CN116367681A - Test method and screening method for decay rate of light-emitting devices - Google Patents

Abstract

The application provides a test method and a screening method of a light-emitting device attenuation rate, wherein the test method is characterized in that a solution to be tested containing a material of a light-emitting layer, a material of a carrier transmission layer and a free radical indicator is provided, then quantum dots in the light-emitting layer are excited by illumination and react with the material of the carrier transmission layer to generate free radicals, and the concentration of the free radicals in the solution to be tested is represented by the free radical indicator, so that the test of the quantum dot light-emitting diode attenuation rate is realized.

Description

Test method and screening method for decay rate of light-emitting devices

technical field

The present application relates to the field of photoelectric devices, in particular to a method for testing and screening the decay rate of light emitting devices.

Background technique

QLED (Quantum Dots Light-Emitting Diode, Quantum Dot Light-Emitting Diode), is an emerging display device, the structure is similar to OLED (Organic Light-Emitting Diode, Organic Light-Emitting Display), that is, hole transport layer, light-emitting layer and electron transport sandwich structure composed of layers. This is a new technology between liquid crystal and OLED. The core technology of QLED is "Quantum Dot (quantum dot)", which is composed of zinc, cadmium, selenium and sulfur atoms. As early as 1983, scientists at Bell Laboratories in the United States conducted in-depth research on it, and a few years later, physicist Mark Reed of Yale University officially named it "quantum dots". Quantum dots are particles with a particle diameter of less than 10nm, composed of zinc, cadmium, sulfur, and selenium atoms. This substance has a very special property: when the quantum dot is stimulated by light, it will emit colored light, and the color is determined by the material making up the quantum dot and its size and shape. Because it has this property, it is able to change the color of the light emitted by the light source. The emission wavelength range of quantum dots is very narrow, and the color is relatively pure and adjustable, so the picture of quantum dot display will be clearer and brighter than that of liquid crystal display.

Compared with OLED, QLED is characterized by the use of more stable inorganic quantum dots as its luminescent material. The unique quantum size effect, macroscopic quantum tunneling effect, quantum size effect and surface effect of quantum dots make them exhibit excellent physical properties, especially their optical properties. Compared with organic fluorescent dyes, quantum dots prepared by colloidal method have the advantages of adjustable spectrum, high luminous intensity, high color purity, long fluorescence lifetime, and multicolor fluorescence can be excited by a single light source. In addition, QLED has a long lifespan, and the packaging process is simple or does not require packaging. It is expected to become the next generation of flat panel displays and has broad development prospects. QLED is based on the electroluminescence of inorganic semiconductor quantum dots. In theory, the stability of inorganic semiconductor quantum dots is higher than that of small organic molecules and polymers; on the other hand, due to the quantum confinement effect, the luminescent line of quantum dot materials The width is smaller, so that it has better color purity. At present, the luminous efficiency of QLED has basically met the needs of commercialization.

However, free radicals in QLEDs will affect the device, so a method to characterize the content of free radicals is needed.

Contents of the invention

The application provides a test method and screening method for the decay rate of a light-emitting device, which can

In the first aspect, an embodiment of the present application provides a method for testing the decay rate of a light-emitting device, the light-emitting device includes a light-emitting layer and a carrier transport layer, and the method includes:

A solution to be detected is provided, the solution to be detected includes the material of the light-emitting layer, the material of the carrier transport layer, a free radical indicator and an organic solvent, the material of the light-emitting layer includes quantum dots, and the free radical The indicator has characteristics characterizing the concentration of free radicals in the solution to be detected; and

Light treatment is performed on the solution to be detected for a predetermined time, so that the material of the light-emitting layer and the material of the carrier transport layer react to generate free radicals, and according to the effect of the free radical indicator on the concentration of free radicals in the solution to be detected The attenuation rate of the light-emitting device was obtained by characterization.

Optionally, the solution to be tested includes:

In the light-emitting device, take a sample of the light-emitting layer and a sample of the carrier transport layer with a predetermined area, and disperse the sample of the light-emitting layer and the sample of the carrier transport layer in the organic solvent , to obtain a dispersion; and

A free radical indicator is added to the dispersion to obtain the solution to be detected.

Optionally, performing light treatment on the solution to be detected for a predetermined time, and obtaining the attenuation rate of the light-emitting device according to the characterization of the concentration of free radicals in the solution to be detected by the free radical indicator, includes: The solution to be detected is subjected to light treatment for a predetermined time, the absorbance of the free radical indicator in the solution to be detected is detected at a specific wavelength, and the decay rate of the light-emitting device is obtained according to the absorbance of the free radical indicator at a specific wavelength.

Optionally, performing light treatment on the solution to be detected for a predetermined time, and obtaining the attenuation rate of the light-emitting device according to the characterization of the concentration of free radicals in the solution to be detected by the free radical indicator, includes: The solution to be detected is subjected to light treatment for a predetermined time, and multiple time points are taken within the predetermined time to detect the absorbance of the free radical indicator in the solution to be detected at a specific wavelength; according to the free radical indicator at multiple time points The absorbance at a specific wavelength is calculated to obtain the scavenging rate of the free radical indicator in the solution to be detected within a predetermined time; and the decay rate of the light-emitting device is obtained according to the scavenging rate of the free radical indicator.

Optionally, in the solution to be detected, the concentration of the free radical indicator is 0.01 mg/mL to 1 mg/mL, and/or, the material of the light-emitting layer and the material of the carrier transport layer The total concentration of 0.001mg/mL to 1mg/mL.

Optionally, the free radical indicator is DPPH.

Optionally, the organic solvent is selected from methanol.

Optionally, the wavelength of the light is 400nm-450nm, and/or, the predetermined time of the light treatment is 10min-1h.

Optionally, the light emitting device is a blue quantum dot light emitting diode.

Optionally, the carrier transport layer includes an electron transport layer, and/or a hole transport layer.

Optionally, the hole transport layer material includes: poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine), polyvinylcarbazole, poly(N,N 'bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4 -phenylenediamine), 4,4',4"-tris(carbazol-9-yl)triphenylamine, 4,4'-bis(9-carbazole)biphenyl, N,N'-diphenyl- N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, 15N,N'-diphenyl-N,N'-(1-naphthyl )-1,1'-biphenyl-4,4'-diamine, graphene, at least one of _C60 , and/or,

The electron transport layer material includes: at least one of ZnO, TiO ₂ , SnO ₂ , Ta ₂ O ₃ , ZrO ₂ , NiO, TiLiO, ZnAlO, ZnMgO, ZnSnO, ZnLiO and InSnO; and/or,

The light-emitting layer is selected from at least one of II-VI compound, III-V compound and I-III-VI compound; the II-VI compound is selected from CdSe, CdS, CdTe, ZnSe, ZnS, At least one of CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe and CdZnSTe; the III-V group compound is selected from InP, InAs, GaP, GaAs, At least one of GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP and InAlNP; the group I-III-VI compound is selected from at least one of CuInS ₂ , CuInSe ₂ and AgInS ₂ .

In a second aspect, the present application provides a method for screening light-emitting devices, the method comprising:

providing a plurality of light emitting devices;

Use the test method described in any embodiment of the first aspect to obtain the decay rate of each of the light-emitting devices, compare the decay rates of each of the light-emitting devices, and screen out the target light-emitting devices.

Optionally, the screening out the target light-emitting device includes: screening out the light-emitting device with a relatively slow decay rate among the plurality of light-emitting devices to obtain the target light-emitting device.

Beneficial effect:

The application provides a method for testing the decay rate of a light-emitting device. The light-emitting device includes a light-emitting layer and a carrier transport layer. Since the decay rate of a quantum dot light-emitting diode is related to free radicals, the application provides a material containing a light-emitting layer, a carrier The material of the carrier transport layer and the solution to be tested of the free radical indicator, and then use light to excite the quantum dots in the luminescent layer and react with the material of the carrier transport layer to generate free radicals. The characteristics of detecting the concentration of free radicals in the solution, so the present application can use the free radical indicator to characterize the concentration of free radicals in the solution to be detected, so as to realize the test of the decay rate of quantum dot light-emitting diodes.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings that need to be used in the description of the embodiments.

Fig. 1 is a schematic flow chart of a method for testing the decay rate of a light-emitting device provided in an embodiment of the present application;

Fig. 2 is a schematic diagram of an upright structure of a light emitting device provided by an embodiment of the present application;

Fig. 3 is a schematic diagram of an inverted structure of a light emitting device provided by an embodiment of the present application;

Fig. 4 is a schematic flowchart of a screening method for a light-emitting device provided in an embodiment of the present application;

Fig. 5 is the schematic diagram of the absorption spectra of test sample 1, test sample 2 and the comparison sample at different times under the dark state environment provided by the embodiment of the present application; wherein, a in Fig. 5 is the absorption change curve of the comparison sample, and b is the test The absorption change curve of sample 1, c is the absorption change curve of test sample 2, and d is the change curve of the test sample absorption normalized with the light time at 513nm;

Fig. 6 is the schematic diagram of the absorption spectra of test sample 1, test sample 2 and comparative sample under different time of 400nm illumination provided by the embodiment of the present application; wherein, a in Fig. 6 is the absorption change curve of the comparative sample, and b is the test sample 1, c is the absorption change curve of test sample 2, and d is the change curve of test sample absorption normalized with light time at 513nm.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the application with reference to the drawings in the embodiments of the application. Apparently, the described embodiments are only some of the embodiments of the application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts belong to the scope of protection of this application.

The embodiment of the present application provides a testing method and screening method for the decay rate of a light emitting device. Each will be described in detail below. It should be noted that the description sequence of the following embodiments is not intended to limit the preferred sequence of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". Various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the application; therefore, the described range should be regarded as The description has specifically disclosed all possible subranges as well as individual values within that range. Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range.

First, as shown in Figure 1, an embodiment of the present application provides a method for testing the decay rate of a light-emitting device, the light-emitting device includes a light-emitting layer and a carrier transport layer, and the method includes:

S10. Provide a solution to be detected, the solution to be detected includes the material of the light-emitting layer, the material of the carrier transport layer, a free radical indicator and an organic solvent, the material of the light-emitting layer includes quantum dots, the The free radical indicator has characteristics characterizing the concentration of free radicals in the solution to be detected; and

S20. Perform light treatment on the solution to be detected for a predetermined time, so that the material of the light-emitting layer and the material of the carrier transport layer react to generate free radicals, and detect the free radicals in the solution to be detected according to the free radical indicator Characterization of the concentration yields the decay rate of the light-emitting device.

The commonality of quantum dots is large specific surface area and strong surface activity. Therefore, in the excited state, combined with OH and oxygen in other functional layers, it is easy to generate free radicals with strong oxidative properties. The existence of free radicals will cause irreversible damage to the organic matter in the device. damage, resulting in attenuation of the device. However, the currently commonly used free radical characterization methods cannot reliably characterize the content of free radicals, so it is impossible to study the effect of free radical content on the decay of devices. It should be noted that the decay rate in the embodiments of the present application does not refer to the decay rate of the device itself, but through other parameters (the concentration of free radicals in the solution to be detected or other concentration-related characterization parameters, such as absorbance or free radicals). The decay rate reflected on the side of the clearance rate of the base indicator. In the embodiment of the present application, the free radical content of the device and the decay rate of the device can be characterized side by side by detecting the concentration of free radicals in the solution to be detected, so as to complete the test of the decay rate of the light emitting device. After illumination, if there are more free radicals generated by the light-emitting layer and the carrier transport layer per unit time, the concentration of free radicals in the solution to be tested is higher, indicating that the free radical content of the device is higher, and the decay rate of the device is faster. If the free radicals generated by the light-emitting layer and the carrier transport layer per unit time are less, the concentration of free radicals in the solution to be tested is lower, indicating that the free radical content of the device is lower, and the decay rate of the device is slower.

In the embodiment of the present application, by providing a solution to be tested containing the material of the light-emitting layer, the material of the carrier transport layer and the free radical indicator, and then using light to excite the quantum dots in the light-emitting layer to form excitons, the free electrons in the excitons and the space The holes separate and react with the material of the carrier transport layer to generate free radicals (if the material of the carrier transport layer is not present in the test, the electrons and holes in the excited state cannot be converted into free radicals). Since the free radical indicator has the characteristics of characterizing the concentration of free radicals in the solution to be detected, the present application can use the free radical indicator to characterize the concentration of free radicals in the solution to be detected, thereby indirectly studying the concentration of free radicals in the quantum dot light-emitting diode. content, to realize the test of the decay rate of quantum dot light-emitting diodes.

In some embodiments, the providing the solution to be tested comprises:

S11. In the light-emitting device, take a sample of the light-emitting layer and a sample of the carrier transport layer with a predetermined area, and disperse the sample of the light-emitting layer and the sample of the carrier transport layer in the organic in a solvent to obtain a dispersion; and

S12. Adding a free radical indicator to the dispersion to obtain the solution to be detected.

In some embodiments, the free radical indicator has the characteristic of changing color by reacting with free radicals, so when it is used as a free radical indicator, the present application can detect the absorbance of the solution to be tested, that is, the free radical indicator in the range of visible light Or scavenging rate, to characterize the concentration of free radicals in the solution to be detected, so as to indirectly study the content of free radicals in quantum dot light-emitting diodes, and realize the test of the decay rate of quantum dot light-emitting diodes.

For example: in the step S20, the light treatment of the solution to be detected is performed for a predetermined time, and the attenuation rate of the light-emitting device is obtained according to the characterization of the concentration of free radicals in the solution to be detected by the free radical indicator, including : Carry out light treatment on the solution to be detected for a predetermined time, detect the absorbance of the free radical indicator in the solution to be detected at a specific wavelength, and obtain the light-emitting device according to the absorbance of the free radical indicator at a specific wavelength decay rate. Within a certain period of time, the smaller the absorbance of the free radical indicator, the more free radicals in the solution react with the free radical indicator, the higher the free radical content of the device, the faster the decay rate of the device.

For another example: in the step S20, the solution to be detected is subjected to light treatment for a predetermined time, and the decay rate of the light-emitting device is obtained according to the free radical concentration in the solution to be detected by the free radical indicator, include:

(1) performing light treatment on the solution to be detected for a predetermined time, and taking multiple time points within the predetermined time to detect the absorbance of the free radical indicator in the solution to be detected at a specific wavelength.

(2) Calculate the scavenging rate of the free radical indicator in the solution to be detected within a predetermined time according to the absorbance of the free radical indicator at a specific wavelength at multiple time points.

(3) Obtaining the decay rate of the light-emitting device according to the scavenging rate of the free radical indicator.

Within a certain period of time, the greater the scavenging rate of the free radical indicator, the higher the free radical content of the device and the faster the decay rate. Using the scavenging rate of the free radical indicator to obtain the decay rate of the light-emitting device can prevent the premature reaction between the free radical indicator and the free radical from affecting the detection discrimination, and can improve the detection accuracy.

In some embodiments, the free radical indicator is DPPH (1,1-diphenyl-2-trinitrophenylhydrazine).

In order to better understand the scavenging rate of the free radical indicator mentioned in the embodiment, the calculation method of the scavenging rate of DPPH is given as an example below:

When the predetermined time of light treatment is 30 minutes, the absorbance of DPPH at a specific wavelength can be detected every 10 minutes within 30 minutes, that is, the DPPH at a specific wavelength can be detected at 10 minutes, 20 minutes and 30 minutes of light treatment respectively. The absorbance at the wavelength, according to the absorbance data of these three points, combined with the time, the DPPH removal rate can be calculated.

In some embodiments, the absorbance at the specific wavelength is the absorbance at any wavelength within the range of 513nm-517nm, for example, the absorbance at a wavelength of 513nm. By recording the absorption of DPPH at a specific wavelength and correlating it with the illumination time, the rate of reaction between DPPH and free radicals, that is, the rate of DPPH absorption and attenuation can be obtained, and thus the attenuation rate of the light-emitting device can be obtained indirectly.

In some embodiments, the organic solvent is selected from but not limited to methanol. In the embodiment of the present application, the function of methanol is to disperse the light-emitting layer and the carrier transport layer. Since methanol has a low polarity, it can be used as a dispersant The solvent of the optical layer and the carrier transport layer of the quantum dot light-emitting diode. It can be understood that the organic solvent can also be selected from other types of solvents known in the art, as long as it can disperse the light-emitting layer and the carrier transport layer That is, no specific limitation is made here.

In some embodiments, the dispersion liquid is obtained by dissolving the sample of the light-emitting layer and the sample of the carrier transport layer in an organic solvent by ultrasonic.

In some embodiments, the wavelength of the light is 400nm-450nm (nanometer). In this wavelength range, quantum dots are more easily excited to generate excitons. It can be understood that the wavelength of the light can be any value within the range of 400nm-450nm, such as 400nm, 405nm, 410nm, 415nm, 420nm, 425nm, 430nm, 435nm, 440nm, 445nm, 450nm, etc., or 400nm-450nm Other values not listed in nanometer range.

In some embodiments, the predetermined time for the light treatment is 10 minutes (minutes) to 1 hour (hours). In this illumination time range, it is beneficial to detect the decay rate of DPPH. It can be understood that the illumination time can be any value within the range of 10min to 1h, such as 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, etc., or 10min to 1h Other values not listed in nanometer range.

In some embodiments, in the solution to be tested, the concentration of the DPPH is 0.01 mg/mL to 1 mg/mL (milligrams per milliliter). If the DPPH is too concentrated, the influence of the reaction on the absorption of DPPH will decrease, and if it is too dilute, it may It will cause the reaction to be too fast, whether it is too concentrated or too dilute, it will affect the discrimination of detection, which is not conducive to the comparison of the free radical concentration between the devices in the later stage. It can be understood that the concentration of the DPPH is 0.01mg/mL to Any value within the range of 1mg/mL, for example: 0.01mg/mL, 0.1mg/mL, 0.2mg/mL, 0.3mg/mL, 0.4mg/mL, 0.5mg/mL, 0.6mg/mL, 0.7mg/mL , 0.8mg/mL, 0.9mg/mL or 1.0mg/mL, etc., or other unlisted values within the range of 0.01mg/mL to 1mg/mL.

In some embodiments, the total concentration of the material of the light-emitting layer and the material of the carrier transport layer is 0.001 mg/mL to 1 mg/mL, the material of the light-emitting layer and the material of the carrier transport layer If the material content is too high, the reaction with DPPH will be too fast, which will reduce the experimental discrimination; if it is too low, the reaction will be too slow, which will affect the sensitivity of the experiment. It can be understood that the total concentration of the material of the light-emitting layer and the material of the carrier transport layer can be any value within the range of 0.01 mg/mL to 1 mg/mL, for example: 0.01 mg/mL, 0.1 mg/mL mL, 0.2mg/mL, 0.3mg/mL, 0.4mg/mL, 0.5mg/mL, 0.6mg/mL, 0.7mg/mL, 0.8mg/mL, 0.9mg/mL or 1.0mg/mL, etc., or Other unlisted values within the range of 0.01 mg/mL to 1 mg/mL.

In some embodiments, the light-emitting device is a quantum dot light-emitting diode, specifically a red quantum dot light-emitting diode, a blue quantum dot light-emitting diode, or a green quantum dot light-emitting diode, especially a blue quantum dot light-emitting diode. Quantum dot light-emitting diodes are easier to attenuate, and their performance needs to be further improved. Therefore, compared with red quantum dot light-emitting diodes or green quantum dot light-emitting diodes, the method provided by this application is used to test blue quantum dot light-emitting diodes, thereby helping to test The decay rate of blue quantum dot LEDs is more necessary.

In some embodiments, the carrier transport layer includes an electron transport layer, and/or a hole transport layer.

The light-emitting device described in the embodiments of the present application may have a positive structure or an inverse structure. In the light-emitting device, the cathode or the anode side away from the quantum dot layer also includes a substrate, the anode is arranged on the substrate in the positive structure, and the cathode is arranged on the substrate in the inversion structure. Whether it is a positive structure or an inverse structure, hole functional layers such as a hole injection layer and an electron blocking layer can also be set between the anode and the quantum dot layer, and between the cathode and the quantum dot layer Electronic functional layers such as an electron injection layer and a hole blocking layer can also be arranged between them.

Fig. 2 shows a schematic diagram of an upright structure of the light-emitting device 10 according to the embodiment of the present application. As shown in Fig. 1, the upright structure light-emitting device 10 includes a substrate 1, an Anode 2, a hole injection layer 3 arranged on the surface of the anode 2, a hole transport layer 4 arranged on the surface of the hole injection layer 3, a light emitting layer 5 arranged on the surface of the hole transport layer 4, The electron transport layer 6 on the surface of the light-emitting layer 5 and the cathode 7 provided on the surface of the electron transport layer 6 .

Fig. 3 shows a schematic diagram of an inverted structure of the light-emitting device 10 according to the embodiment of the present application. As shown in Fig. 2, the inverted-structure light-emitting device 10 includes a substrate 1 and a cathode 7 arranged on the surface of the substrate 1 , the electron transport layer 6 arranged on the surface of the cathode 7, the light emitting layer 5 arranged on the surface of the electron transport layer 6, the hole transport layer 4 arranged on the surface of the light emitting layer 5, the hole transport layer 4 arranged on the surface of the hole transport The hole injection layer 3 on the surface of the layer 4, and the anode 2 arranged on the surface of the hole injection layer 3.

In each embodiment of the present application, the material of each functional layer is a common material in the field, for example:

The substrate can be a rigid substrate or a flexible substrate. Specific materials may include at least one of glass, silicon wafer, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyethersulfone kind.

The hole transport layer material includes: poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine), polyvinylcarbazole, poly(N,N'bis(4 -butylphenyl)-N,N'-bis(phenyl)benzidine), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine ), 4,4',4"-tris(carbazol-9-yl)triphenylamine, 4,4'-bis(9-carbazole)biphenyl, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine,15N,N'-diphenyl-N,N'-(1-naphthyl)-1, At least one of 1'-biphenyl-4,4'-diamine, graphene, and C ₆₀ .

The electron transport layer material includes: at least one of ZnO, TiO ₂ , SnO ₂ , Ta ₂ O ₃ , ZrO ₂ , NiO, TiLiO, ZnAlO, ZnMgO, ZnSnO, ZnLiO and InSnO.

The light-emitting layer is selected from at least one of II-VI compound, III-V compound and I-III-VI compound; the II-VI compound is selected from CdSe, CdS, CdTe, ZnSe, ZnS, At least one of CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe and CdZnSTe; the III-V group compound is selected from InP, InAs, GaP, GaAs, At least one of GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP and InAlNP; the group I-III-VI compound is selected from at least one of CuInS ₂ , CuInSe ₂ and AgInS ₂ .

The material of the anode and the cathode is selected from one or more of metals, carbon materials and metal oxides, and the metal is selected from one or more of Al, Ag, Cu, Mo, Au, Ba, Ca and Mg multiple; the carbon material is selected from one or more of graphite, carbon nanotubes, graphene, and carbon fibers; the metal oxide is selected from doped/non-doped metal oxides or composite electrodes, and the doped The hetero/non-doped metal oxide is selected from one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO and AMO, and the composite electrode is selected from AZO/Ag/AZO, AZO/Al/AZO , ITO/Ag/ITO, ITO/Al/ITO, ZnO/Ag/ZnO, ZnO/Al/ZnO, TiO ₂ /Ag/TiO ₂ , TiO ₂ /Al/TiO ₂ , ZnS/Ag/ZnS, ZnS/Al One or more of /ZnS, TiO ₂ /Ag/TiO ₂ and TiO ₂ /Al/TiO ₂ .

Because the attenuation rate in the embodiment of the present application does not refer to the attenuation rate of the device itself, it is not a quantitative attenuation rate, but through other parameters (the concentration of free radicals in the solution to be detected or other concentration-related characterization parameters, For example, the attenuation rate reflected by the absorbance or the scavenging rate of DPPH), so the embodiment of the present application can also compare the parameters that can reflect the attenuation rate of multiple light-emitting devices, and qualitatively compare the relative attenuation rate of each device, so as to screen out of the target device. Therefore, as shown in FIG. 4, the present application also provides a method for screening light-emitting devices, the method comprising:

S100. Provide multiple light emitting devices.

S200. Use the test method described in any of the above embodiments to obtain the decay rate of each of the light-emitting devices, compare the decay rates of each of the light-emitting devices, and screen out the target light-emitting device.

In some embodiments, the screening out the target light-emitting device includes: screening out the light-emitting device with a relatively slow decay rate among the plurality of light-emitting devices to obtain the target light-emitting device.

For example, when there are two quantum dot light-emitting diodes, the two light-emitting devices can be used to obtain the rate of DPPH absorption decay by the test method described in the embodiment. During the test, these two light-emitting devices except themselves Except for the difference, the test conditions (such as the light time and light wavelength and the concentration of DPPH) are the same. The specific steps can be:

Samples of the light-emitting layer and the carrier transport layer of the same preset area are taken in these two light-emitting devices, thereby ensuring that the ratio of the sample to the material in the actual device is consistent, and then the samples of the two devices are used Ultrasonic dispersion in an organic solvent to obtain a dispersion liquid in which the light-emitting layer material and the carrier transport layer material are dispersed, and DPPH is added to the dispersion liquid to obtain a solution to be detected. Use light to excite the quantum dots in the light-emitting layer to form excitons. The free electrons and holes in the excitons are separated and react with the material of the carrier transport layer to generate free radicals. The free radicals react with DPPH to change color, and the detection is to be detected. The absorbance of the solution in the visible light range, at this time, by recording the absorption spectrum of DPPH, measuring the absorption of DPPH at a specific wavelength, and correlating it with the illumination time, the DPPH in the solution to be detected corresponding to the two devices can be obtained The rate at which absorption decays, known as the clearance rate.

After obtaining the DPPH scavenging rate in the solution to be tested corresponding to the two devices, the relative ratio of the free radical content of the two devices can be obtained indirectly, and by comparing the relative ratio of the free radical content, the relative ratio of the two devices can be compared. Attenuation rate, so as to screen out the target device.

The present application will be described in detail below through examples.

Example:

(1) Provide two different QLED devices, marked as device A and device B, wherein, device A is a blue QLED device, device B is a red QLED device, the thickness of the light-emitting layer in the film layer of device A is 25nm, and the light-emitting wavelength The material of the hole transport layer is TFB with a thickness of 25nm, the material of the electron transport layer is ZnO with a thickness of 40nm; the thickness of the light-emitting layer in the device B film layer is 10nm, and the light-emitting wavelength is 630nm. The material of the hole transport layer is TFB with a thickness of 25nm, and the material of the electron transport layer is ZnO with a thickness of 40nm.

In device A and device B, take each film material with a surface area of 2 × 2 cm ² and ultrasonically disperse it in 10 mL of methanol. Device A is prepared as dispersion 1, and device B is prepared as dispersion 2.

(2) Prepare a DPPH solution (methanol solvent) with a concentration of 0.02mg/mL, take part of the solution and dilute it to 0.002mg/mL and perform exhaust treatment (introduce dry inert gas into it to discharge oxygen and water), as a comparison sample.

(3) Take 1mL of 0.02mg/mL DPPH solution, add 2mL of QLED dispersion solution to it, and add 7mL of methanol, and perform exhaust treatment (introduce dry inert gas into it, and discharge oxygen and water). Test samples (Device A and Device B were formulated as Test Sample 1 and Test Sample 2, respectively).

(4) Test the absorption spectra of the comparison sample, the test sample 1 and the test sample 2 in the initial state.

(5) Place the comparison sample, test sample 1, and test sample 2 under 400nm short-wave light at the same time for 10 minutes. Immediately after the end of the light, the absorption spectrum test is carried out. At the same time, the comparison sample, test sample 1 and Test sample 2 was placed in a dark state for comparison of absorption spectra.

(6) Repeat step (5) 3 times.

(7) Arrange the absorption spectrum and compare the concentration of free radicals produced by system A and system B.

The test results are shown in Figure 5 and Figure 6, and Figure 5 is a schematic diagram of the absorption spectra of the test sample 1, the test sample 2 and the comparison sample at different times in the dark environment; wherein, a in Figure 5 is the absorption change of the comparison sample Curve, b is the absorption change curve of test sample 1, c is the absorption change curve of test sample 2, and d is the change curve of the test sample absorption normalized with the light time at 513nm; The schematic diagram of the absorption spectrum of test sample 1, test sample 2 and contrast sample; Wherein, a in Fig. 6 is the absorption change curve of contrast sample, b is the absorption change curve of test sample 1, c is the absorption change curve of test sample 2 , d is the change curve of the test sample absorption normalized with the light time at 513nm.

It can be seen from Figure 5 that in the dark environment, the absorption spectra of test sample 1, test sample 2 and the comparison sample at different times (10 minutes, 20 minutes and 30 minutes) overlap, and the absorbance at 513nm does not change , indicating that the test sample 1, test sample 2 and the comparison sample did not generate free radicals in the dark state environment.

It can be seen from Figure 6 that under the light of 400nm, the absorbance of test sample 1, test sample 2 and comparative sample changed at different times (10 minutes, 20 minutes and 30 minutes) at 513nm, and the absorbance decreased continuously with time , indicating that free radicals react with DPPH to attenuate DPPH. Comparing the scavenging rate of DPPH, as shown in d in Figure 6, the scavenging rate of DPPH in device A is significantly faster than that of device B, indicating that the generation of device A The free radical content of device A is higher than that of device B, so it can be deduced that the decay rate of device A is greater than that of device B.

The test method and screening method for the attenuation rate of a light-emitting device provided by the embodiment of the present application have been introduced in detail above. In this paper, specific examples are used to illustrate the principle and implementation of the present application. The description of the above embodiment is only used To help understand the method and its core idea of this application; at the same time, for those skilled in the art, according to the idea of this application, there will be changes in the specific implementation and application scope. In summary, the content of this specification It should not be construed as a limitation of the application.

Claims (13)

1. A method for testing the decay rate of a light-emitting device, said light-emitting device comprising a light-emitting layer and a carrier transport layer, characterized in that said method comprises: A solution to be detected is provided, the solution to be detected includes the material of the light-emitting layer, the material of the carrier transport layer, a free radical indicator and an organic solvent, the material of the light-emitting layer includes quantum dots, and the free radical The indicator has characteristics characterizing the concentration of free radicals in the solution to be detected; and Light treatment is performed on the solution to be detected for a predetermined time, so that the material of the light-emitting layer and the material of the carrier transport layer react to generate free radicals, and according to the effect of the free radical indicator on the concentration of free radicals in the solution to be detected The attenuation rate of the light-emitting device was obtained by characterization. 2. testing method according to claim 1, is characterized in that, described solution to be tested is provided, comprises: In the light-emitting device, take a sample of the light-emitting layer and a sample of the carrier transport layer with a predetermined area, and disperse the sample of the light-emitting layer and the sample of the carrier transport layer in the organic solvent , to obtain a dispersion; and A free radical indicator is added to the dispersion to obtain the solution to be detected. 3. The test method according to claim 1, characterized in that, the solution to be detected is subjected to light treatment for a predetermined time, obtained according to the characterization of the concentration of free radicals in the solution to be detected by the free radical indicator The decay rate of the light emitting device includes: performing light treatment on the solution to be detected for a predetermined time, detecting the absorbance of the free radical indicator in the solution to be detected at a specific wavelength, and obtaining the light-emitting device’s decay rate. 4. The test method according to claim 1, characterized in that, said solution to be detected is subjected to light treatment for a predetermined time, obtained according to the characterization of free radical concentration in said solution to be detected by said free radical indicator The decay rate of the light emitting device includes: Perform light treatment on the solution to be detected for a predetermined time, and take multiple time points within the predetermined time to detect the absorbance of the free radical indicator in the solution to be detected at a specific wavelength; according to the free radicals at multiple time points The absorbance of the indicator at a specific wavelength is calculated to obtain the scavenging rate of the free radical indicator in the solution to be detected within a predetermined time; the decay rate of the light-emitting device is obtained according to the scavenging rate of the free radical indicator. 5. The test method according to claim 2, characterized in that, in the solution to be detected, the concentration of the free radical indicator is 0.01 mg/mL to 1 mg/mL, and/or, the luminescent layer The total concentration of the material of the material and the material of the carrier transport layer is 0.001 mg/mL to 1 mg/mL. 6. The test method according to any one of claims 1 to 5, characterized in that the free radical indicator is DPPH. 7. test method according to claim 1, is characterized in that, described organic solvent is selected from methanol. 8. The testing method according to claim 1, characterized in that, the wavelength of the light is 400nm-450nm, and/or, the predetermined time of the light treatment is 10min-1h. 9. The testing method according to claim 1, wherein the light emitting device is a blue quantum dot light emitting diode. 10. The testing method according to claim 1, wherein the carrier transport layer comprises an electron transport layer, and/or a hole transport layer. 11. The test method according to claim 10, wherein the hole transport layer material comprises: poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl) diphenylamine ), polyvinylcarbazole, poly(N,N'bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine), poly(9,9-dioctylfluorene-co- Bis-N,N-phenyl-1,4-phenylenediamine), 4,4',4"-tris(carbazol-9-yl)triphenylamine, 4,4'-bis(9-carbazole) Biphenyl, N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, 15N,N'-diphenyl At least one of -N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, graphene, C ₆₀ , and/or, The electron transport layer material includes: at least one of ZnO, TiO ₂ , SnO ₂ , Ta ₂ O ₃ , ZrO ₂ , NiO, TiLiO, ZnAlO, ZnMgO, ZnSnO, ZnLiO and InSnO; and/or, The light-emitting layer is selected from at least one of II-VI compound, III-V compound and I-III-VI compound; the II-VI compound is selected from CdSe, CdS, CdTe, ZnSe, ZnS, At least one of CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe and CdZnSTe; the III-V group compound is selected from InP, InAs, GaP, GaAs, At least one of GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP and InAlNP; the group I-III-VI compound is selected from at least one of CuInS ₂ , CuInSe ₂ and AgInS ₂ . 12. A screening method for light-emitting devices, characterized in that the method comprises: providing a plurality of light emitting devices; Using the method described in any one of claims 1 to 11 to obtain the decay rate of each of the light-emitting devices, compare the decay rates of each of the light-emitting devices, and screen out the target light-emitting devices. 13. The screening method according to claim 12, wherein the screening out the target light-emitting device comprises: screening out the light-emitting device with a relatively slow decay rate among the plurality of light-emitting devices to obtain the target light-emitting device .

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