CN110299461A - A kind of light emitting diode with quantum dots and preparation method thereof - Google Patents

Abstract

The invention discloses a quantum dot light-emitting diode and a manufacturing method thereof. The transparent substrate is connected to the positive pole of the power supply, and the cathode is connected to the negative pole of the power supply. Hole transport layer, spin-coated quantum dot luminescent layer, spin-coated ZnMgO electron transport layer, evaporated Al electrode. The invention improves the luminous efficiency of the device, widens the radiation recombination area, and enables more quantum dots to work effectively, thereby greatly improving the conversion efficiency of the device. As a result, high-efficiency QLEDs are formed, which prolong the service life of light-emitting devices and greatly improve energy utilization. The materials used are simple and common, the production difficulty is small, the cost is low, and the practicability is strong. It provides and creates for people's lives. Great convenience.

Description

A quantum dot light-emitting diode and its manufacturing method

technical field

The invention relates to a QLED quantum dot light-emitting diode, in particular to a quantum dot light-emitting diode doped with a P-type catalyst in a hole transport layer and a manufacturing method thereof.

Background technique

The size of quantum dot (Quantum Dot) is smaller than or close to the exciton Bohr radius, and the size of its three dimensions is 1~10nm. The quantum confinement effect makes quantum dots have unique photoelectric characteristics. Under the excitation of external energy, different sizes The quantum dots have different emission wavelengths. Compared with organic light-emitting materials, inorganic quantum dot materials have high stability, narrow emission spectrum, and long fluorescence lifetime. Quantum dot light-emitting diodes (QLEDs) using this material as the light-emitting layer have simple preparation methods and excellent performance. Since the "sandwich" structure CdSe quantum dot light-emitting device started people's research on QLED in 1994, over the past two decades, the performance of QLED has improved by leaps and bounds, and it has become a new generation of display technology comparable to organic light-emitting diodes (OLEDs).

However, the improvement of the luminous efficiency of quantum dot light-emitting diodes depends on the balance of holes and electrons. However, the number of holes in current quantum dot light-emitting diodes is often less than the number of electrons. The hole mobility of the hole transport layer is very low, and the lower mobility will limit the injection of holes, and the number of holes injected into the light-emitting layer per unit time is less than the number of electrons, thereby causing charge imbalance. A large number of electrons cannot participate in radiative recombination, making the device less efficient.

Contents of the invention

Aiming at the above technical problems and improving the efficiency of quantum light-emitting diodes, the present invention provides a quantum dot light-emitting diode, which improves hole mobility, balances the number of holes and electrons, and realizes a quantum dot light-emitting device with higher efficiency.

The purpose of the present invention is achieved like this. A quantum dot light emitting diode, comprising a transparent substrate 1, an anode 2, a hole injection layer 3, a first hole transport layer 4, a second hole transport layer 5, a quantum dot light emitting layer 6, an electron injection/ The transmission layer 7 and the cathode 8 are characterized in that the transparent substrate 1 is connected to the positive pole of the power supply, and the cathode 8 is connected to the negative pole of the power supply; the thickness of the anode 2 is 1-100nm; the thickness of the hole injection layer 3 is 35-45nm; the thickness of the first hole transport layer 4 is 25-35nm; the second hole transport layer 5 is composed of pvk-doped B(C ₆ F ₅ ) ₃ , and PVK and B(C The ratio of ₆ F ₅ ) ₃ is 60:0-40:20, its thickness is 25-35nm, and its energy level is -5.8eV; the thickness of the quantum dot light-emitting layer 6 is 20-30nm; the electron injection transport layer The thickness of 7 is 20-100nm; the thickness of the cathode 8 is 10-150nm.

Further, the transparent substrate 1 is transparent glass.

Further, the anode 2 is an ITO, FTO, PET/ITO conductive film.

Further, the hole injection layer 3 is PEDOT:PSS, poly(p-phenylene vinylene), polythiophene, polysilane or triphenylmethane.

Further, the first hole transport layer 4 is poly-TPD or TFB.

Further, the quantum dots in the quantum dot light-emitting layer 6 are composed of CdSe/CdS/ZnS, ZnCdS/ZnS or CdSe/ZnS.

Further, the electron injection/transport layer 7 is zinc oxide, magnesium-doped zinc oxide or titanium dioxide.

Further, the cathode 8 is made of aluminum, silver or a combination of both.

A method for making a quantum dot light-emitting diode, characterized in that the steps are as follows:

1) Clean the transparent substrate 1: In the ultrasonic wave, clean the ITO glass with deionized water plus detergent, deionized water, acetone and isopropanol, each cleaning time is 30 minutes, and then soak in alcohol, Wipe it clean with lens cleaning paper, and finally put it in a UV ozone machine for 25 minutes;

2) Spin-coat the hole injection layer 3: adjust the speed of the homogenizer to 4000rpm, set the time to 45s, spin-coat the hole injection layer 3 with a thickness of 30-40nm, bake at 140°C for 30min, and let it cool for 30min;

3) Spin coating the first hole transport layer 4: Dissolve TPD or TFB in chlorobenzene at a concentration of 8mg/ml, then set the speed of the homogenizer to 3000rpm in the glove box, and take 60~80 Microliter TPD solution, spin coating time is 30s, and bake at 140°C for 30 minutes, then let it cool for 30 minutes;

4) Spin coating the second hole transport layer 5: Dissolve pvk and B(C ₆ F ₅ ) ₃ in chlorobenzene respectively, the concentration is 8 mg/ml, the doping ratio of pvk and B(C ₆ F ₅ ) ₃ 55:5, then set the speed of the homogenizer to 3000rpm in the glove box, take 60 microliters of the doped solution with a pipette gun, spin coat it for 30s, and bake it at 140°C for 30min, then let it cool down 30min;

5) Spin-coat quantum dot luminescent layer 6: Dissolve quantum dots in n-octane to make a 20mg/ml solution, then set the speed of the homogenizer at 2000rpm in the glove box for 30s, pipette Take 70 microliters of quantum dot solution, spin coating and let stand for 20 minutes;

6) Spin-coat ZnMgO electron transport layer 7: Adjust the speed of the prepared ZnMgO solution to 3000rpm for 30s, take 70-80 microliters of ZnMgO solution for spin-coating with a pipette gun, and wipe the edge with toluene ;

7) Evaporation of Al electrode 8: Place the device prepared in the above steps in a vacuum coating machine, evaporate a 100nm thick aluminum electrode, and then use ultraviolet curing glue to package the device; the quantum dot light-emitting diode is completed.

Further, the environmental conditions of the glove box are O ₂ <5ppm, H ₂ O<5ppm.

The present invention increases the hole mobility of the second hole transport layer by doping the p-type boron catalyst, increases the injection number of holes and accelerates the transmission rate, makes the holes and electrons of the device more balanced, thereby improving the performance of the device. The luminous efficiency broadens the radiation recombination area and enables more quantum dots to work effectively, which will greatly improve the conversion efficiency of the device. As a result, high-efficiency QLEDs are formed, which prolong the service life of light-emitting devices and greatly improve energy utilization. The materials used are simple and common, the production difficulty is small, the cost is low, and the practicability is strong. It provides and creates for people's lives. Great convenience.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

In the figure: 1-transparent substrate, 2-ITO anode, 3-hole injection layer, 4-first hole transport layer, 5-second hole transport layer, 6-quantum dot light emitting layer, 7-electron injection/ Transport layer, 8 - cathode.

Detailed ways

The present invention will be further described below in conjunction with drawings and embodiments. Referring to Fig. 1, a quantum dot light-emitting diode doped with a p-type catalyst in the hole transport layer, its structure includes a substrate 1, a transparent anode electrode 2, a hole injection layer 3, a first hole transport layer 4, and a layer stacked in sequence. Two hole transport layers 5 , quantum dot light emitting layers 6 , electron injection transport layers 7 , and cathode electrodes 8 . Its transparent anode 1 is connected to the positive pole of the power supply, and the cathode electrode 8 is connected to the negative pole of the power supply. The second hole transport layer is composed of pvk doped B(C6F5)3.

Example 1:

The quantum dot light-emitting diode of the present invention includes a substrate 1, a transparent anode electrode 2, a hole injection layer 3, a first hole transport layer 4, a second hole transport layer 5, a quantum dot light-emitting layer 6, and an electron injection layer stacked in sequence. Transport layer 7, cathode electrode 8. The transparent positive electrode is ITO, and its thickness is 200nm. The second hole transport layer 5 is composed of pvk and B(C ₆ F ₅ ) ₃ doped, the doping ratio is 55:5, its thickness is 30nm, the first hole transport layer is poly-TPD4, its thickness is 30nm , the hole injection layer 3 is PEDOT:DSS, and its thickness is 40nm. The quantum dot light-emitting layer 6 is CdSe/CdS/ZnS with a thickness of 25nm. The electron injection and transport layer 7 is ZnMgO with a thickness of 40 nm. The cathode 8 is Al and its thickness is 100 nm.

Example 2:

The quantum dot light-emitting diode of the present invention includes a substrate 1, a transparent anode electrode 2, a hole injection layer 3, a first hole transport layer 4, a second hole transport layer 5, a quantum dot light-emitting layer 6, and an electron injection layer stacked in sequence. Transport layer 7, cathode electrode 8. The transparent positive electrode is ITO, and its thickness is 200nm. The second hole transport layer 5 is composed of doped pvk and B(C ₆ F ₅ ) ₃ with a doping ratio of 50:10 and a thickness of 30nm. The first hole transport layer is TFB with a thickness of 30nm. The hole injection layer 3 is PEDOT:DSS, and its thickness is 40 nm. The quantum dot luminescent layer 6 is ZnCdS/ZnS with a thickness of 25nm. The electron injection and transport layer 7 is ZnMgO with a thickness of 40 nm. The cathode 8 is Al and its thickness is 100 nm.

Example 3:

The quantum dot light-emitting diode of the present invention includes a substrate 1, a transparent anode electrode 2, a hole injection layer 3, a first hole transport layer 4, a second hole transport layer 5, a quantum dot light-emitting layer 6, and an electron injection layer stacked in sequence. Transport layer 7, cathode electrode 8. The transparent positive electrode is ITO, and its thickness is 200nm. The second hole transport layer 5 is composed of doped pvk and B(C ₆ F ₅ ) ₃ with a doping ratio of 45:15 and a thickness of 30 nm. The first hole transport layer is TFB with a thickness of 30 nm. The hole injection layer 3 is PEDOT:DSS, and its thickness is 40 nm. The quantum dot luminescent layer 6 is CdSe/ZnS with a thickness of 25nm. The electron injection and transport layer 7 is ZnMgO with a thickness of 40 nm. The cathode 8 is Al and its thickness is 100 nm.

The preparation steps of the quantum dot light-emitting diode doped with p-type catalyst in the hole transport layer of the present invention are as follows: cleaning of ITO glass: in ultrasonic wave, add detergent, deionized water, acetone, isopropanol to Clean the ITO glass for 30 minutes each, then soak it in alcohol, and wipe it clean with lens cleaning paper. Finally, it was irradiated in a UV ozone machine for 25 minutes.

Spin-coat PEDOT:PSS hole injection layer 3: Adjust the speed of the homogenizer to 4000rpm, set the time for 45s, spin-coat a PEDOT:PSS hole injection layer with a thickness of about 40nm, bake it at 140 degrees Celsius for 30 minutes, and let it cool for 30 minutes .

Spin-coat the first hole transport layer 4: dissolve TPD or TFB in chlorobenzene with a concentration of 8 mg/ml, then set the speed of the homogenizer to 3000 rpm in a glove box (O2<5ppm, H2O<5ppm), Take 60-80 microliters of TPD solution with a pipette gun, spin coating for 30 seconds, and bake at 140°C for 30 minutes. Then let it cool down for 30 minutes.

Spin-coat the second hole transport layer 5: dissolve pvk and B(C ₆ F ₅ ) ₃ in chlorobenzene respectively, the concentration is 8mg/ml, dope in an appropriate ratio, and then in a glove box (O2<5ppm, H2O<5ppm), set the speed of the homogenizer to 3000rpm, take 60 microliters of the doped solution with a pipette gun, spin-coat for 30s, and bake at 140°C for 30min. Then let it cool down for 30 minutes.

Spin-coat quantum dot luminescent layer 6: Dissolve quantum dots in n-octane to make a 20mg/ml solution, then set the speed of the homogenizer to 2000rpm in the glove box (O2<5ppm, H2O<5ppm), Time 30s, pipette gun to take 70 microliters of quantum dot solution, spin coating and let stand for 20 minutes.

Spin-coat ZnMgO electron transport layer 7: Spin-coat the prepared ZnMgO solution with the speed of the homogenizer at 3000rpm for 30s, pipette 70-80 microliters of ZnMgO solution, and wipe the edge with toluene.

Evaporation of Al electrode 8: Place the device prepared in the above steps in a vacuum coating machine, evaporate a 100nm-thick aluminum electrode, and then use UV-curable glue to package the device. The quantum dot light-emitting diode is fabricated.

Enhancing charge carrier mobility in solution-processed organic semiconductors is crucial for the development of advanced quantum dot light-emitting diodes. PVK is a hole-transporting material commonly used in QLEDs. As a polymer, PVK solution has good film-forming properties, but the carrier mobility is low, resulting in a high turn-on voltage of QLED devices. In order to promote the hole transport of QLEDs, the scheme of doping B(C ₆ F ₅ ) ₃ in PVK was adopted as the hole transport material. Compared with PVK, B(C ₆ F ₅ ) ₃ is a small molecule hole transport material with high carrier mobility, but the film formation and uniformity of the small molecule solution are poor after spin coating. This patent improves the hole mobility of a wide range of organic semiconductors by doping B(C ₆ F ₅ ) ₃ in the hole material, and discloses a p-type catalyst B(C ₆ F ) doped in the hole transport layer ₅ ) ₃ quantum dot LEDs. The structure of this device is composed of: ITO anode, hole injection layer, first hole transport layer, second hole transport layer, quantum dot light emitting layer, electron injection and transport layer, cathode. Our general quantum dot quantum dot light-emitting diode emits light through the radiative recombination of excitons in quantum dots to emit photons. If the number of holes and electrons is balanced, the recombination of excitons can be increased to improve the efficiency of the device. However, the number of electrons in a general quantum dot light-emitting diode is far more than the number of holes, so the efficiency of the light-emitting diode is very low and the brightness is very low. This patent is to increase the hole mobility of the second hole transport layer by doping the p-type boron catalyst, so that the holes and electrons of the device are more balanced, thereby improving the luminous efficiency of the device.

Claims (10)

1. a kind of light emitting diode with quantum dots, including be cascading transparent substrates 1, anode 2, hole injection layer 3, first Hole transmission layer 4, the second hole transmission layer 5, quantum dot light emitting layer 6, electron injection/transport layer 7 and cathode 8, which is characterized in that The transparent substrates 1 are connected with the anode of power supply, and cathode 8 is connected with the cathode of power supply；The anode 2 with a thickness of 1-100nm； The hole injection layer 3 with a thickness of 35 ~ 45nm；First hole transmission layer 4 with a thickness of 25 ~ 35nm；Described second is empty Cave transport layer 5 adulterates B (C by pvk₆F₅)₃Composition, and PVK and B (C₆F₅)₃Ratio be 60:0 ~ 40:20, with a thickness of 25 ~ 35nm, energy level are -5.8eV；The quantum dot light emitting layer 6 with a thickness of 20 ~ 30nm；The thickness of the electron injection transport layer 7 For 20 ~ 100nm；The cathode 8 with a thickness of 10-150nm.

2. light emitting diode with quantum dots according to claim 1, which is characterized in that the transparent substrates 1 are transparent glass.

3. light emitting diode with quantum dots according to claim 1, which is characterized in that the anode 2 is ITO, FTO, PET/ ITO conductive film.

4. light emitting diode with quantum dots according to claim 1, which is characterized in that the hole injection layer 3 is PEDOT: PSS, poly-phenylene vinylene (ppv) class, polythiophene class, polysilanes or triphenylmethane.

5. light emitting diode with quantum dots according to claim 1, which is characterized in that first hole transmission layer 4 is Ploy-TPD or TFB.

6. light emitting diode with quantum dots according to claim 1, which is characterized in that the amount in the quantum dot light emitting layer 6 Son is that CdSe/CdS/ZnS, ZnCdS/ZnS or CdSe/ZnS are constituted.

7. light emitting diode with quantum dots according to claim 1, which is characterized in that the electron injection/transport layer 7 is oxidation Zinc, Mg-doping ZnO or titanium dioxide.

8. light emitting diode with quantum dots according to claim 1, which is characterized in that the cathode 8 is by aluminium, silver or both group It closes and constitutes.

9. a kind of production method of light emitting diode with quantum dots as described in claim 1, which is characterized in that its step are as follows:

1) transparent substrates 1 are cleaned: in ultrasonic wave, dish washing liquid, deionized water, acetone and isopropanol pair being added with deionized water respectively Ito glass is cleaned, and each scavenging period is 30min, is then placed in alcohol and is impregnated, and with lens wiping paper wiped clean, most After be placed in UV ozone machine and irradiate 25min；

2) spin coating hole injection layer 3: the revolving speed of sol evenning machine is transferred to 4000rpm, the time sets 45s, the sky of spin coating thickness 30-40nm Cave implanted layer 3, and with 140 DEG C of temperature calcination 30min, stand cooling 30min；

3) the first hole transmission layer of spin coating 4: TPD or TFB are dissolved in chlorobenzene, concentration 8mg/ml, then in glove box Middle that the revolving speed of sol evenning machine is set as 3000rpm, liquid-transfering gun takes 60 ~ 80 microlitres of TPD solution, and spin-coating time is 30s spin coating, is used in combination 140 DEG C of temperature calcination 30min, is then allowed to stand cooling 30min；

4) the second hole transmission layer of spin coating 5: by pvk and B (C₆F₅)₃It is dissolved separately in chlorobenzene, concentration 8mg/ml, pvk and B (C₆F₅)₃Doping ratio be 55:5, the revolving speed of sol evenning machine is then set as 3000rpm in glove box, liquid-transfering gun takes 60 micro- Rise doped good solution, spin coating 30s, and with 140 DEG C of temperature calcination 30min, it is then allowed to stand cooling 30min；

5) spin coating quantum dot light emitting layer 6: quantum dot is dissolved in normal octane, the solution of 20mg/ml is made into, then in glove box The revolving speed of sol evenning machine is set as 2000rpm, time 30s, liquid-transfering gun takes 70 microlitres of quantum dot solution, and spin coating stands 20min；

6) spin coating ZnMgO electron transfer layer 7: by the solution of prepared ZnMgO, being adjusted to 3000rpm for the speed of sol evenning machine, when Between 30s, liquid-transfering gun takes 70 ~ 80 microlitres of ZnMgO solution spin coating, and wipes edge with toluene；

7) evaporating Al electrode 8: the ready-made device of above-mentioned steps is placed in vacuum coating equipment, the aluminium electrode of 100nm thickness on vapor deposition, Then with uv-curable glue come packaging；Light emitting diode with quantum dots production finishes.

10. the production method of light emitting diode with quantum dots according to claim 9, which is characterized in that the glove box Environmental condition is O₂< 5ppm, H₂O<5ppm。