CN111454719A - A double perovskite fluoride red luminescent material for white LEDs - Google Patents

Abstract

The invention relates to the field of inorganic luminescent materials, and discloses a fluoride Rb prepared from double perovskite ₂KGaF₆the chemical composition of the double perovskite fluoride red luminescent material is Rb ₂KGa_1‑xF₆:xMn⁴⁺X is Mn as doped ⁴⁺Ion-opposed Ga ³⁺Molar percentage coefficient of ion, 0.0 <the red luminescent material is characterized in that the material generates red light emission mainly with the emission wavelength of 628 nm under blue light of 420-470 nm, and has a strong zero phonon vibration peak at the position of 620 nm.

Description

A double perovskite fluoride red luminescent material for white LEDs

technical field

The invention relates to a double perovskite fluoride red light-emitting material for white light LEDs, in particular to a chemical composition of Rb ₂ KGa _1-x F ₆ :xMn ⁴⁺ , which is excited in blue light (420-470 nm) A series of narrow-band red light emission peaks (610-650 nm) are generated under the fluorophore, which are suitable for fluoride red light-emitting materials of white LEDs, and belong to the field of inorganic light-emitting materials preparation.

Background technique

Compared with other lighting sources (incandescent lamps, tungsten halogen lamps, fluorescent lamps and HID lamps, etc.), white LEDs have the advantages of low voltage, low energy consumption, strong applicability, high stability, and no pollution to the environment. Energy-saving and environmentally friendly green light source. Today, with the increasing attention to environmental protection issues, white LEDs have become the primary choice for developing environmentally friendly light sources.

The blue light chip composite Y ₃ Al ₅ O ₁₂ :Ce ³⁺ phosphor powder produces white light because the preparation process is simple and the technical cost is low, and it is a common way to prepare white light LED devices. The white LED prepared by this method has high _luminous efficiency and good thermal stability, but it also has problems such as _irritation to human eyes and low comfort . < 80). In order to solve this problem, a certain proportion of red phosphor is added to the device to form a "blue-yellow-red" three-color system to achieve warm white light emission, which can reduce the color temperature and improve the color rendering index. Therefore, the development of red light-emitting materials that can be excited by blue light has become a current research focus.

The outermost electron configuration of the Mn ⁴⁺ ion is 3d ³ , and the energy level splitting occurs in the strong octahedral crystal field environment, resulting in the dd transition of the Mn ⁴⁺ ion, which is exhibited in the ultraviolet and blue regions of the excitation spectrum, respectively. The two absorption bands are assigned to the ⁴ A _2g → ⁴ T _1g and ⁴ A _2g → ⁴ T _2g spin-allowed transitions of the Mn ⁴⁺ ion, respectively; meanwhile, the emission spectrum yields ² Eg → ⁴ A The _2g spin-forbidden transition exhibits narrow-band red emission in the red region. This characteristic is just suitable for the white light LED excited by the blue light chip. If it can be applied to the blue light chip, the quality of the white light can be effectively improved. However, the luminescence properties of Mn ⁴⁺ in different host systems are often different. At present, the host materials suitable for Mn ⁴⁺ doping are mainly divided into two categories: oxides and fluorides. When Mn ⁴⁺ is located in the oxide matrix, its strongest absorption is generally located at 300 nm, and its strongest emission is generally located in the long-wave region after 700 nm. Some emission spectra are even beyond the sensitive range of human eyes, and the color purity of red light is not good. High [ Chem. Mater., 2015, 27, 2938.]; in contrast, when Mn ⁴⁺ is located in a fluoride matrix, its strongest absorption is generally located at 460 nm, and its emission is in the range of 600 ~ 650 nm [ ACS Appl. Mater. Interfaces , 2017, 9, 8805.]. Therefore, fluoride-based red light-emitting materials can significantly improve the performance of white LEDs.

Based on this reason, the present invention discloses a red light-emitting material suitable for white light LED, with Mn ⁴⁺ as the light-emitting center and double perovskite fluoride as the host, and its chemical composition is Rb ₂ KGa _1-x F ₆ :xMn ⁴⁺ . This material has excellent luminescent properties of broad blue excitation band and narrow red emission peak, and is a red luminescent material suitable for white LEDs.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a red light-emitting material suitable for use in white light LEDs, with Mn ⁴⁺ ions as the activation center and double perovskite fluorides as the host.

In order to achieve the above purpose, the present invention relates to a double perovskite fluoride red light-emitting material for white light LED, the chemical composition of which is Rb ₂ KGa _1-x F ₆ : xMn ⁴⁺ , where x is doped Mn ⁴ Molar percentage coefficient of ⁺ ions relative to Ga ³⁺ ions, 0.0 < x ≤ 0.20.

The red light-emitting material of the present invention has strong red light emission under the excitation of blue light of 420-470 nm, and the red light emission is composed of the phonon vibration band and the zero phonon vibration peak of the Mn ⁴⁺ ion, wherein the main emission The peak is located at 628 nm, and the zero-phonon vibrational peak is located at 620 nm. The red light-emitting material of the present invention is mixed with Y ₃ Al ₅ O ₁₂ :Ce ³⁺ yellow phosphor and epoxy resin AB glue according to a certain proportion, and is coated on the blue light GaN chip to make low color temperature and high color rendering. Exponential warm white LEDs.

Description of drawings

Fig. 1 is the XRD diffraction pattern of the red luminescent material of the present invention;

Fig. 2 is the EDS energy spectrum of the red luminescent material of the present invention;

Fig. 3 is the excitation and emission spectrum of the red light-emitting material of the present invention at room temperature;

4 is a white light LED device made by coating on a blue light GaN chip after mixing the red luminescent material according to the present invention with Y ₃ Al ₅ O ₁₂ :Ce ³⁺ yellow phosphor and epoxy resin AB glue in a certain proportion. The electroluminescence spectrum under the working condition of 20 mA;

Figure 5 is the electroluminescence spectrum of white LED under different current (20mA, 60mA, 100mA, 140mA) conditions.

Detailed ways

Example 1:

Weigh out 0.03 g of epoxy resin A glue, 0.03 g of B glue, 0.003 g of Y ₃ Al ₅ O ₁₂ : Ce ³⁺ yellow phosphor, 0.012 g of Rb ₂ KGa _{1- x} F ₆ : xMn ⁴⁺ red luminescent material, Mix, stir, and homogenize in a 2.0 ml sample tube. Then, the mixture was coated on the pre-prepared blue-light GaN chips, and then dried in an oven at 120 °C for 2 h, and finally tested under the condition of 20 mA current.

Wherein, the XRD powder diffraction pattern of the Rb ₂ KGa _1-x F ₆ :xMn ⁴⁺ red luminescent material used is shown in Figure 1, and the diffraction peak of the sample is completely consistent with the standard card diffraction peak of the host material Rb ₂ KGaF ₆ , It shows that the crystal phase of the sample is single.

The EDS energy spectrum of the Rb ₂ KGa _1-x F ₆ :xMn ⁴⁺ red light-emitting material is shown in Figure 2. The sample contains six elements of Rb, K, Ga, Mn, F and Au, where Au is the Due to gold spraying, the other five elements are exactly the same as those contained in Rb ₂ KGa _1-x F ₆ :xMn ⁴⁺ .

Figure 3 shows the excitation and emission spectra of Rb ₂ KGa _1-x F ₆ :xMn ⁴⁺ at room temperature. The strongest absorption peaks of the excitation spectrum are located at 358 nm and 462 nm, respectively; the emission spectrum consists of several narrow emission peaks at 610-650 nm, of which the strongest emission of the phonon vibrational band is located at 628 nm, and the zero-phonon vibrational peak is located at 620 nm. nm.

Example 2:

Weigh 0.03 g of epoxy resin A glue, 0.03 g of B glue, 0.003 g of Y ₃ Al ₅ O ₁₂ :Ce ³⁺ yellow phosphor, 0.018 g of Rb ₂ KGa _{1- x} F ₆ :xMn ⁴⁺ red luminescent material, Mix, stir, and homogenize in a 2.0 ml sample tube. Then, the mixture was coated on the pre-prepared blue-light GaN chips, and then dried in an oven at 120 °C for 2 h, and finally tested under the condition of 20 mA current.

FIG. 4 is an electroluminescence spectrum diagram of the white LED made in this example. The Rb ₂ KGa _1-x F ₆ :xMn ⁴⁺ red luminescent material was added into the white light LED light-emitting system, the color temperature T _c of the white light was reduced to 3824 K, and the color rendering index Ra _was increased to 90.2, which optimized the white light LED's performance. various performance indicators.

Example 3:

Weigh out 0.03 g of epoxy resin A glue, 0.03 g of B glue, 0.003 g of Y ₃ Al ₅ O ₁₂ :Ce ³⁺ yellow phosphor, 0.024 g of Rb ₂ KGa _{1- x} F ₆ :xMn ⁴⁺ red luminescent material, Mix, stir, and homogenize in a 2.0 ml sample tube. Then, the mixture was coated on the pre-prepared blue-light GaN chips, and then dried in an oven at 120 °C for 2 h, and finally tested under the condition of 20 mA current.

Example 4:

Weigh 0.03 g of epoxy resin A glue, 0.03 g of B glue, 0.003 g of Y ₃ Al ₅ O ₁₂ :Ce ³⁺ yellow phosphor, 0.018 g of Rb ₂ KGa _{1- x} F ₆ :xMn ⁴⁺ red luminescent material, Mix, stir, and homogenize in a 2.0 ml sample tube. Then, the mixture was coated on the pre-prepared blue-light GaN chips, then dried in a 120 °C oven for 2 h, and finally tested under the condition of 60 mA current.

Example 5:

Weigh 0.03 g of epoxy resin A glue, 0.03 g of B glue, 0.003 g of Y ₃ Al ₅ O ₁₂ :Ce ³⁺ yellow phosphor, 0.018 g of Rb ₂ KGa _{1- x} F ₆ :xMn ⁴⁺ red luminescent material, Mix, stir, and homogenize in a 2.0 ml sample tube. Then, the mixture was coated on the pre-prepared blue-light GaN chips, then dried in a 120 °C oven for 2 h, and finally tested under the condition of 100 mA current.

Example 6:

Weigh 0.03 g of epoxy resin A glue, 0.03 g of B glue, 0.003 g of Y ₃ Al ₅ O ₁₂ :Ce ³⁺ yellow phosphor, 0.018 g of Rb ₂ KGa _{1- x} F ₆ :xMn ⁴⁺ red luminescent material, Mix, stir, and homogenize in a 2.0 ml sample tube. Then, the mixture was coated on the pre-prepared blue-light GaN chips, and then dried in an oven at 120 °C for 2 h, and finally tested under the condition of 140 mA current.

FIG. 5 is the electroluminescence spectra of the white LEDs prepared in Examples 2, 4, 5 and 6 under the driving currents of 20 mA, 60 mA, 100 mA and 140 mA.

Claims (6)

1. A double perovskite fluoride red light-emitting material for white light LED, the chemical composition of which is: Rb ₂ KGa _1-x F ₆ :xMn ⁴⁺ . x is the molar percentage coefficient of the doped Mn ⁴⁺ ions relative to the Ga ³⁺ ions, 0.0 < x ≤ 0.20. 2. The double perovskite fluoride red light-emitting material for white light LED as claimed in claim 1, wherein the adopted host material Rb ₂ KGaF ₆ has a double perovskite structure, and the doping of Mn ⁴⁺ does not change The double perovskite configuration of the host material. 3. double perovskite fluoride red luminescent material for white light LED as claimed in claim 1, is characterized in that under blue light excitation, can produce a series of narrow-band red light emission peaks with wavelength at 610～650 nm. 4. The narrow-band red light emission as claimed in claim 3, characterized in that four sharp red light emission peaks are located at 612 nm, 620 nm, 628 nm, and 645 nm, respectively, wherein 628 nm is the strongest emission peak, and each The half-widths of the emission peaks are all less than 5 nm. 5. The double perovskite fluoride red light-emitting material for white light LED as claimed in claim 1, characterized in that the red light-emitting material is combined with Y ₃ Al ₅ O ₁₂ :Ce ³⁺ yellow phosphor and epoxy resin AB The glue is mixed in a certain proportion and coated on the blue GaN chip to make a warm white LED. 6. The warm white LED of claim 5, characterized by having a lower color temperature ( T _c < 4000 K) and a higher color rendering index ( R _a > 90).

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