CN111326660A - High-dispersion nanocrystalline light-emitting layer applied to electroluminescent device and electroluminescent device based on high-dispersion nanocrystalline light-emitting layer - Google Patents
High-dispersion nanocrystalline light-emitting layer applied to electroluminescent device and electroluminescent device based on high-dispersion nanocrystalline light-emitting layer Download PDFInfo
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Abstract
The invention discloses a high-dispersion nanocrystalline light-emitting layer applied to an electroluminescent device and the electroluminescent device based on the same, wherein the light-emitting layer is a host-guest composite light-emitting layer which is formed by taking conjugated organic micromolecules as a host material and taking a nanocrystalline light-emitting body as a guest material; wherein: the conjugated organic micromolecules are P-type semiconductors and grow in a two-dimensional oriented crystal in the light emitting layer; the nanocrystalline light emitter is distributed in the host material in a substantially discrete form and the volume fraction of the nanocrystalline light emitter in the light emitting layer does not exceed 5%. The invention can improve the hole injection ratio by more than 6 orders of magnitude by reducing the volume fraction of the nano-crystal in the luminescent layer, thereby realizing the high quantum efficiency of the electroluminescenceEmitting light at low power (<1.0mWcm‑2) Under the condition, the fluorescence quantum efficiency can still exceed 80%.
Description
Technical Field
The invention belongs to the field of electroluminescent devices, and particularly relates to a composite luminescent layer with a host-guest structure and composed of a small-molecule organic semiconductor and an inorganic nanocrystalline luminescent body, and an electroluminescent device based on the composite luminescent layer.
Background
The nano-crystal can form a film by a solution method, and the light emission spectrum of the nano-crystal has a relatively narrow spectral bandwidth and a tunable wavelength range. In practical application, the surface defect state of the nanocrystal needs to be repaired through a surface ligand, so that the probability of non-radiative recombination is reduced, and the stability of the nanocrystal in a solvent is improved. However, the surface ligands currently used have relatively poor conductivity, which leads to a large energy loss in the electroluminescent device. In the prior art, the nanocrystalline is directly used as a luminescent layer, the conduction capability of electrons is far higher than that of holes, and the contribution of hole injection to current (hole injection ratio) is as low as 10-8The contribution of hole injection is negligible with respect to the contribution of electron injection. Since the carrier injection pole is not balanced, an electron blocking layer with a certain thickness is required to forcibly realize balanced carrier injection characteristics. The introduction of the barrier layer brings energy loss to a certain extent, and the thickness of the barrier layer is only a few nanometers, which is not easy to be accurately controlled, so that the barrier layer is not beneficial to designing an electroluminescent device with simple structure and reliable performance.
The luminescent layer of the existing electroluminescent device based on the nanocrystalline luminescent layer is prepared by a solution method, and the electroluminescent device is suitable for being used as a planar light source with a planar two-dimensional structure, such as display backlight. The volume ratio of the nanocrystals in the luminescent layer of the device is 100%, and the power per unit area is low and in the milliwatt order, so that the nanocrystalline luminescent body in the device is remarkably characterized in that the concentration of non-equilibrium carriers is low, in this case, the service life of the radiative recombination of the carriers is close to that of the non-radiative recombination, and the non-radiative recombination process is not negligible, so that the quantum efficiency of the device in actual work is obviously lower than that under the high-power condition.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a high-dispersion nanocrystalline light-emitting layer applied to an electroluminescent device and the electroluminescent device based on the high-dispersion nanocrystalline light-emitting layer, so as to achieve the purposes of improving the hole injection ratio and the non-equilibrium carrier concentration in luminescent nanocrystals, thereby improving the electroluminescent quantum efficiency of the device or simplifying the device structure. By reasonably arranging the light-emitting layer structure, the volume ratio of the nanocrystals in the light-emitting layer is reduced, and the quantum efficiency of the device can be improved.
In order to solve the technical problem, the invention adopts the following technical scheme:
the invention firstly discloses a high-dispersion nanocrystalline luminescent layer applied to an electroluminescent device, which is characterized in that: the high-dispersion nanocrystalline light-emitting layer is a host-guest composite light-emitting layer which is formed by taking conjugated organic micromolecules as a host material and taking a nanocrystalline light-emitting body as a guest material; wherein: the conjugated organic micromolecule is a P-type semiconductor, grows in a two-dimensional oriented crystal in a light-emitting layer, and has the in-plane field effect mobility of more than 0.5cm2V-1s-1(ii) a The nanocrystalline light emitter is distributed in the host material in a substantially discrete form and the volume fraction of the nanocrystalline light emitter in the light emitting layer does not exceed 5%.
The invention can continuously adjust the hole injection ratio of the luminescent layer by adjusting the volume fraction of the nanocrystalline luminescent body in the luminescent layer, and the variable range is not less than 6 orders of magnitude, thereby accurately controlling the carrier balance and realizing the electroluminescence with high quantum efficiency.
According to the light-emitting layer, the host material has a larger optical band gap than the guest material; an indirect excitation mode is adopted, namely the photon energy (h v) of excitation light is larger than the optical band gap of the main material, the photoluminescence quantum efficiency of the luminescent layer is measured, and the numerical value is higher than that of an electroluminescent device taking a pure nanocrystalline material as the luminescent layer.
Further, the conjugated organic small molecule is C8-BTBT, and the nanocrystalline light-emitting body is a lead halide perovskite quantum dot. The middle skeleton of the C8-BTBT molecular structure is a pi plane conjugated structure, and two ends or two sides of the middle skeleton are provided with alkyl chains; in the light-emitting layer film formed by self-assembling C8-BTBT and nanocrystals in solution, the X-ray diffraction of C8-BTBT has a (00l) out-of-plane orientation characteristic peak, a pi-plane conjugated structure of molecules is self-assembled along the substrate surface direction (in-plane direction), and the mobility of carriers in the in-plane direction is greater than that perpendicular to the substrate surface.
The invention relates to a preparation method of a high-dispersion nanocrystalline light-emitting layer, which is obtained by uniformly dispersing conjugated organic micromolecules and a nanocrystalline light-emitting body in an organic solvent and then forming a film by a spin coating method or a solution shearing method. The method specifically comprises the following steps:
firstly, preparing a precursor solution: uniformly dispersing the conjugated organic micromolecules and the nano-crystalline luminophor in an organic solvent according to the mass ratio of 1:3-4 of the nano-crystalline luminophor to the conjugated organic micromolecules to obtain a precursor solution, wherein the concentration of the nano-crystalline is 5-15 mg/mL;
then forming a film on the target substrate by the precursor solution through a spin coating method or a solution shearing method to form a high-dispersion nanocrystalline light-emitting layer;
the spin coating method comprises the following specific steps: uniformly coating the precursor solution on a target substrate, and then drying in vacuum to form a high-dispersion nanocrystalline light-emitting layer;
the solution shearing method is to complete the oriented film formation based on the relative directional mechanical motion between the substrate and the solution precursor, and a blade coating method or a pulling method can be adopted. The knife coating method comprises the following specific steps: carrying out blade coating on the precursor solution on a target substrate, simultaneously keeping the temperature of the target substrate at 90 ℃, keeping the shearing rate of a scraper at 1cm/s, keeping the inclination angle of a blade at 45 degrees, and naturally drying after blade coating film forming to form a high-dispersion nanocrystalline luminescent layer; the technological parameters of the Czochralski method are as follows: the dipping speed is 30mm/min, the dipping time is 180s, and the pulling speed is 5 mm/min.
The invention also discloses an electroluminescent device based on the high-dispersion nanocrystalline luminescent layer, which is characterized in that: the ITO conductive glass is used as a substrate (ITO is used as a cathode of a device), a ZnO film (preferably a Mg and Li co-doped ZnO film) used as an electron transport layer, a high-dispersion nanocrystal light emitting layer, a CBP film used as a hole transport layer and MoO used as a hole injection layer are sequentially arranged on the substrate3A layer, and an Al layer as an anode.
Compared with the prior art, the invention has the beneficial effects that:
1. the light-emitting layer of the present invention can efficiently inject electrons and holes, realize a wide injection ratio adjustment range, and particularly, can greatly improve the injection efficiency of holes so that the hole injection ratio is from 10-8Is increased to 10-2Compared with the existing electron barrier layer technology, the method has the advantages of higher regulation and control precision and better repeatability;
2. the volume fraction of the nanocrystalline in the luminescent layer is lower than 5%, so that the concentration of non-equilibrium carriers in the nanocrystalline is greatly improved, and the occurrence probability of radiation recombination is improved;
3. based on the two-dimensional growth layered morphology of the main material, the light-emitting layer film has high coverage rate, is favorable for the transmission of current carriers in the in-plane direction, is a good current carrier transmission layer, and can realize uniform light emission of an electroluminescent device without the need of the current carrier transmission layer;
4. the preparation process of the luminescent layer film is suitable for substrates of different materials or shapes, and has universality;
5. the electroluminescent device based on the luminescent layer can accurately adjust the hole injection ratio of the luminescent layer by adjusting the volume fraction of the nanocrystalline luminescent body in the luminescent layer, and the variable range exceeds 6 orders of magnitude, thereby realizing electroluminescent with high quantum efficiency.
6. The light-emitting layer of the electroluminescent device of the invention is at low power (C)<1.0mWcm-2) Under the condition, the fluorescence quantum efficiency can still exceed 80%, and the fluorescent quantum efficiency has the advantage of more electricity saving when being applied to low-power electronic products.
Drawings
FIG. 1 shows the molecular structure of an exemplary host material C8-BTBT in accordance with embodiments of the present invention;
FIG. 2 is a molecular arrangement of a conjugated small organic molecule C8-BTBT in accordance with an embodiment of the present invention;
FIG. 3 is a polarized microscope photograph of a highly discrete nanocrystalline light emitting layer prepared by spin coating;
FIG. 4 is a fluorescence microscope photograph of a highly discrete nanocrystalline luminescent layer prepared by a doctor blade method;
FIG. 5 shows CsPbBr with different composition ratios prepared by spin coating on a single-crystal silicon substrate3XRD diffraction pattern of the nanocrystalline and C8-BTBT composite luminescent layer;
FIG. 6 shows CsPbBr with different composition ratios prepared on a single-crystal silicon substrate by a solution shearing method3XRD diffraction pattern of the nanocrystalline and C8-BTBT composite luminescent layer;
FIG. 7 is a polarizing microscope photograph of a composite nanocrystalline light-emitting layer prepared at a 1:1 host-guest composite ratio;
FIG. 8 is a polarizing microscope photograph of a highly discrete nanocrystalline light emitting layer prepared at a 3:1 host-guest compound ratio;
FIG. 9 shows fluorescence quantum efficiencies of composite films of different mass ratios (excitation power density of 20. mu. Wcm)-2)；
FIG. 10 is a schematic diagram of an electroluminescent device with ZnO as the electron injection layer;
FIG. 11 is a plot of voltage versus current density for a single electron device and a single hole device;
fig. 12 is a schematic diagram of an electroluminescent device with balanced carrier injection.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, specific embodiments thereof will be described in detail with reference to the following examples. The following is merely exemplary and illustrative of the inventive concept and various modifications, additions and substitutions of similar embodiments may be made to the described embodiments by those skilled in the art without departing from the inventive concept or exceeding the scope of the claims defined thereby.
Example 1
In this embodiment, the highly discrete nanocrystal light emitting layer is formed by using a conjugated organic small molecule C8-BTBT as a host material and perovskite CsPbBr3The nanocrystalline luminous body is used as a host-guest composite luminous layer formed by guest materials; wherein: the conjugated organic micromolecule C8-BTBT is a P-type semiconductor and is grown in a two-dimensional oriented crystal in a light-emitting layer,in-plane field effect mobility greater than 0.5cm2V- 1s-1(ii) a The nanocrystalline light emitter is distributed in the host material in a substantially discrete form and the volume fraction of the nanocrystalline light emitter in the light emitting layer does not exceed 5%.
FIGS. 1 and 2 are a molecular structure and a molecular arrangement diagram of the host material C8-BTBT. C8-the middle skeleton of the BTBT molecular structure is a pi-plane conjugated structure with alkyl chains at both ends or on both sides; c8-BTBT and nanocrystal in a light emitting layer film formed by solution self-assembly, C8The X-ray diffraction of BTBT has a characteristic peak of (00l) out-of-plane orientation, with the pi-plane conjugated structure of the molecule aligned parallel to the substrate surface and the mobility of the carriers in the in-plane direction being greater than the mobility perpendicular to the substrate surface.
The preparation method of the high-dispersion nanocrystalline light-emitting layer is to uniformly disperse the conjugated organic micromolecules and the nanocrystalline luminophor in a solvent and then to form a film by a spin coating method or a solution shearing method. The method comprises the following specific steps:
firstly, preparing a precursor solution: according to the conjugated organic micromolecules C8-BTBT and CsPbBr3Uniformly dispersing the conjugated organic micromolecules and the nanocrystals in an organic solvent (heptane is used as the organic solvent for the spin-coating method, and toluene is used as the organic solvent for the solution shearing method) according to the mass ratio required by the nanocrystal luminophor to obtain a precursor solution, wherein the concentration of the nanocrystals is 5 mg/mL; then forming a film on the target substrate by the precursor solution through a spin coating method or a solution shearing method to form a high-dispersion nanocrystalline light-emitting layer;
the solution shearing method of the embodiment can further realize the control of the thickness and the appearance of the luminescent layer by setting the concentration of the precursor solution, the temperature of the substrate, the shearing speed of the scraper and the inclination angle of the blade, so as to obtain the composite luminescent layer film with good repeatability, full coverage and oriented crystallization. Specifically, the solution shearing method adopts a blade coating method or a pulling method; the knife coating method comprises the following specific steps: carrying out blade coating on the precursor solution on a target substrate, simultaneously keeping the temperature of the target substrate at 90 ℃, keeping the shearing rate of a scraper at 1cm/s, keeping the inclination angle of a blade at 45 degrees, and naturally drying after blade coating film forming to form a high-dispersion nanocrystalline luminescent layer; the technological parameters of the Czochralski method are as follows: the dipping speed is 30mm/min, the dipping time is 180s, and the pulling speed is 5 mm/min.
The specific way of the spin coating method in this embodiment is as follows: uniformly spin-coating the precursor solution on a target substrate (the rotating speed is 2500rpm, the time is 60s), and then carrying out vacuum drying (drying at room temperature for 30min) to form a high-dispersion nanocrystalline light-emitting layer;
in this embodiment, the spin coating method or the solution shear method used for the light-emitting layer has advantages and disadvantages. The spin coating method is mature, and a thin film with uniform and controllable thickness can be easily obtained. However, in this embodiment, since the host material, namely the organic small molecule C8-BTBT, is more prone to oriented growth, the in-plane orientation of the host-guest composite film prepared by the spin coating method is relatively weak; the solution shearing method can obtain thicker film, the crystal orientation of the film is good, the nano-crystal in the high-dispersion nano-crystal composite light-emitting layer is easy to generate preferred orientation in the self-assembly process of the orientation of the small molecules, but the thickness uniformity is not as good as that of the film prepared by the spin coating method.
FIG. 3 is a polarized light microscope photograph of a highly discrete nanocrystalline light emitting layer prepared by spin coating (target substrate is ITO glass deposited with ZnO, CsPbBr)3The mass ratio of the quantum dots to the C8-BTBT is CsPbBr3C8-BTBT 1:3), and fig. 4 is a fluorescence microscope photograph of a highly discrete nanocrystalline luminescent layer prepared by a doctor blade method (target substrate is ITO glass deposited with ZnO, CsPbBr)3The mass ratio of the quantum dots to the C8-BTBT is CsPbBr3C8-BTBT 1: 3). It can be seen that the thin film prepared by the spin coating method has continuous crystallization and uniform appearance, but the thin film prepared by the solution shearing method has certain orientation while obtaining high coverage.
FIG. 5 and FIG. 6 show CsPbBr with different compounding ratios prepared by spin coating and CsPbBr prepared by CsPbBr pulling method3XRD diffraction pattern of the nano-crystalline and C8-BTBT composite luminescent layer. It can be seen that, no matter the luminescent layer film prepared by the spin coating method or the solution shearing method, wider diffraction peaks appear at 15.2 ° and 30.7 °, which is the characteristic of nanocrystalline diffraction. In addition, it can be seen that the composite light-emitting layer prepared by the solution shearing method has strong lattice interaction between the organic small molecules and the nanocrystals. Particularly inIn the high-dispersion composite luminescent layer, the nano-crystals have obvious preferred orientation, and the characteristic diffraction peak of 30.7 degrees is greatly enhanced. Meanwhile, the controllable transformation of the dispersed morphology of the nanocrystals in the host material is proved to occur by reducing the volume fraction of the nanocrystals.
Fig. 7 and 8 are polarization microscope images of the composite light emitting layer prepared by the czochralski method. In CsPbBr3Under the condition that the mass ratio of C8-BTBT is 1:1, the morphology of C8-BTBT presents a one-dimensional linear crystal form, and CsPbBr is3In the high-dispersion composite light-emitting layer with the mass ratio of C8-BTBT of 1:3, the morphology of C8-BTBT presents a two-dimensional plane growth crystal form. According to XRD diffraction spectrum, lattice parameters of small molecular crystal and nano crystal can be obtained (refer to patent PCT/CN2018/083738), and the densities of the small molecular crystal and the nano crystal are respectively 0.65gcm-3And 5.15gcm-3And further obtain the volume fraction of the nano-crystal corresponding to the film with different mass ratios. For example, in a high-dispersion composite light-emitting layer with a mass ratio of 1:3, the volume fraction of the nanocrystals is 4%.
FIG. 9 shows the fluorescence quantum efficiency of composite films with different mass ratios prepared by Czochralski method, and the excitation power density is 20 μ Wcm-2The excitation wavelength was 410 nm. For CsPbBr3The maximum fluorescence quantum efficiency of the high-dispersion composite light-emitting layer with the mass ratio of C8-BTBT of 1:3 is still higher than 80 percent. The fluorescence quantum efficiency is an important index for measuring the photoluminescence characteristics of the luminescent layer, and meanwhile, the high fluorescence quantum efficiency is also a necessary condition for preparing the efficient electroluminescent device. It can be seen that even under low excitation power density, the fluorescence quantum efficiency of the host-guest composite light-emitting layer is improved from 66.8% to 80.2% relative to the pure nanocrystal light-emitting layer, and the energy conversion efficiency of the host-guest composite light-emitting layer is greatly improved.
The morphology of the host material C8-BTBT of the light-emitting layer of the embodiment has the characteristics of oriented crystallization, two-dimensional growth and high coverage rate, has the characteristic of a P-type semiconductor, and has the in-plane field effect mobility of more than 0.5cm2V-1s-1. Research has shown that the growth and morphological characteristics of C8-BTBT are not limited to ZnO substrates only, and such characteristics may exist on a variety of substrates, which provides for the design and optimization of device structuresMore possibilities are available. This example provides an example of a method for designing and optimizing the structure of an electroluminescent device, which uses the ITO/ZnO/CsPbBr shown in FIG. 103:C8-BTBT/CBP/MoO3On the basis of Al, the hole injection ratio is firstly improved by utilizing the high-dispersion composite light-emitting layer, and then the ZnO layer is further doped according to the requirement of carrier injection balance, so that the current density of electron injection is reduced until the current density reaches the same order of magnitude as that of hole injection.
The structural form of the electroluminescent device based on the highly discrete nanocrystal light emitting layer in this embodiment is as follows: indium Tin Oxide (ITO) conductive glass is used as a substrate, and an electron transport layer, a luminescent layer, a hole transport layer, a hole injection layer and an anode are sequentially arranged on the substrate. As shown in FIG. 10, the electron transport layer is a ZnO thin film (70 nm thick), and the light-emitting layer is a conjugated organic small molecule C8-BTBT and perovskite CsPbBr3The high-dispersion nanocrystalline light-emitting layer is composed of nanocrystals, a hole transport layer is a CBP film (the thickness is 50nm), and a hole injection layer is MoO3Layer (thickness 10nm) and electrode is aluminum electrode (thickness 100 nm). The electrons and holes recombine in the light-emitting layer to emit light.
The method for manufacturing the electroluminescent device in the embodiment is as follows:
1. preparation of ZnO thin film as electron transport layer
And (3) coating an ethanol solution (30mg/mL) of zinc oxide on the ITO glass which is cleaned and treated by ultraviolet ozone, adopting spin coating parameters with the rotating speed of 1500rpm and the time of 40s, and then annealing at 150 ℃ for 10min to obtain the ZnO film.
2. Preparation of highly discrete nanocrystalline luminescent layer
A highly discrete nanocrystalline light emitting layer was prepared as described above.
3. Sequentially evaporating CBP film (thickness 50nm) and MoO by using a vacuum coating machine3Layer (thickness 10nm), aluminum electrode (thickness 100 nm).
In order to quantitatively investigate the influence of the volume fraction of nanocrystals in the composite light-emitting layer on the hole injection ratio, a single-hole device (ITO/PEDOT: PSS/light-emitting layer/CBP/MoO) was designed in this example3Al) and single-electron device (ITO/Zn)O/light emitting layer/Ag) and tested for voltage versus current density curves using ITO as the cathode, as shown in fig. 11. For a pure nanocrystalline light emitting layer, the electron injection current density is 8 orders of magnitude higher than the hole injection current density, and the unbalanced carrier injection can cause the quantum efficiency of the electroluminescent device to be extremely low. By gradually increasing the composition of the host material in the light-emitting layer, namely CsPbBr3C8-BTBT is 1:0 to 1:3, the volume fraction of the nano crystal is gradually reduced from 100 percent to 4 percent, the hole injection capability of a corresponding single-hole device is gradually enhanced, the hole injection current density can be increased by 6 orders of magnitude, and the radiation recombination probability of electrons and holes in a light-emitting layer is sharply increased, so that more efficient electroluminescence can be realized.
As can be seen from fig. 11, the electron injection current density is still higher than the hole injection current density by 2 orders of magnitude, and the electron injection current density in the vicinity of the turn-on voltage is too large, so that the electron injection current density needs to be further reduced. For example, by using Mg and Li co-doped zno (mlzo) as the electron injection layer shown in fig. 12, due to the increase of the band gap and the decrease of the quenching site density of surface excitons, both the electron injection current density and the surface non-radiative recombination are suppressed, thereby further improving the external quantum efficiency of the device.
Claims (8)
1. The high-dispersion nanocrystalline light-emitting layer applied to the electroluminescent device is characterized in that: the high-dispersion nanocrystalline light-emitting layer is a host-guest composite light-emitting layer which is formed by taking conjugated organic micromolecules as a host material and taking a nanocrystalline light-emitting body as a guest material;
wherein: the conjugated organic micromolecule is a P-type semiconductor, grows in a two-dimensional oriented crystal in a light-emitting layer, and has the in-plane field effect mobility of more than 0.5cm2V-1s-1(ii) a The nanocrystalline light emitter is distributed in the host material in a substantially discrete form and the volume fraction of the nanocrystalline light emitter in the light emitting layer does not exceed 5%.
2. The highly discrete nanocrystalline light-emitting layer for use in an electroluminescent device according to claim 1, characterized in that: the hole injection ratio of the luminescent layer can be continuously adjusted by adjusting the volume fraction of the nanocrystalline luminescent body in the luminescent layer, and the variable range is not less than 6 orders of magnitude, so that the carrier balance is accurately controlled, and the electroluminescence with high quantum efficiency is realized.
3. The highly discrete nanocrystalline light-emitting layer for use in an electroluminescent device according to claim 1, characterized in that: the conjugated organic micromolecules are C8-BTBT, and the nanocrystalline luminophor is a lead halide perovskite quantum dot.
4. The highly discrete nanocrystalline light-emitting layer for use in an electroluminescent device according to claim 3, characterized in that: the middle skeleton of the C8-BTBT molecular structure is a pi plane conjugated structure, and two ends or two sides of the middle skeleton are provided with alkyl chains; in the light-emitting layer film formed by self-assembling C8-BTBT and nanocrystals in solution, the X-ray diffraction of C8-BTBT has a (00l) out-of-plane orientation characteristic peak, a pi plane conjugated structure of molecules is self-assembled along the surface direction of the substrate, and the mobility of carriers in the in-plane direction is greater than that perpendicular to the surface of the substrate.
5. A method for preparing a highly discrete nanocrystalline light-emitting layer according to any one of claims 1 to 4, characterized in that: the conjugated organic micromolecules and the nanocrystalline luminophor are uniformly dispersed in an organic solvent, and then the film is formed by a spin coating method or a solution shearing method.
6. The method for preparing a highly discrete nanocrystalline light-emitting layer according to claim 5, characterized in that:
firstly, preparing a precursor solution: uniformly dispersing the conjugated organic micromolecules and the nano-crystalline luminophor in an organic solvent according to the mass ratio of 1:3-4 of the nano-crystalline luminophor to the conjugated organic micromolecules to obtain a precursor solution, wherein the concentration of the nano-crystalline is 5-15 mg/mL;
then forming a film on the target substrate by the precursor solution through a spin coating method or a solution shearing method to form a high-dispersion nanocrystalline light-emitting layer;
the spin coating method comprises the following specific steps: uniformly spin-coating the precursor solution on a target substrate by using a spin coating instrument, and then carrying out vacuum drying to form a high-dispersion nanocrystalline light-emitting layer;
the solution shearing method adopts a blade coating method or a pulling method; the knife coating method comprises the following specific steps: carrying out blade coating on the precursor solution on a target substrate, simultaneously keeping the temperature of the target substrate at 90 ℃, keeping the shearing rate of a scraper at 1cm/s, keeping the inclination angle of a blade at 45 degrees, and naturally drying after blade coating film forming to form a high-dispersion nanocrystalline luminescent layer; the technological parameters of the Czochralski method are as follows: the dipping speed is 30mm/min, the dipping time is 180s, and the pulling speed is 5 mm/min.
7. An electroluminescent device based on the highly discrete nanocrystalline light-emitting layer according to any one of claims 1 to 4, characterized in that: ITO conductive glass is used as a substrate, and a ZnO film used as an electron transport layer, a high-dispersion nanocrystalline light-emitting layer, a CBP film used as a hole transport layer and MoO used as a hole injection layer are sequentially arranged on the substrate3A layer, and an Al layer as an anode.
8. An electroluminescent device with a highly discrete nanocrystalline light-emitting layer according to claim 7, characterized in that: the ZnO film is a Mg and Li co-doped ZnO film.
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| WO2022156559A1 (en) * | 2021-01-20 | 2022-07-28 | 上海比英半导体科技有限公司 | Organic semiconductor thin film and preparation method therefor |
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