Achieving high-performance electroluminescence with EQE of 7.20% and CIEy ∼ 0.06 based on bipolar materials with intercrossed excited state characteristics.

Remote chemical detection in the atmosphere or some specific space has always been of great interest in many applications for environmental protection and safety. Laser absorption spectroscopy (LAS) is a highly desirable technology, benefiting from high measurement sensitivity, improved spectral selectivity or resolution, fast response and capability of good spatial resolution, multi-species and standoff detection with a non-cooperative target. Numerous LAS-based standoff detection techniques have seen rapid development recently and are reviewed herein, including differential absorption LiDAR, tunable laser absorption spectroscopy, laser photoacoustic spectroscopy, dual comb spectroscopy, laser heterodyne radiometry and active coherent laser absorption spectroscopy. An update of the current status of these various methods is presented, covering their principles, system compositions, features, developments and applications for standoff chemical detection over the last decade. In addition, a performance comparison together with the challenges and opportunities analysis is presented that describes the broad LAS-based techniques within the framework of remote sensing research and their directions of development for meeting potential practical use.

The wavelength modulation-active laser heterodyne spectroscopy (WM-ALHS), which introduces wavelength modulation technique into active laser heterodyne spectroscopy, is reported to enhance the gas standoff detection capability of weak return optical power. The ALHS gas standoff detection system is developed using a 1.65 μm butterfly packaged distributed feedback laser with tail fiber and an all-fiber structure, which successfully detects methane concentrations at a distance of 35 cm using an aluminum plate as the reflective surface. Allan variance analysis shows that the system has good stability, and the detection limit at 29.2 s integration time is 0.84 ppm m.Standoff detection experiments with direct absorption-active laser heterodyne spectroscopy (DA-ALHS) and wavelength modulation spectroscopy (WMS) are carried out on the basis of the WM-ALHS system and the detection limits of 4.49 and 1.64 ppm m were achieved within integration times of 18.6 and 29 s for DA-ALHS and WMS, respectively. The superiority of the WM-ALHS method compared to these two spectral detection methods is demonstrated.Furthermore, the feasibility of applying WM-ALHS to gas standoff detection has been verified, laying the foundation for the development of this spectroscopic technology.

A hybrid organic light-emitting device with excellent stability has been achieved by introducing an ultra-thick MoO3 layer as a hole transport layer.

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High-performance phosphorescent organic light-emitting devices (PhOLEDs) at high luminance are still a remaining problem that needs to be solved, especially blue PhOLEDs. Here, 5-(5-9H-carbazol-9-yl)­pyridin-2-yl)-8-(9H-carbazol-9-yl)-5H-pyrido­[3,2-b]­indole (p2PCB2CZ) with excellent characteristics as a host is designed to realize a novel host–guest system without hole trapping effect in blue PhOLEDs. The device in which p2PCB2CZ and bis­(3,5-difluoro-2-(2-pyridyl)­phenyl-(2-carboxypyridyl)­iridium­(III) (FIrpic) is used as host and guest, respectively, is proposed to improve the performances of blue PhOLEDs at high luminance, especially at ultrahigh luminance (>30000 cd/m2). The maximum external quantum efficiency (EQE) of this type of blue PhOLEDs is 19.2%, while the maximum EQE of the reference blue PhOLEDs is 18.7%. Nevertheless, the p2PCB2CZ-based devices exhibit significant advantages at high luminance, because its EQE still attains to 10.8% even when the luminance increases to 30000 cd/m2, which is 1.67 times that of the reference device. From measurements based on steady-state and time-resolved spectroscopies, the reduction of triplet-polaron quenching in p2PCB2CZ-based devices is proved to be the main reason for improving the performances of blue PhOLEDs at high luminance.

High color quality and the removal of blue hazard are important for lighting applications. Thermally activated delayed fluorescence (TADF) materials can achieve ≈100% internal quantum efficiency with low cost. However, it is still challenging to achieve high‐color‐quality and blue‐hazard‐free TADF‐based white organic light‐emitting devices (WOLEDs). Here, a bluish‐green TADF material named 10,10′‐[5‐(6‐[1,1′‐biphenyl]‐4‐yl‐2‐phenyl‐4‐pyrimidinyl)‐1,3‐phenylene] bis [9,10‐dihydro‐9,9‐dimethyl‐acridine (DMAC‐BPP) containing two acridines connecting by a phenyl and a pyrimidine is designed and synthesized. Efficient bluish‐green OLED is achieved with DMAC‐BPP emitter. Besides, the yellow and red phosphorescent OLED utilizing DMAC‐BPP as host also shows excellent performance. Thus, a blue‐hazard‐free hybrid WOLED using DMAC‐BPP as host and emitter with maximum external quantum efficiency of 15.6% is achieved. Furthermore, this WOLED shows low efficiency roll‐off and high color quality.