Search

By combining aggregation-induced emission (AIE) effect and a triplet–triplet upconversion (TTU) process, a blue emitter with excellent photoluminescence quantum efficiency and high upconversion efficiency in the film state is developed, from which a highly efficient non-doped blue TTU organic light-emitting diode (TTU-OLED) was realized.

Excellent luminescence and transportation are the most essential features of organic light-emitting diodes (OLEDs); however, many D–A type materials usually facilitate charge transport but have poor luminescence properties. Herein, we designed two triphenylamine-pyrazine compounds, namely 25-TPA2P and 26-TPA2P, with planarized intramolecular charge transfer character to overcome this problem. Both single crystal XRD and computational analysis show an asymmetric configuration for 26-TPA2P, which furnishes 26-TPA2P with relatively strong ICT and better charge transport balance, as compared with the symmetric 25-TPA2P. A non-doped device containing 25-TPA2P displays sky-blue electroluminescence with a maximum external quantum efficiency (ηext) of 6.09%, by virtue of its strong emission in the solid state and its orientation; for 26-TPA2P, a deep blue OLED with a CIEy of 0.07 and ηext of 4.88% is achieved. Thanks to the balanced transport ability of 26-TPA2P, a series of high efficiency orange/red phosphorescent OLEDs and two-color hybrid WOLEDs are obtained based on 26-TPA2P as the host material. The ηext of the orange OLED exceeds 28%, and the warm-white OLED exhibits a total ηext of 30.11%. These results suggest that PLICT materials could satisfy both conditions of good charge transportation and luminescence, which could bring about bright prospects for displays and illuminations.

Triplet-triplet upconversion (TTU), where two low-energy triplet excitons are converted to one higher energy singlet exciton, is excellent approach to break through the theoretical limit of the pure fluorescent organic light-emitting diodes (OLEDs) by 5%. To data, however, the reported emitters with high emission efficiency and efficiently TTU in film state are rare. Herein, we design the blue aggregation-induced emission luminogens (AIEgens) and investigate their upconversion efficiency. TPA-An-mPhCz can not only achieve high emission efficiency in the film state, but also show high upconversion efficiency of close to 50% even though the calculated energy level of the triplet excitons (T2) is lower than 2T1. A possible upconversion mechanism is proposed according to the transient electroluminescence spectra and theoretical calculation. This strategy may provide a new platform for the construction of highly efficient non-doped blue OLEDs based on TTU and AIEgens.

With the advent of the big data era, information storage and security are becoming increasingly important. However, high capacity information storage and multilevel anti-counterfeiting are typically difficult to achieve simultaneously. To address this challenge, herein, two electrochromic and electrofluorochromic dual-functional polymers with aggregation-induced emission (AIE) characteristics were rationally designed and facilely prepared. Upon applying voltages, the absorption and fluorescence spectra of the AIE polymers can undergo reversible changes, accompanied by variation of their color and emission. By utilizing the controllable characteristics of the polymers, dual-mode display devices were fabricated via a simple spraying technique. More interestingly, a four-dimensional color code device was constructed by adding color change multiplexing to the two-dimensional space, thereby achieving high capacity information storage. Moreover, the color code device can also be applied in the multilevel anti-counterfeiting area. The encrypted information can be dynamically converted under different voltages. Thus, the AIE polymers show great promise for applications in multidimensional information storage and dynamic anti-counterfeiting, and the design strategy may provide a new avenue for advanced information storage and high security technology., By using electrical stimuli-responsive AIE polymers, dual-mode display devices, multidimensional information storage and anti-counterfeiting devices were constructed.

Aggregation-induced emission luminogens (AIEgens) have been widely used in organic light-emitting diodes (OLEDs), but few works have reported on utilizing AIEgens as hosts in doped OLEDs. In this work, a new AIEgen of TPP-mCP was designed and synthesized by integrating a typical AIE moiety of tetraphenylpyrazine (TPP) with a conventional host of 1,3-di(9H-carbazol-9-yl)benzene (mCP). TPP-mCP exhibits better thermal and conformational stability and carrier capacity, and higher emission efficiency in the film state than those of mCP. More importantly, the OLEDs fabricated with TPP-mCP as the host show much higher electroluminescent performance than those with mCP. Thus, this work not only generates a new AIE-active host of TPP-mCP with high device performance, but also provides a strategy to construct more effective hosts by decorating conventional ones with AIE units, which will potentially promote the development of OLEDs.

The reported organic light-emitting diodes (OLEDs) based on hybridized local and charge-transfer (HLCT) state emitters mostly exhibit low photoluminescence quantum yields (PLQYs) in aggregates, failing to achieve optimal device efficiency although they exhibit good exciton utilization efficiencies (EUEs). In this work, by introducing an aggregation-induced emission (AIE) moiety (tetraphenylethene, TPE) and a cyano group (CN) to the HLCT-typed core, phenanthroimidazole (PI), six luminescent compounds with different conjugation patterns at the C2 and N1 substituent positions were obtained, and their excited states were regulated effectively. Based on systematic photophysical analysis, the impacts of molecular conjugation patterns on the regulation of the locally excited (LE) and charge-transfer (CT) components are disclosed, and their AIE characteristics that ensure the high PLQYs of these compounds in aggregates were observed. Exciton conversion channels from triplets to singlets via the tuning of excited states were proposed based on theoretical calculations. The non-doped OLED based on ppCTPI compounds exhibited excellent performance with a maximum luminance, current efficiency, and external quantum efficiency of up to 31 070 cd m−2, 18.46 cd A−1, and 7.16%, respectively, and a very small efficiency roll-off of 4.0% at 1000 cd m−2 luminance. The successful design of these HLCT-based AIEgens not only provides more optimization choices for OLED emitters, but also demonstrates that the strategy of reasonably superposing the AIE unit onto HLCT emitters is feasible in materials design.

Radix Angelicae Sinensis, known as Danggui in China, is an effective and wide applied material in Traditional Chinese Medicine (TCM) and it is used in more than 80 composite formulae. Danggui from Minxian County, Gansu Province is the best in quality. To rapidly and nondestructively discriminate Danggui from the authentic region of origin from that from an unauthentic region, an electronic nose coupled with multivariate statistical analyses was developed. Two different feature extraction methods were used to ensure the authentic region and unauthentic region of Danggui origin could be discriminated. One feature extraction method is to capture the average value of the maximum response of the electronic nose sensors (feature extraction method 1). The other one is to combine the maximum response of the sensors with their inter-ratios (feature extraction method 2). Multivariate statistical analyses, including principal component analysis (PCA), soft independent modeling of class analogy (SIMCA), and hierarchical clustering analysis (HCA) were employed. Nineteen samples were analyzed by PCA, SIMCA and HCA. Then the remaining samples (GZM1, SH) were projected onto the SIMCA model to validate the models. The results indicated that, in the use of feature extraction method 2, Danggui from Yunnan Province and Danggui from Gansu Province could be successfully discriminated using the electronic nose coupled with PCA, SIMCA and HCA, which suggested that the electronic-nose system could be used as a simple and rapid technique for the discrimination of Danggui between authentic and unauthentic region of origin.

OBJECTIVE To distinguish the ginseng and American ginseng pieces accurately and rapidly by electronic nose technology and principal component analysis (PCA) method. METHOD The optimum conditions of electronic nose for ginseng and American ginseng pieces, such as sample size and volume, headspace volume, incubation time and temperature were determined by the orthogonal test, the data were processed by the normalization method and the preprocessed data were analyzed PCA. RESULT The detection methods of ginseng and American ginseng pieces was established by electronic nose, and the odor fingerprint figures of ginseng and American ginseng pieces were obtained, and ginseng and American ginseng pieces were distinguished by PCA recognition pattern. CONCLUSION A new accurate and rapid method to distinguish ginseng and American ginseng pieces was established by electronic nose detection.