Yellow fluorescent powder, preparation method thereof and electroluminescent device

Abstract

The invention provides yellow fluorescent powder, a preparation method thereof and an electroluminescent device, and relates to the technical field of luminescent material preparation. Benzomelamine and 4, 4 ', 4' '-nitrile triphenyl nitrile are used as raw materials to be calcined, phenyl and cyano are introduced to graphite phase carbon nitride, electron delocalization is promoted, structural conjugation is enhanced, non-radiative transition is reduced, and therefore the photoluminescence quantum yield is increased; due to the structure of graphite-phase carbon nitride and introduction of phenyl, rigidity is improved, and excellent thermal stability is achieved; the ratio of phenyl to cyano is controlled by controlling the ratio of benzotripolycyanamide to 4, 4 ', 4' '-nitrile triphenyl nitrile, so that the light-emitting wavelength of the fluorescent powder is regulated and controlled in a yellow light range.

Description

Technical Field

[0001] The invention belongs to the technical field of luminescent material preparation, and in particular relates to a yellow fluorescent powder and a preparation method thereof and an electroluminescent device. Background Art

[0002] The widely used lighting materials include incandescent lamps and fluorescent lamps. Incandescent lamps have disadvantages such as low luminous efficiency, high energy consumption, fragility and heat radiation, while fluorescent lamps contain mercury and therefore require special treatment after being discarded. White light emitting diodes (WLEDs) have many advantages such as non-toxicity, long life, high efficiency and energy saving, and low heat generation, so they are widely used in the fields of lighting and display.

[0003] Currently, commercial WLEDs usually use a blue light emitting chip and a yellow phosphor to emit light. The yellow phosphor in commercial WLEDs is mainly cerium-doped yttrium aluminum garnet, which contains two rare earth elements, cerium (Ce) and yttrium (Y). Rare earth elements are limited in resources, expensive, and have environmental persistence and bioaccumulation. Accumulation in soil and water will be toxic to the ecosystem. Therefore, developing a low-cost, green and environmentally friendly (safe, harmless, and sustainable) new yellow phosphor has become a key direction for WLED research.

[0004] Graphite carbon nitride can generate visible light. As an emerging two-dimensional material, it has significant advantages such as abundant reserves, simple preparation process, excellent biocompatibility and low environmental impact. Graphite carbon nitride that emits green light can be prepared by thermal polycondensation, and graphite carbon nitride can emit blue light after acid treatment. However, the phosphors prepared by graphite carbon nitride in the prior art can only emit green and blue light, and cannot directly emit yellow light; and the fluorescence quantum efficiency of most graphite carbon nitride materials is low, which limits their application in the field of phosphors; in addition, the thermal stability of graphite carbon nitride materials cannot meet the requirements. Summary of the invention

[0005] The object of the present invention is to provide a yellow phosphor and a preparation method thereof and an electroluminescent device. The preparation method provided by the present invention can prepare a yellow phosphor with higher fluorescence quantum efficiency and stronger thermal stability.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing yellow phosphor, comprising the following steps:

[0008] (1) mixing benzoguanamine and 4,4′,4″-nitrile triphenylnitrile and grinding them to obtain a precursor powder;

[0009] (2) calcining the precursor powder obtained in step (1) to obtain yellow phosphor.

[0010] In the step (1), the mass ratio of 4,4',4"-nitrile triphenylnitrile to benzoguanamine is 0.001-0.003:1.

[0011] Preferably, in step (1), the mass ratio of 4,4′,4″-nitrile triphenylnitrile to benzoguanamine is 0.002-0.003:1.

[0012] Preferably, the grinding operation in step (1) is grinding in a mortar.

[0013] Preferably, the calcination device in step (2) is a tubular furnace, and the calcination atmosphere is air.

[0014] Preferably, the heating rate of calcination in step (2) is 2-5°C / min, the calcination temperature is 400-450°C, and the calcination time is 1-1.5h.

[0015] Preferably, in the step (2), cooling is performed after calcination, and the cooling is natural cooling.

[0016] The present invention also provides yellow fluorescent powder prepared by the preparation method described in the above technical solution.

[0017] The present invention also provides an electroluminescent device, comprising a mixed silica gel and a blue light-emitting chip, wherein the mixed silica gel comprises yellow phosphor and silica gel; the yellow phosphor is the yellow phosphor described in the above technical solution.

[0018] Preferably, the concentration of the yellow phosphor in the mixed silica gel is 20-60 mg / L.

[0019] More preferably, the concentration of the yellow phosphor in the mixed silica gel is 30-50 mg / L.

[0020] The invention provides a method for preparing yellow fluorescent powder, comprising: mixing benzoguanamine and 4,4',4"-nitrile triphenylnitrile and grinding the mixture to obtain a precursor powder; calcining the precursor powder to obtain the yellow fluorescent powder; the mass ratio of the 4,4',4"-nitrile triphenylnitrile to the benzoguanamine is 0.001-0.003:1. The invention uses benzoguanamine and 4,4',4"-nitrile triphenylnitrile as raw materials for calcination, introduces phenyl and cyano groups on graphite phase carbon nitride, promotes electron delocalization, enhances structural conjugation, reduces non-radiative transitions, and thus improves photoluminescence quantum yield; the structure of the graphite phase carbon nitride itself and the introduction of phenyl groups lead to improved rigidity and achieve excellent thermal stability; the ratio of phenyl and cyano groups is controlled by controlling the ratio of benzoguanamine and 4,4',4"-nitrile triphenylnitrile, thereby regulating the luminous wavelength of the phosphor within the yellow light range; and the yellow phosphor prepared by the invention contains only three elements of carbon, nitrogen and hydrogen, does not contain rare earth elements, has low cost, and is green and environmentally friendly. Experimental results show that the fluorescence emission peak of the yellow phosphor prepared by the preparation method provided by the present invention is between 560 and 588 nm, within the range of yellow-green light to yellow light, and covers the entire yellow light region; the fluorescence quantum yield can reach 98%, and the fluorescence quantum efficiency is high; and the fluorescence intensity at 150°C is still 90% of that at room temperature (25°C), and has strong thermal stability; the yellow phosphor of the present invention can be simply combined with a commercially available blue light-emitting chip to emit bright white light. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the XRD pattern of the yellow phosphor prepared in Examples 1 to 3 of the present invention;

[0022] Figure 2 is the XRD pattern of the blue phosphor prepared in Comparative Example 1 of the present invention;

[0023] Figure 3 is the infrared spectrum of the yellow phosphor prepared in Examples 1 to 3 of the present invention;

[0024] Figure 4 is the infrared spectrum of the blue phosphor prepared in Comparative Example 1 of the present invention;

[0025] Figure 5 is a fluorescence excitation spectrum diagram of the yellow phosphor prepared in Example 2 of the present invention;

[0026] Figure 6 is a normalized fluorescence spectrum of the yellow phosphor prepared in Examples 1 to 3 of the present invention;

[0027] Figure 7 is a normalized fluorescence spectrum of the blue phosphor prepared in Comparative Example 1 of the present invention;

[0028] Figure 8is a thermogravimetric analysis curve of the yellow phosphor prepared in Example 2 of the present invention;

[0029] Fig. 9 is a graph showing the change in fluorescence intensity of the yellow phosphor prepared in Example 2 of the present invention as a function of temperature;

[0030] Fig.10 This is a graph showing the change in fluorescence intensity of the yellow phosphor prepared in Example 2 of the present invention at 150° C. over time;

[0031] Fig.11 The data diagram of the fluorescence quantum yield of the yellow phosphor prepared in Examples 1 to 3 of the present invention;

[0032] Fig.12 The electroluminescence spectrum of the electroluminescent device prepared in Example 4 of the present invention;

[0033] Fig.13 This is an electroluminescence spectrum diagram of the electroluminescent device prepared in Example 5 of the present invention;

[0034] Fig.14 This is an electroluminescence spectrum diagram of the electroluminescent device prepared in Example 6 of the present invention;

[0035] Fig.15 is a chromaticity coordinate diagram of the electroluminescent device prepared in Example 4 of the present invention;

[0036] Fig.16 is a chromaticity coordinate diagram of the electroluminescent device prepared in Example 5 of the present invention;

[0037] Fig.17 This is a chromaticity coordinate diagram of the electroluminescent device prepared in Example 6 of the present invention. DETAILED DESCRIPTION

[0038] The present invention provides a method for preparing yellow phosphor, comprising the following steps:

[0039] (1) mixing benzoguanamine and 4,4′,4″-nitrile triphenylnitrile and grinding them to obtain a precursor powder;

[0040] (2) calcining the precursor powder obtained in step (1) to obtain yellow phosphor.

[0041] The invention mixes benzoguanamine and 4,4',4"-nitrile triphenylnitrile and grinds them to obtain precursor powder.

[0042] The present invention has no special limitation on the sources of the benzoguanamine and 4,4′,4″-nitrile triphenylnitrile, and commercially available ones can be used. In the present invention, benzoguanamine is mainly used to prepare graphite phase carbon nitride and provide phenyl groups, and 4,4′,4″-nitrile triphenylnitrile is mainly used to provide cyano and phenyl groups.

[0043] In the present invention, the mass ratio of the 4,4′,4″-nitrile triphenylnitrile to benzoguanamine is preferably 0.001 to 0.003:1, more preferably 0.002 to 0.003:1; as an embodiment of the present invention, the mass ratio of the 4,4′,4″-nitrile triphenylnitrile to benzoguanamine can be 0.001:1, 0.002:1, or 0.003:1. The present invention can control the ratio of phenyl and cyano groups in the product by controlling the mass ratio of 4,4′,4″-nitrile triphenylnitrile to benzoguanamine, thereby adjusting the fluorescence emission peak of the yellow phosphor within the range of yellow-green light to yellow light, covering the entire yellow light region. The greater the mass ratio of 4,4′,4″-nitrile triphenylnitrile to benzoguanamine, the greater the wavelength corresponding to the fluorescence emission peak, and as the specific gravity of the amount of cyano group increases, the fluorescence emission peak shifts to the right.

[0044] The present invention has no special limitation on the operation of mixing the benzoguanamine and 4,4′,4″-nitrile triphenylnitrile, and the technical scheme well known to those skilled in the art can be adopted.

[0045] In the present invention, the grinding operation of the benzoguanamine and 4,4′,4″-cyanotriphenylnitrile is preferably carried out in a mortar, and there is no specific requirement for the particle size of the grinding, as long as it is ground into fine powder without granularity.

[0046] After obtaining the precursor powder, the present invention calcines the precursor powder to obtain yellow phosphor.

[0047] In the present invention, during the calcination process, benzoguanamine and 4,4',4"-nitrile triphenylnitrile undergo a polycondensation reaction to generate graphite phase carbon nitride and phenyl and cyano groups grafted onto the graphite phase carbon nitride.

[0048] In the present invention, the calcining device is preferably a tube furnace, and the calcining atmosphere is preferably air. The tube furnace can conveniently control the calcining atmosphere, can provide a relatively uniform temperature distribution, and is conducive to the uniform calcination of the precursor powder.

[0049] In the present invention, the heating rate of the calcination is preferably 2 to 5°C / min; as an embodiment of the present invention, the heating rate can be 2°C / min, 3°C / min, or 5°C / min. The calcination temperature is preferably 400 to 450°C, more preferably 400 to 440°C, and more preferably 410°C. The calcination time is 1 to 1.5h; as an embodiment of the present invention, the calcination time can be 1h, 1.25h, or 1.5h. The present invention can ensure uniform heating of the material and prevent the generation of structural defects by controlling the heating rate within the above range; the present invention can ensure that the precursor is fully decomposed and polymerized to form a stable graphite phase carbon nitride structure by controlling the calcination temperature and time, and can retain and graft phenyl and cyano groups on the graphite phase carbon nitride.

[0050] In the present invention, the calcination is preferably followed by cooling, and the cooling is preferably natural cooling. Natural cooling helps to reduce thermal stress, ensure structural stability, and improve crystallinity.

[0051] In the present invention, after the cooling is completed, the product is preferably ground in a mortar to obtain yellow phosphor. The present invention has no specific requirements for the particle size of the ground product, as long as it is ground into fine powder without granularity.

[0052] The present invention also provides a yellow phosphor prepared by the preparation method described in the above technical solution, comprising graphite phase carbon nitride and phenyl and cyano groups grafted on the graphite phase carbon nitride. In the present invention, the yellow phosphor has high fluorescence quantum efficiency and strong thermal stability, and can emit bright white light by simply combining with a commercially available blue light-emitting chip.

[0053] The present invention also provides an electroluminescent device, comprising a mixed silica gel and a blue light-emitting chip, wherein the mixed silica gel comprises yellow phosphor and silica gel; the yellow phosphor is the yellow phosphor described in the above technical solution.

[0054] In the present invention, the mixed silica gel preferably includes yellow phosphor and silica gel; the concentration of the yellow phosphor in the mixed silica gel is preferably 20-60 mg / L, more preferably 30-50 mg / L; as an embodiment of the present invention, the concentration of the yellow phosphor in the mixed silica gel can be 30 mg / L, 40 mg / L, or 50 mg / L. The present invention can adjust the color temperature by adjusting the concentration of the yellow phosphor within the above range to obtain an electroluminescent device of white light, cold white light, and warm white light.

[0055] In the present invention, there is no special requirement for silica gel, and commercially available silica gel can be used. In the embodiment of the present invention, the silica gel used is commercially available Super Easy 725 silica gel, which can be initially cured in half an hour in the air, and completely cured in 6 to 8 hours.

[0056] In the present invention, there is no special requirement for the blue light emitting chip, and a commercially available one can be used. In an embodiment of the present invention, the blue light emitting chip is a commercially available 450nm blue light emitting chip.

[0057] In the present invention, the method for preparing the electroluminescent device preferably comprises the following steps:

[0058] The yellow phosphor and silica gel are mixed and then dropped onto the blue light-emitting chip for solidification to obtain an electroluminescent device.

[0059] In the present invention, the amount of the mixture of yellow phosphor and silica gel added to the blue light-emitting chip is 5.0-6.5 μL / cm 2 .

[0060] In the present invention, the curing is preferably natural curing. In the present invention, after the mixture of the yellow phosphor and silica gel is dripped and cured naturally, the lid of the blue light emitting chip is covered, and the gap between the blue light emitting chip and the lid is filled with silica gel.

[0061] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] Example 1

[0063] The preparation method of yellow phosphor is as follows:

[0064] 1) 2 g of benzoguanamine and 0.002 g of 4,4′,4″-nitrile triphenylnitrile were mixed and ground thoroughly in a mortar to obtain a precursor powder.

[0065] 2) The precursor powder was transferred to an alumina crucible with a lid, and the temperature was raised to 410°C at a rate of 5°C / min in an air atmosphere in a tube furnace, and kept at that temperature for 1 hour. After natural cooling, the powder was taken out and ground in a mortar to obtain a yellow phosphor.

[0066] Example 2

[0067] The difference between the preparation method of Example 1 and Example 1 is that step 1) is different:

[0068] 1) 2 g of benzoguanamine and 0.004 g of 4,4′,4″-nitrile triphenylnitrile were mixed and ground thoroughly in a mortar to obtain a precursor powder.

[0069] Example 3

[0070] The difference between the preparation method of Example 3 and that of Example 1 is that step 1) is different:

[0071] 1) 2 g of benzoguanamine and 0.006 g of 4,4′,4″-nitrile triphenonitrile were mixed and ground thoroughly in a mortar to obtain a precursor powder.

[0072] Example 4

[0073] The yellow phosphor prepared in Example 2 was mixed with silica gel to prepare a mixture of yellow phosphor and silica gel with a yellow phosphor concentration of 30 mg / L. A drop of the mixture was dropped on a commercial 450nm blue light-emitting chip, and the gel was allowed to solidify naturally to obtain an electroluminescent device.

[0074] Example 5

[0075] The difference between Example 5 and Example 4 is that the yellow phosphor prepared in Example 2 is mixed with silica gel to prepare a mixture of yellow phosphor and silica gel with a yellow phosphor concentration of 40 mg / L.

[0076] Example 6

[0077] The difference between Example 6 and Example 4 is that the yellow phosphor prepared in Example 2 is mixed with silica gel to prepare a mixture of yellow phosphor and silica gel with a yellow phosphor concentration of 50 mg / L.

[0078] Comparative Example 1

[0079] The difference between the preparation method of Comparative Example 1 and Example 1 is that step 1) is different:

[0080] 1) Grind 2 g of melamine in a mortar to obtain a precursor powder.

[0081] XRD test

[0082] (The instrument used is XRD; PANalytical BV, X'Pert-PRO MPD diffractometer, Holland)

[0083] The XRD patterns of the yellow phosphors prepared in Examples 1 to 3 are shown in Figure 1 ;

[0084] The XRD pattern of the blue phosphor prepared in Comparative Example 1 is shown in Figure 2 .

[0085] FT-IR testing

[0086] (The instrument used is FT-IR; Thermo Fisher, Nicolet 6700 FT-IR spectrometer, USA)

[0087] The infrared spectra of the yellow phosphors prepared in Examples 1 to 3 are shown in Figure 3 ;

[0088] The infrared spectrum of the blue phosphor prepared in Comparative Example 1 is shown in Figure 4 .

[0089] Fluorescence spectrum test

[0090] The fluorescence excitation spectrum of the yellow phosphor prepared in Example 2 is shown in Figure 5 ;

[0091] The normalized fluorescence spectra of the yellow phosphors prepared in Examples 1 to 3 are shown in Figure 6 ;

[0092] The normalized fluorescence spectrum of the blue phosphor prepared in Comparative Example 1 is shown in Figure 7 .

[0093] Thermogravimetric testing

[0094] Thermogravimetric analysis curve of the yellow phosphor prepared in Example 2 is shown in Figure 8 .

[0095] Fluorescence intensity changes with temperature

[0096] The fluorescence intensity value of the yellow phosphor prepared in Example 2 varies with temperature. Fig. 9 .

[0097] Fluorescence intensity change over time at 150°C

[0098] The change of the fluorescence intensity value of the yellow phosphor prepared in Example 2 at 150°C over time is shown in FIG. Fig.10 .

[0099] Fluorescence quantum yield test

[0100] The fluorescence quantum yield data of the yellow phosphor prepared in Examples 1 to 3 are shown in Fig.11 .

[0101] Electroluminescence spectrum test

[0102] The electroluminescence spectrum of the electroluminescent device prepared in Example 4 is shown in Fig.12 ;

[0103] The electroluminescence spectrum of the electroluminescent device prepared in Example 5 is shown in Fig.13 ;

[0104] The electroluminescence spectrum of the electroluminescent device prepared in Example 6 is shown in Fig.14 .

[0105] Chromaticity coordinates test

[0106] The chromaticity coordinate diagram of the electroluminescent device prepared in Example 4 is shown in Fig.15 ;

[0107] The chromaticity coordinate diagram of the electroluminescent device prepared in Example 5 is shown in Fig.16 ;

[0108] The chromaticity coordinate diagram of the electroluminescent device prepared in Example 6 is shown in Fig.17 .

[0109] from Figure 1 and Figure 2 A characteristic diffraction peak at 27.6° can be observed in the XRD pattern, which is the (002) graphite-like plane stacked by the conjugated system of graphite phase carbon nitride, indicating that the main components of the yellow-green to yellow phosphors prepared in Examples 1 to 3 and the blue phosphor prepared in Comparative Example 1 are both graphite phase carbon nitride.

[0110] from Figure 3 In the FT-IR image, the vibration peak of phenyl can be observed (the out-of-plane vibration of CH of benzene ring usually appears at 900~650cm -1 , para-substituted phenyl is generally at 700cm -1 Nearby, observed peak position 696cm -1 ), no obvious cyano vibration peak was observed. Figure 3 The enlarged image on the right side of the FT-IR shows the evidence of the presence of cyano groups. Figure 3 The cyano position is at 2221 cm -1 And with the increase of the amount of 4,4′,4″-nitrile triphenonitrile, the vibration peak intensity increases obviously.

[0111] from Figure 4 The vibration peaks of phenyl and cyano groups cannot be observed in the FT-IR diagram, indicating that comparative example 1 does not have grafted cyano groups and grafted phenyl groups.

[0112] from Figure 5 From the fluorescence excitation spectrum diagram in FIG. 1 , it can be seen that the yellow phosphor prepared in Example 2 has an excitation peak within 400 to 500 nm.

[0113] Figure 6 The fluorescence emission peaks of the yellow phosphors of Examples 1, 2 and 3 are 560nm, 570nm and 588nm respectively. Figure 6It can be seen from the normalized fluorescence spectra in Examples 1 to 3 that as the mass ratio of 4,4′,4″-nitrile triphenylnitrile to benzoguanamine changes, the fluorescence emission peak of the yellow phosphor is 560 to 588 nm, and is continuously adjustable in the wavelength range from yellow-green to yellow.

[0114] from Figure 7 It can be seen from the normalized fluorescence spectrum that the fluorescence emission peak of Comparative Example 1 is in the range of 440-470 nm, which belongs to the blue light range, and cannot be assembled with a blue light-emitting chip to obtain an electroluminescent device that emits white light.

[0115] from Figure 8 It can be seen from the thermogravimetric analysis curve in that the weight of the yellow phosphor prepared in Example 2 remains substantially unchanged within 200° C., indicating that the yellow phosphor has good thermal stability.

[0116] Fig. 9 The fluorescence intensity values ​​corresponding to 25℃, 50℃, 75℃, 100℃, 125℃ and 150℃ are 100%, 102%, 101%, 99%, 97% and 92% respectively. Fig. 9 The fluorescence intensity of the yellow phosphor prepared in Example 2 varies with temperature. Fig. 9 It can be seen that the fluorescence intensity at 150°C is still 92% of that at room temperature (25°C), which shows strong thermal stability.

[0117] Fig.10 The fluorescence intensity values ​​corresponding to 0 day, 1 day, 2 days, 3 days, 4 days, 5 days, 6 days, 7 days, 9 days, 11 days, 13 days, 15 days, 17 days, 19 days, 22 days, 25 days, 28 days and 31 days are 100%, 99%, 98%, 96%, 95%, 95%, 95%, 93%, 92%, 91%, 91%, 91%, 90%, 88%, 88%, 88%, 87% and 87%, respectively. Fig.10 The graph of the fluorescence intensity value of the yellow phosphor at 150° C. versus time shows that the fluorescence intensity value of the yellow phosphor prepared in Example 2 can still be maintained at about 87% after 31 days at 150° C., and the thermal stability of the prepared yellow phosphor is very good.

[0118] Fig.11 The fluorescence quantum yields corresponding to Comparative Example 1, Example 1, Example 2, and Example 3 are 8%, 63%, 98%, and 75%, respectively. Fig.11 The fluorescence quantum yield data of the yellow phosphor shows that the fluorescence quantum yields of the yellow phosphors prepared in Examples 1 to 3 are 63 to 98%, respectively, which are much higher than the fluorescence quantum yield of Comparative Example 1 of 8%.

[0119] from Fig.12Electroluminescence spectra of electroluminescent devices in Fig.15 From the chromaticity coordinate diagram of the electroluminescent device, it can be seen that Example 4 obtained a white light-emitting electroluminescent device with a power efficiency of up to 135lm / W. The chromaticity coordinates of the electroluminescent device are (0.33, 0.33) and the color temperature is 5815K, which belongs to the white light range.

[0120] from Fig.13 Electroluminescence spectra of electroluminescent devices in Fig.16 From the chromaticity coordinate diagram of the electroluminescent device in, it can be seen that Example 5 obtained a warm white light-emitting electroluminescent device with a power efficiency of up to 112 lm / W. The chromaticity coordinates of the electroluminescent device are (0.43, 0.43) and the color temperature is 3316K, which belongs to the warm white light range.

[0121] from Fig.14 Electroluminescence spectrum of electroluminescent devices and Fig.17 From the chromaticity coordinate diagram of the electroluminescent device, it can be seen that Example 6 obtained a white light-emitting electroluminescent device with a power efficiency of up to 90lm / W. The chromaticity coordinates of the electroluminescent device are (0.28, 0.27) and the color temperature is 11473K, which belongs to the cold white light range.

[0122] It can be seen from the above embodiments and comparative examples that the fluorescence quantum yield of the yellow phosphor provided by the present invention can reach 98%, and the fluorescence quantum efficiency is high; the fluorescence intensity at 150°C is still 90% of that at room temperature (25°C), and it has strong thermal stability; the yellow phosphor of the present invention can be simply combined with a commercially available blue light-emitting chip to emit bright white light, cold white light and warm white light.

[0123] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing yellow phosphor, characterized in that: The following steps are involved: (1) mixing benzoguanamine and 4,4′,4″-nitrile triphenylnitrile and grinding them to obtain a precursor powder; (2) calcining the precursor powder obtained in step (1) to obtain a yellow phosphor; In the step (1), the mass ratio of 4,4',4"-nitrile triphenylnitrile to benzoguanamine is 0.001-0.003:

1.

2. The preparation method according to claim 1, characterized in that: In the step (1), the mass ratio of 4,4′,4″-nitrile triphenylnitrile to benzoguanamine is 0.002-0.003:

1.

3. The preparation method according to claim 1, characterized in that: The grinding operation in step (1) is grinding in a mortar.

4. The preparation method according to claim 1, characterized in that: The calcination device in step (2) is a tubular furnace, and the calcination atmosphere is air.

5. The preparation method according to claim 1 or 4, characterized in that: The heating rate of calcination in step (2) is 2-5°C / min, the calcination temperature is 400-450°C, and the calcination time is 1-1.5h.

6. The preparation method according to claim 1, characterized in that: In the step (2), cooling is performed after calcination, and the cooling is natural cooling.

7. The yellow phosphor prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The invention comprises graphite phase carbon nitride and phenyl groups and cyano groups grafted on the graphite phase carbon nitride.

8. An electroluminescent device, characterized in that: It comprises mixed silica gel and a blue light-emitting chip, wherein the mixed silica gel comprises yellow phosphor and silica gel; the yellow phosphor is the yellow phosphor as claimed in claim 7.

9. The electroluminescent device according to claim 8, characterized in that The concentration of the yellow fluorescent powder in the mixed silica gel is 20-60 mg / L.

10. The electroluminescent device according to claim 9, characterized in that The concentration of the yellow fluorescent powder in the mixed silica gel is 30-50 mg / L.

Images