CN115605061A

CN115605061A - Preparation method of quantum dot light-emitting device, quantum dot light-emitting device and display device

Info

Publication number: CN115605061A
Application number: CN202110768553.1A
Authority: CN
Inventors: 敖资通; 严怡然; 张建新; 杨帆; 莫新娣; 洪佳婷
Original assignee: TCL Technology Group Co Ltd
Current assignee: TCL Technology Group Co Ltd
Priority date: 2021-07-07
Filing date: 2021-07-07
Publication date: 2023-01-13

Abstract

The embodiment of the application discloses a preparation method of a quantum dot light-emitting device, the quantum dot light-emitting device and a display device, wherein the preparation method of the quantum dot light-emitting device comprises the following steps: providing a quantum dot light-emitting half-device comprising an electron transport layer and a cathode, the cathode being disposed on the electron transport layer; and carrying out electric field treatment on the cathode, wherein the electric field direction in the electric field treatment is from the cathode to the electron transport layer. The application reduces the quenching probability of the quantum dot luminescent device.

Description

Preparation method of quantum dot light-emitting device, quantum dot light-emitting device and display device

Technical Field

The application relates to the technical field of display, in particular to a preparation method of a quantum dot light-emitting device, the quantum dot light-emitting device and a display device.

Background

A Quantum dot Light-Emitting Diode (QLED) is an emerging display device. The luminescent material of the QLED adopts inorganic quantum dots, and the QLED shows excellent optical performance due to the unique quantum size effect, macroscopic quantum tunneling effect, quantum size effect and surface effect of the inorganic quantum dots, so that the QLED becomes the mainstream of the next-generation flat panel display.

The emission mechanism of QLEDs is based on the electroluminescence of inorganic quantum dots. In the QLED, since the injection capability of electrons is stronger than that of holes, the electron transport layer needs to have a higher carrier mobility to match the rate of electron injection. However, in the existing preparation process of the QLED, the carrier mobility of the electron transport layer is low, so that charge accumulation is likely to occur in the electron transport layer, at the interface between the electron transport layer and the cathode, and/or at the interface between the electron transport layer and the quantum dot light emitting layer, thereby quenching the quantum dot light emitting device.

Disclosure of Invention

The embodiment of the application provides a preparation method of a quantum dot light-emitting device, the quantum dot light-emitting device and a display device, and aims to solve the problem of device quenching caused by low carrier mobility of an electron transport layer in the quantum dot light-emitting device in the prior art.

The embodiment of the application provides a preparation method of a quantum dot light-emitting device, which comprises the following steps:

providing a quantum dot light-emitting half-device comprising an electron transport layer and a cathode, the cathode being disposed on the electron transport layer;

and performing electric field treatment on the cathode, wherein the direction of an electric field in the electric field treatment is from the cathode to the electron transport layer.

Optionally, in some embodiments of the present application, an included angle between the electric field direction and a plane where the cathode is located is 80 degrees to 100 degrees.

Optionally, in some embodiments of the present application, the electric field intensity in the electric field treatment is 5kV/cm to 10kV/cm.

Optionally, in some embodiments of the present application, the time of the electric field treatment is 10min to 20min.

Optionally, in some embodiments of the present application, the step of subjecting the cathode to an electric field includes:

and in any time of carrying out thermal annealing treatment on the cathode, carrying out electric field treatment on the cathode, wherein the thermal annealing temperature in the thermal annealing treatment is 25-80 ℃.

Optionally, in some embodiments of the present application, in the step of performing the electric field treatment on the cathode at any time during the thermal annealing treatment on the cathode, the thermal annealing temperature is 60 ℃ to 80 ℃; and/or

The time of the electric field treatment is 5min-8min.

Optionally, in some embodiments of the present application, the material of the electron transport layer is a metal oxide.

Optionally, in some embodiments of the present application, the thickness of the electron transport layer is 20nm to 100nm, and the thickness of the cathode is 20nm to 80nm.

The embodiment of the application further provides a quantum dot light-emitting device which is manufactured by the manufacturing method of the quantum dot light-emitting device according to any one of the embodiments.

The embodiment of the application also provides a display device, the display device comprises a quantum dot light-emitting device, and the quantum dot light-emitting device is the quantum dot light-emitting device in the embodiment.

Compared with the preparation method of the quantum dot light-emitting device in the prior art, in the preparation method of the quantum dot light-emitting device provided by the application, the cathode is subjected to electric field treatment, so that the diffusion speed of the metal elements in the cathode to the electron transmission layer is increased under the action of an electric field, the quantity of the metal elements diffused to the electron transmission layer is increased after the electric field treatment, the semiconductor depletion region of the electron transmission layer is narrowed, the resistance is reduced, and the electric conductivity of the electron transmission layer is improved, so that the carrier mobility of the electron transmission layer is improved, the charge accumulation probability of the inside of the electron transmission layer, the interface between the electron transmission layer and the cathode and/or the interface between the electron transmission layer and the quantum dot light-emitting layer is reduced, and the quenching probability of the quantum dot light-emitting device is reduced.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic flow chart of a method for manufacturing a quantum dot light-emitting device provided in the present application.

Fig. 2 is a schematic structural view of the quantum dot light-emitting device according to the present application when an electric field treatment is performed in example 1 of the method for manufacturing the quantum dot light-emitting device.

Fig. 3 is a graph of atomic content percentage-depth in an electron transport layer, an interface layer between the electron transport layer and a cathode, and a cathode in the quantum dot light emitting devices prepared in example 1 and comparative example.

Fig. 4 is a graph of luminance versus time for a quantum dot light emitting device fabricated using the method of fabricating a quantum dot light emitting device of example 1.

Fig. 5 is a light-emitting topography of the quantum dot light-emitting device manufactured by the method of manufacturing the quantum dot light-emitting device of example 1.

Fig. 6 is a comparison diagram of the proportion of the quenching device and the standard device in the quantum dot light-emitting device manufactured by the method of manufacturing the quantum dot light-emitting device of example 1.

Fig. 7 is a comparative graph of the quenching device and the standard device in the quantum dot light emitting device prepared by the method for preparing the quantum dot light emitting device of example 2.

Fig. 8 is a current density-voltage graph for device 1, device 2, and device 3.

Fig. 9 is a schematic structural diagram of a quantum dot light-emitting device provided in the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. Furthermore, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present application, are given by way of illustration and explanation only, and are not intended to limit the present application. In the present application, unless indicated to the contrary, the use of the directional terms "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, and more particularly to the orientation of the figures of the drawings; while "inner" and "outer" are with respect to the outline of the device.

The application provides a preparation method of a quantum dot light-emitting device, the quantum dot light-emitting device and a display device. The following are detailed below. It should be noted that the following description of the embodiments is not intended to limit the preferred order of the embodiments.

The quantum dot light emitting device in the present application may be a positive quantum dot light emitting device or a negative quantum dot light emitting device, and the following embodiments of the present application are only described by taking the quantum dot light emitting device as a positive quantum dot light emitting device as an example, but not limited thereto.

Referring to fig. 1, the present application provides a method for manufacturing a quantum dot light emitting device, which includes the following steps:

b1: providing a quantum dot light-emitting half-device comprising an electron transport layer and a cathode, the cathode being disposed on the electron transport layer;

b2: and carrying out electric field treatment on the cathode, wherein the electric field direction in the electric field treatment is from the cathode to the electron transport layer.

Therefore, according to the preparation method of the quantum dot light-emitting device, the cathode is subjected to electric field treatment, so that the diffusion speed of metal elements in the cathode to the electron transport layer is increased under the action of an electric field, after the electric field treatment, the quantity of the metal elements diffused to the electron transport layer is increased, the semiconductor depletion region of the electron transport layer is narrowed, the resistance is reduced, the electric conductivity of the electron transport layer is improved, the carrier mobility of the electron transport layer is improved, the charge accumulation probability of the inside of the electron transport layer, the interface between the electron transport layer and the cathode and/or the interface between the electron transport layer and the quantum dot light-emitting layer is reduced, and the quenching probability of the quantum dot light-emitting device is reduced.

In the conventional QLED manufacturing process, a thermal annealing process is usually used to improve the carrier mobility of the electron transport layer, wherein the thermal annealing temperature in the thermal annealing process can reach 120 ℃ or higher. However, the inventors have studied and found that: due to the fact that the quantum dot material has high heat sensitivity, if the heat annealing treatment is carried out on the electron transmission layer in the QLED preparation process, the quantum dot light-emitting layer can be damaged, and therefore the device performance and the service life of the QLED are reduced. Therefore, how to improve the carrier mobility of the electron transport layer without damaging the quantum dot light emitting layer becomes a technical problem to be solved urgently.

In view of the above technical problems, the present application provides a first embodiment (hereinafter, referred to as embodiment 1) of a method for manufacturing a quantum dot light emitting device. In embodiment 1, the quantum dot light-emitting half-device further includes a quantum dot light-emitting layer and an anode, the quantum dot light-emitting layer is located between the anode and the cathode, and the electron transport layer is located between the cathode and the quantum dot light-emitting layer. In embodiment 1, the electric field is used to replace thermal annealing in the prior art, so that the carrier mobility of the electron transport layer can be improved and the quenching probability of the quantum dot light emitting device can be reduced without damaging the quantum dot light emitting layer. Referring to fig. 1 and fig. 2 together, a method for manufacturing the quantum dot light emitting device provided in embodiment 1 is described in detail below.

It should be noted that the quantum dot light-emitting half device is a part of a quantum dot light-emitting device, and further, the quantum dot light-emitting device may further include a hole injection layer and a hole transport layer, where the hole injection layer and the hole transport layer in the quantum dot light-emitting device provided by the present application may be prepared by using an evaporation process or a solution method, the solution method may be a spin coating process, a blade coating process, an inkjet printing process, and the like, and this embodiment is described only by taking as an example that the hole injection layer and the hole transport layer both adopt a spin coating process, but is not limited thereto.

B11: a substrate 1 is provided, and a solution containing a hole injection material is spin-coated on the substrate 1 to form a hole injection layer 2.

The substrate 1 may be a substrate provided with an anode, such as an indium tin oxide substrate. The hole injection material may include, but is not limited to, one or more of an organic material, a doped or undoped transition metal oxide, a doped or undoped metal chalcogenide compound. Specifically, the organic material may include, but is not limited to, one or more of poly (3, 4-ethylenedioxythiophene) -polystyrene sulfonic acid (PEDOT: PSS), copper phthalocyanine (CuPc), 2,3,5, 6-tetrafluoro-7, 7', 8' -tetracyanoquinone-dimethane (F4-TCNQ), 2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-Hexaazatriphenylene (HATCN). The transition metal oxide may include, but is not limited to NiO _x 、MoO _x 、WO _x 、CrO _x And CuO. The metal chalcogenide compound may include, but is not limited to, moS _x 、MoSe _x 、WS _x 、WSe _x And CuS.

In the present embodiment, the hole injection material is PEDOT PSS. The specific method for forming the hole injection layer 2 on the substrate 1 is as follows:

firstly, a solution of PEDOT and PSS with the concentration of 15mg/mL to 25mg/mL is prepared. Specifically, the concentration may be 15mg/mL, 18mg/mL, 20mg/mL, 22mg/mL, 25mg/mL, or the like. In this example, the concentration of PEDOT: PSS in the PEDOT: PSS solution was 20mg/mL.

Next, a solution of PEDOT: PSS is spin coated onto the substrate 1 at a spin speed of 4000r/min to 6000 r/min. Wherein the rotation speed can be 4000r/min, 4500r/min, 5000r/min, 5500r/min or 6000 r/min. The spin coating time of the PEDOT PSS solution is 20s-40s, such as 20s, 25s, 30s, 35s or 40s. In this embodiment, the rotation speed is 5000r/min, and the spin coating time is 30s.

Finally, heating treatment is carried out at the temperature of 100-300 ℃, and the heating temperature can be specifically 100 ℃, 150 ℃, 200 ℃, 250 ℃ or 300 ℃. Wherein the heating time is 10min-30min, such as 10min, 15min, 20min, 25min or 30min. In this embodiment, the heating temperature is 150 ℃ and the heating time is 15min.

The thickness of the hole injection layer 2 is 10nm to 60nm, and may be 10nm, 20nm, 25nm, 30nm, 40nm, 50nm, or 60nm, for example.

B12: a solution containing a hole transport material is spin-coated on the hole injection layer 2 to form a hole transport layer 3.

The hole transport material may include, but is not limited to, an organic material having a hole transport ability and/or an inorganic material having a hole transport ability. Specifically, the organic material having a hole transport ability may include, but is not limited to, one or more of poly (9, 9-dioctylfluorene-CO-N- (4-butylphenyl) diphenylamine) (TFB), polyvinylcarbazole (PVK), poly (N, N 'bis (4-butylphenyl) -N, N' -bis (phenyl) benzidine) (poly-TPD), poly (9, 9-dioctylfluorene-CO-bis-N, N-phenyl-1, 4-Phenylenediamine) (PFB), 4',4 ″ -tris (carbazol-9-yl) triphenylamine (TCTA), 4' -bis (9-Carbazole) Biphenyl (CBP), N '-diphenyl-N, N' -bis (3-methylphenyl) -1,1 '-biphenyl-4, 4' -diamine (TPD), N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine (NPB). The inorganic material having hole transport ability may include, but is not limited to, doped graphene, undoped graphene, C60, doped or undoped NiO _x 、MoO _x 、WO _x 、CrO _x 、CuO、MoS _x 、MoSe _x 、WS _x 、WSe _x And CuS.

In this embodiment, the hole transport material is TFB. The specific method for forming the hole transport layer 3 on the hole injection layer 2 is as follows:

first, a TFB solution was prepared at a concentration of 5mg/mL to 15 mg/mL. Specifically, the concentration may be 5mg/mL, 8mg/mL, 10mg/mL, 12mg/mL, 15mg/mL, or the like. In this example, the concentration of TFB in the TFB solution was 8mg/mL.

Then, TFB solution is spin-coated on the hole injection layer 2 at a rotation speed of 2000r/min to 4000 r/min. Wherein, the rotating speed can be 2000r/min, 2500r/min, 3000r/min, 3500r/min or 4000r/min, etc. The spin coating time of the TFB solution is 20s-40s, such as 20s, 25s, 30s, 35s or 40s. In this embodiment, the rotation speed is 3000r/min, and the spin coating time is 30s.

Finally, heating at 100-250 deg.C (100 deg.C, 120 deg.C, 150 deg.C, 200 deg.C or 250 deg.C). Wherein the heating time is 5min-20min, such as 5min, 10min, 15min, 18min or 20min. In this embodiment, the heating temperature is 120 ℃, and the heating time is 10min.

The thickness of the hole transport layer 3 is 20nm-60nm, such as 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm or 60nm.

B13: and spin-coating a solution containing a quantum dot material on the hole transport layer 3 to form a quantum dot light-emitting layer 4.

Wherein the quantum dot material may be selected from nanocrystals of group II-VI semiconductors such as CdS, cdSe, cdTe, znS, znSe, znTe, hgS, hgSe, hgTe, pbS, pbSe, pbTe and other binary, ternary, quaternary II-VI compounds; the quantum dot material may be selected from nanocrystals of group III-V semiconductors such as GaP, gaAs, inP, inAs, and other binary, ternary, quaternary III-V compounds; the quantum dot material can also be selected from one or more of II-V group compounds, III-VI compounds, IV-VI group compounds, I-III-VI group compounds, II-IV-VI group compounds and IV group simple substances.

In particular, the quantum dot material may include, but is not limited to, a doped or undoped inorganic perovskite-type semiconductor and/or an organic-inorganic hybrid perovskite-type semiconductor. For example, the general structural formula of the inorganic perovskite type semiconductor is AMX ₃ Wherein A is Cs ⁺ Ions, M is a divalent metal cation, M includes but is not limited to Pb ²⁺ 、Sn ²⁺ 、Cu ²⁺ 、Ni ²⁺ 、Cd ²⁺ 、Cr ²⁺ 、Mn ²⁺ 、Co ²⁺ 、Fe ²⁺ 、Ge ²⁺ 、Yb ²⁺ 、Eu ²⁺ X is a halide anion, X includes but is not limited to Cl ^- 、Br ^- 、I ^- . The structural general formula of the organic-inorganic hybrid perovskite type semiconductor is BMX ₃ Wherein B is an organic amine cation, M is a divalent metal cation, and M includes but is not limited to Pb ²⁺ 、Sn ²⁺ 、Cu ²⁺ 、Ni ²⁺ 、Cd ²⁺ 、Cr ²⁺ 、Mn ²⁺ 、Co ²⁺ 、Fe ²⁺ 、Ge ²⁺ 、Yb ²⁺ 、Eu ²⁺ X is a halide anion, X includes but is not limited to Cl ^- 、Br ^- 、I ^- 。

In this embodiment, a specific method for forming the quantum dot light emitting layer 4 on the hole transport layer 3 is as follows:

firstly, a quantum dot solution with the concentration of 15mg/mL-30mg/mL is prepared. Specifically, the concentration may be 15mg/mL, 18mg/mL, 20mg/mL, 25mg/mL, 30mg/mL or the like. In this example, the concentration of the quantum dot material in the quantum dot solution was 20mg/mL.

And then, spin-coating the quantum dot solution on the hole transport layer 3 at a rotating speed of 1000r/min-3000 r/min. Wherein, the rotating speed can be 1000r/min, 1500r/min, 2000r/min, 2500r/min or 3000 r/min. The spin coating time of the quantum dot solution is 20s-40s, such as 20s, 25s, 30s, 35s or 40s. In the present embodiment, the rotation speed is 2000r/min, and the spin coating time is 30s.

The thickness of the quantum dot light-emitting layer 4 may be 10nm-60nm, such as 10nm, 20nm, 25nm, 30nm, 40nm, 45nm, 50nm or 60nm.

B14: and spin-coating a solution containing an electron transport material on the quantum dot light emitting layer 4 to form an electron transport layer 5.

In this embodiment, the electron transport material may be an oxide. Specifically, theThe electron transport material is oxide semiconductor nano-particle material with electron transport capacity, including but not limited to ZnO, tiO ₂ 、SnO ₂ 、Ta ₂ O ₃ 、ZrO ₂ One or more of NiO, tiLiO, znAlO, znMgO, znSnO, znLiO and InSnO.

In some embodiments, the electron transport material may also be other organic materials with oxidation effect, which are not described herein again.

In this embodiment, the electron transport material is ZnO. The specific method for forming the electron transport layer 5 on the quantum dot light-emitting layer 4 is as follows:

first, a ZnO solution having a concentration of 20mg/mL to 40mg/mL is prepared. Specifically, the concentration may be 20mg/mL, 25mg/mL, 30mg/mL, 35mg/mL, 40mg/mL or the like. In this example, the concentration of ZnO in the ZnO solution was 30mg/mL.

And then, spin-coating the ZnO solution on the quantum dot light-emitting layer 4 at a rotating speed of 2000r/min-4000 r/min. Wherein, the rotating speed can be 2000r/min, 2500r/min, 3000r/min, 3500r/min or 4000r/min, etc. The spin coating time of the ZnO solution is 20s-40s, such as 20s, 25s, 30s, 35s or 40s. In this embodiment, the rotation speed is 3000r/min, and the spin coating time is 30s.

Finally, heating at 100-250 deg.C (100 deg.C, 120 deg.C, 150 deg.C, 200 deg.C or 250 deg.C). Wherein the heating time is 20min-60min, such as 20min, 30min, 40min, 50min or 60min. In this embodiment, the heating temperature is 120 ℃ and the heating time is 30min.

The thickness of the electron transport layer 5 may be 20nm to 100nm, such as 20nm, 25nm, 30nm, 40nm, 50nm, 60nm, 80nm or 100nm.

B15: a cathode material is vapor-deposited on the electron transport layer 5 to form a cathode 6.

Wherein, the cathode material can include but is not limited to one or more of Al, ag, cu, mo, au, ba, ca and Mg.

In this embodiment, the cathode materialThe material is Ag. The specific method for forming the cathode 6 on the electron transport layer 5 is as follows: adopting thermal evaporation process to make vacuum degree less than or equal to 3x10 ^-4 Vapor deposition of Ag under Pa pressure at a thermal evaporation rate of

The time period was 200s.

Wherein, the thickness of the cathode 6 is 20nm-80nm, such as 20nm, 25nm, 30nm, 35nm, 40m, 45nm, 50nm, 60nm, 70nm or 80nm.

B16: the cathode 6 is subjected to an electric field treatment in which the electric field direction is directed from the cathode 6 toward the electron transport layer 5.

In this embodiment, after the electric field treatment, the substrate 1, the hole injection layer 2, the hole transport layer 3, the quantum dot light emitting layer 4, the electron transport layer 5, and the cathode 6 form a quantum dot light emitting device 10.

With reference to fig. 2, when an electric field E is applied to the cathode 6, the diffusion speed of the metal element such as Ag ions in the cathode 6 to the electron transport layer 5 increases, so that the amount of Ag ions diffused to the electron transport layer 5 increases, and the electron E in the cathode 6 increases ^- The speed of movement in the direction away from the electron transport layer 5 increases. Under the action of the electric field E, the side of the cathode 6 far away from the electron transport layer 5 has partial electrons E ^- Gathering electrons e from the cathode 6 on the side close to the electron transport layer 5 ^- The number of (2) is reduced. Due to electrons e ^- Has an effect of reducing Ag, and therefore, electrons e of the cathode 6 on the side close to the electron transport layer 5 ^- The reduction of the quantity is beneficial to the oxidation of ZnO to Ag, so that the reduction probability of Ag ions can be reduced, the doping rate of the Ag ions in the electron transmission layer 5 is accelerated, the carrier mobility of the electron transmission layer 5 can be further improved, and the quenching probability of the quantum dot light-emitting device is reduced.

Wherein, the included angle R between the electric field direction X and the plane of the cathode 6 is 80-100 degrees. Specifically, the included angle R may be 80 degrees, 85 degrees, 90 degrees, 95 degrees, or 100 degrees. Within the above range, it is advantageous to improve the uniformity of the diffusion of Ag ions to the electron transport layer 5, and thus the performance of the quantum dot light emitting device can be improved.

In this embodiment, an included angle R between the electric field direction X and the plane of the cathode 6 is 90 degrees, that is, the electric field direction X is perpendicular to the plane of the cathode 6. The above arrangement can further improve the uniformity of diffusion of Ag ions to the electron transport layer 5.

Wherein the electric field intensity in the electric field treatment is 5kV/cm-10kV/cm, such as 5kV/cm, 6kV/cm, 7kV/cm, 8kV/cm, 9kV/cm or 10kV/cm. Wherein the electric field treatment time is 10min-20min, such as 10min, 12min, 14min, 15min, 16min, 18min or 20min. Within the above range, while the carrier mobility of the electron transit layer 5 is significantly improved, the performance of the cathode 6 and the electron transit layer 5 itself is not affected at all. In addition, since the present embodiment uses the electric field treatment instead of the thermal annealing process in the conventional process, the present embodiment can reduce the damage to the quantum dot light emitting layer 4 while improving the carrier mobility of the electron transport layer 5, so as to improve the efficiency and the lifetime of the quantum dot light emitting device.

In this embodiment, the electric field intensity in the electric field treatment is 5kV/cm, and the time of the electric field treatment is 15min. Under the electric field intensity and the electric field processing time, the carrier mobility of the electron transport layer 5 is improved, and meanwhile damage to the quantum dot light emitting layer 4 can be completely avoided.

B17: and packaging the quantum dot light-emitting device 10.

Specifically, the quantum dot light emitting device 10 is encapsulated with an encapsulation adhesive, and the encapsulation adhesive is cured to form an encapsulation structure on the quantum dot light emitting device 10. The specific type of the packaging adhesive can be selected according to the actual application requirements, for example, when the packaging adhesive is an ultraviolet light curing adhesive, the packaging adhesive is subjected to UV curing; when the packaging adhesive is a heat curing adhesive, the packaging adhesive is subjected to heat curing, and the like.

It should be noted that the step of the electric field treatment in the present embodiment is after the cathode 6 is formed and before the quantum dot light emitting device 10 is packaged. In some embodiments, the electric field treatment may be performed after the quantum dot light emitting device 10 is packaged, and this embodiment is not to be construed as limiting the application.

On the basis of example 1, the present application also provides a comparative example (hereinafter referred to as comparative example) of a method for producing a quantum dot light-emitting device. The comparative example differs from example 1 in that: no electric field treatment was used in the comparative example. Further, after step B17, step B18': and carrying out thermal annealing treatment on the quantum dot light-emitting device. Wherein the temperature of the thermal annealing treatment is 120 ℃, and the time of the thermal annealing treatment is 10min.

It is understood that when Ag ions in the cathode 6 diffuse into the electron transport layer 5, at the interface between the electron transport layer 5 and the cathode 6, the Ag ions in the cathode 6 and ZnO in the electron transport layer 5 undergo a redox reaction, so that an interface layer in which Ag ions and Zn ions are in a coexisting state is formed at the interface between the electron transport layer 5 and the cathode 6. Based on the X-ray Photoelectron Spectroscopy (XPS) technique, the present application determines the atomic percentage-depth distribution of the electron transport layer 5, the interface layer between the electron transport layer 5 and the cathode 6, and the cathode 6 in the qd-led devices prepared in example 1 and comparative example, as shown in fig. 3. Wherein the depth represents the thickness of the corresponding film layer.

As can be seen from fig. 3, in the comparative example, the interface layer formed between the electron transit layer 5 and the cathode 6 had a depth of 12nm after the thermal annealing treatment was applied; in example 1, when the electric field treatment was applied, the depth of the interface layer formed between the electron transport layer 5 and the cathode 6 was increased to 25nm. That is, the present example can increase the depth of the interfacial layer formed by Ag ions and Zn ions by applying the electric field treatment to the cathode 6, that is, the diffusion rate of Ag ions to the electron transport layer 5 is significantly increased in example 1, as compared with the thermal annealing treatment in the comparative example. Therefore, the electric field treatment can improve the diffusion speed of the Ag ions in the cathode 6 to the electron transport layer 5, and further increase the quantity of the Ag ions in the electron transport layer 5, so that a good ohmic contact is formed between the cathode 6 and the electron transport layer 5, and the electric performance of the quantum dot light-emitting device is improved.

Therefore, in the preparation method of the quantum dot light emitting device in embodiment 1, the cathode 6 is subjected to the electric field treatment to replace a thermal annealing process in the prior art, so that the carrier mobility of the electron transport layer 5 can be improved on the premise of not damaging the quantum dot light emitting layer 4, and the quenching probability of the quantum dot light emitting device is reduced.

However, although the electric field treatment can accelerate the diffusion rate of the metal ions in the cathode 6 to the electron transport layer 5, under the long-time electric field treatment, the metal ions may be diffused to the quantum dot light emitting layer 4, and further the fluorescence of the device may be quenched, as shown in fig. 4 and 5, after the quantum dot light emitting device is tested for a certain time, the brightness suddenly decreases to 0, and thus the device is judged to be quenched, and meanwhile, the light emitting morphology of the device is greatly attenuated or not bright, and the problem of light emitting flicker and the like is caused.

Therefore, the present application also provides a second embodiment (hereinafter referred to as embodiment 2) of the method for manufacturing a quantum dot light-emitting device. Specifically, example 2 differs from example 1 only in the difference in step B16 (hereinafter referred to as B16'). Wherein, the step B16' is as follows: in any time of performing the thermal annealing treatment on the cathode 6, performing the electric field treatment on the cathode (i.e. the time period of performing the thermal annealing treatment on the cathode 6 and the time period of performing the electric field treatment on the cathode 6 are overlapped, i.e. a part of the treatment time of the two treatment processes is overlapped), wherein the thermal annealing temperature in the thermal annealing treatment is 25-80 ℃.

In this embodiment, the cathode 6 is subjected to an electric field annealing process and a thermal annealing process at the same time, so as to reduce the quenching probability of the device to the maximum extent. After electric field treatment and thermal annealing treatment, the substrate 1, the hole injection layer 2, the hole transport layer 3, the quantum dot light emitting layer 4, the electron transport layer 5 and the cathode 6 form a quantum dot light emitting device 10.

On the one hand, when the electric field E is applied to the cathode 6, the diffusion rate of Ag ions in the cathode 6 into the electron transport layer 5 increases, so that the Ag ions diffused into the electron transport layer 5The number of Ag ions increases and electrons e in the cathode 6 ^- The speed of movement in the direction away from the electron transport layer 5 increases. Under the action of the electric field E, part of electrons E will be generated on the side of the cathode 6 far away from the electron transport layer 5 ^- Gathering electrons e from the cathode 6 on the side close to the electron transport layer 5 ^- The number of (2) is reduced. Due to electrons e ^- Has an effect of reducing Ag, and therefore, electrons e of the cathode 6 on the side close to the electron transport layer 5 ^- The reduction of the quantity is beneficial to the oxidation of ZnO to Ag, and the reduction probability of Ag ions can be reduced, so that the doping rate of the Ag ions in the electron transmission layer 5 is accelerated, the carrier mobility of the electron transmission layer 5 can be further improved, and the quenching probability of a quantum dot light-emitting device is reduced.

Wherein the electric field direction X in the electric field treatment is from the cathode 6 towards the electron transport layer 5. And the included angle R between the direction X of the electric field and the plane where the cathode 6 is positioned is 80-100 degrees. Specifically, the included angle R may be 80 degrees, 85 degrees, 90 degrees, 95 degrees, or 100 degrees. Within the above range, it is advantageous to improve the uniformity of the diffusion of Ag ions to the electron transport layer 5, and thus to improve the performance of the device.

In this embodiment, an included angle R between the electric field direction X and the plane of the cathode 6 is 90 degrees, that is, the electric field direction X is perpendicular to the plane of the cathode 6. The above arrangement can maximize the uniformity of the diffusion of Ag ions to the electron transport layer 5.

On the other hand, at the thermal annealing temperature of 25 ℃ to 80 ℃, the activity of metal elements such as Ag ions in the cathode 6 is enhanced, so that the arrangement order of the Ag ions is improved, the diffusion controllability of the Ag ions can be improved, the probability that the Ag ions penetrate through the electron transport layer 5 and are diffused to the quantum dot light emitting layer 4 is reduced, and the quenching phenomenon caused by doping of the Ag ions in the quantum dot light emitting layer 4 is reduced. In addition, because the quantum dot material has heat sensitivity, the quantum dot light-emitting layer 4 can be prevented from being damaged within the temperature range, so that the service life of the quantum dot device can be further prolonged. Wherein the thermal annealing temperature can be 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃.

Further, the thermal annealing temperature is 60 ℃ to 80 ℃, such as 60 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃. The arrangement can shorten the electric field treatment time to the maximum extent so as to further improve the controllability of Ag ion diffusion, thereby further improving the service life of the quantum dot light-emitting device. Wherein the electric field treatment time is 5min-8min, such as 5min, 5.5min, 6min, 6.5min, 7min, 7.5min or 8min.

In this embodiment, the thermal annealing temperature is 70 ℃, and the electric field treatment time is 5min. Under the thermal annealing temperature and the electric field treatment time, the carrier mobility of the electron transport layer 5 is improved, and meanwhile, the controllability of Ag ion diffusion in the cathode 6 can be greatly improved, so that the quenching probability of the quantum dot light-emitting device is reduced, and the service life of the quantum dot light-emitting device is prolonged.

The same number of devices are prepared by the method for preparing the quantum dot light-emitting device in example 1 and the method for preparing the quantum dot light-emitting device in example 2, and the percentages of the quenching devices in the quantum dot light-emitting devices prepared by the methods for preparing the quantum dot light-emitting devices in example 1 and example 2 are respectively measured, and are respectively shown in fig. 6 and fig. 7. Wherein, the standard device refers to a device which is not quenched in the prepared device.

It can be seen that the percentage of quenching devices in the device prepared using example 1 was only 21.4%, and further that the percentage of quenching devices in the device prepared using example 2 was reduced to 8.7%. That is, by combining the electric field treatment and the thermal annealing treatment in embodiment 2, the electric field treatment time can be shortened, so that the controllability of the diffusion of the metal element is better, thereby further reducing the quenching probability of the quantum dot light emitting device and improving the lifetime of the quantum dot light emitting device.

On the premise that the light emitting area and the driving current of the quantum dot light emitting device are consistent, the quantum dot light emitting device (hereinafter referred to as device 1) prepared in embodiment 1, the quantum dot light emitting device (hereinafter referred to as device 2) prepared in embodiment 2 and quantum dots prepared in proportion are providedThe performance of the light-emitting device (hereinafter referred to as device 3) was measured. Specifically, the present application measured the luminance L (cd/m) of the device 1, the device 2, and the device 3 ² ) The time T95 (h) taken for the luminance to decay from 100% to 95%, the time T95-1K (h) taken for the luminance to decay from 100% to 95% at 1000nit luminance, and the current efficiency c.e (cd/a) are shown in table 1. Where fig. 8 is a current density-voltage graph for device 1, device 2, and device 3.

TABLE 1

	L(cd/m ² )	T95(h)	T95-1K(h)	C.E(cd/A)
					Device 1	65810	12.36	15245	103.3217
Device 2	66210	12.21	15215	103.9497
					Device 3	47210	9.24	6479	74.1197

From this, at a constant drive current (2 mA):

(1) The luminance of the device 1 and the device 2 is higher than that of the device 3, which shows that the efficiency of the quantum dot light-emitting device prepared by the method is higher than that of the comparative example.

(2) The T95 value of the device 1 and the device 2 is higher than that of the device 3, which shows that the quantum dot luminescent device prepared by the method has better performance than that of a comparative example and better stability.

(3) The current efficiency of the device 1 and the device 2 is higher than that of the device 3, which shows that the quantum efficiency of the quantum dot light-emitting device prepared by the method is superior to that of a comparative example.

Referring to fig. 9, an embodiment of the present application further provides a quantum dot light emitting device 20, where the quantum dot light emitting device 20 includes a substrate 1, a hole injection layer 2, a hole transport layer 3, a quantum dot light emitting layer 4, an electron transport layer 5, and a cathode 6, which are sequentially disposed. The quantum dot light-emitting device 20 can be prepared by the preparation method of the quantum dot light-emitting device provided in embodiment 1 or embodiment 2, and details are not repeated here.

The embodiment of the present application further provides a display device, the display device includes a quantum dot light emitting device, and the quantum dot light emitting device may be the quantum dot light emitting device 20 described in the foregoing embodiment. The structure of the quantum dot light-emitting device 20 and the manufacturing method thereof can refer to the description of the foregoing embodiments, and are not described herein again.

Compared with the preparation method of the quantum dot light-emitting device in the prior art, in the preparation method of the quantum dot light-emitting device provided by the application, the cathode is subjected to electric field treatment, so that the diffusion speed of the metal elements in the cathode to the electron transport layer is increased under the action of an electric field, the quantity of the metal elements diffused to the electron transport layer is increased after the electric field treatment, the semiconductor depletion region of the electron transport layer is narrowed, the resistance is reduced, and the electric conductivity of the electron transport layer is improved, so that the carrier mobility of the electron transport layer is improved, the charge accumulation probability of the inside of the electron transport layer, the interface between the electron transport layer and the cathode and/or the interface between the electron transport layer and the quantum dot light-emitting layer is reduced, and the quenching probability of the quantum dot light-emitting device is reduced.

The above detailed description is made on the preparation method of the quantum dot light emitting device, the quantum dot light emitting device and the display device provided in the embodiment of the present application, and a specific example is applied in the description to explain the principle and the implementation manner of the present application, and the description of the above embodiment is only used to help understanding the method and the core idea of the present application; meanwhile, for those skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.

Claims

1. A preparation method of a quantum dot light-emitting device is characterized by comprising the following steps:

2. The method of claim 1, wherein the electric field direction is at an angle of 80-100 degrees with respect to the plane of the cathode.

3. The method of manufacturing a quantum dot light-emitting device according to claim 1, wherein the electric field intensity in the electric field treatment is 5kV/cm to 10kV/cm.

4. The method for manufacturing a quantum dot light-emitting device according to any one of claims 1 to 3, wherein the time of the electric field treatment is 10min to 20min.

5. The method for manufacturing a quantum dot light-emitting device according to any one of claims 1 to 3, wherein the step of subjecting the cathode to an electric field comprises:

6. The method for manufacturing a quantum dot light-emitting device according to claim 5, wherein in the step of performing the electric field annealing treatment on the cathode at any time during the thermal annealing treatment on the cathode, the thermal annealing temperature is 60 ℃ to 80 ℃; and/or

The time of the electric field treatment is 5min-8min.

7. The method of claim 1, wherein the electron transport layer is made of a metal oxide.

8. The method of claim 1, wherein the electron transport layer has a thickness of 20nm to 100nm and the cathode has a thickness of 20nm to 80nm.

9. A quantum dot light-emitting device produced by the method for producing a quantum dot light-emitting device according to any one of claims 1 to 8.

10. A display device characterized in that it comprises a quantum dot light-emitting device according to claim 9.