AU2021102697A4 - A low-cost blue-emitting eu2+-activated phosphor for nuv excited wleds and solar cell applications - Google Patents
A low-cost blue-emitting eu2+-activated phosphor for nuv excited wleds and solar cell applications Download PDFInfo
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- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical class [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 title claims abstract description 35
- -1 Rare earth activated silicate Chemical class 0.000 claims abstract description 17
- 230000005284 excitation Effects 0.000 claims abstract description 8
- 229910017639 MgSi Inorganic materials 0.000 claims description 12
- 239000000463 material Substances 0.000 abstract description 16
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 8
- 238000000295 emission spectrum Methods 0.000 abstract description 8
- 229910052710 silicon Inorganic materials 0.000 abstract description 8
- 239000010703 silicon Substances 0.000 abstract description 8
- 238000000034 method Methods 0.000 abstract description 7
- 150000002500 ions Chemical class 0.000 abstract description 5
- 239000000126 substance Substances 0.000 abstract description 4
- 238000005424 photoluminescence Methods 0.000 abstract description 3
- 229910052761 rare earth metal Inorganic materials 0.000 abstract description 3
- 238000004020 luminiscence type Methods 0.000 abstract description 2
- 230000007704 transition Effects 0.000 abstract description 2
- 238000011835 investigation Methods 0.000 abstract 1
- 238000002441 X-ray diffraction Methods 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 6
- 238000000695 excitation spectrum Methods 0.000 description 5
- 238000000576 coating method Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 230000005855 radiation Effects 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000012190 activator Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 239000002019 doping agent Substances 0.000 description 2
- 230000005274 electronic transitions Effects 0.000 description 2
- 229910052747 lanthanoid Inorganic materials 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 230000003595 spectral effect Effects 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910002483 Cu Ka Inorganic materials 0.000 description 1
- 239000001856 Ethyl cellulose Substances 0.000 description 1
- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical compound CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 description 1
- 229910052693 Europium Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- WUOACPNHFRMFPN-UHFFFAOYSA-N alpha-terpineol Chemical compound CC1=CCC(C(C)(C)O)CC1 WUOACPNHFRMFPN-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003610 charcoal Substances 0.000 description 1
- 239000002800 charge carrier Substances 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical group [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- SQIFACVGCPWBQZ-UHFFFAOYSA-N delta-terpineol Natural products CC(C)(O)C1CCC(=C)CC1 SQIFACVGCPWBQZ-UHFFFAOYSA-N 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007606 doctor blade method Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 229920001249 ethyl cellulose Polymers 0.000 description 1
- 235000019325 ethyl cellulose Nutrition 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 239000012456 homogeneous solution Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 150000002602 lanthanoids Chemical class 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N nitrate group Chemical group [N+](=O)([O-])[O-] NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000001699 photocatalysis Effects 0.000 description 1
- 238000007146 photocatalysis Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 229940116411 terpineol Drugs 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 229910052724 xenon Inorganic materials 0.000 description 1
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 1
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- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
- C09K11/7728—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing europium
- C09K11/77342—Silicates
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
- H01L31/054—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means
- H01L31/055—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means where light is absorbed and re-emitted at a different wavelength by the optical element directly associated or integrated with the PV cell, e.g. by using luminescent material, fluorescent concentrators or up-conversion arrangements
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
- H01L33/50—Wavelength conversion elements
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/52—PV systems with concentrators
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Abstract
A LOW-COST BLUE-EMITTING EU2+-ACTIVATED PHOSPHOR FOR NUV
EXCITED WLEDS AND SOLAR CELL APPLICATIONS
The present invention relates to a low-cost blue-emitting eu2+-activated phosphor for nuv
excited welds and solar cell applications. Rare earth activated silicate-based phosphors have
attract a lot of attention in recent years in the field of lighting application. In this study, Sr2
xMgSi 207:xEu2+phosphorhas been synthesized by wet chemical method. The luminescence
behavior of synthesized phosphors was observed via Photoluminescence (PL) techniques. The
PLbehavior of the synthesized phosphors were measuredusing RF-5301 PC Spectro
fluorophotometer. Under NUV excitation, emission spectrum of Eu activated phosphors show
strong and broad blue emission band centered at 460 nm, which is ascribed due to 4f65d -*4f7
transition of the Eu2+ions.The CIE chromaticity coordinates and color purity of the synthesized
materials are determined. In addition, the synthesized material was coated with a commercial
solar cell and it was found that silicon-based solar cell efficiency increased around 24.06% under
the solar simulator and 33.20% under direct sunlight.The entire investigation demonstrated that
the synthesized materials are excellent blue components for WLEDs and solar cell applications.
1/4
Our Exprimental wrk
E
Reference Code 98-016-5300
1502303504 50 155 60 6570 7580
Figure1I
1500- 2W
im
Soo5E
250 3i0 350 400 4k0 00 45 40 475 500 w2 w5
Wavelength (nm) WavOeoeigM (nl)
Figure 2
Description
1/4
Our Exprimental wrk
Reference Code 98-016-5300
1502303504 50 155 60 6570 7580
Figure1I
1500- 2W
im Soo5E
250 3i0 350 400 4k0 00 45 40 475 500 w2 w5 Wavelength (nm) WavOeoeigM (nl)
Figure 2
A LOW-COST BLUE-EMITTING EU2+-ACTIVATED PHOSPHOR FOR NUV EXCITED WLEDS AND SOLAR CELL APPLICATIONS
Technical field of invention
Present invention, in general, relates to the field of solid state of lighting and morespecifically to a low-cost blue-emitting eu2+-activated phosphorwhich precisely use for nuv excited welds and solar cell applications.
Background of the invention
The background information herein below relates to the present disclosure but is not necessarily prior art.
In recent years, inorganic luminescent materials have attracted a great deal of attention for the development and fabrication of white light-emitting diodes (WLEDs). WLEDs are the latest entrants in the field of lighting. Currently, WLEDs has the ability to replace traditional incandescent and fluorescent lamps because it's had amazing advantages such as energy saving performance, high efficiency, low cost, long operation lifetime, environmentally friendly behavior and good reliability, etc.
Nowadays, the luminescent efficiency achieved by LEDs has exceeded 260 lm/W, which is far superior to those of traditional light sources, such as Edison-style incandescent lamps (-16 lm/W) and fluorescent lamps (< 100 lm/W). Light emitting diodes (LEDs) are semiconductor light emitters. They are especially useful in display lights, warning lights, and indicator lights or in other applications where colored lighting is desired. The color of the light produced by an LED is dependent on the type of semiconductor material used in its manufacture.
The two popular methods to achieve white light currently are fabricating a blue LED chip with yellow YAG: Ce3+ phosphor or combine the RGB (red, green and blue) phosphor with an ultraviolet (UV) or near-ultraviolet (n-UV) chip. At present, yellow emitting Y3A15012: Ce3+ (YAG: Ce3+) phosphor is used for the fabrication of commercial WLEDs with the combination of blue light-emitting InGaN chip. This approach was extensively used for many years, since it resulted in lower energy loss as compared to those in tricolour LED. But unfortunately, this phosphor has some drawbacks such as high CCT and poor CRI of white light. Thus, the researchers are focusing on the near ultraviolet (near-UV) LED coated with a single-phase phosphor with tri-color emission to obtain white light-emitting based on the energy transfer from sensitizers to activators. On the basis of the above points, it is very important to find new red, green or blue phosphors that can be effectively excited by NUV light currently.
Luminescent materials in which the rare-earth ions act as the activators have garnered great interest because of their promising applicability in diverse fields including photocatalysis, solid-state lighting, biomedical science, optical thermometer, and solar cell. Silicon-based solar cells have been a subject of focus due to their large market use, but a major problem that limiting the conversion efficiency of Si-solar cell is spectrum mismatch between solar radiation and response spectrum of Si-solar cell. The thermalization and transmission of charge carriers generated by absorption of either high energy or low energy incident photons are the main losses by which energy is wasted in Si-solar cell. These losses can be mitigated by using a layer of suitable down-converting and up-converting phosphor materials with solar cell to improve the efficiency. In the present work, one promising scheme of solar spectrum conversion through down-converting phosphors for efficiency enhancement in Si-solar cell has been demonstrated. Recently, more efforts have been put on improving the efficiency of Si-solar cell by using down conversion luminescent materials owing to environment friendly nature causes less utilization of fossil fuels. An improvement in the efficiency of Si-solar cells upto 36.6% was reported by Trupke et. al by assuming the coating of down-converting phosphor on front side of Si-solar cell. The lanthanides ions possess fascinating role in down conversion due to their wide range of energy levels that give possibility of efficient spectral conversion. It has been found that there are various lanthanides ions Eu2+, Tb3+, Nd3+, Yb3+, Er3+ etc, which shows efficient down-conversion phenomenon to enhance the efficiency of solar cells.
Objective of the invention
An objective of the present invention is to attempt to overcome the problems of prior art and provide a low-cost blue-emitting eu2+-activated phosphornuv excited welds and solar cell applications.
The present invention Eu2+ activated Sr2MgSi 2 07phosphorsis synthesized by wet chemical method.
It is therefore an object of the invention shows Sr2MgSi2 0 7 :Eu 2+phosphors can be excited with a 354nm-emitting InGaN chips giving bright blue emission.
These and other objects and characteristics of the present invention will become apparent from the further disclosure to be made in the detailed description given below.
Summary of the invention
Accordingly, the following invention provides a low-cost blue-emitting eu2+-activated phosphorwhich precisely use for nuv excited welds and solar cell applications. In present invention a novel Eu2+ activated Sr2MgSi 207 phosphors was synthesized by wet chemical method. The XRD pattern of synthesized phosphor well-matched with standard data and there is no impurity peak. Under 354 nm excitation, PL emission spectra of Eu2+ activated phosphors show broad band emission with the peak centered at 460 nm due to the allowed 4f'5d 1 -4f 7 electronic transition of Eu2 ions. The PL emission band of commercial blue LEDs is also seen and a comparison with our synthesized phosphors is discussed. The chromaticity coordinates of proposed phosphor are in blue region of CIE diagram and color purity was calculated. In addition, the synthesized material was coated with a commercial silicon solar cell and it was found that silicon-based solar cell efficiency increased around 24.06% under the solar simulator and 33.20% under direct sunlight. These all results show
that, the present Sr2MgSi 20 7 :Eu2+ phosphors can be excited with a 354nm-emitting InGaN chips giving bright blue emission, indicating a promising phosphor as a blue component for the fabrication of NUV LEDs applications. This sample also has the potential for solar cell application.
Brief description of drawing
This invention is described by way of example with reference to the following drawing where,
Figure shows a graph of XRD pattern of synthesized SrMgSi 2 07 phosphor. Figure 2 shows (a): PL excitation spectrum of Sr 2 MgSi 2O 7 :0.7mol%Eu2+ phosphor monitered at 460nm emission wavelength (b) Figure 2: PL emission spectrum of Sr2 MgSi 2O 7
:0.7 molEu2+ phosphor monitered at 354 nm excitation wavelength. Figure 3 showsPL emission spectra of commercial blue LED. Figure 4 shows aimages of synthesized phosphor under (a) Normal light (b) UV light (~365nm). Figure 5 shows CIE Chromaticity coordinate of synthesized Sri.9 9 3 MgSi 2 7 :0.007Eu2+phosphor and commercial blue LED.
Figure 6 shows (a) Silicon solar cell without coating, (b) Silicon solar cell coated with
Sri. 993 MgSi 2 O 7 :0.007Eu 2+phosphor. Figure 7 shows IV characteristics of Sr. 9 9 3 MgSi 2 7 :0.007Eu2+ phosphor under solar simulator. Figure 8 shows IV characteristics of Sr. 993 MgSi 2O 7 :0.007Eu2+ phosphor under direct sunlight.
Detailed description of the invention
Exemplary embodiments the Eu2+ doped Sr2MgSi 207 luminescent phosphors have been synthesized through wet chemical method by varying the doping ions of Eu2, Dy . The Sr(N0 3) 2 (99.0%), Mg(N0 3)2-6H 2 0 (98%), SiO2 , and Eu 2 03 (99.99%) were taken as starting materials in stoichiometric ratio. Rare earth ions Eu is available in the form of oxides, they are converted into nitrate form by dissolving stoichiometric amount of europium ions in a conc. solution of HNO3 . The solution of RE ions in nitric acid is, then, heated with stirring and some drops of distilled water are added to dilute the solution.The appropriate amounts of the used base compounds were weighed using a weighing machine and placed in a 150ml beaker then distilled water (10 ml) was added to mix well all the compounds with the help of a magnetic stirrer. After 1 h stirring, the obtained homogeneous solution kept in a hot oven (90°C) for overnight to make it dry gel. The acquired dried gel was crushed and then kept at 600 °C for 6 hours to release all the nitrates. The obtained powder materials were again put up in crucible and it is tightly bound with wire and placed these crucibles in the charcoal box further undergoes for reduction at 900° C for 6 h in muffle furnace. Again, furnace was cooled to room temperature and grinded for better characterization.
Phase and crystalline nature of powered sample were confirmed by using Rigaku miniflex d 600 X-ray diffractometer with Cu Ka radiation (X = 0.154056 nm) operated at 40 kV, 15 mA. The XRD pattern was recorded in the range of 10-90 ° with step size 0.02 0. The photoluminescence excitation and emission spectra were recorded on the Shimadzu RF5301PC Spectrofluorophotometer with a Xenon flash lamp (150 W). The same amount of sample was used in each case. Emission and excitation spectra were recorded using a spectral slit width of 1.5 nm at high and low sensitivity. These characterizations were performed were room temperature. IV characteristics of the blank and coated solar cell were checked on solar simulator and under direct sunlight at 40 °C for comparison.
X-Ray diffraction is used to phase confirmation of the synthesized Sr2MgSi 2 07 phosphor. Fig. 1 shows XRD pattern. The XRD peaks are found to be well matched with the standard data available in the ICDD #98-015-5300, which confirms the formation of compound. Some lower intensity peaks are missing due to background noise resulting from instrumental error. The XRD pattern shows sharp peaks they indicate the homogeneous and crystalline nature of prepared phosphor material. Due to the doping of Eu2, it was expected that the Eu takings the position of Sr2+ ion according to ionic radii (Sr2+ = 1.26 A and Eu2+ = 1.17 A).
Doping of Eu2+ ion does not cause any significant change in the host lattices. The dopant Eu2+ doesn't change the XRD patterns and phase of Sr2MgSi 207 significantly. The XRD pattern exhibits prominent diffraction peaks of tetragonal structure of space group P -4 21 m having 113 space group numbers. The calculated lattice parameters are a = 8.0110 A, b = 8.0110 A, c = 5.1630 A and unit cell volume is 331.34 A3.
The PL excitation spectra of Sr. 9 93 MgSi 2 07 :0.7mol% Eu2+ phosphors is shown in Fig.2 (a), which is monitored under 460 nm emission wavelength. This PL excitation spectrum represents broad excitation band centered at 354 nm with two small humps at around 289nm and 420 nm. Since the excitation band peaks at 354 nm, it was used as the excitation wavelength to record the emission spectra. A broad band emission with the peak centered at 460 nm was observed, as shown in Fig. 2(b). This broad band emission is assigned to the allowed 45d -- 4f7 electronic transition of Eu2+ ions. As a result, the line shape is independent of Eu2+ concentration. Indeed, in these PL emission spectra, it is cleared that emission peaks are not shifted with the increase in concentration of Eu2+ ions. The Sr2
xMgSi 2 0 7 :x Eu2+ (x=0.1, 0.3, 0.5, 0.7, 1.0, 1.5 mol%) phosphors show similar profile for each concentration of Eu2+ ions. The variation in the PL emission intensity was observed for different concentrations of Eu2+ ions.
The variation in the area under the PL curve for the 4f'5d -- 4f7 transition of the Eu2+ with the varying concentration of Eu2+ ions have been also observed. Optimum PL intensity was observed for the 0.7 mol% of Eu2+ ions doped in the host material. When the concentration of Eu2+ ions exceeded 0.7 mol%, the luminescence quenching was observed. This phosphor material when mixed with green and red colour emitting phosphor can provide white light. Using Blasse formula, the critical energy transfer distance (Rc) can be
"3V 1/3 2( Rc=2(4TEXcN)
Where V is the unit cell volume, Xc is the critical concentration of Eu2+ ions, and N is the number of available sites for the dopant in the unit cell. In the Sr2 MgSi 2O7 host, V = 331.34 A3 , N = 2 and Xc is 0.07 for Eu2+ doped Sr2 MgSi 2 O7 phosphor, and this leads to the value of Re to be 8.26 A. From this value of R, it can be concluded that the energy transfer between the Eu2+ ions in the Sr2MgSi 207 host occurs as a result of the electric multipole-multipole interaction.
The chromaticity diagram of the Commission International del'Eclairage (CIE) indicates thatcoordinates are highly useful in determining the exact emission color and color purity of a sample.Fig.5 represents CIE chromaticity coordinate of synthesized phosphor. The CIE(Commission Internationaledel'Eclairage) diagram is another way to check the nature of emittedcolor by the phosphor materials. The CIE coordinate of synthesized materials were calculated and given in Table 1, which is shows emission of color in the blue region. According to 1953 color National Television Standard Committee (NTSC) standard CIE coordinated values for blue phosphor is (0.14, 0.08). The CIE coordinates of Sri. 9 9 3 MgSi 2 O7 :0.007Eu2+ phosphor very close to NTSC standard CIE coordinates. The CIE diagram represents synthesized phosphorshave great potential for White LED application. The color purity of specific dominant emission colorof a light source can be obtained by using below given expression that expression described byFred Schubert
Color Purity = - rill X100% V(xd -Xi)2_t _(d y,)2
Where (x, y) is the CIE Chromaticity coordinate, (xi,y) is the coordinate of perfect white light, and(xd, yd) is coordinate of the dominant wavelength. The dominant wavelength is deviation from theperfect white light which corresponds to a point in the boundary of the curve and can be obtainedby the intersection of the line that connects the center with the color point of the material. Thecolor purity of prepared phosphors is determined around 90.06%.This indicates high color purity and excellent chromaticity coordinate characteristics.
Table: 1 CIE chromaticity coordinate and color purity of synthesized phosphors
1.Srl.93MgSi207:0.007Eu + 354 n A (0. 1329, 0.0615)
2. Commercial Blue LED 365 nm B (0.1558, 0.0189)
To determine the efficiency of the solar cell of synthesized phosphor, experiments were carried out by IV characteristics at 12 o'clock in the afternoon at 40 C temperature and open condition at the Department of Physics, RTM Nagpur University, Nagpur. Temperature was measured by a simple thermometer. In the process of experimentation, firstly the characteristics of the blank silicon solar cell were measured in a solar simulator and sunlight at a temperature of 40 °C. Subsequently, the synthesized phosphor is coated on a blank silicon solar cell as shown in Fig. 6. The coating process is done by the doctor blade method. In this work terpineol, ethyl cellulose, ethanol and acetic acid have been used with synthesized phosphor.
The main electrical characteristics of a solar cell or module are summarized in the relationship between the current and voltage produced on a typical solar cell I-V characteristics curve. The intensity of the solar radiation (insolation) that hits the cell controls the current (I), while the increases in the temperature of the solar cell reduces its voltage (V). Solar cells produce direct current (DC) electricity and current times voltage equals power, so we can create solar cell I V curves representing the current versus the voltage for a photovoltaic device.
Solar Cell I-V Characteristics Curves are basically a graphical representation of the operation of a solar cell or module summarising the relationship between the current and voltage at the existing conditions of irradiance and temperature.
In the present invention, the IV characteristics of the coated solar cell are recorded under solar simulator and sunlight. We have plotted a graph between voltage (V) and current (mA). Then obtained curves are linearly fitted. The curve shows straight line with negative value of the slope. It is observed that the coating solar cell efficiency of the sample is increases up to 24.06% under the solar simulator and 33.20% under direct sunlight. In both situations the increase in solar cell efficiency is determined by the following formula
Slope of coated cell EfficiencyS% = * 100 Slope of without coated cell
Claims (4)
1. A low-cost blue-emitting phosphor comprises of; Eu2+ activated Sr2MgSi 2O 7phosphors; InGaN chips;
2. The low-cost blue-emitting eu2+-activated phosphoras claimed in claim 1 wherein Sr2 MgSi 2 0 7 :Eu2+phosphors can be excited with a 354 nm-emitting InGaN chips giving bright blue emission and broad band emission with the peak centered at 460 nm under NUV and visible excitation.
3. The low-cost blue-emitting eu2+-activated phosphoras claimed in claim 1 wherein the CIE coordinates of Sr. 993 MgSi 2 0 7 :0.007Eu2+ phosphorvery close to NTSC standard CIE coordinates.
4. The low-cost blue-emitting eu2+-activated phosphoras claimed in claim 1 wherein solar cell efficiency has been enhanced 24.06% under the solar simulator and 33.20% under direct sunlight.Discovery of low cost blue-emitting Eu2+-activated phosphor for NUV excited WLEDs and solar cell applications.
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