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Ba3Ca2(PO4)3F, having been proven beneficial for ancient geological surveys, was also found to be an efficient fluorescence emitter when doped with various rare-earth and transition ions. Advancing the respective properties further, dysprosium (Dy3+) was added as an activator into the Ba3Ca2(PO4)3F host lattice. The Dy ion in its trivalent form possesses emission in two regions, blue at 481 nm and green at 575 nm, opening a new window towards its plausible use in white-light-emitting diode (LED) lighting appliances. Subsequent analyses including x-ray diffraction, Rietveld refinement, photoluminescence, and lifetime observed in milliseconds (ms) revealed a similar nature of the decay curves as given in the literature. Further, a CIE coordinate calculation predicted near-ideal white light emission. [ABSTRACT FROM AUTHOR]

CaWO4 nanoparticles were obtained by facile mechanochemical synthesis at room temperature, applying two different milling speeds. Additionally, a solid-state reaction was employed to assess the phase composition, structural, and optical characteristics of CaWO4. The samples were analyzed by X-ray diffraction (XRD), transition electron microscopy (TEM), and Raman, infrared (IR), ultraviolet–visible (UV–Vis) reflectance, and photoluminescence (PL) spectroscopies. The phase formation of CaWO4 was achieved after 1 and 5 h of applied milling speeds of 850 and 500 rpm, respectively. CaWO4 was also obtained after heat treatment at 900 °C for 12 h. TEM and X-ray analyses were used to calculate the average crystallite and grain size. The Raman and infrared spectroscopies revealed the main vibrations of the WO4 groups and indicated that more distorted structural units were formed when the compound was synthesized by the solid-state method. The calculated value of the optical band gap of CaWO4 significantly increased from 2.67 eV to 4.53 eV at lower and higher milling speeds, respectively. The determined optical band gap of CaWO4, prepared by a solid-state reaction, was 5.36 eV. Blue emission at 425 (422) nm was observed for all samples under an excitation wavelength of 230 nm. CaWO4 synthesized by the solid-state method had the highest emission intensity. It was established that the intensity of the PL peak depended on two factors: the morphology of the particles and the crystallite sizes. The calculated color coordinates of the CaWO4 samples were located in the blue region of the CIE diagram. This work demonstrates that materials with optical properties can be obtained simply and affordably using the mechanochemical method. [ABSTRACT FROM AUTHOR]

The present investigation describes the synthesis of luminescent terbium‐doped strontium aluminate nanoparticles emitting bright green light, which were synthesized through a solid‐state reaction method assisted by microwave radiation. Various samples containing different concentrations of Tb were synthesized, and an analysis of their structural and morphological features was conducted using powder x‐ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The band gaps of the samples were determined utilizing the Kubelka–Munk method. The quenching mechanism observed was identified to be due to dipole–dipole interaction using the Dexter theory. The optimized sample with a terbium concentration of 4 at.% has a luminescence lifetime of 1.05 ms with 20.62% quantum efficiency. The results of this study indicate that the terbium‐doped strontium aluminate fluorescent nanoparticles exhibit promising potential for a wide range of applications, including bioimaging, sensing and solid‐state lighting. [ABSTRACT FROM AUTHOR]

Synthesis and characterization of Eu3+-doped Er2SiO5 phosphor are reported. The samples are prepared using the modified conventional solid-state synthesis technique with variable concentrations of doping ions and their structural studies are carried out by X–ray diffraction (XRD). The information on the morphology of the samples prepared with optimized doping ion concentrations is obtained by scanning electron microscopy (SEM). A photoluminescence (PL) analysis of the phosphor samples is also done for the fixed doping ion concentrations. The identified PL emission bands are attributed to the intra 4f transitions of a Eu3+ ion, such as 5D0→7F1 at 590 nm, 5D0→7F0 at 602 and 5D0→7F2 at 613 nm. The corresponding transitions of the doping ions and the concentration quenching effect are studied in detail. The 1931 Commission Internationale de l'éclairage (CIE) (x, y) chromaticity coordinates show the spectral distribution calculated from the PL emission spectrum. A thermoluminescence (TL) glow curve analysis is performed for variable doping ion concentrations, and the corresponding trap parameters are calculated using the Computerized Glow Curve Deconvolution (CGCD) technique. Our study shows that as-prepared phosphor may be useful for display devices. [ABSTRACT FROM AUTHOR]

A series of Er3+ ions doped Sr9Y2W4O24 (SYW) phosphors have been synthesised using solid‐state reaction technique. For optical thermometry and solid state lighting applications, the crystal structure, morphological, and luminescence features of the SYW : Er3+ phosphors were explored. X‐ray diffraction (XRD) reveal that synthesized phosphors having single phase with a tetragonal crystal structure and I41/a space group. Scanning electron microscopy (SEM) was used to examine the morphological behaviour and presence of composition elements. The optical bandgap of the phosphor was evaluated using UV‐Vis diffuse reflection spectra (DRS). The photoluminescence (PL) emission spectra were captured under 380 nm excitation, and the peak with the maximum intensity was identified at 563 nm ascribed to transition 4S3/2→4I15/2, that emits green color in visible region. The temperature dependent PL (TD‐PL) spectra show that SYW phosphor is substantially more thermally stable, having thermal activation energy of about 0.247 eV. Additionally, the fluorescence intensity ratio (FIR) was used to study the optical sensing characteristics of the thermal quenching transitions (2H11/2, 4S3/2) with maximum relative sensitivity (SR) and an absolute sensitivity (SA) being 1.33 % K−1and 0.307 % K−1, respectively. All of the aforementioned findings demonstrate that SYW : Er3+ ions doped phosphors have potential for optical thermometry and other photonic devices. [ABSTRACT FROM AUTHOR]

This manuscript presents research on the optoelectronic and energy transfer properties of conjugated polymer poly (N,N′-bis-4-butylphenyl-N,N'-bisphenyl)benzidine (poly-TPD) and laser dye Fluorol 7GA (F7GA) hybrid thin films prepared via solution blending technique. Various weight ratios of F7GA were added to a fixed concentration of poly-TPD to form homogeneous hybrids. The hybrid thin films were characterized using absorption and photoluminescence spectroscopy. The results showed enhanced absorption, widened optical bandgaps, slight blue-shifted emission, and decreased refractive index in the hybrid films compared to pristine poly-TPD. The significant spectral overlap between the emission spectrum of poly-TPD and the absorption spectrum of F7GA, allowing for efficient Förster resonance energy transfer. Parameters including efficiency, distance, lifetime, and probability of energy transfer were calculated to quantitatively analyze energy transfer. Modulation of F7GA content led to tunable emission colors across the visible spectrum. Overall, the successful energy transfer demonstrated in this study paves the way for exciting future directions in the field of poly-TPD/F7GA hybrid materials for advanced optoelectronic applications. [ABSTRACT FROM AUTHOR]

Y2Sr3B4O12 phosphors doped with europium ions were synthesized by a modified conventional solid-state reaction method. Characterizations of the prepared samples, viz., X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and Commission Internationale de I'Eclairage were studied. The XRD analysis confirmed the formation of mixed phase due to polyborate and has a hexagonal crystalline yttrium orthoborate phosphor. SEM images showed the irregular morphology of the sample. The grain size distribution was broad and the average size was found to range from 2 μm to 100 nm. PL measurements showed excitation and emission characteristics of the prepared phosphor with different concentrations of the doping ion. From the emission spectra, it was clearly observed that the emission intensity of the magnetic dipole was higher than that of electric dipole transition owing to the Eu3+ ions occupying a higher symmetry site in the Y2Sr3B4O12 host. The intensity of PL increased with increasing concentration of the doping ion up to 2.0 mol.%; after that, the PL intensity decreased owing to the concentration-quenching phenomenon. The results indicated that Y2Sr3B4O12:Eu3+ phosphors can be selected as a potential candidate for solar cell/photovoltaic application. [ABSTRACT FROM AUTHOR]

Structural, optical and photoluminescent properties of La2−xPrx(MoO4)3 phosphors with different doping concentrations of Pr3+, synthesized by conventional solid-state and solution combustion routes were studied. X-ray diffraction studies of compounds synthesized through conventional solid-state ceramic route confirm that all samples crystallized in monoclinic La2(MoO4)3 structure with c2/c space group, while combustion synthesized compounds show the existence of two different crystal environments. Analysis of UV–visible diffuse reflectance spectra (DRS) shows characteristics of absorption bands in blue and red regions for Pr3+ substituted La2(MoO4)3 samples, synthesized by both methods. The calculated band gap from the DR spectrum showed an inverse dependence with Pr3+ doping concentration for solid-state synthesized La2−xPrx(MoO4)3 samples, while for combustion synthesized La2−xPrx(MoO4)3 compounds the variation of band gap with concentration is not monotonous. The photoluminescence emission spectrum of blue excited La2−xPrx(MoO4)3 phosphors synthesized by both routes showed similar multicoloured emission bands. Maximum emission intensity was observed for Pr3+ concentration of x = 0.05 in both synthesis methods. The exchange interaction between nearest activator ions leads to concentration quenching of luminescence for solid-state synthesized La2−xPrx(MoO4)3 compounds and dipole–dipole interaction for combustion synthesized La2−xPrx(MoO4)3 compounds. The average emission colour of the blue excited La2−xPrx(MoO4)3 phosphors lies in the yellow–orange region. The CCT values lie in the warm light region and the luminescence lifetime of 8 µs for red emission peak showed promising applications requiring fast switching response. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate the photoluminescence properties of Dy3+-activated YNbO4, LuNbO4, and mixed YxLu1−xNbO4:Dy3+ (x = 0.25, 0.5, 0.75) phosphors. For this purpose, five samples with a fixed Dy3+ concentration (2 mol%) were prepared by the solid-state reaction method. X-ray diffraction measurements showed that all phosphors crystallize in a monoclinic fergusonite-beta-(Y) structure with a C2/c space group. Scanning electron microscopy clearly shows that samples are composed of dense, well-developed micron-sized, cube-shaped grains with rounded edges. The photoluminescent emission spectra feature Dy3+ peaks at standard positions corresponding to transitions from the 4F9/2 excited emitting level to the 6HJ (J = 15/2; 13/2; 11/2 and 9/2) lower levels with two dominant emission bands placed in the blue (~ 479 nm, B) and yellow (~ 576 nm, Y) spectral region. It is observed that with Lu increase in the host lattice Y/B ratio decreases toward the desired ratio of unity to obtain white light. To evaluate the suitability of these phosphors for use in solid-state lighting, their photoluminescence emission was analyzed in detail by calculating CIE coordinates, correlated color temperature (CCT) and Delta u,v (DUV). It is shown that CIE chromaticity coordinates of all Dy3+-activated YxLu1−xNbO4 samples (x = 0, 0.25, 0.5, 0.75, and 1) fall into the white portion of the diagram and that with the increase of Lu in the host lattice color becomes whiter. CCT values for all samples are in the cooler 4000–4500 K range with positive DUVs indicating that color points are placed above the black body curve. The average lifetime of 4F9/2 level is calculated to be ~ 0.2 ms for all Dy3+-activated YxLu1−xNbO4 samples, indicating that there is no influence of the Y-to-Lu ratio in the host niobate material on the luminescence kinetics. [ABSTRACT FROM AUTHOR]

We discuss new features of Sm3+-doped LaCePO4 phosphor as a potential candidate for display applications. Mainly, the traditional modified solid-state synthesis technique was used to prepare the samples. The X-ray diffraction technique was used for the structural studies. LaCePO4:Sm3+ phosphor production was verified by Fourier transform infrared studies. It was customary to use scanning electron microscopy to learn more about the morphology of the prepared samples. Additionally, photoluminescence (PL) analysis of the phosphor samples was presented for different doping ion concentrations with various excitations. In the presence of Sm3+, LaCePO4 emits powerful blue and orange emissions. In-depth research was carried out on the transitions between the concentration quenching effect and the doping ion. The distribution of the spectral region estimated from PL emission spectra was shown in the 1931 Commission International de l'Éclairage (x, y) chromaticity coordinates and was located (0.20, 0.22) in the blue region. According to our research, as-prepared phosphor may find useful application in display devices, especially because of its blue and orange content. [ABSTRACT FROM AUTHOR]

The study examines the optical and electrical characteristics of n-ZnO:Al (AZO) thin films that were deposited on p-Si using the sol-gel dip-coating process, with thicknesses ranging from three to six cycles. The I-V characteristics of the diode device exhibited a high and low current under forward and reverse bias, respectively. The ideality factors were found to decrease from 2.78 to 2.13 with an increase in the number of layers from 3C to 6C. However, it was revealed that the barrier height increased from 0.72 to 0.79 eV. Similarly, the rectification ratio increased from 3196 at ±4 V to 5253 at ±4 V with an increase in the thickness of the emitter layer. Some diode parameters were calculated according to the thermionic and Chueng models and found to be in a range comparable to the literature. The optical study based on photoluminescence under UV excitation showed typical emission spectra of n-AZO/-Si heterostructure characterized by a high emission band around 389 nm, which is due to the recombination of excitons (e-=h+). The various intrinsic defects present in ZnO-doped Al thin films are attributed to the broad emission band in the visible range. The chromaticity study with color properties indicated that the correlated color temperature value of the sample 3C (1380 K) falls in the warm white light region. However, the correlated color temperature value of sample 6C (4454 K) is located in the cool white light source region, which is more suitable as an LED lighting source. It was found that by increasing the emitter layer thickness, the correlated color temperature value of the 6C sample is getting closer to 6504 K - the Commission Internationale de l'Eclairage (CIE) standard for daylight (D65). However, unlike the Duv value of the 6C sample (0.011), the one of the 3C sample (0.0032) is located within the acceptable shift range (±0:006). Based on this study, these heterostructures might be an appealing option for manufacturing W-LEDs with n-UV/blue LED chips as the excitation source for use in displays and lighting. [ABSTRACT FROM AUTHOR]

Different concentrations of Sm2O3‐doped lead borosilicate glass were synthesized using a melt–quenching method and their characteristics were analyzed using X‐ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy absorption, emission, and decay curves. From the XRD patterns, the noncrystalline nature of titled glass was confirmed. The structural groups that existed in the host glass were observed from FTIR spectra. The Judd–Ofelt (JO) intensity parameters and oscillator strengths were derived from the absorption spectra and compared with various reported systems. The excitation luminescence levels of the Sm3+ ion radiative properties were further computed using the JO intensity parameters. Effective bandwidth, emission cross‐sections (σe), and several lasing properties were assessed from emission spectra and compared with other reported glass systems. The decay curves of the 4G5/2 level of Sm3+ ion were also been measured and examined. Additionally, the colour coordinates of the Commission International de I'Éclairage chromaticity were assessed. The titled glass were suitable for visible reddish orange luminescence devices based on all obtained parameters. [ABSTRACT FROM AUTHOR]

We prepare glasses with a chemical composition of 10NaO2-10SrO2-10Gd2O3-69P2O5-1Dy2O3 (NSrODy) and 10NaF-10SrO2-10GdF3-69P2O5-1Dy2O3 (NSrFDy) melt-quenching method and study the effect of Gd2O3 and GdF3 compounds on their physical and luminescence properties. We observed higher emission spectra intensity of NSrFDy glass than that of NSrODy glass. The difference in the intensity is attributed to the difference in OH concentrations in each samples and the efficient energy transfer from Gd3+ ions to Dy3+ ions in the case of NSrFDy glass. We also find that the 6H15/2 → 6F11/2 + 6H9/2 transition has a high oscillator strength and the relation among the J-O parameters, Ωλ (λ = 2, 4, 6), is Ω2 > Ω4 > Ω6 for both glasses. The NSrFDy glass demonstrates a high value of stimulated emission cross-section and, hence, considered good for laser gain medium. We find that CIE coordinates are (0.37, 0.42) and (0.37, 0.41), while CCT values are 4378 K and 4426 K for NSrODy and NSrFDy glasses, respectively. [ABSTRACT FROM AUTHOR]

1 mol% Re2O3–99 mol% Ca3(PO4)2 (Re = Sm, Dy and Er) powder samples were prepared by solid-state sintering method. The structural, thermal, vibrational and optical properties were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), Raman and photoluminescence techniques. XRD studies confirm the formation of β-Ca3(PO4)2 with the rhombohedral crystal structure. FESEM images reveal the formation of flake-like agglomerated particles of size in the range of 100–700 nm. DSC analysis shows that β-TCP → α-TCP structural phase transition occurs at 1286 ºC, followed by α-TCP → α'-TCP transformation at 1469 ºC. Raman spectra of the samples show antisymmetric and symmetric stretching and bending vibration bands of P-O linkages. Photoluminescence studies found intense reddish-orange emission in Sm-doped samples, white light emission in Dy-doped samples and yellow emission in Er-doped samples. The luminescence intensity of Sm and Dy-doped β-TCP samples is found to be significantly higher than that of Er-doped samples. [ABSTRACT FROM AUTHOR]

A new red‐emitting Eu3+ (1−17 mol%)‐doped Na3Mg4LiSi12O30 (NMLS) phosphor was prepared using a conventional solid‐state reaction method at low temperature. The prepared samples belong to a hexagonal structure with a good match to JCPDS card no. 73–0934. The photoluminescence (PL) emission spectrum showed an intense peak at 612 nm when excited at 393 nm. The variation of electric dipole transition (5D0–7F2) emission intensity with increasing Eu3+ ion concentration was investigated. The concentration quenching at 11 mol% is due to the dipole–dipole interaction mechanism in the NMLS host. The optimized NMLS:Eu3+phosphor shows 2.18 times higher luminescence intensity than the (Y,Gd)BO3 (YGB) commercial phosphor. The NMLS:Eu3+showed an intense red emission, having Commission Internationale de l'éclairage (CIE) coordinates (0.6280, 0.3691) and colour purity of 99.2%. The resulting phosphor exhibits good thermal stability of 80% at 423 K. The magnified images of fingerprint showed various minute features such as bridges, sweat pores, ridge end, bifurcation, island and core with better visualization under 393 nm excitation. Furthermore, the optimized NMLS:Eu3+ was used for pc‐LED, latent fingerprints, and anticounterfeit applications as a promising red phosphor. [ABSTRACT FROM AUTHOR]

Improving photophysical properties of poly[2-methoxy-5-(3,7-dimethyl-octyloxy)-1,4-phenylenevinylene]-end capped with dimethylphenyl, MDMO-PPV-DMP, was achieved via incorporation anatase titania nanoparticles (TiO2 NPs). Various contents of TiO2 NPs (up to 50 wt%) were dispersed into fixed concentration of the MDMO-PPV-DMP (5 mg/mL) via solution blending method followed by spin coating onto cleaned glass substrates to form their thin films. The formation of MDMO-PPV-DMP/TiO2 nanocomposites was evidenced from the results of X-ray diffractograms and Fourier transform infrared spectra, while the homogeneity of the films was detected by field emission-scanning electron microscopy (FE-SEM). Increasing the contents of TiO2 NPs resulted in a slight decrease (up to ~ 0.07 eV) in both direct and indirect energy band gaps of the MDMO-PPV-DMP in the nanocomposite thin films. A higher degree of disorder in the electronic structure of the MDMO-PPV-DMP/TiO2 nanocomposite and increasing the localized states density within the forbidden gap can be achieved by increasing the energy tail values and decreasing the steepness parameter with rising the TiO2 NPs content. The enhancement in emission intensity and broadening of emission spectra with increasing the TiO2 NPs content can be explained by the charge trapping effect and particle size distribution, respectively. Moreover, the incorporation of TiO2 NPs into the MDMO-PPV-DMP led to tuning its emitted light color which is of distinct interest in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Tb3+‐doped Na4Ca4Si6O18 (NCMS:Tb3+) phosphors were synthesized using a solid‐state reaction route with increasing dopant concentration. The phase identification studies for NCMS:Tb3+ phosphors were carried out using an X‐ray diffraction (XRD) technique. The XRD patterns for the as‐synthesized phosphors showed satisfactory agreement with the standard pattern (JCPDS card no. 75‐1687) for the pure phase of the Na4Ca4Si6O18 compound. The morphology and size of particles were illustrated from scanning electron microscope (SEM) micrographs. The photoluminescence excitation (PLE) spectrum of Tb3+‐doped Na4Ca4Si6O18 phosphor depicts the strong excitation peak obtained in the UV spectral region. The trivalent terbium‐activated NCMS phosphors excited in the UV region (232 nm wavelength) exhibited intense emission in the blue (350–470) and green (470–650) spectral regions. When increasing the concentration of Tb3+ ions in the host matrix, the emission colour shifted from the blue to the green region due to cross‐relaxation energy transfer (CRET) mechanisms and showed the tunable behaviour of the Tb3+‐activated as‐synthesized NCMS phosphor. These results demonstrated that the Tb3+‐activated sodium calcium metasilicate phosphor has immense potential to contribute as a green‐ and blue–green‐emitting component in lighting and display device applications. [ABSTRACT FROM AUTHOR]

In this paper, we present new aspects of Sm3+‐doped pure Li2CaSiO4 as a suitable candidate for white light emitting diode (WLED) applications. The samples were mainly prepared using a conventional modified solid‐state synthesis technique. The structural studies were done using X‐ray diffraction and Rietveld refinement. Instruments such as a scanning electron microscope (SEM) were used to obtain information about the morphology of the as‐prepared samples. Photoluminescence (PL) analysis of phosphor samples for variable concentrations of doping ions with variable excitations were presented. When doped with Sm3+ in host Li2CaSiO4 it emitted intense blue, green and red emissions and a more intense red emission peak (605 nm) under 408 nm excitation (near‐UV–blue). Our study shows that the as‐prepared phosphor may be useful for optical devices and mainly for WLEDs. The corresponding transitions of doping ions and concentration quenching effect were studied in detail. The 1931 Commission Internationale de l'Eclairage (x, y) chromaticity coordinates showed the distribution of spectral regions calculated from PL emission spectra and this was found (0.63, 0.36) in the red region, so the phosphor may be useful for near‐UV–blue excited WLED applications. [ABSTRACT FROM AUTHOR]

Antimony-lead-oxyfluoroborate (SbPbOFB) glasses doped with various concentrations of Eu3+ ions were prepared by employing melt quenching and their luminescence activity was characterized using different spectroscopic methods such as optical absorption, photoluminescence (PL) excitation, PL emission, and PL decay. The Raman spectrum was recorded for an un-doped SbPbOFB glass to identify various functional groups present. The optical absorption spectra recorded for Eu3+ ion-doped SbPbOFB glasses showed five bands corresponding to 7F0→5L6, 7F0→5D2, 7F1→5D1, 7F0→7F6 and 7F1→7F6 transitions. The PL spectra measured under 394-nm excitation wavelength show five peaks corresponding to 5D0→7F0, 5D0→7F1, 5D0→7F2, 5D0→7F3 and 5D0→7F4 transitions at 578, 592, 613, 652 and 701 nm, respectively. Among them, that pertaining to the 5D0→7F2 transition appeared at 613 nm in the visible red region showing relatively high intensity. The Judd-Ofelt (J-O) parameters evaluated from the absorption spectral data are correlated with the prominent emission spectral features such as 5D0→7F1 (592 nm), 5D0→7F2 (613 nm) and 5D0→7F4 (701 nm) to estimate radiative properties such as transition probabilities (AR), branching ratios (βR) and emission cross sections (σ se). Quantum efficiency (η%) of the prepared glasses was estimated by correlating the radiative lifetimes with the experimental lifetimes measured from the PL decay spectral features. The PL emission spectral features are used to estimate the CIE color coordinates (x, y) of the studied glasses. The measured βR, σ se, η%, and the CIE coordinates estimated for the studied glasses revealed their suitability for visible red light-emitting device applications. [ABSTRACT FROM AUTHOR]

Ce3+/Dy3+ (CDBB) and Ce3+/Sm3+ (CSBB) co-doped barium borate glasses were prepared by melt quenching technique. These glasses are made of B2O3 as a glass former and contain the luminescence activators of Ce3+, Dy3+ and Sm3+ rare earth ions. FT–IR spectra figured out the presence of various stretching and bending vibrations of borate groups in the prepared glasses energy dispersive X-ray spectroscopy (EDX) combined with SEM, enabled the study of near-surface elements and their quantities at various locations, resulting in a sample map. Optical absorption, optical band gap energy (Eg), Urbach energy (ΔE) and the linear refractive index (n) were calculated from the wavelength range observed from 1200 to 200 nm using UV-Vis spectrometer. The emitting wavelengths including 435 (blue), 560 (green), 600 (reddish orange) and 645 nm (red) were observed simultaneously in the luminescent spectra of CSBB at the prominent excitation wavelength of 400 nm, and the mixture of these four emissions yields the white light emission. Further, the energy transfer process occured due to sensitizer-activator ion pairs via a non-radiative mechanism. Notably, co-doping Ce3+and Sm3+ ions increased red emission by efficiently transferring energy from Ce3+ to Sm3+ in the CSBB glass. The CIE chromatograph coordinate (x = 0.339, y = 0.331) of the emission from the CSBB glass is close to the standard white-light illumination (0.320, 0.348). The measured excitation purity (Pe) and colour purity (Pc) of these glasses revealed the quality of their light emission. Furthermore, the synthesized CDBB glasses have reasonable non-linear optical (NLO) properties with stronger SHG intensity of 11.0 mV. [ABSTRACT FROM AUTHOR]

Calcium borophosphate (CBP) phosphors doped with Dy3+ were synthesized by solid-state reaction method. These phosphors were characterized by photoluminescence spectra and decay curves in the visible region. These phosphors were excited at 350 nm, and emission spectra were studied. Decay curves were obtained for the transition, 4F9/2 → 6H13/2 of Dy3+, and lifetimes were measured for different concentrations of Dy3+ ions. CIE chromaticity coordinates were obtained for these Dy3+-doped CBP phosphors. Correlated color temperature was also calculated using the standard formula. [ABSTRACT FROM AUTHOR]

Here, we report the synthesis of Sr2−xEuxSiO4 (Sr2SiO4:Eu3+) [x = 0.01, 0.015, 0.02, 0.025, 0.03] silicate phosphors via high-temperature solid-state reaction method. The prepared phosphors were X-ray diffraction (XRD) characterized, and the analysis of XRD data conveyed that all the samples are crystalline, single-phased and have crystallized to orthorhombic structure (Pmnb). The structure, space group (Pmnb) and other structure concerned parameters were further verified using Rietveld refinement for x = 0.01 phosphor. The XRD pattern for all the synthesized phosphors was identical in appearance, and there is no evidence of the new peak with increased doping of Eu3+ ion. This behavior may be attributed to the uniform distribution of rare earth Eu3+ ion at Sr2+ site due to comparative ionic size of the host and guest ion. The formation of Sr2SiO4:Eu3+ phosphors is verified further by FTIR spectroscopic technique. To investigate optical band gap of prepared phosphors, UV–Vis diffuse reflectance spectroscopic studies have been carried out. Photoluminescence property of Sr2SiO4:Eu3+ phosphors was studied. The emission spectrum displayed characteristic emission peaks corresponding to Eu3+ around 587, 612 and 702 nm. The Commission International de I'Eclairage color coordinates were found lying in orange-red region. [ABSTRACT FROM AUTHOR]

Visible Light Communication (VLC) technology uses white Light Emitting Diodes (LED) for providing illumination and communication at the same time. White LEDs have excellent illumination properties but their communication properties need improvement. This article proposes a way how to evade the communication limitations of white LEDs. A part of original white LED spectrum is suppressed by an optical filter. Then the suppressed part is replaced by another LED. The correct choice of suitable LED enables to reconstruct the original spectrum. This solution removes the limitations because the white LED emits continuously. Data are carried by the communication LED only. The evaluation of reconstruction of original white light is measurement of the colour coordinates x and y. Furthermore, the communication properties of this transmitter were tested and obtained results are shown in this paper. EVM parameter was measured. [ABSTRACT FROM AUTHOR]

A derivative of 2-phenylpyridine (Hppy), 5-nitro-2-(3′,5′-di(trifluoromethyl)phenyl)pyridine (HL), is prepared. TheL-containing cyclometalated iridium(III) complexes with mono- and bidentate ancillary ligands, [Ir(L)2(PPh3)Cl] (1) and [Ir(L)2(pic)] (2, pic = picolinic acid), are synthesized and characterized. The photoluminescence (PL) spectra of1and2in CH2Cl2solutions show emission maxima at 558 and 560 nm, corresponding to yellow light emission with the Commission Internationale de L’éclairage (CIE) coordinates of (0.45, 0.54) and (0.46, 0.52), respectively. However, the luminescence intensity of2with PL quantum yield of 0.71 is obviously stronger that of1with PLQY of 0.19. The two-band white PL properties of2and [Ir(dfppy)2(PPh3)(NCS)] (3, dfppy = 2-(4,6-difluorophenyl)pyridine) with efficient blue light emission are investigated. The CH2Cl2solutions of2and3in the molar ratio of 1 : 5 show white light emission with the CIE coordinates of (0.33, 0.41). [ABSTRACT FROM PUBLISHER]

Nano and polycrystalline ZnS thin films play a crucial role in photovoltaic technology and optoelectronic devices. In this work, we report the photoluminescence (PL) characterization of nanocrystalline ZnS thin films synthesized by dip coating method. The PL spectra exhibit broad nature with multiple emission peaks which are due to the different defect levels in the prepared film. [ABSTRACT FROM AUTHOR]

Flexible displays and electronics fascinate the researchers all around the globe due to their less thickness and light weight. ITO coated PET substrate is the most commonly used flexible substrate for fabricating organic and polymeric electronic and photonic devices for future displays and light sources. Due to the presence of residual stress and other defects, the electro-optical characterization of these substrates is essential. In this paper, we report the measurement of spectral properties of light transmitted through ITO/PET substrate. Spectral changes and modulations were observed on bending the PET substrate. Experimental results of spectral changes and modulations using the R, G, B, and W LEDs as well as broad band halogen source are reported. CIE coordinates were also reported for the change in the spectral profile. Spectral changes in presence of flexible substrate are attributed due to residual stress and due to bending the substrate leading to change in refractive index. [ABSTRACT FROM PUBLISHER]

We report the generation of efficient white light based on upconversion (UC) in Tm/Er/Yb:YO nanocrystalline phosphor synthesized by simple and cost effective solution combustion technique on 976 nm laser excitation. The calculated color coordinates (using 1931 CIE standard) for samples annealed at different temperatures vary from (0.16, 0.30) to (0.32, 0.33) with dopant concentration, annealing temperature and the pump power; thus providing a wide color tunability including the white one. White emission is observed even at a very low laser power (60 mW). The maximum upconversion efficiency obtained for white emission is 2.79% with the color coordinates (0.30, 0.32) at laser power of 420 mW which is quite close to the standard white color coordinates. [ABSTRACT FROM AUTHOR]