Concentration effect of the near-infrared quantum cutting of 1788-nm luminescence of Tm^(3+) ion in(Y_(1-x)Tm_x)_3Al_5O_(12) powder phosphor

In the present paper, the concentration effect of near-infrared quantum cutting of Tm3＋ ion in （Y1-xTmx）3Al5Ol2 powder phosphor is studied by means of experiments and calculations. In addition, the absorption spectra, visible-to-near- infrared excitation and emission spectra, and fluorescence lifetimes are measured. It is found that （Y1-xTmx）3Al5O12 powder phosphor has a strong four-photon near-infrared quantum cutting luminescence of 1788.0-nm 3F4 →3H6 fluores- cence of Tm3＋ ion, when excited by 357.0-nm light. It is also found that the up-limit of the four-photon near-infrared quantum cutting luminescence efficiency of （Yo.700Tmo.300）3Al5 O12 powder phosphor is approximately 302.19%. To the knowledge of the authors, this is the first time that a near-infrared quantum cutting efficiency up-limit exceeding 300% has been reported. The results of this manuscript are valuable in aiding the probing of the new generation Ge solar cell.

Preparation of(Lu,Y)_(3)(Al,Sc,Cr)_(2)Al_(3)O_(12)phosphor ceramics with high thermal stability for near-infrared LED/LD

Near-infrared(NIR)phosphor-converted light-emitting diodes/laser diodes(LEDs/LDs)are prospective lighting sources for NIR spectroscopy.However,developing NIR phosphor materials with desired thermal robustness and high photoelectric efficiency is a crucial challenge for their applications.In this work,based on the cationic radius matching effect,a series of(Lu,Y)_(3)(Al,Sc,Cr)_(2)Al_(3)O_(12)NIR phosphor ceramics(LuYScCr NIR-PCs)were fabricated by vacuum sintering.Excellent thermal stability(95%@150℃)was obtained in the prepared NIR-PCs,owing to their weak electron-phonon coupling effect(small Huang-Rhys factor).Being excited at 460 nm,NIR-PCs realized a broadband emission(650-850 nm)with internal quantum efficiency(IQE)of 60.68%.Combining NIR-PCs with LED/LD chips,the maximum output power of the encapsulated LED prototype was 447 mW@300 mA with photoelectric efficiency of as high as 18.6%@180 mA,and the maximum output power of the LD prototype was 814 mW@2.5 A.The working temperatures of NIR-PCs were 70.8℃@300 mA(LED)and 102.8℃@3 A(LD).Finally,the prepared NIR-PCs applied in food detection were verified in this study,demonstrating their anticipated application prospects in the future.

Six-and five-coordinated Cr^(3+)in Ga_(2)GeO_(5) invokes tunable broadband near-infrared emission toward night-vision applications

Broadband near-infrared(NIR)light sources play a critical role in widespread applications such as advanced spectroscopy analysis and nondestructive testing.One of the most promising techniques is the fabrication of broadband NIR phosphor-converted light emitting diode(pc-LED).However,the purposeful design of a tunable ultra-broadband NIR-emitting phosphor in a single host is still a challenge.In this work,Ga_(2)GeO_(5) with two sites of six-coordinated[Ga1O_(6)]and five-coordinated[Ga2O_(5)]is chosen to host Cr^(3+),successfully producing tunable broadband NIR luminescence(680-1350 nm).It can be tuned largely from 828 to 970 nm with the full-width at half maximum(FWHM)varied from 208 to 258 nm just by simply adjusting the Cr^(3+)-doping content.The tailoring of the Cr^(3+)NIR spectral emission is ascertained to the site occupation preference and competition.The encapsulation of a prototype of NIR pc-LED with an output power of 29.5mW@390 mA is conducted for the implementation of night-vision application.This work provides a novel broadband NIR phosphor by Cr^(3+)-doping in both the sixand five-coordination field,meanwhile,further demonstrating the feasibility of discovering new host material with more than one crystallographic site for Cr^(3+)to trigger tunable broadband NIR emission.

Broadband near-infrared luminescence and energy transfer of Cr^(3+),Ce^(3+) co-doped Ca_(2)LuHf_(2)Al_(3)O_(12) phosphors

Broadband near-infrared phosphors are highly desirable for food testing.Targeted Ca_(2)LuHf_(2)Al_(3)O_(12):Cr^(3+)(CLHA:Cr^(3+)) and Ca_(2)LuHf_(2)Al_(3)O_(12):Ce^(3+),Cr^(3+)(CLHA:Ce^(3+),Cr^(^(3+))) phosphors were synthesized by the conventional high-temperature solid state reaction.The CLHA:Cr^(3+)phosphor,with a good thermal stability,shows a red shift owing to radiation reabsorption and non-radiative transition with increasing Cr^(3+)content.For co-doped sample,the emission intensity of Cr^(3+)can be enhanced by three times due to the energy transfer from Ce^(3+)to Cr^(3+),which can be evidenced by a significant overlap between the PLE of Cr^(3+)single-doped phosphor and the PL of Ce^(3+)single-doped phosphor.In addition,the mechanism of energy transfer is identified as a quadrupole-quadrupole interaction according to decay Lifetime and Dexter’s energy transfer formula.The broadband NIR emission peaked at 775 nm of CLHA:Cr^(3+),Ce^(3+)phosphor shows a bright prospect in nondestructive quality-control analysis systems for food.

Broadband asymmetric transmission for linearly and circularly polarization based on sand-clock structured metamaterial

We proposed a sandwich structure to realize broadband asymmetric transmission(AT) for both linearly and circularly polarized waves in the near infrared spectral region. The structure composes of a silica substrate and two sand-clock-like gold layers on the opposite sides of the substrate. Due to the surface plasmons of gold, the structure shows that the AT parameters of linearly and circularly polarized waves can reach 0.436 and 0.403, respectively. Meanwhile, a broadband property is presented for the AT parameter is over 0.3 between 320 THz and 340 THz. The structure realizes a diode-like AT for linearly wave in forward and circularly wave in backward, respectively. The magnetic dipoles excited by current in the two gold layers contribute to the broadband AT. The current density in top and bottom metallic layers illustrates the mechanism of the polarization conversion for broadband AT in detail.

新型宽带近红外BaSnO_(3):Fe^(3+)荧光粉的特性研究

宽带近红外荧光粉转换的近红外LED光源广泛应用于生物医学、物性分析及夜视等领域中,而Fe^(3+)由于具有生物环境友好型特点,被视为一种有巨大潜力用于开发新型宽带近红外荧光粉的激活离子。采用高温固相法合成了一款Fe^(3+)掺杂的新型近红外荧光粉BaSnO_(3):Fe^(3+),并对Fe^(3+)宽带近红外发光机理进行了研究。结果表明:荧光粉BaSnO_(3):Fe^(3+)在波长380 nm的近紫外光激发下,发射出750—1 150 nm的宽带近红外光,其峰值位于896 nm处、半高宽为105 nm;BaSnO_(3):Fe^(3+)在380 nm处的电子跃迁对应于^(6)A_(1)(6S)→4E(4D)的跃迁,而在896 nm处的电子跃迁对应于^(4)T_(1)(4G)→^(6)A_(1)(6S)的跃迁;当Fe^(3+)掺杂浓度(摩尔分数)达到0.03%时,其发射强度达到最大、激活能约为0.657 eV。说明,将所合成的材料封装成宽带近红外LED器件,可实现夜视照明。

Ca_(2)TbHf_(2)Al_(3)O_(12)∶Ce^(3+),Cr^(3+)石榴石荧光材料的宽带近红外发射与能量传递

近红外荧光转换型发光二极管(pc‐LED)在光谱分析、生物成像、夜视照明等领域有重要应用价值,得到了人们的广泛关注。本文采用高温固相法制备了一系列Ca_(2)TbHf_(2)Al_(3)O_(12)∶Ce^(3+),xCr^(3+)(CTHAO∶Ce^(3+),xCr^(3+))近红外荧光材料,通过粉末XRD表征结合结构精修技术确定制备的CTHAO∶Ce^(3+),xCr^(3+)为纯相石榴石结构。在该样品中,Tb^(3+)作为基质组成,与掺杂离子Ce^(3+)共同作为Cr^(3+)离子的敏化剂,三者之间存在多种能量传递效应,通过光谱及荧光寿命表征证实存在Ce^(3+)→Tb^(3+)、Ce^(3+)→Cr^(3+)、Tb^(3+)→Cr^(3+)的能量传递过程;重点分析了Tb^(3+)向Cr^(3+)的能量传递机制,以偶极‐四极交互作用为主导,能量传递效率可达79.5%。CTHAO∶Ce^(3+),0.02Cr^(3+)在100℃时的近红外发射强度能保持初始强度的36%,计算得到活化能为0.30 eV。将该样品与410 nm芯片相结合制成器件,在驱动电流为200 mA时,近红外最大输出功率可达7.5 mW,光电转换效率为1.2%。本工作研究了通过多重能量传递提高Cr^(3+)的发光,对于设计和开发Cr^(3+)激发的高效近红外发光材料有一定的指导意义。

宽带近红外荧光粉KScP_(2)O_(7)∶Cr^(3+)的发光特性研究及近红外LED器件应用

近红外(NIR)器件的小型化和智能化需求推动了高效宽带近红外荧光粉的设计与发展。目前,Cr3+激活的宽带近红外荧光粉主要采用传统的多格位共占据策略设计实现。然而,由于处在不同晶体学格位的Cr3+热猝灭行为不一致和光谱稳定性差等问题,导致其实际应用受限。本文基于单格位占据策略,采用高温固相法制备了一系列宽带近红外荧光粉KSc1-xP_(2)O_(7)∶xCr^(3+)(x=0.01~0.09),并对其晶体结构、发光性能及热猝灭机理进行分析。研究结果表明,在x=0.03时,KSc_(0.97)PO_(7)∶0.03Cr^(3+)(KSP∶0.03Cr^(3+))样品发光强度达到最大值,随后出现浓度猝灭现象,该现象主要归因于相邻Cr^(3+)‐Cr^(3+)之间的能量传递。在蓝光激发下,KSP∶0.03Cr^(3+)样品光谱覆盖700~1200 nm,发射主峰位于857 nm,半高宽为149 nm。此外,通过晶体结构和低温光谱分析以及对Cr^(3+)所处晶体场强度计算,表明该宽带近红外发射的实现归因于Cr^(3+)占据处于弱晶体场(Dq/B=1.98)的Sc^(3+)晶体学格位。在高温373 K时,样品的发光强度为室温下发光强度的60.2%,表明该荧光粉具有良好的热稳定性。最后,利用该荧光粉与蓝光LED芯片制备了近红外荧光粉转换型LED(NIR pc‐LED)器件,证实该荧光粉在生物医学成像、夜视以及食品检测方面具有潜在应用价值。

PbS quantum dots and Ba F_(2):Tm^(3+) nanocrystals co-doped glass for ultra-broadband near-infrared emission [Invited]

With the rapid growth of optical communications traffic,the demand for broadband optical amplifiers continues to increase.It is necessary to develop a gain medium that covers more optical communication bands.We precipitated PbS quantum dots(QDs) and Ba F_(2):Tm^(3+) nanocrystals (NCs) in the same glass to form two independent emission centers.The Ba F_(2)NCs in the glass can provide a crystal field environment with low phonon energy for rare earth (RE) ions and prevent the energy transfer between RE ions and PbS QDs.By adjusting the heat treatment schedule,the emission of the two luminescence centers from PbS QDs and Tm^(3+) ions perfectly splices and covers the ultra-broadband near-infrared emission from 1200 nm to 2000 nm with bandwidth over 430 nm.Therefore,it is expected to be a promising broadband gain medium for fiber amplifiers.

(Lu_(0.99-x)Y_(x)Bi_(0.01))_(2)WO_(6)宽带绿色荧光粉的制备、性能调控及其在高显色指数白光LED中的应用

高质量宽带绿色荧光粉是克服荧光粉转换白光LED(pc-wLED)“青光鸿沟”问题,实现高质量固态照明的关键.通过普适的固相法制备出尺寸均匀分散性良好的(Lu_(0.99-x)Y_(x)Bi_(0.01))_(2)WO_(6)宽带绿色荧光粉.采用共掺杂Y^(3+)的策略对系列荧光粉的物相、形貌及发光性能进行调控,并采用X-射线衍射、Rietveld精修、场发射扫描电子显微镜及光致发光等检测手段对所得样品进行了系统的研究.研究表明(Lu_(0.99-x)Y_(x)Bi_(0.01))_(2)WO_(6)荧光粉呈现宽带激发,激发范围覆盖200~400 nm波长区域,与商用紫外LED对应良好.在346 nm波长激发下,(Lu_(0.99-x)Y_(x)Bi_(0.01))_(2)WO_(6)荧光粉在400~800 nm范围内呈现出宽带绿光发射,半峰宽(FWHM)可达135 nm,最强峰值约为510 nm,对应于Bi^(3+)的^(3)P_(1)→^(1)S_(0)跃迁.Y^(3+)掺杂可显著提高(Lu_(0.99-x)Y_(x)Bi_(0.01))_(2)WO_(6)样品的结晶性及发光强度.采用所得的(Lu_(0.94)Y_(0.05)Bi_(0.01))_(2)WO_(6)与商用CaAlSiN3∶Eu^(2+)红色荧光粉、BaMgAl_(10)O_(17)∶Eu^(2+)蓝色荧光粉及365 nm紫外芯片制作出具有较高的显色指数(R_(a)=96,R_(9)=94),较低的相关色温(CCT=3846 K)高性能暖白光LED器件.

三价铬离子掺杂氟化物宽带近红外荧光粉研究进展

宽带近红外光源在夜视成像、无损检测、医疗成像和信息识别等领域中具有广泛应用场景。在众多近红外光源中,荧光粉转换的宽带近红外LED,(pc-LED)凭借其结构紧凑、成本低、效率高等优势逐渐崭露头角。作为宽带近红外pc-LED的关键组成,Cr^(3+)离子掺杂的氟化物荧光粉表现出卓越的近红外发光性能、出色的热稳定性及低晶格声子能级等独特特性,因此近年来受到研究人员的广泛关注。从合成方法、材料设计和应用探索3个方面,综述了Cr^(3+)掺杂氟化物荧光粉的最新研究进展。同时,提出了一些需要进一步研究的问题,以帮助读者深入了解该领域的研究现状和未来发展趋势。

SrCO_3∶Eu^(2+)荧光粉的制备及其发光性能研究

首先采用微波辅助共沉淀制备SrCO3∶Eu3+前驱物,然后高温还原得到SrCO3∶Eu2+样品。通过X射线衍射仪(XRD)和荧光光度仪分析样品的结构和发光性能,确定样品的最佳煅烧温度为1100℃,助熔剂硼酸的最佳用量为15%。研究表明,样品的激发图谱由220～320 nm和400～580 nm两个宽带光谱组成;发射图谱位于550～700 nm宽带吸收峰,其特征发射峰值位于610 nm(λex=475 nm),属于红色发光。这种宽带激发和发射的碳酸锶基质的稀土荧光粉可望用于制造荧光玻璃。

适用于色敏解调的光位移传感器宽带LED

为保证光位移传感器的工作性能,输入光源在500～800nm波长范围内需具有较高的光谱能量,照明用LED波长在700nm以上光谱能量陡降,限制了传感器的工作范围.针对照明用LED光谱能量不足的问题,研制出适用于色敏解调光位移传感器的宽带LED光源.首先利用单色仪对光位移传感器色敏元件WS7.56的性能进行了测试,依据色敏解调结果提出了光位移传感器正常工作所需的输入光源的光谱能量阈值.在照明用LED光谱特性基础上,配比掺杂氮氧化物红色荧光粉提升LED红光及近红外光光谱能量,得到了满足输入光源光谱能量阈值的宽带LED.最后,对该宽带LED光位移传感器进行了位移测量实验,实验结果较使用照明用LED光源有明显改善,位移解调线性度良好.本文研制的宽带LED光源体积小、效率高,是光位移传感器较为理想的宽带光源.

NaAlP_(2)O_(7)∶Cr^(3+)荧光粉近红外发光特性

宽带近红外荧光粉转换型LED光源在医学成像、食品检测以及传感等领域展现出了巨大的应用前景,该类光源的光谱和效率与所用近红外荧光粉的性能紧密相关,Cr^(3+)离子激活的近红外发光材料具有可被蓝光有效激发、发射光谱可调等优点,因此得到了重点关注。本文采用高温固相法制备了NaAlP_(2)O_(7)∶Cr^(3+)宽带近红外发光荧光粉,该材料在450 nm蓝光激发下,发射出650~1000 nm的近红外光,峰值位于780 nm,半高宽为1580 cm-1;其在423 K下的发光强度能够维持室温下的71%,表现出良好的发光热稳定性。对材料的晶体结构和变温光谱(8~503 K)进行了系统的分析,计算得到了Cr^(3+)离子在NaAlP_(2)O_(7)基质中的晶体场强度等参数;利用8 K低温光谱,并结合计算,分析了Cr^(3+)各能级零声子线;基于高温变温光谱,讨论了材料的电⁃声子耦合效应及荧光热猝灭机理。

用于宽谱带发射白色发光二极管的黄色荧光粉Sr_(8)MgAl(PO_(4))_(7)∶xEu^(2+)的制备及发光性能

通过高温固相反应合成了一系列宽谱带发射黄色荧光粉Sr_(8)MgAl(PO_(4))_(7)∶xEu^(2+)(SMAP∶xEu^(2+)),并对其物质结构、发光性能及其在白色发光二极管(WLED)领域的应用进行了探究。X射线衍射(XRD)测试结果表明,SMAP∶xEu^(2+)系列荧光粉具有单斜结构和C2/m空间群,激活剂Eu^(2+)离子能够很好地进入SMAP基质中并占据Sr2+离子的晶格位点。漫反射光谱分析显示SMAP基质属于宽带隙材料,带隙宽度为3.60 eV。此外,SMAP∶xEu^(2+)具有较宽的激发范围(280~500 nm),对应于Eu^(2+)离子的4f 7→4f 65d1跃迁;在380 nm近紫外光激发下,呈现出450~800 nm的多发光中心的非对称黄光发射,发射峰位于590 nm处。基于高斯多峰拟合结果,得到3个发光中心,分别位于528、600和680 nm。最后,将已制备的黄色荧光粉SMAP∶0.05Eu^(2+)与商业化蓝粉BaMgAl_(10)O_(17)∶Eu^(2+)混合涂覆到400 nm芯片上制得色温较好(3344 K)、显色指数较高(90.1)的WLED。

宽带激发BaBi_(2)(MoO_(4))_(4):Eu^(3+)荧光粉的制备与发光性能

Eu^(3+)激活红色荧光粉由于光吸收较弱从而限制了其应用,虽然在BaBi_(2)(MoO_(4))_(4):Eu^(3+)荧光粉中实现了宽带激发的目的,但是对其结构及其发光机理还需进一步研究,同时还需进一步提高其光吸收强度。为此,采用固相法在不同的温度下制备了BaBi_(2)(MoO_(4))_(4):Eu^(3+)红色荧光粉,通过掺杂Sr^(2+)离子和Y^(3+)离子探讨结构变化和Bi^(3+)离子的分布对BaBi_(2)(Mo O_(4))_(4):Eu^(3+)发光性能的影响。结果表明:当煅烧温度为750℃时,在不同近紫外光激发下基本上可以获得最强发光;添加Sr^(2+)离子会导致其结构发生转变;添加Y^(3+)离子后,改变了Bi^(3+)离子分布形式,进一步提高了激发强度,但是Y^(3+)离子浓度过高时,激发强度反而会降低。以上结果对于理解Bi^(3+)离子在Eu^(3+)激活红色荧光粉中的作用机制具有较大的借鉴作用。

发射峰为875 nm的高热稳定性立方相Sc(PO_(3))_(3):Cr^(3+)荧光粉

近红外(NIR)荧光粉转换型发光二极管(pc-LED)具有尺寸小、效率高以及光谱易于调节的特点,在特种照明、传感、微型近红外光谱仪等各领域有很好的应用前景.目前,已报道的发射波长超过850 nm的近红外荧光粉的荧光热稳定性较差.在本项研究中,我们合成了一种立方相结构的Sc(PO_(3))_(3):xCr^(3+)(x=0,1,5,10,12,14,16,18 at%)荧光粉,其具有725–1150 nm的宽发射带,发射峰为875 nm,与之前报道的发射峰超过850 nm的荧光粉相比,其表现出优异的热稳定性,在423 K下,5 at%样品的积分发光强度保留了室温下的73.4%.通过对比研究立方相和单斜相Sc(PO_(3))_(3):Cr^(3+)荧光粉变温X射线衍射,发现立方相荧光粉优异的荧光热稳定性可能归因于高温下较小的键长和键角变化.利用该荧光粉制备的NIR pc-LED在150 mA电流驱动下,产生了26.62 mW的NIR辐射功率.驱动电流为10 mA时,最高电光转换效率为11.87%.这项工作为开发具有优异荧光热稳定性的Cr^(3+)离子掺杂近红外荧光粉提供了思路.

Unconventionally anisotropic growth of PbSe nanorods:Controllable fabrication under solution-solid-solid regime over Ag2Se catalysis for broadband photodetection

Broadband optoelectronic devices intrigue enormous interests on account of their promising potential in optical communications,sensors and environmental monitoring.PbSe nanocrystals are promising candidates for the construction of next-generation photodetectors due to their fascinating intrinsic properties and solution-processed compatibility with varied substrates.Here,we report the fabrication of a broadband photodetector on the basis of high-quality solution-processed PbSe nanorods in rock-salt phase grown along unconventionally anisotropic growth direction of<112>zone axis.The rock-salt PbSe nanorods are synthesized in solution phase over the catalysis of Ag2Se with relatively high-temperature body-centered cubic phase via a solution-solid-solid growth regime using oleylamine and oleic acid as solvents and stabilizer surfactants,from which the PbSe nanorods with the unconventionally anisotropic growth direction are controllably grown in size and shape in the synthetic procedure typically with about 17 nm in diameter and 58 nm in length on average.Meanwhile,the PbSe nanorods-based photodetector exhibits a broadband response from 405 to 1,064 nm with a high responsivity of 0.78 A·W^(-1)and a fast response time of 17.5μs.The response time is much faster in comparison with most of the PbSe-based photodetectors with response time in millisecond level.

宽带近红外荧光粉LaMgGa11O19:Cr^(3+),Nd^(3+)的发光特性与LED器件应用

具有体积小、响应快等特点的荧光转换型宽带近红外LED(NIR pc-LED)光源在食品成分分析、生物制药、癌症早期诊断、健康管理、NIR光谱技术等领域具有重要的应用价值。作为NIR pc-LED的核心组件,NIR荧光粉直接决定了这类光源的光学性能,因此开发新型高效的NIR荧光粉对于推进NIR光谱技术的普及具有重要意义。本文通过过渡族金属离子Cr^(3+)到稀土离子Nd^(3+)的能量传递设计了一种可被蓝光LED高效激发的宽带NIR荧光粉LaMgGa11O19:Cr^(3+),Nd^(3+),其发射光谱范围覆盖650~1100 nm。此外,得益于Cr^(3+)→Nd^(3+)的高效能量传递和Nd^(3+)4F3/2能级优异的发光热稳定性,该荧光粉具有优异的发光热稳定性,其发光强度在150℃时仍能维持室温的92%。最后,将LaMgGa11O19:Cr^(3+),Nd^(3+)荧光粉与蓝光LED芯片结合,所制备的NIR pc-LED原型器件,在350 mA驱动电流下,NIR输出功率高达120 mW。以上结果表明,LaMgGa11O19:Cr^(3+),Nd^(3+)荧光粉有潜力应用于NIR pc-LED器件。

Cr^(3+)掺杂LiScSi_(2)O_(6)近红外荧光粉的荧光性能及pc-LED器件研究

红外荧光粉是制备基于蓝光芯片宽带近红外光源的关键。采用高温固相法制备了LiScSi_(2)O_(6):Cr^(3+)近红外荧光粉样品并制备了相应的pc-LED器件,详细研究了样品的光致发光特性及pc-LED的性能。荧光粉在460nm蓝光激发下产生中心波长为850nm,半高宽约为156nm的宽带近红外光谱。在温度为160℃时,发光峰的强度下降为室温下的75.38%。把粉体涂覆在InGaN蓝光芯片(P_(max)=5W)表面制备的近红外pc-LED,得到最大近红外光输出功率为436.7mW@300mA,最大电光转化效率为18.3%@1mA。采用pc-LED作为红外光源,隐藏在油墨下的文字信息清晰可见,表明该红外荧光粉可用于制备基于蓝光芯片的宽带红外光源,且在夜视和信息防伪领域有良好的应用前景。