Method for regulating and controlling QLED carrier balance by using liquid crystal molecules

Abstract

The invention relates to a method for regulating and controlling QLED carrier balance by using liquid crystal molecules, and belongs to the field of QLED display. The method comprises the following steps: sequentially depositing a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a metal cathode on an ITO (Indium Tin Oxide) layer of a transparent conductive substrate; the liquid crystal molecules are doped into the hole transport layer or the electron transport layer, and injection and transmission of surrounding carriers are regulated and controlled through electric field response and thermal response characteristics of the liquid crystal molecules, so that the balance of the QLED carriers is regulated and controlled, and the performance of the QLED device is improved.

Description

Technical Field

[0001] The present invention belongs to the field of QLED display, and specifically relates to a method for regulating QLED carrier balance by using liquid crystal molecules. Background Art

[0002] The light-emitting principle of QLED is that electrons and holes are injected into the light-emitting layer through the carrier transport layer for radiative recombination and light emission.

[0003] The hole transport layer is generally an organic material, while the electron transport layer is generally an N-type inorganic semiconductor material.

[0004] For the hole transport layer, the organic matter in the hole transport layer has a weaker Van der Waals force interaction between molecules, and its mobility is lower than that of inorganic materials, resulting in unbalanced carrier transport. Current research includes using a double-layer hole transport layer structure to reduce the hole injection barrier and doping the hole transport layer. The doping materials include: PEDOT:PSS, TPD, NPD, NiO, etc.

[0005] In QLED, the electron transport layer material is usually ZnO. As a wide bandgap semiconductor material, ZnO has the advantages of excellent electron transport performance, high exciton binding energy, and low stimulated emission threshold. Doping ZnO can improve the injection and transmission of electrons in QLED. According to current research, the doping elements are very wide, including group I elements (Li), group II elements (Si, Ti, Ge, Zr, Sn, Hf, Pb), group V elements (N, P, As, Sb, Bi), group VI elements (Cr, Mo, Se), group VII elements (Mn), group VIII elements (Fe, Co, Ni, Pd, Pt), precious metals (Ag, Cu, Au) and rare earth elements (La, Ce, Nd, Er, Eu, Nb, Ta). The doped ZnO film usually has a more uniform and dense surface and good crystallinity. Doping substances can improve the electron transport characteristics of the electron transport layer, improve the photoelectric performance, enhance the stability or adjust the photoelectric performance. Summary of the invention

[0006] The purpose of the present invention is to provide a method for regulating the carrier balance of QLED using liquid crystal molecules. This method incorporates liquid crystal molecules into a hole transport layer or an electron transport layer, and regulates the injection and transmission of surrounding carriers through the electric field response and thermal response characteristics of the liquid crystal molecules, thereby regulating the carrier balance of QLED and improving the performance of QLED devices.

[0007] To achieve the above object, the technical solution of the present invention is: a method for regulating QLED carrier balance using liquid crystal molecules, comprising: 1) A hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a metal cathode are sequentially deposited on the ITO layer of the transparent conductive substrate; wherein the hole transport layer or the electron transport layer is mixed with liquid crystal molecules and has the function of self-regulating the electric field; 2) The preparation process of the hole transport layer or the electron transport layer is as follows: S1, adding liquid crystal molecules to the ink of the hole transport layer or the electron transport layer to form a mixed dispersion; S2, using a coating machine to spin-coat the mixed dispersion into a film; S3, placing the mixed dispersion into a film under a preset electric field, and performing a drying heat treatment.

[0008] In one embodiment of the present invention, the liquid crystal molecules are nematic liquid crystals, cholesteric liquid crystals or blue phase liquid crystals.

[0009] In one embodiment of the present invention, the material of the hole transport layer is one or a mixture of polymers TFB, Poly:TPD, PVK, and PTAA.

[0010] In one embodiment of the present invention, the material of the electron transport layer is one of ZnMgO, ZnO, ZnO doped with metal cations, and a mixture of ZnO and a polymer.

[0011] In one embodiment of the present invention, the material of the hole injection layer is one of polymer PEDOT:PSS, molybdenum oxide, nickel oxide, and cuprous thiocyanate.

[0012] In one embodiment of the present invention, the material of the quantum dots in the light-emitting layer is one of CdSe, InP, ZnSe, and halogen perovskite.

[0013] In one embodiment of the present invention, the material of the metal cathode is silver or aluminum.

[0014] In one embodiment of the present invention, the ITO layer of the transparent conductive substrate is prepared as follows: (1) An ITO conductive film prepared by magnetron sputtering is used as the anode substrate; (2) The anode substrate was placed in glass cleaning agent, deionized water, acetone, and ethanol in turn for ultrasonic treatment. The ultrasonic treatment time for each time was 10 minutes.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention prepares a QLED device by adding a hole transport layer or an electron transport layer into liquid crystal molecules, and the performance of the obtained device is significantly improved compared with the original QLED device; (2) The present invention does not involve damage to quantum dots and damage to hole transport layer or electron transport layer materials; (3) The present invention has no restrictions on the type of liquid crystal molecules and is universally applicable; (4) The preparation process adopted by the present invention is safe and pollution-free, does not generate by-products, and is simple and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 , Figure 2 It is a schematic diagram of the structure of the experimental device of the present invention; Figure 3 The device flow chart prepared in Example 1 and Example 2; Figure 4 This is a comparison diagram of the EQE effects of the device manufactured in Example 1. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0018] The present invention provides a method for regulating QLED carrier balance using liquid crystal molecules, comprising: 1) A hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a metal cathode are sequentially deposited on the ITO layer of the transparent conductive substrate; wherein the hole transport layer or the electron transport layer is mixed with liquid crystal molecules and has the function of self-regulating the electric field; 2) The preparation process of the hole transport layer or the electron transport layer is as follows: S1, adding liquid crystal molecules to the ink of the hole transport layer or the electron transport layer to form a mixed dispersion; S2, using a coating machine to spin-coat the mixed dispersion into a film; S3, placing the mixed dispersion into a film under a preset electric field, and performing a drying heat treatment.

[0019] The following are specific implementation examples of the present invention.

[0020] Embodiment 1 In this embodiment, reference Figure 1 , specifically comprising the following steps: 1) An ITO conductive film with a thickness of about 80 nm to 150 nm is prepared on white glass by magnetron sputtering to form an anode substrate.

[0021] 2) The anode substrate is sequentially placed in glass cleaning agent, deionized water, acetone, and ethanol for ultrasonic treatment. The ultrasonic treatment lasts for 10 minutes each time. After the ultrasonic treatment, the residual solution on the surface of the anode substrate is blown dry with nitrogen.

[0022] 3) Prepare the hole injection layer by spin coating, PEDOT:PSS is used as the hole injection layer material, the annealing temperature is 120°C, and the thickness is about 30nm to 60nm.

[0023] 4) Prepare the hole transport layer by spin coating, TFB is used as the hole transport layer material, the annealing temperature is 120°C, and the thickness is about 30nm to 60nm.

[0024] 5) The light-emitting layer is spin-coated by a spin coating method and formed into a film at an annealing temperature of 80°C with a thickness of about 20nm to 40nm.

[0025] 6) Prepare the electron transport layer by spin coating. The electron transport layer material is usually ZnO, ZnMgO, etc. HRM 001 is used as a mixed substance, mixed in the required proportion, and stirred for 30 minutes to form a mixed uniform dispersion.

[0026] 7) After spin coating the electron transport layer, place the substrate under an appropriate external electric field to pre-regulate the direction of the internal liquid crystal molecules to prevent excessive deflection of the liquid crystal molecules from adversely affecting the film layer. At the same time, the annealing temperature is 80°C and the film thickness is about 40nm to 80nm.

[0027] 8) A Ag electrode or an Al electrode is deposited by vacuum evaporation method with a thickness of 90 nm to 130 nm.

[0028] Embodiment 2 In this embodiment, reference Figure 2 , specifically comprising the following steps: 1) An ITO conductive film with a thickness of about 80 nm to 150 nm is prepared on white glass by magnetron sputtering to form an anode substrate.

[0029] 2) The anode substrate is sequentially placed in glass cleaning agent, deionized water, acetone, and ethanol for ultrasonic treatment. The ultrasonic treatment lasts for 10 minutes each time. After the ultrasonic treatment, the residual solution on the surface of the anode substrate is blown dry with nitrogen.

[0030] 3) Prepare the hole injection layer by spin coating, PEDOT:PSS is used as the hole injection layer material, the annealing temperature is 120°C, and the thickness is about 30nm to 60nm.

[0031] 4) Prepare the hole transport layer by spin coating. The hole transport layer material is usually TFB, PVK, PTTA, etc. HRM 001 is used as a mixed substance. Mix them in the required proportion and stir for 30 minutes to form a mixed uniform dispersion.

[0032] 5) After spin coating the electron transport layer, place the substrate under an appropriate external electric field to pre-regulate the direction of the internal liquid crystal molecules to prevent excessive deflection of the liquid crystal molecules from adversely affecting the film layer. At the same time, the annealing temperature is 120°C and the film thickness is about 30nm to 40nm.

[0033] 6) The light-emitting layer is spin-coated by a spin coating method, and the film thickness is about 20nm to 40nm under the condition of annealing temperature of 80°C.

[0034] 7) The electron transport layer was prepared by spin coating with an annealing temperature of 80°C and a thickness of about 40 nm to 80 nm.

[0035] 8) A Ag electrode or an Al electrode is deposited by vacuum evaporation method with a thickness of 90 nm to 130 nm.

[0036] Figure 3 This is a flow chart of the devices prepared in Example 1 and Example 2.

[0037] Figure 4 This is a comparison diagram of the EQE effects of the device manufactured in Example 1.

[0038] The above are preferred embodiments of the present invention. Any changes made according to the technical solution of the present invention, as long as the resulting functions do not exceed the scope of the technical solution of the present invention, belong to the protection scope of the present invention.

Claims

1. A method for regulating QLED carrier balance using liquid crystal molecules, characterized in that: include: 1) A hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer and a metal cathode are sequentially deposited on the ITO layer of the transparent conductive substrate; wherein the hole transport layer or the electron transport layer is mixed with liquid crystal molecules and has the function of self-regulating the electric field; 2) The preparation process of the hole transport layer or the electron transport layer is as follows: S1, adding liquid crystal molecules to the ink of the hole transport layer or the electron transport layer to form a mixed dispersion; S2, using a coating machine to spin-coat the mixed dispersion into a film; S3, placing the mixed dispersion into a film under a preset electric field, and performing a drying heat treatment.

2. The method for regulating QLED carrier balance using liquid crystal molecules according to claim 1, characterized in that: The liquid crystal molecules are nematic liquid crystals, cholesteric liquid crystals or blue phase liquid crystals.

3. The method for regulating QLED carrier balance using liquid crystal molecules according to claim 1, characterized in that: The material of the hole transport layer is one or a mixture of polymer TFB, Poly:TPD, PVK, and PTAA.

4. The method for regulating QLED carrier balance using liquid crystal molecules according to claim 1, characterized in that: The material of the electron transport layer is one of ZnMgO, ZnO, ZnO doped with metal cations, and a mixture of ZnO and polymer.

5. The method for regulating QLED carrier balance using liquid crystal molecules according to claim 1, characterized in that: The material of the hole injection layer is one of polymer PEDOT:PSS, molybdenum oxide, nickel oxide and cuprous thiocyanate.

6. The method for regulating QLED carrier balance using liquid crystal molecules according to claim 1, characterized in that: The material of the quantum dots in the light-emitting layer is one of CdSe, InP, ZnSe and halogen perovskite.

7. The method for regulating QLED carrier balance using liquid crystal molecules according to claim 1, characterized in that: The material of the metal cathode is silver or aluminum.

8. The method for regulating QLED carrier balance using liquid crystal molecules according to claim 1, characterized in that: The ITO layer of the transparent conductive substrate is prepared as follows: (1) An ITO conductive film prepared by magnetron sputtering is used as the anode substrate; (2) The anode substrate was placed in glass cleaning agent, deionized water, acetone, and ethanol in turn for ultrasonic treatment. The ultrasonic treatment time for each time was 10 minutes.

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