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The Luminescent Down Shifting Effect of Single-Junction GaAs Solar Cell with Perovskite Quantum Dots
(2019-01-01)
Cho, Yu-Yun
;
Huang, Yu -Ming
;
Hsu, Shun-Chieh
;
Kao, Sheng-Feng
;
Shih, Hsiang-Yun
In this work, we demonstrate the Luminescent Down Shifting (LDS) effect of the single-junction GaAs solar cell with 514 nm Perovskite quantum dots with and without bake treatment. One of results shows that Jsc from 22.22 mA/cm(2) to 23.38 mA/cm(2) and the efficiency from 17.70% to 18.96% as high as 5.22% and 7.12% enhancement. The enhancement includes antireflection and LDS effect, via our calculated the increase J. from LDS effect was 31.65% Further storage lifetime test shows great reliability from these devices can be expected.
All Inorganic Perovskite Quantum Dots Hybrid Green Light-Emitting Diode with Stable Performance
(2018-01-01)
Yu, Chung-Ping
;
Chung, Meng-Ting
;
Chen, Tzu-Yu
;
Huang, Yu-Ming
;
Huang, Chung-Ping
A silica-coated inorganic perovskite quantum dot hybrid light-emitting diodes is aged continuously in high and low light intensity conditions. Both blue and ultra-violet-pumped samples showed stable performances up to 104 hours.
An Investigation on Stable and Continuous Operation of Hybrid Perovskite Quantum Dot Light Emitting Diodes
(2019-01-01)
Cho, Yu-Yun
;
Hsu, Shun-Chieh
;
Huang, Yu-Ming
;
Shih, Hsiang-Yun
;
Lee, Ting-Yu
Two different package structures of hybrid perovskite quantum dots light emitting diodes were demonstrated with stable and continuous light emission. With boron nitride nanoparticles, the lifetime of device is expected to be thousands of hours.
Multisite-Occupancy-Driven Intense Narrow-Band Blue Emission from Sr5SiO4Cl6:Eu2+ Phosphor with Excellent Stability and Color Performance
(2020-02-03)
Dutta, Somrita
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Som, Sudipta
;
Meena, Mohan Lal
;
Chaurasiya, Rajneesh
;
Chen, Teng-Ming
The development of an efficient blue phosphor with remarkable thermal stability required for high-quality white-lightemitting diodes (WLEDs) remains an exigent task and mainly concerned BaMgAl10O17:Eu2+ (BAM:Eu). Despite the outstanding performance of BAM:Eu, the reduction in luminescence efficiency under long-term operation results in numerous researches on new hosts having lattice rigidity with symmetrical coordination environment. Therefore, we have synthesized a competent blue-emitting Eu2+-activated Sr5SiO4Cl6 (SSC) phosphors. The admirable rigidity of these phosphors with three Sr polyhedra Sr(I)O-9, Sr(II)O-7, and Sr(III)O-8 assessed from Rietveld refinement indicate the dense connectivity in the crystal structure, and the ab initio calculations further support the firm electronic band structure. The broad excitation from 250 to 450 nm suitably matches the absorption band of a near-UV (n-UV) LED chip. The phosphor exhibited bright blue emission with internal quantum yield and color purity > 90% which contribute to the slender fwhm of 33 nm. The first-principle calculation indicates the most stable site for Eu2+ substitution as Sr(III)O-8, and the experimental results agreed with this fact as well. The synthesized phosphor displayed an excellent thermal stability which is superior to that of the commercial BAM:Eu phosphor. The excellent thermal stability may be owed to the highly symmetric coordination environment of Eu2+ in the SSC host that are revealed from the distortion and charge density distribution calculation by density functional theory. The blue phosphor was further utilized for WLEDs and displayed white light with a high color-rendering index and suitable correlated color temperature, which is ideal for practical applications in warm WLEDs.
Enhanced photovoltaic performance of Y2O3:Ho3+/Yb3+ upconversion nanophosphor based DSSC and investigation of color tunability in Ho3+/Tm3+/Yb3+ tridoped Y2O3
(2020-04-25)
Tadge, Prachi
;
Yadav, Ram Sagar
;
Vishwakarma, Pradeep Kumar
;
Rai, S. B.
;
Chen, Teng-Ming
The present study reports the upconversion (UC) based color tuning in Y2O3:Ho3+/Yb3+, Y2O3:Tm3+/Yb3+ and Y2O3:Tm3+/Ho3+/Yb3+ phosphors synthesized through complex based precursor solution method. The Y2O3:Ho3+/Yb3+ phosphor emits intense green and weak red colors whereas the Y2O3:Tm3+/Yb3+ emits NIR and blue colors on excitation with 976 nm. The impact of the enhancement in the concentration of Yb3+ on the color point of codoped as well as tridoped phosphors has been studied in detail. When Y2O3:Tm3+/Ho3+/Yb3+ phosphor is excited by 976 nm laser, the phosphor emits dominant green color. This is due to energy transfer from Tm3+ to Ho3+ ions. The increase in the concentration of Yb3+ ion leads to a color tunability not only in the co-doped but also in the tridoped phosphors. Furthermore, we have incorporated Y2O3:Ho3+,Yb3+ UC phosphor into TiO2 electrode to form an UC based DSSC for converting near IR (NIR) light into visible where DSSCs typically have high sensitivity. The short-circuit current density (Jsc) as well as the open-circuit voltage (Voc) of the UC-TiO2 based cell was found to be 8.46% and 5.18% higher which in turn, resulted into a 10.33% enhancement in power conversion efficiency as compared to that of bare TiO2 based DSSC. Thus, the UC based Y2O3:Ho3+/Yb3+ may be useful in color tunability and DSSC applications. (C) 2019 Elsevier B.V. All rights reserved.
Composition-driven anionic disorder-order transformations triggered single-Eu2+ -converted high-color-rendering white-light phosphors
(2020-01-15)
Dai, Pengpeng
;
Wang, Qingling
;
Xiang, Mei
;
Chen, Teng-Ming
;
Zhang, Xintong
Single-component, single-activator-converted high-color-rendering index (CRI) white-light phosphors have sparked much interest for phosphor-converted white light-emitting diodes. However, manipulating the distribution and locations of single activators to target desired sites in a given host lattice is still a challenge. Herein, we report the remote regulation of the distribution of Eu2+ ions by engineering and controlling the structural ordering in Sr-3(Ce1-xLax)(PO4)(3):0.05Eu(2+) (SCLP:Eu2+) compound, which are designed by using two-color phosphors with different anionic structural ordering, viz., Sr3Ce(PO4)(3):Eu2+ (yellow) with disordered state of PO4 tetrahedra, and Sr3La(PO4)(3):Eu2+ (blue) with ordered state of PO4 tetrahedra. The successive substitution of Ce by La triggers a pronounced disorder-to-order structural transformation of PO4 tetrahedra within SCLP:Eu2+ compounds and guides remotely the distribution of Eu2+ activators, which is demonstrated by a detailed analysis of synchrotron X-ray diffraction refinement, electron paramagnetic resonance spectra, electron spin-echo envelope modulation spectra, Raman spectra, nuclear magnetic resonance spectra and micro-cathodoluminescence spectrum. Benefitting from the controllable structural ordering transformation, as-prepared samples form a unique disorder-order crystal structure, exhibiting controllable microstructure acting on Eu2+ ions, tunable-color emissions including a high CRI (Ra = 90) white-light, increased structural rigidity and thermal stability. These interesting findings in the local structure-dependent luminescence properties demonstrate that structural ordering engineering may be an effective approach to regulate the migration of Eu2+ activators and improve the thermal stability of phosphors.
Synthesis and luminescent properties of polymer-silica multilayer-encapsulated perovskite quantum dots for optoelectronics
(1970-01-01)
Liu, Shuang-De
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Chen, Teng-Ming
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應用化學系
;
Department of Applied Chemistry
Hydrophobic all-inorganic perovskite quantum dots (IPQDs) CsPbX3 (X = Cl, Br, and I) were synthesized using conventional solution methods. IPQDs are potential materials for lasers, solar cells, and displays because of their narrow full width at half-maximum, optically tunable wavelength, and great photoluminescence quantum yield. Their shortcomings are structurally unstable and moisture sensitive. To overcome the poor stability, we have developed a chemical modification to form GQD + PMAO@SiO2 that enhances their photoluminescence quantum yield (from 60 to similar to 90%), thermal stability (from 60 to similar to 90 degrees C), and photochemical stability. The combination of the green-emitting GQD + PMAO@SiO2 and red-emitting RQD + PMAO with a 450 nm blue InGaN-based LED chip was used to fabricate a white light emitting diode with the correlated color temperature (CCT) value of 6,943 K and Commission Internationale del'Eclairage of (0.312, 0.290).
Evaluation of Luminescent Downshifting Effect of Perovskite Quantum Dots on Semiconductor Solar Cells
(2018-01-01)
Chen, Chun-Hong
;
Yu, Chung-Ping
;
Huang, Yu-Ming
;
Chan, Yueh-Lin
;
Huang, Chung-Ping
The luminescent down-shifting effect of the perovskite quantum dots on single junction GaAs solar cells are examined and discussed. The perovskite quantum dots can provide an effective way to convert ultra-violet photons in solar spectrum to visible ones which can be transformed into electron-hole pairs more efficiently. Three different designs are tried: direct-dispense, ITO nano-whisker up and ITO nano-whisker down. In this experiment, we use perovskite quantum dots(QDs) with the concentration of 1mg/ml and emit photons of the wavelength 530nm (CsPbBr3), and the various volume of perovskite QDs were deposited on the solar cell to observe the possible luminescent down-shifting phenomenon.
Resonant-enhanced full-color emission of quantum-dot-based micro LED display technology
(2015-12-14)
Han, Hau-Vei
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Lin, Huang-Yu
;
Lin, Chien-Chung
;
Chong, Wing-Cheung
;
Li, Jie-Ru
Colloidal quantum dots which can emit red, green, and blue colors are incorporated with a micro-LED array to demonstrate a feasible choice for future display technology. The pitch of the micro-LED array is 40 mu m, which is sufficient for high-resolution screen applications. The method that was used to spray the quantum dots in such tight space is called Aerosol Jet technology which uses atomizer and gas flow control to obtain uniform and controlled narrow spots. The ultra-violet LEDs are used in the array to excite the red, green and blue quantum dots on the top surface. To increase the utilization of the UV photons, a layer of distributed Bragg reflector was laid down on the device to reflect most of the leaked UV photons back to the quantum dot layers. With this mechanism, the enhanced luminous flux is 194% (blue), 173% (green) and 183% (red) more than that of the samples without the reflector. The luminous efficacy of radiation (LER) was measured under various currents and a value of 165 lm/Watt was recorded. (C)2015 Optical Society of America
An efficient green-emitting Ba5Si2O6Cl6:Eu2+ phosphor for white-light LED application
(2017-01-01)
Dutta, Somrita
;
Chen, Teng-Ming
;
應用化學系
;
Department of Applied Chemistry
A series of novel green-emitting Ba5Si2O6Cl6:Eu2+ (BSOC:Eu2+) phosphors were synthesized via the high-temperature solid-state reaction route. The phase identification, elemental distribution, reflectance spectra, luminescence, and thermal stability of the BSOC:Eu2+ phosphor and its applicability in white light-emitting diodes (WLEDs) were investigated in detail. The broad excitation spectrum was observed from UV to blue light which generated a broadband emission peaking at 510 nm for the present phosphor with a good quantum efficiency of 44% and thereby it is promising for solid-state lighting applications. Temperature-dependent luminescence measurements of the BSOC:Eu2+ phosphor from 25 degrees C to 250 degrees C were performed to obtain the thermal stability of the present phosphor. Finally, a WLED was fabricated using the green-emitting BSOC:Eu2+ phosphor and commercially available red and blue phosphors pumped with a 400 nm blue chip. The CIE parameters such as color coordinate, color rendering index, color correlated temperature and luminous efficacy of radiation of the fabricated LED were measured. The suitable excitation spectra, efficient and broad emission band and excellent color parameters suggest that the synthesized phosphor could be a potential material for WLED application.

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