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Al-doped ZnO, which emits a yellowish orange light at the excitation of blue light, is prepared by means of a sol-gel combustion method, using zinc acetate, aluminium nitrate, and urea as precursors. XRD analysis reveals that the obtained material shows hexagonal wurtzite structure of ZnO. This phosphor material is excitable in a wide range of wavelength from 350 to 500 nm with an excitation maximum at 470 nm. The concentration of Al varies from 5 mol% to 15 mol% with respect to Zn and a maximum photo-luminescent emission intensity is obtained at 15 mol%. At 455 nm excitation, Al-doped ZnO shows a broad band yellowish orange emission starting from 470 to 620 nm with an emission maximum at 530 nm. At a blue LED excitation, it emits a warm white light with a CRI of 91 and CIE color co-ordinates of (x = 0.50, y = 0.39). This Al-doped ZnO can be used as a blue light converted yellowish- orange emitting phosphor material for applications in WLEDs. [ABSTRACT FROM AUTHOR]

YAG:Ce 3+ phosphor materials with a higher conversion of blue light to yellow light through its submicron particles are prepared by sol–gel derived liquid phase sintered using Na 2 CO 3 -SiO 2 -NaF flux and its luminescent properties are compared with the solid phase sintered phosphor. The liquid phase sintered phosphor material shows a strong absorbance in the blue light region and its luminescent intensity is about 30% higher with a better CIE color co-ordinate, color rendering index (CRI) and correlated color temperature (CCT) when compared with the solid phase sintered phosphor. This enhancement is possible owing to the improved optical properties of the liquid phase sintered phosphor that indicate high crystallinity, better microstructure with morphological control, and porous free close packing of phosphor particles with good dispersibility in the polymer matrix. [ABSTRACT FROM AUTHOR]

Cost-effective white-light emitting highly-defective ZnO is synthesized by a sol–gel combustion method using urea and zinc salt at a low temperature. The obtained ZnO can be excited in a wide range of wavelength from 270 to 480 nm. The excitation of ZnO by blue light emits a bright white-light which covers from blue to red wavelength region. The stable white-light emission is found to have originated from the defective structure of ZnO by the synthesis method. This could be highly useful for producing cost-effective white-light emitting diodes. The structural, morphological and optical properties of ZnO particle are analyzed by XRD, SEM, PL Spectra and DRS. [ABSTRACT FROM AUTHOR]

The structural and photoluminescent (PL) properties of Zn2(1−x)Mn x SiO4 (1⩽ x⩽ 5) thin film phosphors grown using a pulsed laser deposition technique have been investigated. The effect of systematic variation of oxygen partial pressures (O2 pp) (100, 300, 500 and 700mTorr) during the growth of these thin films has been studied. Thin film grown on silicon substrate at 750°C and in situ annealed in 300mTorr of O2 pp exhibits superior PL property; ex situ annealing at higher temperatures improves the PL intensity. [Copyright &y& Elsevier]

Abstract: We report here on an ecologically friendly carbothermal reduction method to realize SrS:Ce phosphor. The method effectively reduces the preparation temperature by 100°C. The effect of sulfur and charge compensator were studied separately and in combination, on the luminescent properties of SrS:Ce phosphor prepared from SrSO4:Ce(SO4)2·4H2O using this method without inert gas or hazardous gas (H2S) environment. To analyze the role of charge compensator on the luminescent emission property of SrS:Ce, various fluxes, viz., NH4Cl, NaCl were used. The synthesized products were characterized by XRD, photoluminescence emission and excitation spectroscopy (PLE). SrS:Ce showed a bright blue–green emission at 480 and 540nm corresponding to energy bands originating from 2T2g (5d) to 2F7/2, 2F5/2 (4f) of Ce3+ transitions. The characterization results showed the formation of SrS calcined at 900°C for 5h with an increase in blue–green luminescence intensity after the addition of sulfur and charge compensator, separately. When the sulfur and NH4Cl were jointly added, the intensity of blue emission was enhanced, whereas, that of green emission was suppressed. The excitation spectrum showed a fundamental absorption of SrS host crystal lattice at 283nm and Ce3+ absorption at 430nm respectively. The CIE (Commission International de’Eclairge) chromaticity coordinates of the phosphor are also reported. [Copyright &y& Elsevier]

A bright green light emitting Zn2SiO4:Mn phosphor has been prepared at low temperature 800°C through gel combustion synthesis using. zinc nitrate, manganese acetate, urea in a silica gel matrix. The structure and morphology of the phosphors using scanning electron microscopy along with thermogravimetric analysis/differential thermal analysis/Fourier transform infrared study along with X-ray diffraction, diffuse reflectance spectroscopy, and photoluminescence (PL) data show interesting trends with respect to the phase evaluation of Zn2SiO4:Mn phosphor. Photoluminescent and crystalline properties are examined as a function of firing temperature and Mn concentration. Maximum PL intensity is observed at λem = 522 nm for 0.03 Mn2+ concentration, which can be attributed to the 4T1(G) - 6A1(S) transition of Mn2+ under short ultraviolet excitation. The PL emission intensity of these phosphors is found to be more superior to that of the corresponding samples prepared using the conventional solid state method implying the suitability of this route for the preparation of device worthy phosphor materials. [ABSTRACT FROM AUTHOR]

Abstract: Manganese doped zinc gallate powder was synthesised using a citrate gel method and subsequently deposited as a thin film by pulsed laser deposition technique at different temperatures on quartz and glass substrates. The luminescence behaviour of the deposited film was studied and the results reported. [Copyright &y& Elsevier]

Near UV excitable, white light emitting Y 2 O 2 S:Eu3+ entrapped ZnO has been prepared by sol-gel combustion method from zinc acetate, urea and Y 2 O 2 S:Eu red phosphor. In order to study the generation of white light, red phosphor has been entrapped in ZnO in various weight ratios (90:10, 50:50, 70:30). At the excitation of near UV light at 375 ​nm, this phosphor entrapped ZnO composite shows an white light emission, and it also comprises bluish green and red light emission in the wide range of wavelength starting from 420 to 650 ​nm, originated from the ZnO and Y 2 O 2 S:Eu3+, respectively. A highest photo-luminescent intensity with white light could be obtained for Y 2 O 2 S:Eu3+ and ZnO in the weight ratio of 70:30.The obtained light shows a warm white light with a CRI of 75 and color co-ordinates of (x ​= ​0.44, y ​= ​0.35). This phosphor composite could be useful for white light emitting diode applications. Image 1 • White Light Emitting Y 2 O 2 S:Eu 3+ entrapped ZnO has been prepared by sol-gel combustion method. • To generate white light, red phosphor has been entrapped in ZnO in various weight ratios (90:10, 50:50, 70:30). • A highest photo-luminescent intensity with white light could be obtained for Y 2 O 2 S:Eu3+ and ZnO in the weight ratio of 70:30. [ABSTRACT FROM AUTHOR]

Abstract: A new Mn activated Ba co-doped ZnS phosphor shows an interesting shift in the spectral emission from amber-yellow (570nm) to red (620nm) colour. To realize the phosphor material physics, attempts were made to fine tune the band gap of ZnS by co-doping Ba within the concentration range 2.50–10mol%. Ba co-doping in ZnS host was achieved by sintering BaSO4 with ZnS at 900°C by carbothermal reduction method. Measurement of the CIE (Commission International deEchairge) chromaticity colour coordinates (x, y) of Zn0.99S:Mn0.01 and Ba0.10Zn0.89S:Mn0.01 phosphors shown to be (0.53,0.47) and (0.65,0.32), respectively. [Copyright &y& Elsevier]

This study aims at giving a prologue to the nontracking, concentrating solar waveguides called luminescent solar concentrators. It deliberates the major factors of loss in such systems that limit photon collection and conversion efficiency. Identifying fluorescent molecules possessing a larger Stokes shift value with a broad degree of absorption in the UV-Vis continuum, with sharper and narrower near infra-red emission spectra at a higher quantum yield that achieves a perpetual total internal reflection, remains a challenge now. Geometrical and material properties also play a strategic role in accomplishing waveguides, with minimal loss, through total internal reflection of trapped photons for photovoltaic conversion. [ABSTRACT FROM AUTHOR]

Zn co-doped and undoped Y 2 O 3 -Eu red phosphor was prepared by citric acid gel method and it was investigated to know its cathodoluminesecent properties at low voltage excitation (<2 kVs). In this connection the cathodoluminescence (CL) spectra of Zn co-doped and undoped phosphors were taken and they showed various line emissions along with a sharp red emission at 611 nm, irrespective of Zn concentration, due to 5 D 0 – 7 F 2 transitions from Eu luminescent center. It was found that the incorporation of Zn could significantly enhance the CL emission intensity of Eu at about 33% when compared with Zn undoped phosphor. It was also found the Zn co-doping could not alter the crystal structure whereas it could change the morphology of the particles. The promising results revealed the possible application of this phosphor materials as red phosphor for field emission displays [FEDs]. [ABSTRACT FROM AUTHOR]