materials is important for organic light‐emitting diodes (OLEDs). Here, two TADF emitters, APTT and APTI, which have the same D/A backbone but different attaching groups at acenaphtho‐[1,2‐b]pyrazine‐8,9‐dicarbonitrile (APDC) core, are reported. The appended regulating groups can not only suppress the D/A rotation due to the space confinement effects but also modulate the locally excited triplet state (3LE). The improved molecular rigidity suppresses the non‐radiative process, accounting for the improved photoluminescence quantum yields (PLQYs), while the modulated 3LE promotes the reverse intersystem crossing (RISC) process due to the high utilization efficiency of triplets. Consequently, both APTT and APTI demonstrate high PLQY and fast RISC process, thereby enhancing TADF efficiency. The doped devices based on APTT and APTI achieve maximum external quantum efficiency (EQEmax) values of 20.5% and 25.4% with emission peaks at 664 and 670 nm, respectively. The non‐doped devices of APTT and APTI achieve the EQEmax of 2.8% and 2.9% with emission peaks at 788 and 794 nm, respectively. Encouragingly, the non‐doped devices of APTI have set new records for near‐infrared TADF OLEDs based on the APDC core. This study provides an efficient approach to modulating the optoelectronic properties of highly efficient NIR TADF OLEDs. [ABSTRACT FROM AUTHOR]

Red to near-infrared organic light-emitting diodes (OLEDs) utilizing thermally activated delayed fluorescence (TADF) emitters continue to exhibit significant external quantum efficiency (EQE) roll-off at high luminance levels exceeding 1000 cd m−2, attributed to the relatively modest reverse intersystem crossing rate constant (kRISC) of approximately 103–104 s−1. This study presents a novel TADF molecule, TCPP-DTPA, featuring a structurally rigid π-stacked multiple donor/acceptor design. The enhanced donor/acceptor interactions minimize the energy gap between the singlet and triplet states of the TCPP-DTPA, allowing for an efficient RISC process with a high rate constant of 4.67 × 106 s−1. The OLED utilizing TCPP-DTPA demonstrates a peak EQE of 23.5% at a wavelength of 618 nm. Additionally, notable EQE values of 7.8% and 14.9% are observed at a luminance of 1000 cd m−2 for OLEDs without and with an energy-transfer assistant dopant in the emissive layer, respectively. This research contributes to enhancing the efficiency of high-brightness red TADF OLEDs, while also offering valuable insights for the optimization of molecular design and device engineering to mitigate the electroluminescence efficiency roll-off. [ABSTRACT FROM AUTHOR]

Conformational engineering is essential to further reinforce the luminescent properties of thermally activated delayed fluorescence (TADF) materials featuring through‐space charge transfer (TSCT) characteristics. Herein, two TSCT‐TADF emitters (8MeDM‐B and 8FDM‐B) with the methyl and fluorine moieties substituted at the C8 site of the rigid spiro‐fluorene bridge is reported. Derivation of the C8 site is first proposed to control the molecular configuration with the ability to indirectly tune the intramolecular interaction between donor and acceptor groups. As a result, 8MeDM‐B and 8FDM‐B both present small singlet‐triplet energy gaps, fast reverse intersystem crossing rates, and high photoluminescence quantum yields. Interestingly, the smaller fluorine atom not the bigger methyl group exhibits more evident electrostatic repulsive force onto the central donor and thus rectifies the central spiro structure. Consequently, the high external quantum efficiency values of 28.8% and 31.7% for 8MeDM‐B and 8FDM‐B‐based electroluminescence devices are achieved, respectively. This study offers a measure for enhancing TSCT‐TADF emitters without directly modifying the donor or acceptor. [ABSTRACT FROM AUTHOR]

Power efficiency (PE) at high brightness is considered as the rigorous standard of high-quality white organic light-emitting diodes (WOLEDs), for which the host material plays a significant role in energy conservation for practical lighting applications. Herein, PE is successfully enhanced to a new level through the method of π-stacked host molecular with spirofluorene scaffold. We design host materials by confining two donor units in a very short distance to enlarge the π-electron spatial delocalization for facilitating the hole hopping process and engaging a rigid donor as the space-lock to suppress the quenching effect as well as induce host bipolar property. Based on this unique molecular design, the red, green, and blue (RGB) monochromic organic light-emitting diodes (OLEDs) demonstrate high external quantum efficiencies (EQEs) of 28.4%, 26.0%, and 31.2% with ultralow roll-off, respectively. More encouragingly, the warm WOLEDs achieve record-high current efficiency (CE) of 109.5 cd A−1, PE of 109.1 lm W−1, and EQE of 32.9%. Even under operating brightness of 1,000 cd m−2, the devices can still realize 94.7 lm W−1 of PE, which represents the highest applicable PE value in the reported WOLEDs and for the first time single host based WOLEDs with a performance exceeding that of a conventional fluorescent tube (70 lm W−1) without any light extraction technique. [ABSTRACT FROM AUTHOR]

We study the research status of thermal simulation experiment and put forward three issues worthy of attention and five important development directions. Classification according to thermal simulation system is the most widely used classification scheme. Different thermal simulation experimental systems have their own characteristics, and a suitable thermal simulation experiment system can be selected according to different experimental purposes. The closed experimental system is more suitable for the thermal simulation experiment of humic source rocks. The online analysis of open system has unique advantages in the study of volatile components. The semi open system is the most close to the thermal simulation system of the thermal evolution of the source rocks in the actual geological condition. Three key issues concerning the thermal simulation experiment are presented. The first is influence of water on the thermal simulation experiment. The second is whether convincing isotope reversal can be presented expect Fischer-Tropsch synthesis. The third is that, in the study of thermal simulation experiment, the model of hydrocarbon generation must be built in combination with the actual geological background. Five key development directions concerning the thermal simulation experiment are proposed. The first is thermal simulation experimental study on relatively low temperature and long time with water participation. The second is experimental research on thermal simulation of unconventional petroleum. The third is study on the development of pore microcracks in source rocks and the correlation of the interaction of fluid discharge in thermal simulation experiments. The fourth is experimental study on thermal simulation of carbonate source rock. The fifth is experimental study of thermal simulation related to abnormal pressure. [ABSTRACT FROM AUTHOR]

Efficient blue phosphors remain a formidable challenge for organic light-emitting diodes (OLEDs). To circumvent this obstacle, a series of Ir(III)-based carbene complexes bearing asymmetric di-N-aryl 6-(trifluoromethyl)-2H-imidazo[4,5-b]pyridin-2-ylidene chelates, namely, f-ct6a‒c, are synthesized, and their structures and photophysical properties are comprehensively investigated. Moreover, these emitters can undergo interconversion in refluxing 1,2,4-trichlorobenzene, catalyzed by a mixture of sodium acetate (NaOAc) and p-toluenesulfonic acid monohydrate (TsOH·H 2 O) without decomposition. All Ir(III) complexes present good photoluminescence quantum yield (Φ PL = 83-88%) with peak maximum (max.) at 443-452 nm and narrowed full width at half maximum (FWHM = 66-73 nm). Among all the fabricated OLED devices, f-ct6b delivers a max. external quantum efficiency (EQE) of 23.4% and Commission Internationale de L'Eclairage CIE x , y coordinates of (0.14, 0.12), whereas the hyper-OLED device based on f-ct6a and 5H,9H,11H,15H-[1,4] benzazaborino [2,3,4-kl][1,4]benzazaborino[4',3',2':4,5][1,4]benzazaborino[3,2-b]phenazaborine-7,13-diamine, N7,N7,N13,N13,5,9,11,15-octaphenyl (ν-DABNA) exhibits max. EQE of 26.2% and CIE x , y of (0.12, 0.13). Finally, the corresponding tandem OLED with f-ct6b as dopant gives a max. luminance of over 10 000 cd m -2 and max. EQE of 42.1%, confirming their candidacies for making true-blue OLEDs., (© 2023 Wiley‐VCH GmbH.)

A multiple resonance thermally activated delayed fluorescence (MR-TADF) molecule with a fused, planar architecture tends to aggregate at high doping ratios, resulting in broad full width at half maximum (FWHM), redshifting electroluminescence peaks, and low device efficiency. Herein, we propose a mono-substituted design strategy by introducing spiro-9,9'-bifluorene (SBF) units with different substituted sites into the MR-TADF system for the first time. As a classic steric group, SBF can hinder interchromophore interactions, leading to high device efficiency (32.2-35.9 %) and narrow-band emission (≈27 nm). Particularly, the shield-like molecule, SF1BN, seldom exhibits a broadened FWHM as the doping ratio rises, which differs from the C3-substituted isomer and unhindered parent emitter. These results manifest an effective method for constructing highly efficient MR-TADF emitters through a spiro strategy and elucidate the feasibility for steric modulation of the spiro structure in π-framework., (© 2022 Wiley-VCH GmbH.)