Achieving Tunable Cold/Warm White‑Light Emission in a Single Perovskite Material with Near‑Unity Photoluminescence Quantum Yield

Single materials that exhibit efficient and stable white-light emission are highly desirable for lighting applications.This paper reports a novel zero-dimensional perovskite,Rb_(4)CdCl_(6):Sn^(2+),Mn^(2+),which demonstrates exceptional white-light properties including adjustable correlated color temperature,high color rendering index of up to 85,and near-unity photoluminescence quantum yield of 99%.Using a co-doping strategy involving Sn^(2+)and Mn^(2+),cyan-orange dual-band emission with complementary spectral ranges is activated by the self-trapped excitons and d-d transitions of the Sn^(2+)and Mn^(2+)centers in the Rb_(4)CdCl_(6)host,respectively.Intriguingly,although Mn^(2+)ions doped in Rb_(4)CdCl_(6)are difficult to excite,efficient Mn^(2+)emission can be realized through an ultra-high-efficient energy transfer between Sn^(2+)and Mn^(2+)via the formation of adjacent exchange-coupled Sn–Mn pairs.Benefiting from this efficient Dexter energy transfer process,the dual emission shares the same optimal excitation wavelengths of the Sn^(2+)centers and suppresses the non-radiative vibration relaxation significantly.Moreover,the relative intensities of the dual-emission components can be modulated flexibly by adjusting the fraction of the Sn^(2+)ions to the Sn–Mn pairs.This co-doping approach involving short-range energy transfer represents a promising avenue for achieving high-quality white light within a single material.

Fabrication of High Color Rendering Index White Light Emitting Diodes from Gold Nanoclusters

We demonstrated gold nanoclusters as color tunable emissive light converters for the application of white light emitting diodes (WLEDs). A blue LED providing 460 nm to excite gold nanoclusters mixed with UV curable material generates broad bandwidth emission at the visible range. Increasing the amount of gold nanoclusters, the correlated color temperature of WLEDs tuned from cold white to warm white, and also results in the variation of color rendering index (CRI). The highest CRI in the experiment is 92.

Effects of Different Light Qualities on the Growth Characteristics of Populus trinervis

Populus trinervis is native to China and plays an irreplaceable role in maintaining the ecological balance of boreal and temperate forests.P.trinervis mainly grows in high-altitude areas.At present,there are limited studies on the response of P.trinervis to different light qualities,so it is necessary to investigate the photosynthetic physiological changes of P.trinervis in different light environments.In our study,P.trinervis was grown for 8 months under light filtered by three different colored films.The three treatments were blue film,green film,and white plastic film.The effects of blue(B),green(G),and white(W)light on photosynthetic pigment content,absolute growth,photosynthetic parameters,soluble sugar content,and chlorophyll fluorescence parameters were studied,respectively.Compared to the Wtreatment,the chlorophyll a and b,carotenoids,total chlorophyll content(a+b),absolute growth of seedling height,net photosynthetic rate(PN),water use efficiency(WUE),total soluble sugars,sucrose,and nonphotochemical quenching(NPQ)of P.trinervis were significantly increased under B treatment.Meanwhile,chlorophyll a and b,carotenoids,total chlorophyll(a+b),transpiration rate(Tr),intercellular CO_(2) concentration(Ci),stomatal conductance(gs),absolute growth of seedling height and leaf length,reducing sugar,total soluble sugar content,and NPQ were significantly increased under G treatment.The results showed that the absolute growth and chlorophyll content of P.trinervis were increased under B light,while the sugar and photosynthetic parameters were increased under G light.Additional studies may look into how B light impacts absolute growth and promotional mechanisms,as well as how G light affects the accumulation of sugar levels.

Color-stable,reduced efficiency roll-off hybrid white organic light emitting diodes with ultra high brightness

High-brightness and color-stable two-wavelength hybrid white organic light emitting diodes （HWOLEDs） with the configuration of indium tin oxide （ITO）/ N, N, N, N-tetrakis（4-methoxyphenyl）-benzidine （MeO-TPD）： tetrafluoro-tetracyanoqino dimethane （F4-TCNQ）/N,N-di（naphthalene-1-yl）-N,N-diphenyl-benzidine （NPB）/ 4,4-N,N-dicarbazolebiphenyl （CBP）： iridium （III） diazine complexes （MPPZ） 2 Ir（acac）/NPB/2-methyl-9,10-di（2-naphthyl）anthracene （MADN）： p-bis（p-N,N-di-phenyl-aminostyryl）benzene （DSA-ph）/bis（10-hydroxybenzo[h] quino-linato）beryllium complex （Bebq2）/LiF/Al have been fabricated and characterized. The optimal brightness of the device is 69932 cd/m2 at a voltage of 13 V, and the Commission Internationale de l’Eclairage （CIE） chromaticity coordinates are almost constant during a large voltage change of 6–12 V. Furthermore, a current efficiency of 15.3 cd/A at an illumination-relevant brightness of 1000 cd/m2 is obtained, which rolls off slightly to 13.0 cd/A at an ultra high brightness of 50000 cd/m2. We attribute this great performance to wisely selecting an appropriate spacer together with effectively utilizing the combinations of exciton-harvested orange-phosphorescence/blue-fluorescence in the device. Undoubtedly, this is one of the most exciting results in two-wavelength HWOLEDs up to now.

Very-High Color Rendering Index Hybrid White Organic Light-Emitting Diodes with Double Emitting Nanolayers

A very-high color rendering index white organic light-emitting diode(WOLED) based on a simple structure was successfully fabricated. The optimized device exhibits a maximum total efficiency of 13.1 and 5.4 lm/W at 1,000 cd/m2. A peak color rendering index of 90 and a relatively stable color during a wide range of luminance were obtained. In addition, it was demonstrated that the 4,40,400-tri(9-carbazoyl) triphenylamine host influenced strongly the performance of this WOLED.These results may be beneficial to the design of both material and device architecture for high-performance WOLED.

Temperature effects on photoluminescence of YAG:Ce^(3+) phosphor and performance in white light-emitting diodes

The well crystalline YAG：Ce^3＋ phosphor was synthesized by sold-state method, and the temperature dependence of excitation and emission spectra of YAG：Ce^3＋ phosphor were investigated in the temperature range from room temperature to 573 K. With temperature increasing, it was noted that the emission intensity of as-repared phosphors decreased considerably more rapidly when pumped by 460 nm than by 340 nm. The temperature-intensity curves under different excitation wavelengths were obtained using an Arrhenius function, and the corresponding activation energies were also obtained respectively. Thus, the experimental phenomenon was discussed in terms of nonradiative decay rate. The effects of as-prepared phosphors on the performance of the white LED with changing temperature were also studied.

A Novel White Light Emitting Long-lasting Phosphor

A novel white light emitting long-lasting phosphor Cd1-xDyxSiO3 is reported in this letter. The Dy3+ doped CdSiO3 phosphor emits white light. The phosphorescence can be seen with the naked eye in the dark clearly even after the 254 nm UV irradiation have been removed for about 30 min. In the emission spectrum of 5% Dy3+ doped CdSiO3 phosphor, there are two emission peaks of Dy3+, 580 nm (4F9/26H13/2) and 486 nm (4F9/26H15/2), as well as a broad band emission located at about 410 nm. All the three emissions form a white light with CIE chromaticity coordinates x=0.3874, y=0.3760 and the color temperature is 4000 K under 254 nm excitation. It indicated that this phosphor is a promising new luminescent material for practice application.

Comparison of the autofluorescence bronchoscope and the white light bronchoscope in airway examination

Background and Objective: The sensitivity and accuracy of white light bronchoscopy (WLB) in airway examination are low. Autofluorescence bronchoscope (AFB) can determine early lesions in bronchial mucosa more sensitively, but it has seldom performed in China. To assess the clinical value of the AFB in airway examination, we compared the sensitivity and specificity of the AFB and WLB in detecting cancer of the airway mucosa. Methods: Between September 2009 and May 2010, bronchoscope examinations using both the AFB and WLB were performed on 136 patients, 95 men and 41 women with a median age of 61.5 years (ranged from 25 to 84 years). There were 46 lesions located in the central airway, 84 in the peripheral lung parenchyma, and 6 in the mediastinal region. All patients received local and general anesthesia and were subsequently examined with the WLB and AFB in tandem. All procedures were completed safely. Abnormal visual findings were recorded, and biopsies of the affected regions were collected for pathologic examination. Results: Of 241 regions sampled for biopsy, 76 sites contained malignant lesions, whereas 165 sites contained benign lesions. The AFB detected 72 of the 76 malignant lesions, but the WLB detected only 50. The sensitivities of the AFB and WLB were 94.7% and 65.8%, respectively, and the specificities were 57.0% and 83.6%, respectively. The negative predictive values of the AFB and WLB were 95.9% and 84.1%, respectively. Conclusions: The AFB is more sensitive than the WLB in detecting cancerous lesions in the mucosa, and is an effective airway examination.

Rare Earth Luminescent Materials for White LED Solid State Lighting

Solid-state white LED will be a new generation of energy-saving light source in 21 century. In order to emitting white light, one of important approaches is using luminescence conversion technology with rare earth phosphors, which can be excited by the 460 nm blue light or 400 nm near violet light emitted from the InGaN chip and then emit white light. The rare earths doped phosphors prepared by us such as YAG ： Ce^3＋, Ca1-xSrxS ： Eu^2＋, Ga2S3 ： Eu^2＋, MGa2S4：Eu^2＋ （M = Ca, Sr, Ba）, SrGa2＋xS4＋y ：Eu^2＋,（Ca1 - xSrx ） Se ： Eu^2 ＋ , SrLaGaaS6O ： Eu^2 ＋ , （ M1, M2 ） 10 （PO4）6XE（M1 = Ca, Sr, Ba; Ms = Eu, Mn; X = F, Cl, Br） and NaEu0.92 Sm0.08 （MoO4）5 were reported. They emit blue, green, yellow or red color light. Some white LEDs were made by these phosphors with blue or near violet InGaN chips and their chromaticity coordinate （x, y）, correlated color temperature Tc, and color rendering index Ra are reported.

Luminescence characteristics of Eu^(3+) activated borate phosphor for white light emitting diode

In this paper, the Sr3Y2 （BO3）4 ：Eu^3＋ phosphor was synthesized by high temperature solid-state reaction method and the luminescence characteristics were investigated. The emission spectrum exhibits one strong red emission at 613 nm corresponding to the electric dipole 5^Do-7^F2 transition of Eu^3＋ under 365 nm excitation, this is because Eu^3＋ substituted for Y^3＋ occupied the non-centrosymmetric position in the crystal structure of Sr3Y2（BO3）4. The excitation spectrum indicates that the phosphor can be effectively excited by ultraviolet （254 nm, 365 nm and 400 nm） and blue （470 nm） light. The effect of Eu^3＋ concentration on the red emission of Sr3Y2（BO3）4 ：Eu^3＋ was measured, the result shows that the emission intensities increase with increasing Eu^3＋ concentration, then decrease. The Commission Internationale del＇Eclairage chromaticity （x, y） of Sr3Y2（BO3）4 ：Eu^3＋ phosphor is （0.640, 0.355） at 15 mol% Eu^3＋.

Multicenter randomised controlled trial comparing the high definition white light endoscopy and the bright narrow band imaging for colon polyps

AIM To compare high definition white light endoscopy and bright narrow band imaging for colon polyps' detection rates. METHODS Patients were randomised to high definition white light endoscopy(HD-WLE) or the bright narrow band imaging(b NBI) during withdrawal of the colonoscope. Polyps identified in either mode were characterised using b NBI with dual focus(b NBI-DF) according to the Sano's classification. The primary outcome was to compare adenoma detection rates(ADRs) between the two arms. The secondary outcome was to assess the negative predictive value(NPV) in differentiating adenomas from hyperplastic polyps for diminutive rectosigmoid lesions.RESULTS A total of 1006 patients were randomised to HD-WLE(n = 511) or b NBI(n = 495). The mean of adenoma per patient was 1.62 and 1.84, respectively. The ADRs in b NBI and HD-WLE group were 37.4% and 39.3%, respectively. When adjusted for withdrawal time(OR = 1.19, 95%CI: 1.15-1.24, P < 0.001), the use of b NBI was associated with a reduced ADR(OR = 0.69, 95%CI: 0.52-0.92). Nine hundred and thirty three polyps(86%) in both arms were predicted with high confidence. The sensitivity(Sn), specificity(Sp), positive predictive value and NPV in differentiating adenomatous from non-adenomatous polyps of all sizes were 95.9%, 87.2%, 94.0% and 91.1% respectively. The NPV in differentiating an adenoma from hyperplastic polyp using b NBI-DF for diminutive rectal polyps was 91.0%.CONCLUSION ADRs did not differ between b NBI and HD-WLE, however HD-WLE had higher ADR after adjustment of withdrawal time. b NBI surpassed the PIVI threshold for diminutive polyps.

Bright White Organic Light-emitting Device Based on 1,2,3,4,5,6-Hexakis(9,9-diethyl-9H-fluoren-2-yl)benzene

Organic light-emitting devices（OLEDs） with the structure of indium-tin-oxide（ITO）/N,N＇-bis-（1-naphthyl）-N,N＇-diphenyl-（1,1＇-biphenyl）-4,4＇-diamine（NPB）/2,9-dimenthyl-4,7-diphenyl-1,10-phenanthroline（BCP）/tris（8-hydroxyquinoline）aluminum（Alq3）/Mg：Ag or that of ITO/NPB/1,2,3,4,5,6-hexakis（9,9-diethyl-9H-fluoren-2-yl）benzene（HKEthFLYPh）/Alq3/Mg：Ag were studied.White light emission was achieved with the two devices when the thicknesses of BCP and HKEthFLYPh were 1.5 nm（device B） and 5 nm（device Ⅱ）,respectively.The obvious difference was that the EL spectrum of device Ⅱ was not sensitive to the thickness of HKEthFLYPh compared to that of BCP layer.Moreover,the maximum luminance of device Ⅱ was about 1000 cd/m^2 higher than that of device B at a forward bias of 15 V,and it exhibited a maximum power efficiency of 1.0 lm/W at 5.5 V,which is nearly twice that of device B.The performance of device Ⅱ using a novel star-shaped hexafluorenylbenzene organic material was improved compared with that of BCP.

Regulating Charge and Exciton Distribution in High-Performance Hybrid White Organic Light-Emitting Diodes with n-Type Interlayer Switch

The interlayer(IL) plays a vital role in hybrid white organic light-emitting diodes(WOLEDs); however,only a negligible amount of attention has been given to n-type ILs. Herein, the n-type IL, for the first time,has been demonstrated to achieve a high efficiency, high color rendering index(CRI), and low voltage trade-off.The device exhibits a maximum total efficiency of 41.5 lm W^(-1), the highest among hybrid WOLEDs with n-type ILs. In addition, high CRIs(80–88) at practical luminances(C1000 cd m^(-2)) have been obtained, satisfying the demand for indoor lighting. Remarkably, a CRI of 88 is the highest among hybrid WOLEDs. Moreover, the device exhibits low voltages, with a turn-on voltage of only 2.5 V([1 cd m^(-2)), which is the lowest among hybrid WOLEDs. The intrinsic working mechanism of the device has also been explored; in particular, the role of n-type ILs in regulating the distribution of charges and excitons has been unveiled. The findings demonstrate that the introduction of n-type ILs is effective in developing high-performance hybrid WOLEDs.

Hydrothermal Preparation and White-Light-Controlled Resistive Switching Behavior of BaWO_4 Nanospheres

In this work, BaWO4 nanospheres were successfully prepared by hydrothermal process. The bipolar resistive switching behavior of Ag/BaWO4/FTO device is observed. Moreover, this resistive switching behavior can be modulated by white light. The device can maintain superior stability in the dark and under white-light illumination. This study is useful for developing the light-controlled nonvolatile memory devices.

Novel Dy^(3+)-doped Gd(PO_3)_3 white-light phosphors under VUV excitation for Hg-free lamps application

Novel Dy^3＋-doped Gd（PO3）3 white light phosphors each with an orthorhombic system are successfully synthesized by solid-state reaction.The luminescence properties of white-light Gd1-x（PO3）3：xDy^3＋（0 〈 x ≤ 0.25） under vacuum ultraviolet（VUV） excitation are investigated.The strong absorption at around 147 nm in excitation spectrum energy can be transferred to the energy levels of Dy^3＋ ion from the host absorption.Additionally,the white light phosphor is activated by a single Dy^3＋ ion.Therefore,the luminescence of Gd1-x（PO3）3：xDy（0 〈 x ≤ 0.25） under VUV excitation is effective,and it has the promise of being applied to mercury-free lamps.

3D Displacement Measurement by White Light Digital Image Analysis in Frequency Domination Area

In this paper, white light digital image analysis in frequency domination area for measuring 3D displacement is put forward. The measuring system has the characteristics of whole-field, non-contact and omni-bearing measurement. It is simple and the coherent light is not demanded. Gray images before and after deformation are recorded using two CCDs at two different shooting angles, then digitalized and analyzed by frequency domination correlation arithmetic. The 2D displacement obtained is used to formulate 3D displacement via mathematical transformation. The experimental plate is 40,mm in length, 30,mm in width and 10 mm in height. The definite displacement is given using a 3D precise adjusting frame. The 3D displacement is calculated and compared with the definite displacement. The error is 4%-11% and the availability of this method was certified. Using this method, the compression deformation of a thin-wall cylinder with 140 mm in height, 64 mm in inner diameter and 64.6,mm in external diameter, was also measured. This method is proper to measure dynamic deformation.

Structure and luminescence of Ca_2Si_5N_8:Eu^(2+) phosphor for warm white light-emitting diodes

We have synthesized Ca2Si5N8：Eu^2＋ phosphor through a solid-state reaction and investigated its structural and luminescent properties. Our Rietveld refinement of the crystal structure of Ca1.9Eu0.1Si5N8 reveals that Eu atoms substituting for Ca atoms occupy two crystallographic positions. Between 10 K and 300 K, Ca2Si5N8：Eu^2＋ phosphor shows a broad red emission band centred at -1.97 eV-2.01 eV. The gravity centre of the excitation band is located at 3.0 eV 3.31 eV. The centroid shift of the 5d levels of Eu^2＋ is determined to be -1.17 eV, and the red-shift of the lowest absorption band to be - 0.54 eV due to the crystal field splitting. We have analysed the temperature dependence of PL by using a configuration coordinate model. The Huang-Rhys parameter S = 6.0, the phonon energy hv = 52 meV, and the Stokes shift △S = 0.57 eV are obtained. The emission intensity maximum occurring at -200 K can be explained by a trapping effect. Both photoluminescence （PL） emission intensity and decay time decrease with temperature increasing beyond 200 K due to the non-radiative process.

Diffraction of white-light supercontinuum by femtosecond laser-induced transient grating in carbon bisulfide

Experiments on fs laser-induced transient grating （LITG） in carbon bisulfide （CS2） are carried out to explore the chirp characteristics of a white-light supercontinuum （SC） generated by a 800-nm, 160-fs laser pulse in a 4-mm thick Al2O3 crystal. Two orders of diffraction signals of SC by fs LITG in CS2 are observed, demonstrating that both the third-order process and the fifth-order process are present simultaneously. The experimental results also imply that the formation of an fs transient refractive-index grating in CS2 is mainly due to the electronic polarization process.

Enhancing The Efficiency of White Organic Light-emitting Diode Using Energy Recyclable Photovoltaic Cells

We demonstrate that power recycling is feasible by using a semi-transparent stripped Al electrode as interconnecting layer to merge a white organic light-emitting devices(WOLED) and an organic photovoltaic(OPV) cell.The device is called a PVOLED.It has a glass / ITO / CuPc / m-MTDATA ∶ V 2 O 5 / NPB / CBP ∶ FIrpic ∶ DCJTB / BPhen / LiF / Al / P3HT∶ PCBM / V 2 O 5 / Al structure.The power recycling efficiency of 10.133% is achieved under the WOLED of PVOLED operated at 9 V and at a brightness of 2 110 cd / m 2,when the conversion efficiency of OPV is 2.3%.We have found that the power recycling efficiency is decreased under high brightness and high applied voltage due to an increase input power of WOLED.High efficiency(18.3 cd / A) and high contrast ratio(9.3) were obtained at the device operated at 2 500 cd / m 2 under an ambient illumination of 24 000 lx.Reasonable white light emission with Commission Internationale De L'Eclairage(CIE) color coordinates of(0.32,0.44) at 20 mA / cm 2 and slight color shift occurred in spite of a high current density of 50 mA / cm 2.The proposed PVOLED is highly promising for use in outdoors display applications.

Pure blue and white light electroluminescence in a multilayer organic light-emitting diode using a new blue emitter

We characterized the 6,12-bis{[N-（3,4-dimethylphenyl）-N-（2,4,5-trimethylphenyl）]amino} chrysene （BmPAC）, which has been proven to be a blue fluorescent emission with high EL efficiency. The blue fluorescent device exhibits good performance with an external quantum efficiency of 5.8% and current efficiency of 8.9 cd/A, respectively. Using BmPAC, we also demonstrate a hybrid phosphorescence/fluorescence white organic light-emitting device （WOLED） with high efficiency of 36.3 cd/A. In order to improve the relative intensity of blue light, we plus a blue light-emitting layer （BEML） in front of the orange light emitting layer （YEML） to take advantage of the excess singlet excitons. With the new emitting layer of BEML/YEML/BEML, we demonstrate the fluorescence/phosphorescence/fluorescence WOLED exhibits good performance with a current efficiency of 47 cd/A and an enhanced relative intensity of blue light.