scholarly journals New White Light-Emitting Halochromic Stilbenes with Remarkable Quantum Yields and Aggregation-Induced Emission

2021 ◽  
Author(s):  
Farhad Panahi ◽  
Ali Mahmoodi ◽  
Sajjad Ghodrati ◽  
Ali Ashtiani ◽  
Fazlolah Eshghi
Keyword(s):  
White Light ◽  
High Performance ◽  
Density Functional ◽  
Light Emission ◽  
Visible Region ◽  
Emission Spectra ◽  
Cost Effective ◽  
Quantum Yields ◽  
Light Quantum ◽  
Light Emitting

Abstract Highly efficient single-component white light emitters (SWLEs), are attractive candidates for the simple and cost-effective fabrication of high-performance lighting devices. This study introduced a donor–π–acceptor and a donor–π–donor stilbene-based chromophores, representing pH-responsive fluorescence. The emitters showed yellow and green fluorescence in their neutral form. At the same time, protonation of the chromophores caused blue fluorescence color with a strong hypsochromic shift. The white light emission (WLE) for these chromophores was observed at approximately pH=3 due to the simultaneous presence of the neutral and protonated forms of the chromophores, covering almost all the emission spectra in the visible region (400-700 nm). These chromophores presented exceptional white light quantum yields (Φ) between 31-54%, which was desirable for producing white light-emitting devices. Density functional theory (DFT) and time-dependent (TD)-DFT were applied to study the structural and electronic properties of the chromophores.

Utilizing an effective framework to dye energy transfer in a carbazole-based metal–organic framework for high performance white light emission tuning

2018 ◽  
Vol 5 (11) ◽  
pp. 2868-2874 ◽  
Author(s):  
Yu-Pei Xia ◽  
Chen-Xue Wang ◽  
Lian-Cai An ◽  
Da-Shuai Zhang ◽  
Tong-Liang Hu ◽  
...  
Keyword(s):  
Energy Transfer ◽  
White Light ◽  
High Performance ◽  
Light Emission ◽  
Metal Organic Framework ◽  
White Light Emission ◽  
Transfer Mechanism ◽  
Energy Transfer Mechanism ◽  
Light Emitting ◽  
Metal Organic

By introducing dyes into a MOF, a white-light-emitting luminophor was obtained based on effective framework to dye energy transfer mechanism.

The self-reduction synthesis and luminescent properties of Eu2+-Eu3+ activated BaZr0.2Si2O5.4 phosphors with white light emission for white light-emitting diodes

2018 ◽  
Vol 32 (04) ◽  
pp. 1850047 ◽  
Author(s):  
Jianlin Zhong ◽  
Lixin Yu ◽  
Songchu Li ◽  
Xiaoqin Man ◽  
Wei Sun
Keyword(s):  
White Light ◽  
Light Emission ◽  
Emission Spectra ◽  
Luminescent Properties ◽  
White Light Emission ◽  
Photoluminescence Properties ◽  
X Ray Diffraction ◽  
Light Emitting ◽  
Broadband Emission ◽  
White Light Emitting Diodes

The BaZr[Formula: see text]Si2O[Formula: see text]: Eu[Formula: see text]/Eu[Formula: see text] phosphors were prepared with different concentrations of Eu2O3 by a self-reduction method under air condition. The X-ray diffraction and the photoluminescence properties of the prepared samples were analyzed. The emission spectra consisting of a broadband emission from the 4f[Formula: see text]5d transitions of Eu[Formula: see text] and sharp emissions from 5D0-7F[Formula: see text] (J = 0, 1, 2, 3, 4) transitions of Eu[Formula: see text] are observed. The different luminescent colors can be obtained and modulated by doping different concentrations of Eu2O3 and the white light emission can be observed as the concentration of europium is 6%.

Eu3+/Eu2+/Tb3+ co-activated single-phase Gd2O2S: A high-performance white light emitting phosphor for light emitting diode

2021 ◽  
Vol 11 (1) ◽  
pp. 54-62
Author(s):  
Jinpeng Xie ◽  
Bonan Liu ◽  
Qingtao Qong ◽  
Zhicheng Xu ◽  
Zhiqiang Jin ◽  
...  
Keyword(s):  
White Light ◽  
High Performance ◽  
Single Phase ◽  
Light Emission ◽  
Light Emitting Diode ◽  
Energy Transfer Mechanism ◽  
Excitation Spectra ◽  
Phosphor Material ◽  
Light Emitting ◽  
Co Doped

In this work, we report Eu3+/Tb3+/Eu2+ co-activated Gd2O2 S as novel phosphor materials that can be effectively applied in the white-light emitting diode based on a near-UV chip with sensational performances. The luminescent properties and energy transfer mechanism have been thoroughly investigated. The as-prepared europium/terbium co-doped Gd2O2 S phosphors exhibit strong fluorescence with tunable color output under UV-vis light excitation. Furthermore, a high response to ultraviolet illumination of 398 nm wavelength was observed in the excitation spectra, indicating an excellent match with a light-emitting-diode chip in the dominant emissions. It is found that a tricolor (blue, green and red) emission band which results in a white light emission can be acquired when Eu3+, Eu2+ and Tb3+ ions are all co-doped into the single phase Gd2O2S, and an optimum ion doping level (10 at.% Eu and 0.7 at.% Tb) can effectively emit nearly pure white color photoluminescence with lifetime effectively tuned from 0.55 ms to 1.10 ms. The CIE (Commission International de I'Eclairage 1931 chromaticity) is X = 0.3507, Y = 0.3029. It is therefore expected that the newly found phosphor material with high-performance properties possess great potentials for the future advanced white LED applications.

scholarly journals White-Light Emitting Di-Ureasil Hybrids

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2246 ◽  
Author(s):  
Ming Fang ◽  
Lianshe Fu ◽  
Rute Ferreira ◽  
Luís Carlos
Keyword(s):  
White Light ◽  
Light Emission ◽  
Relative Concentration ◽  
Sol Gel ◽  
Quantum Yields ◽  
Excitation Wavelength ◽  
Light Sources ◽  
Efficient Energy Transfer ◽  
Visible Absorption ◽  
Light Emitting

White-light emitting materials have emerged as important components for solid state lighting devices with high potential for the replacement of conventional light sources. Herein, amine-functionalized organic-inorganic di-ureasil hybrids consisting of a siliceous skeleton and oligopolyether chains codoped with lanthanide-based complexes, with Eu3+ and Tb3+ ions and 4,4′-oxybis(benzoic acid) and 1,10-phenanthroline ligands, and the coumarin 1 dye were synthesized by in situ sol–gel method. The resulting luminescent di-ureasils show red, green, and blue colors originated from the Eu3+, Tb3+, and C1 emissions, respectively. The emission colors can be modulated either by variation of the relative concentration between the emitting centers or by changing the excitation wavelength. White light emission is achieved under UV excitation with absolute quantum yields of 0.148 ± 0.015, 0.167 ± 0.017, and 0.202 ± 0.020 at 350, 332, and 305 nm excitation, respectively. The emission mechanism was investigated by photoluminescence and UV–visible absorption spectroscopy, revealing an efficient energy transfer from the organic ligands to the Ln3+ ions and the organic dye, whereas negligible interaction between the dopants is discerned. The obtained luminescent di-ureasils have potential for optoelectronic applications, such as in white-light emitting diodes.

scholarly journals Adjusting White OLEDs with Yellow Light Emission Phosphor Dye and Ultrathin NPB Layer Structure

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Jun Wang ◽  
Weizhi Li
Keyword(s):  
Thin Layer ◽  
White Light ◽  
Power Efficiency ◽  
High Efficiency ◽  
Light Emission ◽  
Layer Structure ◽  
Emission Spectra ◽  
Device Structure ◽  
Phosphor Material ◽  
Light Emitting

High efficiency white organic light emission devices were demonstrated with phosphor material dye bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2′]iridium (acetylacetonate) and ultrathin layer structure. The ultra thin layer be composed of 4,4′-bis[N-1-naphthyl-N-phenyl-amino]biphenyl (NPB) or 4,4′-N,N′-dicarbazole-biphenyl : NPB mixed layer with blue light emission. The emission spectra of devices could be adjusted by different phosphor doping concentrations and ultra thin layer structure. Warm white light emitting device could be obtained with 5 wt% doping concentration and power efficiency of 9.93 lm/W at 5 V. Pure white light with Commission Internationale de l'Eclairage (CIE) coordinates of (0.33, 0.30) and external quantum efficiency of 4.49% could be achieved with ultra thin layer device structure and 3 wt% phosphor doped device.

scholarly journals Preparation and Inverstigation of MEH-PPV Films Used for White Light Emitting Diodes

2011 ◽  
Vol 21 (2) ◽  
pp. 153
Author(s):  
Nguyen Nang Dinh ◽  
Do Ngoc Chung ◽  
Nguyen Phuong Hoai Nam ◽  
Pham Hong Duong
Keyword(s):  
White Light ◽  
Light Emission ◽  
Light Emitting Diode ◽  
Emission Spectra ◽  
Luminous Flux ◽  
Heat Treatment Condition ◽  
Integrating Sphere ◽  
Light Emitting ◽  
Treatment Conditions ◽  
White Light Emitting Diodes

With the aim to prepare white Light Emitting Diode (WLED), the conjugate polymer films like (Poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) were investigated. Spectroscopic (absorption and emission) spectra of the MEH-PPV films showed that this polymer is suitable for casting onto the chips of the blue InGaN LED to make WLED. The luminous flux measured on the WLEDs in the integrating sphere proved that the white light emission can be obtained from the combination of inorganic LED and conjugate (MEH-PPV) polymers with an optimal thickness and a high quality. The aging process of MEH-PPV films was found to be strongly dependent post-treatment conditions. Reasonable heat treatment condition for the MEH-PPV polymers was suggested as in vacuum of 5×10-2 Pa at a temperature of 120°C in, for 2 hous.

White Light Emission from Pr, Dy Doped ZnSiCa Glass

2020 ◽  
Vol 12 (2) ◽  
pp. 154-160
Author(s):  
Pingsheng Yu ◽  
Wei Guo ◽  
Yilu Cheng ◽  
Liangbi Su ◽  
Jun Xu
Keyword(s):  
White Light ◽  
Light Emission ◽  
Light Emitting Diode ◽  
Visible Region ◽  
Color Temperature ◽  
Potential Candidate ◽  
Rare Earth Ion ◽  
Light Emitting ◽  
Light Region ◽  
Chromaticity Coordinates

Background:: Luminescence glass is a potential candidate for developing white light emitting diode (W-LED) due to its good rare earth ion solubility, efficient luminescence, easy fabrication and good mold ability. Pr3+ ion has various visible emission bands from blue to red spectral region, and has attracted considerable attention for potential application to LEDs, ultraviolet laser, and scintillator. The Dy3+ ions can exhibit emission in blue and greenish-yellow (4F9/2→6H15/2, 13/2 transitions of Dy3+) spectral regions under excitation at near UV (ultraviolet). It is possible to obtain white luminescence if Pr3+ ions and Dy3+ ions can be excited simultaneous, due to their multiple luminescence in the visible region. Methods: The Pr, Dy doped ZnSiCa glass samples were prepared by the conventional melting quenching procedure. The XRD, absorption spectra, emission spectra, and ICP-OES measurements were performed to investigate the properties of the materials. Results: The Pr and Dy co-doped ZnSiCa glasses under 443 nm excitation show emission band peaking at about 483 nm, 575 nm and 670 nm / 676 nm. The glass samples exhibit chromaticity coordinates in the white light region in the CIE 1931 diagram, with a Correlated Color Temperature (CCT) at about 7000 K. Conclusion: Pr, Dy codoped ZnSiCa glass samples show chromaticity coordinates in the white light region in the CIE 1931 diagram, with a CCT at about 7000 K. It is suggested that the Pr, Dy codoped ZnSiCa glasses might be considered as promising candidates for white light emitting sources.

scholarly journals White Light Emission from Thin-Film Samples of ZnO Nanocrystals, Eu3+ and Tb3+ Ions Embedded in an SiO2 Matrix

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 1997 ◽  
Author(s):  
Vivek Mangalam ◽  
Kantisara Pita
Keyword(s):  
Thin Film ◽  
White Light ◽  
Light Emission ◽  
Emission Spectra ◽  
White Light Emission ◽  
Thin Film Sample ◽  
Film Sample ◽  
Colour Space ◽  
Light Emitting ◽  
Zno Nanocrystals

In this work, a method was developed to determine the concentration of Eu3+ and Tb3+ ions in a thin-film sample of SiO2, co-doped with ZnO-nanocrystals (ZnO-nc), to produce a sample of any desired colour in the International Commission on Illumination (CIE) colour space. Using this method, a white light emitting sample was fabricated. The thin-film sample combines red, green and blue emissions from the Eu3+ ions, Tb3+ ions and ZnO-nc, respectively, to create white light or light of any desired colour. The emissions at 614 nm and 545 nm from Eu3+ and Tb3+ ions, respectively, is due to the energy transfer from the excited ZnO-nc to the rare-earth (RE) ions. In this way, only a single excitation wavelength is needed to excite the ZnO-nc, Eu3+ and Tb3+ ions in the sample to produce emission of a desired colour from the sample. We developed an empirical 4th-degree polynomial equation to determine the concentrations of Eu3+ and Tb3+ ions to produce light of any desired colour in the CIE colour space. Based on the above empirical equation, the concentration of Eu3+ and Tb3+ ions for a white light emitting sample was found to be 0.012 and 0.024 molar fractions, respectively. The white light emission from the sample was confirmed by fabricating the sample using the low-cost sol–gel process. The stimulated emission spectra and the experimental emission spectra of the white light sample fit very well. The results presented in this work are important to develop energy efficient solid state lighting devices.

scholarly journals Manipulation of parity and polarization through structural distortion in light-emitting halide double perovskites

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Tamilselvan Appadurai ◽  
Ravi Kashikar ◽  
Poonam Sikarwar ◽  
Sudhadevi Antharjanam ◽  
Birabar Ranjit Kumar Nanda ◽  
...  
Keyword(s):  
Excited State ◽  
White Light ◽  
Density Functional ◽  
Light Emission ◽  
Density Functional Theory Calculations ◽  
White Light Emission ◽  
Photogenerated Carrier ◽  
Double Perovskites ◽  
Light Emitting ◽  
Excited State Lifetimes

AbstractHalide perovskite materials recently attracted wide attention for light-emitting applications. The intense white light emission and excited state lifetimes greater than 1 μs are the hallmarks of a good light-emitting material. Here, we provide a clear design strategy to achieve both of these aforementioned properties in a single material via the introduction of octahedral asymmetry in halide double perovskites Cs2AgMCl6 through iso-trivalent substitution at the M site. In the substituted Cs2AgMCl6, the presence of mixed M3+ sites distorts the [AgCl6]5- octahedra, affecting the parity of the valence and conduction band edges and thereby altering the optical transitions. The distortion also creates a local polarization that leads to an effective photogenerated carrier separation. Considering perovskite series with three M3+ cations, namely Bi3+, In3+ and Sb3+, the mixed trivalent cationic compounds with specific ratios of In3+ and Bi3+ show white light emission with intensity nearly 150 times larger than that of the parent compounds, and are characterised by excited state lifetimes nearing 1 μs. Using single crystal X-ray diffraction, far-infrared absorption, steady-state and time-resolved photoluminescence, bias-dependent photoluminescence, P-E loop traces and density-functional theory calculations, we hence demonstrate the role of octahedral distortion in enhancing white light emission and excited state lifetimes of halide double perovskites.

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