最新刊期
      卷 44 ， 期 12 ， 2023

        Cover Story

      • OU Jiaqi,PENG Zengyi,WANG Junjie,LI Danyang,SONG Jianing,PENG Junbiao
        Vol. 44, Issue 12, Pages: 2085-2097(2023) DOI: 10.37188/CJL.20230228
        摘要：The morphology of quantum dots （QDs） films fabricated by inkjet printing makes a marked impact on the performance of multi-layer photoelectronic devices， such as quantum dot light emitting diodes， where coffee-ring and bulge phenomena behave as the typical poor morphology types. Realizing high-quality QDs films through droplet modulation is key to the development of QDs electroluminescent displays. Ink engineering has been proven effective in adjusting the film morphology. However， a well-tailored ink with precise rheological properties to eliminate coffee ring or bulge requires multiple time-consuming experimental attempts， resulting in lower working efficiency. In this work， we sought to directly bridge the gap between the rheological properties of solvents and the profiles of inkjet-printed QDs films with post-mortem film analysis and machine learning methods adopted for mutual proof. With red QDs as the solutes， and alkanes or chain esters as solvents， work on unitary-solvent and binary-solvent ink systems was investigated to find out that generally， the boiling point of the used solvent displayed significant importance higher than that of surface tension or viscosity in both unitary and binary systems. Specifically， the film profile was closely related to the solvent with a higher boiling point in binary systems and uniform films were revealed. A boiling point range of 250-265 ℃ for the solvent in the unitary-solvent ink system or for the higher-boiling-point solvent in the binary-solvent ink systems can promisingly result in uniform films after drying.  
        关键词：quantum dot ink;inkjet printing;solvent;machine learning   
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        发布时间：2024-01-05

        Invited Review

      • ZHANG Min,LIU Dongjie,WEI Yi,DANG Peipei,LI Guogang,LIN Jun
        Vol. 44, Issue 12, Pages: 2098-2119(2023) DOI: 10.37188/CJL.20230232
        摘要：Trivalent bismuth ions（Bi3+） are excellent activators and sensitizers of luminescent materials and have been extensively studied recently. Bi3+ ions have attracted much attention due to their susceptibility to crystal field strengths and their ability to obtain rich emission colors covering the entire visible region under UV and NUV excitation， as well as NIR luminescence. These phosphor materials show potential applications in solid-state lighting， display， biomedical and optical sensing. In this review， the luminescence characteristics of Bi3+ and the research progress of Bi3+-doped phosphor materials were summarized， and the relationship between their photoluminescence properties and crystal structure was introduced in detail. In view of the key problems for precise regulation and optimization of luminescence properties of Bi3+ doped luminescent materials， the mechanism induced by design strategies such as component substitution， energy transfer and mixed valence state was discussed in this review. Finally， we discussed some future challenges and opportunities in Bi3+-doped luminescent materials， with a view to guiding the discovery and development of new phosphor materials for pc-LED applications.  
        关键词：LED;Bi3+ doping;luminescent materials;precise regulation   
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        发布时间：2024-01-05

        Views on Basic Knowledge of Luminescence

      • LIN Litian
        Vol. 44, Issue 12, Pages: 2120-2127(2023) DOI: 10.37188/CJL.20230227
        摘要：The multi-site occupations and the energy transfers are ubiquitous in various fields of rare-earth ions activated luminescence materials and have important scientific and practical significance. The Ce3+ 4f-5d and the Eu3+ 4f-4f transitions represent two typical electronic transition types of rare-earth ions. We take Ce3+/Eu3+-activated E（δ）-Gd2Si2O7（Pnma）， G-La2Si2O7（P21/n）， and F-Eu2Si2O7（P1¯） as the representative cases to discuss and revisit the multi-site occupations and the non-radiative energy transfers， focusing on the crystal structure， the phase purity of samples， the doping concentration， the spectral characterization， the energy transfer between lattice sites， and the spectral resolution. In the studies of luminescence materials activated by rare-earth ions， we must not only consider the self-consistency of the materials’ crystal structures and their spectra， but also analyze the energy transfers （including the outgoing energy and the receiving energy） between lattice sites from the spectra and the luminescence decay dynamics. We hope that these contributions could inspire experiments and characterization for readers who are new to the related fields.  
        关键词：Rare-earth luminescence materials;site occupation;energy transfer;crystal structure;Spectral resolution   
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        发布时间：2024-01-05

        Synthesis and Properties of Materials

      • CHEN Ping,GAO Yanpeng,HE Yong,DAI Nengli
        Vol. 44, Issue 12, Pages: 2128-2135(2023) DOI: 10.37188/CJL.20230212
        摘要：Self-referencing optical thermometers have shown competitive advantages on fast response and high accuracy as they can avoid inevitable external factors like concentration change， excitation fluctuation， and detector loss. Herein， we report the triple-emitting photoluminescence of Eu/Tb/SnO2 nanocrystals co-doped silica glasses. The temperature-dependent fluorescence intensity ratio of non-thermal coupled levels of Eu3+（5D0-7F2 transition， 620 nm）/Eu2+（4f65d-8S7/2 transition， 434 nm） and Eu3+（5D0-7F2 transition， 620 nm）/Tb3+（5D4-7F5 transition， 542 nm） can be used for self-referencing temperature probing in a wide range of 298-773 K. The maximum relative thermal sensitivity Sr values can reach 2.3%·K-1 at 773 K， which is higher than most Eu/Tb co-doped materials. This work will contribute a new Eu/Tb co-doped material to self-referencing optical temperature measurement with triple activators.  
        关键词：rare earth ions;SnO2 nanocrystals;photoluminescence;temperature measurement;silica glasses   
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      • ZHANG Fangming,LI Ce,LI Jianwei,LIU Wenxing,FU Yueying,JI Junjie,ZHENG Tao,GUO Yanyan
        Vol. 44, Issue 12, Pages: 2136-2148(2023) DOI: 10.37188/CJL.20230209
        摘要：Borosilicate glass possess natural advantage using as a scintillating material for detection field. To enrich the application requirements， the Ce3+ ions doped borosilicate glass scintillation material 60B2O3-6SiO2-3Al2O3-5BaO-15Na2O-10La2O3-1Sb2O3 was prepared. The structure was discussed based on density and FT-IR spectra indicating that the Ce3+ ions exist as network modifiers. The ultraviolet（UV） absorption boundary was lower than 400 nm and the optical band gap was shorted to 2.93 eV. All these factors are conducive to the luminescent properties of Ce3+ ions. The best emission spectrum was obtained at 372 nm with a 306 nm pumping. The optical basicity was increased with the concentration of Ce3+ ions（0.539 2-0.541 7）， which resulted in a light red shift of emission spectra. The fluorescence lifetime was as short as 24.39 ns， which shows obvious advantages compared with other Ce3+ ions doped scintillation glass. These results provided a new material choice for the development of the detection field.  
        关键词：borosilicate glass;Ce3+ doped;optical performance   
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      • WEN Haiyang,ZHANG Chenjie,ZHOU Tianliang,XIE Rongjun
        Vol. 44, Issue 12, Pages: 2149-2157(2023) DOI: 10.37188/CJL.20230225
        摘要：The red-near-infrared spectrum is widely used in many fields such as medical treatments. However， there is an excess of blue luminescence caused by red-near-infrared device excited by 450 nm LEDs. In this work， we proposed to construct the Ce3+→Cr3+ energy transfer to suppress the blue emission from the lighting devices. The Ce3+/Cr3+ co-doped Ba3Sc4O9 phosphors were prepared and their photoluminescence were investigated. The Ba3Sc4O9∶Ce3+/Cr3+ phosphors exhibit double emission bands centered at 585 nm and 835 nm， respectively. The blue emission remained in the prepared LED device is reduced by 78%， and the emission intensity of Cr3+ is increased up to 181% due to the energy transfer efficiency as high as 50.92% between Ce3+ and Cr3+.  
        关键词：near-infrared;Ce3+/Cr3+ co-doped;Ba3Sc4O9;energy transfer   
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        发布时间：2024-01-05
      • MA Ziting,ZHANG Xianzhe,DAI Pengpeng,SHEN Lina
        Vol. 44, Issue 12, Pages: 2158-2167(2023) DOI: 10.37188/CJL.20230218
        摘要：The miniaturization and enhanced intelligence of near infrared （NIR） devices have stimulated the design and advancement of high-efficiency broadband NIR phosphors. It is widely believed that multisite co-occupancy strategy by Cr3+ ions is a very effective method for designing broadband near-infrared phosphors. However， Cr3+ ions at different crystallographic sites often exhibit distinct thermal-quenching behaviors， leading to poor spectral stability， which hampers their practical applications. In our work， we prepared a series of KSc1-xP2O7∶xCr3+（x = 0.01-0.09） broadband NIR phosphors via the high temperature solid-state method using the one-site occupation strategy. The crystal structure， luminescence performance and thermal quenching mechanism of KSc1-xP2O7∶xCr3+ were investigated in detail. At x = 0.03 ， the luminescence intensity of KSc0.97P2O7∶0.03Cr3+（KSP∶0.03Cr3+） reaches its maximum. The concentration quenching appears when x exceeds 0.03， which is attributable to energy transfer between adjacent Cr3+-Cr3+. Under blue light excitation of ~ 471 nm， the KSP∶0.03Cr3+ phosphor exhibits a broadband emission ranging from 700 nm to 1 200 nm， with a peak centered at 857 nm and a full width at half-maximum （FWHM） of ~149 nm. Structural analysis and low temperature spectroscopy indicate that the broadband NIR emission originate from Cr3+ occupying a single Sc3+ site with the weak crystal field （Dq/B = 1.98） in the KSP host. At 373 K， the integrated emission intensity of KSP∶0.03Cr3+ sample keeps 60.2% of that at room temperature， suggesting good PL thermal stability. Finally， we prepared a near-infrared phosphor-converted LED device （NIR pc-LED） by utilizing the KSP∶0.03Cr3+ NIR phosphor and a blue light LED chip， and confirm its potential applications in night vision， biomedical imaging， and food detection.  
        关键词：Near-infrared phosphor;one-site occupation strategy;broadband emission;Cr3+;NIR pc-LED   
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      • WANG Tao,ZHANG Xiaoshuai,LI Xiaotong,WANG Zhijun,LI Panlai
        Vol. 44, Issue 12, Pages: 2168-2179(2023) DOI: 10.37188/CJL.20230208
        摘要：A series of Ca9.15La0.9（PO4）7∶0.05Eu2+，yMn2+ and Ca9.3La0.8（PO4）7∶0.05Eu2+，yMn2+ were synthesized by the high temperature solid-state method. The energy transfer from Eu2+ to Mn2+ was confirmed by the emission spectra and fluorescence decay curves. With increasing the concentration of Mn2+， the phosphor can produce the tuning emission from blue or green to white light. In addition， the thermal stability of the samples revealed that the two emission peaks of Eu2+ with different colors exhibited different temperature quenching behaviors. The color coordinates of Ca9.15La0.9（PO4）7∶0.05Eu2+，0.35Mn2+ are close to standard white light and the color temperature is similar to sunlight， which proves its potential application in white light emitting diodes （LEDs）.  
        关键词：Phosphor;Luminescence;energy transfer;Ca9.15La0.9（PO4）7∶0.05Eu2+，yMn2+   
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        发布时间：2024-01-05
      • JIANG Qiongfang,YANG Qilin,LI Xianggui,HU Xuemei,ZHOU Qiang,WANG Zhengliang
        Vol. 44, Issue 12, Pages: 2180-2187(2023) DOI: 10.37188/CJL.20230224
        摘要：Herein， K2TiF6∶Mn4+ red-emitting crystals doped with different amounts of Mn4+ were successfully grown by vaporing the solvent at room temperature. These crystals exhibit two broad excitation bands in the UV and blue light regions， which are due to 4A2 → 4T1 and 4A2 → 4T2 transitions of Mn4+. Meanwhile， they present a series of narrow-band red emissions with the strongest emission peak at 631 nm. Among these samples， the K2TiF6∶Mn4+ （13.18%） sample exhibits the strongest emission intensity with a high internal quantum efficiency of 97.2% and a high external quantum efficiency of 83.3%. It is worth noting that K2TiF6∶Mn4+ （13.18%） crystals show an obvious negative thermal effect. The emission intensity at 120 ℃ is 1.81 times higher than the initial value. The warm white LED based on K2TiF6∶Mn4+ （13.18%） crystals and the commercial YAG∶Ce3+ yellow phosphor shows excellent performance with a high luminous efficiency （LE） of 180.9 lm/W， a low correlated color temperature （3 859 K） and an ideal color rendering index （91.3）. The white LED based on β-SiAlON∶Eu2+ also has a LE of 101.5 lm/W， and its color gamut is up to 94% of NTSC （National Television System Committee） standard value. Hence， K2TiF6∶Mn4+ red-emitting crystals exhibit potential application in white LEDs.  
        关键词：Red-emitting crystals;fluorides;luminescent properties;white LEDs   
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        发布时间：2024-01-05
      • LU Siyu,LI Siyuan,ZHU Qi
        Vol. 44, Issue 12, Pages: 2188-2201(2023) DOI: 10.37188/CJL.20230211
        摘要：LaAlO3， a typical distorted perovskite structure， is an excellent luminescent host owing to its low phonon energy， wide band gap and great structural stability. The luminescence properties of Mn4+ and Pb2+， which show great sensitivity to the micro-coordination environment， can be optimized by tuning the lattice environment. This review summarizes the recent research progress in regulating the ZPL （zero-phonon line） emission of Mn4+ and the luminescence performance of Pb2+. The effects of unit co-substitution on the crystal structure， and the luminescence properties of Mn4+ and Pb2+ are systematically discussed. The structure-activity relationship between the lattice environment and the luminescence of activated ions is also analyzed in detail.  
        关键词：LaAlO3;Mn4+;Pb2+;unit co-substitution   
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        发布时间：2024-01-05
      • HE Ling,WEN Shun,SUN Weimin,DONG Qizheng,XU Yangtao,YANG Xiaofeng
        Vol. 44, Issue 12, Pages: 2202-2210(2023) DOI: 10.37188/CJL.20230214
        摘要：Sr2MgSi2O7∶Eu2+，Eu3+ fibers were prepared by electrospinning under different atmospheres， and their crystal structure and morphology were studied. Composite materials of Sr2MgSi2O7∶Eu2+，Eu3+-PDMS were obtained by combining fibers with polydimethylsiloxane （PDMS）， and their photoluminescence and mechanoluminescence properties were studied. The research results show that the XPS spectrum exhibits characteristic peaks of binding energy of Eu2+ and Eu3+ under nitrogen or air conditions. In the photoluminescence spectra of composite materials excited at 360 nm and 395 nm， there are not only blue broadband emissions of Eu2+ at 469 nm， but also multiple red narrowband emissions of Eu3+ at 615 nm. Because Eu3+ is reduced to Eu2+ under charge compensation and is not oxidized under the protection of a rigid structure， it confirms the self reduction phenomenon of Eu3+ in Sr2MgSi2O7. As the doping concentration of Eu increases， the photoluminescence and mechanoluminescence intensities first increase and then decrease. The emission of Eu2+ and Eu3+ reaches their strongest at 5% and 10%， respectively. The intensity of mechanoluminescence is linearly related to the growth of stress， and the emission growth of Eu2+ is greater than that of Eu3+. In physical photos and CIE coordinates， it was observed that the photoluminescence color gradually approached red from blue， and the mechanoluminescence color gradually changed from pink to purple pink as the stress increased. The study of this material will provide reference for luminescence regulation， and has potential usage value in fields such as stress sensing and anti-counterfeiting.  
        关键词：Sr2MgSi2O7∶Eu2+，Eu3+;fibers;Self reduction;mechanoluminescence;luminescence regulation   
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        发布时间：2024-01-05
      • ZHANG Lifu,CHEN Gang,YAN Ao,ZHANG Rui,LYU Zehua,JIANG Zhaoyi,ZHANG Yufei,MENG Shuai,LI Kun,QIN Zhenxing,SONG Kai
        Vol. 44, Issue 12, Pages: 2211-2221(2023) DOI: 10.37188/CJL.20230226
        摘要：All inorganic lead cesium halide perovskite nanocrystal CsPbX3（X = Cl， Br， I） has become attractive candidate in solid state lighting and display， solar cells， resistive memory and other fields due to its unique photoelectric characteristics. Mn2+-doped CsPbCl3 perovskite nanocrystals could achieve orange emission at the wavelength of around 600 nm， where Mn2+ with a small radius can partially replace Pb2+ to reduce toxicity. However， Mn2+-doped halide perovskite nanocrystals are still susceptible to the erosion of water molecules in the environment， leading to the severe degradation of their fluorescence properties. Herein， a double-layer coating method was adopted for Mn2+- doped CsPbCl3 using TMOS and PMMA， and the mechanism of improving the stability of perovskite nanocrystals by the double-layer coating method was also analyzed. Furthermore， the luminescence properties of double-layer coated Mn2+ ion doped CsPbCl3 perovskite nanocrystals in toluene and dichloromethane solvents were compared. The orange Mn2+ emission intensity has not significantly reduced， and the photoluminescence quantum yield（PLQY） can be maintained at about 25%. Based on this， the corresponding luminescence nanocrystal powder was prepared and 　applied to latent fingerprint identification， which can effectively detect the latent fingerprint information for a long time.  
        关键词：Mn2+-doped;halide perovskite nanocrystals;double-layer coating;luminescence powder;latent fingerprints identification   
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        发布时间：2024-01-05

        Device Fabrication and Physics

      • WANG Jianbin,TANG Xiaosheng,ZHOU Bi,ZENG Xiahui,LI Jincheng,ZHOU Yingwu
        Vol. 44, Issue 12, Pages: 2222-2230(2023) DOI: 10.37188/CJL.20230257
        摘要：Photodetectors with strong near-infrared response are more conducive to detecting human heart rate. Furthermore， broadband photodetectors with a response range covering both red and near-infrared region can be used to detect blood oxygen saturation. Therefore， improving the red and near-infrared response capabilities of broadband photodetectors is of great significance. However， classic binary bulk-heterojunction broadband photomultiplication-type organic photodetectors typically exhibit weak or even no response to red and near-infrared light due to significant ratio-difference between donor and acceptor in the active layer. This paper fabricates ternary bulk-heterojunction photomultiplication-type organic photodetectors with a structure of ITO/PEDOT∶PSS/P3HT∶PCE10∶IEICO-4F（90∶10∶1）/Al by using a small amount of donor material PCE10 to replace some of P3HT in the active layer of P3HT∶IEICO-4F（100∶1）. Under -20 V bias， the ternary devices obtain a relatively even EQE spectrum from ultraviolet to near-infrared（330-810 nm）， with the EQEs at 660 nm and 810 nm（134000% and 147000%） being 78 and 106 times as large as those of the binary devices under same conditions， and corresponding detectivity values （5.4×1013 Jones and 7.27×1013 Jones） being increased by 26 and 36 times， respectively. The red and near-infrared light detection capabilities of ternary devices have been significantly improved， providing a strategy for fabricating high-performance photodetectors to detect human heart rate and blood oxygen saturation.  
        关键词：near-infrared;heart rate;blood oxygen saturation;bulk-heterojunction;photomultiplication-type organic photodetector;ternary   
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      • FU Dingyang,GAO Xin,ZHAO Renze,ZHANG Yue,SU Peng,BO Baoxue
        Vol. 44, Issue 12, Pages: 2231-2241(2023) DOI: 10.37188/CJL.20230216
        摘要：In order to improve the output characteristics of 1 μm-band superluminescent diodes， this article studies the epitaxial structure and J-type waveguide structure. Based on the research results， the parameters of the epitaxial structure and waveguide structure are determined， and the electrode window preparation process and single-layer hafnium oxide film formation conditions are optimized. The research has shown that reducing the difference in Al composition between the waveguide and the limiting layer AlGaAs material is beneficial for improving the beam characteristics of the device. In addition， increasing the etching depth， ridge width， and curvature radius will reduce the loss coefficient and improve the output power of the device. Based on simulation results， a three quantum well structure device with non-uniform well width and large well depth was prepared. A single-layer hafnium oxide film with a reflectivity of about 0.5% was deposited on the front cavity surface， and a high reflection film was evaporated on the back cavity surface. The cavity length was about 2 mm， and the waveguide curvature radius was 21.8 mm. Under 500 mA continuous current injection， an output power of 118.1 mW and a spectral half width of 32.5 nm were achieved. The horizontal and vertical far-field divergence angles of the device are 13.2° and 21.1°， respectively. In addition， the design of a single-layer anti-reflective film effectively suppresses the lasing of devices with high gain， simplifies process complexity， and avoids stress issues between different materials of the multi-layer anti-reflective film.  
        关键词：superluminescent diodes;curved waveguide;curvature radius;loss coefficient;output characteristic   
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      • GUO Yunyun,WENG Shuchen,ZOU Zhenyou,XU Hailong,WANG Haonan,ZHOU Xiongtu,WU Chaoxing,ZHANG Yongai
        Vol. 44, Issue 12, Pages: 2242-2249(2023) DOI: 10.37188/CJL.20230234
        摘要：The miniaturization of Micro-LED devices presents a series of challenges， including size effects， high-speed mass transfer， and high-density bonding between light-emitting devices and driving backplanes. In this paper， an alternating current （AC）-driven non-electric contact （NEC） GaN-based Micro-LED device was prepared by metal organic chemical vapor deposition （MOCVD） and atomic layer deposition （ALD） and its photoelectric characteristics were also investigated. The results indicate that the circuit model of NEC Micro-LED devices can be represented by an equivalent RC circuit. The equivalent impedance initially decreases rapidly and then stabilizes with increasing AC-driven signal frequency. When the signal frequency keeps constant， the current-voltage （I⁃V） curves exhibit linear relationships and the equivalent impedance remains stable. The luminance increases continuously with increasing working voltage. When the driving voltage remains constant， the luminance of the device initially rises and then falls with the gradual increase in frequency， reaching a maximum luminance in the frequency range of 16-22 MHz. Additionally， the luminescence of the device is delayed and there is a current leading effect due to the capacitive property of the circuit. Compared with the traditional Micro-LED devices， the NEC Micro-LED devices have non-electrical contact with external electrodes and the luminescence of devices is attributed to inherent charge carriers under AC driving conditions. This development offers a promising solution to the technical challenges from the miniaturization of Micro-LED devices.  
        关键词：Micro-LED device;GaN;Non-electrical contact;Alternating-current drive;photoelectric characteristics   
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      • CHU Guanghui,YANG Guohao,LIU Tianhong,LI Jinping,CHANG Weijie,FAN Xinye,TONG Cunzhu
        Vol. 44, Issue 12, Pages: 2250-2257(2023) DOI: 10.37188/CJL.20230221
        摘要：In addition to the focusing and imaging functions， Metalens can also manipulate light field polarization， wavelength， and amplitude through kinds of meta-units. Due to the small size， light weight， low cost and easy integration， Metalens has become a research hotspot and important trend in optoelectronic integration area. In this paper， finite-difference time-domain （FDTD） algorithm is used to design and optimize Metalens based on in⁃situ integration of InGaAs avalanche detectors， and the focusing efficiency and transmittance of the Metalens are calculated. The simulation results show that the Metalens converges incident light into the absorption layer of detector， the transmittance reaches 82.8%， and the focusing efficiency reaches 84.89% when the target focal length is 150 μm and the Metalens radius is 50 μm. To further increase the transmittance， an anti-reflection（AR） layer is added. The results show that the maximum transmittance is 86.6% and 87.6% for 300 nm SiO2 and 250 nm SiN. Compared with the Metalens without AR layer， the max transmittance increased by 3.8% and 4.8%， respectively. Finally， it is estimated that the energy of the light field in the absorption region integrated with Metalens is 250.96 times higher than that of the detector without Metalens， which can greatly improve the responsivity of detector. This paper proposes a monolithic integrated method for avalanche detector with Metalens， which can concentrate the energy outside the detection area into absorption area， improves the quantum efficiency of detector without bandwidth reduction. This will provide a new sight for high responsivity and high bandwidth detectors.  
        关键词：Metalens;detector;focusing efficiency;quantum efficiency   
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        发布时间：2024-01-05
      • WANG Wei,YANG Shuting,WANG Yaxin,WANG Yuxuan,WANG Ru,YU Qingnan
        Vol. 44, Issue 12, Pages: 2258-2264(2023) DOI: 10.37188/CJL.20230249
        摘要：InGaAs/GaAs semiconductor lasers have shown great application potential in many fields with their excellent optical properties. The emission scaling factor is an important physical parameter in assessing and revealing semiconductor laser performance. In this paper， a novel experimental measurement approach of emission scaling factor for 980 nm InGaAs/GaAs quantum well structures is proposed and described， which is used to reveal and analyze the carried-injected band-filling effect and radiation characteristics of semiconductor lasers. The theoretical formula between photoluminescence （PL） spectra and emission scaling factor of InGaAs/GaAs quantum well structures are established. In this method， the PL spectra emitted from the dual facets of InGaAs/GaAs edge-emitting laser structure are collected at room temperature 300 K， which is pumped by 808 nm fiber coupled lasers. The emission scaling factors of InGaAs/GaAs structure are obtained with the various carrier densities of 9.0×1017， 9.2×1017， 9.4×1017， 9.6×1017 cm-3. The measurement results show that the emission scaling factor has an almost uniform distribution under the same thermal equilibrium state. In addition， the factors gradually increase to 7.98×1010， 1.68×1011， 2.65×1011， 3.36×1011 W-1·eV-1·s-1 with the rise of carrier densities. This is because the band-filling levels of electrons and holes gradually increase as the carrier densities increase， which lead to the separation of the quasi-Fermi levels of electrons（EFn） and holes（EFp） and a move to conduction band and valence band， respectively. The Fermi level represents the boundary between quantum states that are basically occupied or empty. Therefore， the quantum state within the quasi-Fermi energy spacing is basically filled by carriers， and the quantum state larger than that is basically empty. This causes the emission scaling factor to gradually decrease at the quasi-Fermi energy spacing. The great significance of this work lies in that it can not only propose a novel experimental method for the emission scaling factor， but also reveal the energy filling levels of non-equilibrium carrier under different thermal equilibrium states. This study has important research value for revealing the radiation mechanism and promoting the development of semiconductor lasers.  
        关键词：InGaAs/GaAs;emission scaling factor;photoluminescence spectra;band-filling effect   
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        Luminescence Applications and Interdisciplinary Fields

      • YAN Lidong,HU Chaoshuai,CHENG Junxia,ZHU Yaming,ZHAO Xuefei
        Vol. 44, Issue 12, Pages: 2265-2276(2023) DOI: 10.37188/CJL.20230244
        摘要：Nitrogen-doped carbon quantum dots （N-CQDs） were synthesized by a one-step hydrothermal method using Hailaer brown coal pyrolytic extract and nitric acid as carbon， nitrogen sources. The fluorescent probe based on N-CQDs was developed for the recognition of Cr（Ⅵ）. The morphology， structure， composition and optical properties of N-CQDs were characterized by TEM， FT-IR， Raman， XPS analysis， fluorescence spectra， and UV⁃Vis absorption spectra， respectively. The results show that the N-CQDs exhibits a good dispersion with the particle size of about 2.01 nm in water. Lots of nitrogen- and oxygen-containing groups of hydroxyl， epoxy， carboxyl and nitro groups were found on the surface. The as-prepared N-CQDs emits yellow-green photoluminescence under 340 nm UV light with an absolute quantum yield of 1.26%. The fluorescence spectra show that the maximum excitation wavelength of N-CQDs is 340 nm and the maximum emission wavelength is 556 nm. The fluorescence emission is non-excitation dependent （280-440 nm）. In addition， N-CQDs exhibit excellent optical properties in the pH range between 4 and 11 as well as at a low concentration of NaCl and KCl. The quenching effect of various anions on their fluorescence intensity was analyzed. The linear relationship between Cr（Ⅵ） and N-CQDs （F0/F） fluorescence quenching was found at range of 0-200 μmol/L with the detection limit of 0.56 μmol/L， and the detection results are consistent with the ICP-OES method.  
        关键词：carbon quantum dots;Cr（Ⅵ）;ion detection   
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      • XIAO Hua,WANG Yanju,WANG Zhanlang,GUO Chuang,JIANG Haoyu
        Vol. 44, Issue 12, Pages: 2277-2286(2023) DOI: 10.37188/CJL.20230223
        摘要：We proposed a method to solve the problem of inaccurate positioning for unmanned aerial vehicles （UAVs） in visible-light communication （VLC）. To sense the light source and find the optimum position for communication， the proposed method expands the search path first and then regularly narrows the search path. In order to improve the success rate （η） of this method， we analyzed the influence of light distribution of the light source on η and the searching distance， and also studied the influence of the position and the receiving angle of the photodetector on the receiving power and η. Three-dimensional （3D） coverage range of the light source， which is determined by the Lambert coefficient and the threshold optical power that can be sensed by the photodetector， is obtained to estimate η of UAV under different circumstances. Taking the searching path of the equilateral hexagonal for example， η can reaches up to 0.74 with the covering radius of the light source of 0.78 m by using idea Lambert-distributed light source. The proposed method avoids the inaccurate positioning of UAV， which causes the problem for the UAV to find the communication position in VLC. We theoretically proposed a solution to improve η by light-emission designing and path optimizing， providing the solution for UAVs to realize VLC.  
        关键词：visible light communication;unmanned aerial vehicles;light distribution;optimization method   
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