Abstract：With the rapid development of smart materials， photoresponsive metal-organic frameworks （MOFs） has attracted extensive attention of researchers. Under the alternating irradiation of ultraviolet and visible light， photoresponsive MOFs can be reversibly switched between different morphologies， accompanied by changes in physical and chemical properties， which have broad development prospect in the fields of drug transport， gas separation， photo-controlled catalysis and smart sensing. Most of the photoresponsive MOFs are formed by the coordination of photoresponsive ligands and metal ions. Different photoresponsive ligands make the systems have unique properties and application scenarios. In this article， the recent research progress of photoresponsive MOFs is reviewed， including the main types of photoresponsive MOFs and their applications in different fields such as gas separation， material transport， dynamic anti-counterfeiting， and optoelectronic devices. Finally， the future development of photoresponsive MOFs is prospected.
Cong Yao,Xinpeng Fu,Yanxin Shen,Wenyuan Li,Xihong Fu
Abstract：The effect of pump focusing characteristic on output laser characteristics of passively Q-switched solid-state （PQS） laser is studied. Using a 10 W laser diode （LD） and a coupling focusing lens with focal length of 4 mm， without changing the cavity structure and the distance between LD and resonator （15 mm）， five coupling focusing lens positions were selected to research the effect of pump focusing characteristic on output laser characteristics， especially on the stability of the output pulse. When the distance between LD and the coupling focusing lens is 7.50 mm， at a continuous-wave pump power of 3.550 W， a passively Q-switched laser with higher repetition rate （160 kHz）， higher average output power （360 mW）， higher single-pulse energy （2.250 μJ） and lower time jitter （120 ns） was obtained. The experimental results indicates that the match degree between pump focusing spot and fundamental mode spot is good when the distance between LD and the coupling focusing lens is 7.50 mm. The theoretical calculation results indicates that the ratio of the fundamental mode spot size to the focusing spot size is 0.854 when the distance between LD and the coupling focusing lens is 7.50 mm. The ratio can be used as a reference for the research of high repetition-frequency PQS laser.
Keywords：LD-pumped;passively Q-switched;coupling focusing lens position
Abstract：A method to one-pot synthesize solid fluorescent materials by coating carbon dots via the crystallization of phthalic acid precursor as matrix is reported. The crystalline CDs， emitting blue and green fluorescence respectively， are synthesized by changing the solvent in microwave method. After detailed structural and spectral characterizations， it is found that a crystalline matrix is grown around the CDs by the phthalic acid precursor when the CDs is formed， and the dispersion effect of the matrix on the CDs effectively blocked the aggregation of the CDs， thus preventing the occurrence of fluorescence quenching of the CDs. Furthermore， the change of crystalline matrix structure in G-CDs leads to the increase of pyridine nitrogenous groups at the interface between core and matrix in the CDs， resulting in a change of fluorescent color of the CDs with different crystalline structures. The resultant crystalline CDs are also used to fabricate white-light emitting diode devices （WLED） in view of its excellent luminescence performance， which achieves a warm-white light with the Correlated Color Temperature （CCT） of 4061 K， Color Rendering Index （CRI） of 88.4 at the chromaticity coordinates of （0.37， 0.36） using B-CDs combined with the commercial phosphors and anther warm-white light with the CCT of 4478 K， CRI of 85 at the chromaticity coordinates of （0.36， 0.34） using G-CDs combined with the commercial phosphors. The excellent photometric parameters give these fluorescent nanomaterials potential application value in optoelectronic field.
Abstract：Purely organic room-temperature phosphorescence （RTP） materials have received extensive attention in the field of organic electroluminescence in recent years for the direct utilization of the 75% triplet excitons generated by electro-excitation. However， due to the theoretical spin-forbidden properties of purely organic materials， triplet excitons generally possess slow radiation rates and long exciton lifetimes， making it prone to non-radiative dissipation. Therefore， achieving enhanced spin-orbit coupling through efficient molecular design strategies is essential to promote fast intersystem crossing and phosphorescence radiation processes， thereby achieving high phosphorescence quantum efficiency and suppressing non-radiative deactivation of long-lived triplet excitons. In this article， based on the structural design principles of RTP materials， we reviewed recent progresses of purely organic RTP electroluminescence materials and devices， and summarized the application of RTP materials containing different non-metallic heavy atoms in electroluminescent devices. Also， we pointed out the key problems that need to be solved in the current research， and prospected the potential application of purely organic RTP materials in the field of electroluminescence.
Abstract：Broad-spectrum near-infrared light sources have a wide range of applications in non-invasive detection， military surveillance， food inspection， medical imaging， etc. In practical applications， a near-infrared （NIR） phosphor and a blue LED chip are used to form a fluorescent conversion light-emitting diode. As a NIR light source， it has the advantages of mature technology， compact structure and low cost. In this paper， the research progress of Cr3+ doped near-infrared phosphors excited by blue LEDs is reviewed. First， the crystal field theory of Cr3+ luminescence is briefly introduced， and the recently reported Cr3+ doped near-infrared phosphors are sorted out according to the material system. Secondly， in view of the shortcomings of near-infrared phosphors in terms of spectral range， temperature resistance， output power， electro-optical conversion efficiency， etc.， the existing research work from related mechanisms to optimize spectral performance， improve thermal quenching performance and electro-optical conversion efficiency is summarized. Finally， the researches on the device application of NIR light source are comprehensively summarized and compared.
Abstract：The biomedical applications of aggregation-induced emission （AIE） nanoprobes that emit fluorescence in the second near-infrared（NIR-II）optical window is an emerging research area. In comparison with traditional fluorescent materials， NIR-II AIE nanoprobes have been established to show superiority in deeper tissue penetration ability， minimized light damage， and good quantum yield in aggregated state. It has been proven that rational molecular engineering could realize the controllable regulation between the radiative and nonradiative dispersion of the excited state energy of the NIR-II AIE chromophores. The unique propeller-like conformation of AIE luminogens determines its easily modulable attribute between radiative decay which can be used for fluorescence imaging （FLI） and nonradiative decay which can be harnessed to conduct photothermal imaging （PTI）/photoacoustic imaging （PAI）/photothermal therapy （PTT）/photodynamic therapy （PDT）. At present， AIE luminogens have developed into an alternative candidate to build integrated “one-for-all” theranostic platform. Herein， this review systematically summarizes the latest research advancements of NIR-II AIE probes， on the aspects of molecular design and biomedical applications. Besides， the current challenges and future research directions of NIR-II AIE nanoprobes are briefly discussed in the end.
Ran Su,Xifeng Zheng,Yu Chen,Fengxia Liu,Xin Zhang,Yang Wang,Hui Cao,Jing Miao
Abstract：Image quality has always been a hot topic in LED display field， one of momentous contributing factors is white balance parameter， which directly determines the luminance and chroma fidelity. Generally， white balance is adjusted by fixed ratio of luminance of the primaries. Furthermore， balance ratio is relatively stable. But for each primary of the LED， changes in environmental factors will cause changes in the primary parameters. As a result， the white balance of the display panel drifts， which seriously affects the image display quality. Based on the theory of chromaticity and characteristics of LED， this paper builds a gamut model of a specific LED display to discuss the effect of each primary on white balance parameters in different temperature environments only when the brightness changes. The variation of white balance parameters and hue distortion under temperature fluctuation are mainly quantitative analyzed. In that， this paper provides a valuable theoretical basis for the revision of the high-definition LED display control system， which helps to enhance the qualities of high-end LED display products.
Abstract：A metal-semiconductor-metal （MSM） structure solar blind UV detector was constructed by preparing interdigital Au electrode on polycrystalline diamond films grown by DC plasma jet chemical vapor deposition （DC-PJCVD）. The effects of different photolithography processes on the performance of the diamond detector were studied， and the results show that the performance of the device prepared by lift-off photolithography is significantly better than that prepared by wet procedure photolithography. The photocurrent of the device is increased by 4.4 times， the light-dark current ratio is increased by 6.8 times， and the responsivity is increased by 9 times to 0.15 A/W at 25 V. On this basis， the interdigitated electrodes of Au， Ti， Ti/Au and Ag were prepared by lift-off photolithography. The performance differences of diamond UV detectors prepared by different metal electrodes were compared. The Ag electrode has the best performance among the four electrodes due to the gain caused by the barrier tunneling effect. At 25 V bias， the light current is 0.21 μA， and responsivity increases to 0.78 A/W. Compared with common Au electrode， the photocurrent， light-dark current ratio and responsivity are increased by 5.2 times， 7 times and 5.2 times respectively.
Abstract：A facile ligand-assisted solution process was proposed to synthesize quasi-2D CsPbBr3 perovskite nanoplatelets （NPs） with ultrapure green photoluminescence （PL） at room temperature. The as-synthesized CsPbBr3 NPs exhibit an ideal emission peak at 526 nm with a narrow FWHM of 16 nm and a high photoluminescence quantum yield （PLQY） of 87%. As a green downconverter， the CsPbBr3 NP shows a CIE coordinate at （0.145， 0.793） and covers 91% of the Rec. 2020 standard in the CIE 1931 color space， which was much better than that of all the present green phosphors. Moreover， a WLED was successfully fabricated based on these ultrapure green light-emitting CsPbBr3 NPs， which exhibit a luminous efficiency 39 lm/W with a CIE （0.33， 0.29） under a 20 mA driving current.
Keywords：CsPbBr3 perovskite;nanoplatelets;ultrapure green photoluminescence;WLED
Abstract：In this paper， the luminescence process of Cs0.05FA0.81MA0.14PbI2.55Br0.45 （hereinafter referred to as CsFAMA mixed cationic perovskite） thin film was studied by steady-state and transient photoluminescence （PL） spectroscopy. The phase transition induced PL spectra red shift was observed at about 245 K. According to the results of Saha-Langmuir equation， it is confirmed that electron hole recombination dominates the luminescence process of CsFAMA mixed cation perovskite when the temperature is higher than 65 K. The PL spectra of CsFAMA mixed cation perovskite were fitted by the combined model of interband luminescence and band tail luminescence. The band tail extendsion E0 （0.023 eV-0.045 eV） and the carrier equivalent temperature were obtained in the temperature range of 65 K-295 K. The experimental results show that the electron hole recombination rate constant Reh decreases with the increase of thermodynamic temperature （65 K-295 K） on the basis of analysis of the luminescence kinetics curve of CsFAMA mixed cationic perovskite. The increase of thermodynamic temperature causes the enhancement of lattice vibration， which is conducive to the heat exchange between free carriers and lattice. Meanwhile it increases the thermal disorder， leading to suppress of electron and hole radiative recombination and accelerate of carrier nonradiative recombination.
Abstract：Ultraviolet/near ultraviolet （UV/NUV） organic light-emitting diodes （OLEDs） have attracted extensive research due to its great application potential in biological and chemical sensing， laser， high-density information storage and optoelectronic circuits， etc. This paper reviews the recent development of ultraviolet organic light-emitting diodes （UV-OLEDs）， including organic chromophores， device structures and practical applications. Firstly， the materials with high efficiency shortwave emission are introduced， focusing on the characteristics of the materials themselves and their structural characteristics. Then， we give an overview of device structures to improve the performance of devices. Finally， we discuss the progress and challenges of using UV-OLEDs as excitation sources in emerging applications， and expect that this will promote the development of ultraviolet light sources in more fields in the future.
Abstract：In this study， response surface methodology （RSM） was used to study the effects of microwave action time （T）， microwave power （W） and the ratio of common lophatherum herb to deionized water （R） on the fluorescence quantum yield （QY） of N/Si-CQDs prepared by microwave method. The significance order of the influence of the above process parameters on QY， and the corresponding QY regression model and the best process parameters are obtained， and the optimization results are proved to be reliable through validation experiments. The average particle size of N/Si-CQDs obtained by the best process is small and evenly distributed， with good dispersion in water， excitation dependent emission characteristics， high fluorescence stability， low cytotoxicity to HEK293 cells， and can be absorbed by cells to illuminate cells， so as to clearly distinguish cytoplasm and nucleus， which shows that the N/Si-CQDs can be used for cell imaging. This study not only provides a new idea for the high-value utilization of bamboo leaves， but also has reference value for improving the efficiency of microwave preparation of biomass carbon quantum dots and promoting their application in biomedical fields such as cell imaging.
Abstract：Pyrimidine can be used as a common acceptor for the construction of D-A type thermally activated delayed fluorescent（TADF） materials. Its strong electron absorption characteristics and flexible substitution effect are advantageous to the formation of diversified molecular structures， which lends probability to realize efficient organic electroluminescence. In recent years， important progress has been made in the molecular structure design based on pyrimidine acceptor. The research direction has transformed from symmetrical molecules dominated by D-A-D type to asymmetric molecules gradually. Quinazoline is a new acceptor of TADF materials with fused bicyclic structure of benzene and pyrimidine rings， which shows good potential as a result of extended conjugate plane. Through the reasonable molecular modification， it can improve the luminescence performance of the device effectively. In this review， we summarize the research progress of thermally activated delayed fluorescent materials based on pyrimidine and its derivative quinazoline acceptors briefly with molecular structure， photophysical properties and device performances， and look forward to the broad development prospect of TADF materials based on quinazoline.
Xin-yue ZHAO,Qiang QIU,Ying-bo CHU,Neng-li DAI,Jin-yan LI
Abstract：Space Division Multiplexing technology based on few-mode fiber （FMF） and multi-core fiber is considered to be one of the most important technologies to greatly improve the data transmission capacity of a single fiber in the future. If we want to employ FMF in space division multiplexing to realize a long-haul transmission system， few-mode erbium-doped fiber amplifiers （FM-EDFAs） will be a key block to compensate for the fiber transmission loss while its performance is determined by few-mode erbium-doped fiber （FM-EDF）. In addition to fundamental indexes like gain， bandwidth and noise figure， few-mode erbium-doped fiber has a unique index---differential modal gain （DMG） compared with the single-mode erbium-doped fiber. Minimizing DMG to maintain signal quality is critical in FM-EDFAs as the high differential modal gain can improve the potential for system outage. In this paper， the generation mechanism and improvement strategies of differential modal gain are systematically described， the different designs of FM-EDF are summarized， the performance characteristics of FM-EDF based on different pumping methods and different designs are compared， and the research on the performance of FM-EDF is prospected.
Abstract：Micro light-emitting diode（Micro-LED）， with many advantages such as high-resolution， high color gamut， and high stability， has broad prospects for near-eye display. However， two major technical issues in Micro-LED need to be solved， including mass electroluminescence detection and mass metal bonding. In this work， a working mode for Micro-LED with single-terminal carrier-injection is proposed， and a single-injection type Micro-LED related to the working mode is fabricated. The working process is studied by experiments and simulations in order to explore the working mechanisms. The current-voltage， current-frequency， brightness-frequency relationship and the periodic variation of the energy band of single-injection type Micro-LED under sinusoidal alternating current are studied. Moreover， the carrier transport model of single-injection Micro-LED are proposed. Finally， the application of single-injection mode used in the detection of vertical structure Micro-LED is demonstrated， which provides new ideas for Micro-LED detection.
Keywords：micro-LED;Single-terminal carrier-injection;Electroluminescence detection;Alternating current
Ri-lang GUO,Shao-hang WU,Cui-ling ZHANG,Yi XIE,Ya-qing LIU,Yao-hua MAI
Abstract：One of the prerequisites for realizing high efficiency photovoltaic devices is that the incident light is effectively absorbed by the light absorbing layer. Therefore， it is very important to improve efficiency to systematically analyze the optical loss mechanism of perovskite photovoltaic cells and optimize the light absorption of the light absorbent layer. In this paper， for inverted planar perovskite solar cells， combining with the external quantum efficiency （EQE） of the cell， the light absorption characteristics of the film and theoretical simulation， the effects of the thickness changes of perovskite thin film as the light absorption layer and ［6，6］-phenyl-C61-butyric acid methyl ester （PCBM） thin film as the interface layer on photogenerated current were compared and studied. The results show that in addition to parasitic absorption， the adjustment of the optical field by the interface layer can affect the optical absorption of the light absorption layer in the device. The simulation results show that 660 nm perovskite film and 40 nm PCBM film can be used as the optimal choice， and the corresponding integral current is 24.93 mA/cm2. This paper also explored the influence of the addition of PbI2 layer on the absorption characteristics of the perovskite light absorbing layer. The results indicate that when PbI2 accumulates on the side of the perovskite layer near the incident light， it leads to significant optical loss， while when PbI2 accumulates on the side of the perovskite layer near the back electrode， the influence is relatively small.
Abstract：Organic light emitting diodes （OLEDs） are light-emitting devices based on organic semiconductors. They are considered as a new generation of display and lighting technology because of their advantages such as self-illumination， fast response， adjustable light-emitting color， lightness， large area flexibility and foldability， etc. The emission of OLEDs is a process of the radiative decay of excitons formed by recombination of injected electrons and holes. Therefore， how to effectively use excitons， especially the use of triplet excitons， has become an important topic in the research on materials and devices of OLEDs. Among them， how to convert triplet exciton energies into singlet excitons and finally realize the fluorescence emission of 100% excitons has more application value. In recent years， significant progresses have been made in this field. This paper introduces the effective methods for the fabrication of high efficiency fluorescence OLEDs in detail based on working mechanism and luminescence processes of OLEDs and their latest progresses， and prospects the future development directions， which provide an important reference for the research on materials and devices of OLEDs.
Keywords：Organic light-emitting;excitons;Efficient utilization;Singlet and triplet states
Abstract：3d transition metal （3d-TM） activated phosphors exhibit great potential applications in relevant fields. Generally， how to determine the ground state position of 3d-TM ion and engineer their valence state is significantly important in designing phosphor with target properties. This article reviews the spectroscopic data and optical transition levels of 3d-TM activated phosphors. Combining with the first-principle calculations， the evolution principle of the 3d-TM ground state in compounds are summarized. The charge transition tendencies and their theoretical understanding are revealed. Finally， the future design methods are prospected with above principles.
Keywords：transition metal ions;Ground state energy level;Luminescence property engineering
Abstract：Organic Light Emitting Diodes （OLED） technology is considered to be the next generation of display technology， and has gradually occupied the mainstream of the market， but the performance of OLED is still largely limited by electron transport materials， especially in high-performance deep blue light devices. This is because it is difficult for organic molecules to obtain high electron mobility， and the recombination zone in the device is usually close to the interface of the electron transport layer， which requires the electron transport material to have a high triplet energy level to confine the exciton， especially the blue light exciton with high energy. However， high triplet states （poor conjugation） and high mobility （strong conjugation） have always been difficult to reconcile in the design of organic molecules， and a wider band gap will also lead to poorer thermal stability. These problems have been affecting the development of OLED electronic transport materials. In this paper， several elements of high performance electronic transport materials are introduced， including thermal stability， photochemical stability， electron mobility， the frontier orbital and the triplet energy level and so on， and summarizes the important research progresses of the micromolecular electron transport materials in 21st century， in order to develop the ideal electronic transfer materials to provide the reference in the future.
Keywords：organic light-emitting diodes;Electronic transport materials;stability;Electron Mobility;Triplet Energy
Abstract：As a popular inorganic luminescent materials， up-conversion fluorescent fluosilicate glass ceramics is promising in solid-state laser， solid-state illumination， optical anti-counterfeiting encode and optical thermometry. Research and applications of up-conversion fluorescent fluosilicate glass ceramics containing binary-elements nanocrystal， ternary-elements nanocrystal were reviewed. In which， we compared the effect of composition on nanocrystallization and up-conversion photoluminescence， and listed the issues need to be solved for the further development. We hope this review can provide inspiration and guidance to the future research of up-conversion fluorescent fluosilicate glass ceramics.
Keywords：fluosilicate glass;glass ceramics;composite glass with nanocrystal;up-conversion photoluminescence;rare earth ions