CN102646795B - Organic electroluminescence device for reducing patterning graphene electrodes based on laser and manufacturing method therefor - Google Patents

Abstract

The invention belongs to the technical field of optoelectronics, and in particular relates to an organic electroluminescent device based on a laser reduction patterned graphene electrode and a preparation method thereof. The device consists of a substrate, a gold electrode with a channel structure as an extraction electrode, a micron-scale patterned graphene electrode lapped on the gold electrodes on both sides of the channel, an organic functional layer and a cathode. The micron-scale pattern The graphene electrode is prepared by laser direct writing processing system with exciting point-by-point scanning. The surface roughness of the obtained graphene electrode is relatively low, and the surface is relatively flat, and the bottom-emitting organic electroluminescent device prepared based on the electrode has high luminous uniformity. The invention breaks the conventional thinking of large-area devices in the past, reduces the area of the electrode to the order of microns, and introduces patterns into it, so that the light-emitting area of the device is a miniaturized pattern structure, so that organic photoelectric devices and laser micro-nano processing cleverly combined.

Description

Fabrication method of organic electroluminescent devices based on laser reduction patterned graphene electrodes

technical field

The invention belongs to the technical field of optoelectronics, and in particular relates to an organic electroluminescent device based on a laser reduction patterned graphene electrode and a preparation method thereof. the

technical background

In recent years, the world's demand for information has grown rapidly, and the information industry has developed rapidly around the world. Information technology has become the cornerstone of today's economic activities and social life. Among them, as an important part of information technology - information display technology has played a key role in the acquisition of human knowledge and the improvement of life. the

As a new generation of display technology, flat panel display (FPD) has outstanding advantages such as light weight, small size, low power consumption, and no radiation, and has become the mainstream demand in the display field. Currently, FPDs mainly include liquid crystal displays (LCDs), plasma displays (PDPs), field emission displays (FEDs), organic electroluminescent devices (OLEDs), and the like. Among them, LCD occupies a large share in the flat panel display market due to its excellent characteristics and mature market-oriented production. Although LCD maintains its primary position in the display market for the time being, there are still some essential shortcomings: low brightness, slow response speed, non-active light source, etc., which prompts researchers to develop and explore new display devices. the

Along with people's strong demand and continuous research breakthroughs in the scientific community, a new generation of flat panel display technology - Organic Light Emitting Devices (OLEDs) has emerged as the times require and has entered people's field of vision. It has developed strongly in recent years. . Compared with traditional displays, it has the following advantages:

1) Since the main body of the device is organic, the selection of materials is wide, and full-color solid-state display can be realized;

2) The device is light in weight and thin in thickness;

3) Self-illuminating without backlight;

4) The response speed is fast (less than 1μs), which can present ultra-fast dynamic images without afterimage effects; the image refresh rate can be increased, and the effect is good when displaying fast dynamic images;

5) The temperature range used is wide, and the display work can be performed under low temperature conditions;

6) Can be prepared into flexible devices;

7) The production process is relatively simple, which is convenient for large-scale production and processing. the

For OLED, the material is the main body of the device, and the selection and application of materials are important factors to maintain the normal operation of the device and affect its performance. In OLEDs, the selection of electrode materials has always been a research hotspot in academia. The traditional electrode material ITO (Indium Tin Oxide) has always been the mainstream electrode in organic electroluminescent devices due to its excellent conductivity and transparency. In addition, due to the scarcity of indium element on the earth, the cost of OLED devices will gradually increase. Therefore, it is necessary to find a new alternative electrode for ITO. the

Graphene, a new material, was born in 2004. Its structure is single-layer graphite, only one carbon atom thick. It has many excellent physical and chemical properties: high carrier mobility, good electrical and thermal conductivity, good flexibility, high transparency and so on. It has the innate conditions of flexible transparent electrodes and is a new electrode material that is expected to replace ITO. the

At present, the synthesis and application of graphene materials continue to trigger academic upsurge in the field of scientific research. In the application of the microscopic field, the patterning of graphene is a relatively new research direction, which belongs to the field of micro-nano processing technology. At present, there are three main methods of patterning: mask method, transfer printing method and direct writing method. As a classification of the direct writing method, laser processing uses the high heat focused by the laser beam to remove the oxygen in the graphene oxide, thereby reducing the graphene electrode; due to the high precision (up to 1nm) positioning of the laser processing, it can be used in While reducing, the graphene electrode is processed into a specific pattern, thus completing the preparation of the patterned graphene electrode. the

Contents of the invention

The object of the present invention is to provide an organic electroluminescent device based on laser reduction patterned graphene electrodes. It is to apply the micron-scale patterned graphene electrode processed by laser into OLED. the

The invention specifically relates to patterned graphene prepared by laser micro-nano processing technology as an electrode material, and its application to prepare an organic electroluminescent device. This idea broke the conventional thinking of large-area devices in the past, reduced the area of the electrode to the order of microns, and introduced patterns into it, so that the light-emitting area of the device has a miniaturized pattern structure, so that organic optoelectronic devices and laser micro-nano The processing is skillfully combined. the

The invention uses spin coating technology, laser micro-nano processing technology and vacuum evaporation deposition technology. On a clean substrate, gold is first evaporated as an extraction electrode, and a micron-scale channel is left in the middle. Then, the graphene oxide is spin-coated on the gold electrode, so that the spin-coated material completely covers the gold electrode and the channel, and then dried in a vacuum oven. After that, the laser micro-nano processing system is used to reduce the spin-coated graphene oxide film, and the patterned graphene electrode material is prepared under the control of the graphics program. The electrode patterns include ladder type and bow tie type. Finally, vacuum evaporation deposition technology is used to vapor-deposit various organic functional layers and cathodes on the patterned graphene electrodes, thereby making organic electroluminescent devices. the

The laser micro-nano processing system used in the present invention is a point-by-point scanning laser direct writing processing system, which includes: a light source system (laser and optical path adjustment components), a software control system, a three-dimensional precision movement system and a real-time monitoring system. the

The three-dimensional precision moving system includes a sample stage and a rotating mirror. The laser emitted by the laser is focused on the surface of the sample (graphene oxide film) to be processed on the sample stage through the optical path adjustment element, and the software control system controls the precise movement of the sample stage and the rotating mirror. , so that the focused laser spot moves three-dimensionally within the sample, thereby realizing three-dimensional processing, and monitoring the processing status through a real-time monitoring system. the

The software control system refers to a three-dimensional point-by-point scanning control program written in VB or C language, and the program can control the three-dimensional precision moving system through a microcomputer. The three-dimensional precision moving system includes a piezoelectric platform (109 in FIG. 1) and a rotating mirror (104 in FIG. 1). Controlling the movement of the rotating mirror can control the movement of the laser spot on the surface of the sample and inside the sample. The T8306 rotating mirror of Beijing Century Nissan Co., Ltd. can make the laser move in the X and Y directions with a range of 100 μm and 100 μm respectively. The one-dimensional precision ceramic piezoelectric platform of the German Physik Instrumente company P622 was used as the sample stage, and the moving range in the Z direction was 250 μm; the three-dimensional mobile piezoelectric platform of the German Physik Instrumente company P517.3 model was used as the sample stage, and the X , The moving ranges in the Y and Z directions are 100 μm, 100 μm, and 20 μm, respectively. The movement accuracy of the sample stage and the rotating mirror can reach 1nm. the

The general illumination source of the real-time monitoring system (112 as shown in Figure 1) is located above the piezoelectric platform and the sample, and the visible light it sends enters the CCD camera after passing through the lens 111, the sample 110, the objective lens 108, the dielectric mirror 107, and the lens 106 (as shown in Figure 1). 1 in 105), in the laser processing process, the different refractive index of the material before and after photocuring is used to make the CCD image, directly monitor the processed image, and monitor the whole processing process in real time. the

In addition, the homogenizer used in the spin coating technology is provided by the Institute of Microelectronics of the Chinese Academy of Sciences, and the film thickness and growth rate are controlled by Shanghai Gloss Vacuum Instruments-Film Thickness Controller. For the observation of device luminescence, first apply voltage to the device through the Keithley-2400 current-voltage tester, and then use the Japanese Olympus fluorescence microscope to observe. The test conditions are carried out in the atmosphere at room temperature. the

The present invention includes the following contents:

An organic electroluminescent device based on laser reduction patterned graphene electrodes, its structure sequentially includes a substrate, a gold electrode with a channel structure, and micron-scale patterned graphene lapped on the gold electrodes on both sides of the channel Electrode (ladder type, bow tie type), organic functional layer and cathode, as shown in Fig. The layer doubles as an electron transport layer (40-60nm); the micron-scale patterned graphene electrode is prepared by laser micro-nano processing technology, the thickness of the gold electrode is 15-20nm, the width of the channel is 50-120μm, and the thickness of the graphene electrode is 15-30nm, the lateral length is 20-150μm, and the vertical length is 40-300μm. the

An organic electroluminescent device based on laser reduction patterned graphene electrodes according to the present invention is prepared by the following method: considering that the prepared graphene electrodes are on the order of microns, in order to facilitate the device in the later stage To apply a voltage, first of all, on the cleaned cover glass substrate, a metal deposition system is used to grow a gold electrode with a channel structure as an extraction electrode. During the growth process, the vacuum degree of the system is controlled at 1×10 ^-3 ~ 3×10 ^-3 Pa, leave a channel with a width of 50-120 μm in the middle of the gold electrode through a copper wire mask, and the thickness of the gold electrode is 15-20 nm; then spin-coat the suspension of graphene oxide on the gold electrode , completely cover the gold electrode and the channel in the middle position, the spin-coating speed is 1000-3000rpm, the spin-coating time is 15-20s, the thickness of the graphene oxide is 80-100nm, and the spin-coated graphene oxide The substrate is placed in a vacuum oven and dried in a vacuum environment at 35-40°C for 40-60 minutes; then the graphene oxide is reduced by point-by-point scanning laser direct writing processing system. A graphene electrode with a specific pattern is prepared on the alkene oxide, and the graphene electrode overlaps the gold electrodes on both sides of the channel. The structure of the graphene electrode and the gold electrode is shown in Figure 2(b), where the graphene electrode The thickness of the electrode is 15-30nm, the lateral length is 20-150μm, and the vertical length is 40-300μm; finally, in the multi-source organic molecule vapor deposition system, a hole injection layer, a hole transport layer, and a luminescent layer are sequentially grown on the graphene electrode. The layer doubles as an electron transport layer and a cathode, thereby preparing an organic electroluminescent device with patterned graphene as an electrode.

The suspension of graphene oxide is prepared by the following method: 1-2g flake graphite (average size is 500-600μm), 1-2g sodium nitrate, 48-96mL concentrated sulfuric acid, 6-12g potassium permanganate Stir the mixture in a water bath at 0°C for 60-90 minutes, then raise the temperature to 25-35°C and continue stirring for 2-3 hours; then slowly add 40-80 mL of ultrapure water to the mixed solution within 30 minutes, and then sequentially Add 100-200mL ultrapure water and 5-10mL hydrogen peroxide (H ₂ O ₂ ) with a mass concentration of 30%; then use high-speed centrifugation to extract the precipitate after graphite oxidation, and the centrifugation speed is 9000-12000r/s. The time is 10-15 minutes, and then the precipitate is repeatedly washed with ultrapure water, so that the acidity is greatly weakened, so that the pH value is close to 7; finally, the near-neutral precipitate is ultrasonically treated (80W) for 5-10 minutes, so that the graphite Layer-by-layer exfoliation yielded a suspension of graphene oxide.

The electrode (anode) of the device is patterned graphene, which is obtained by laser direct writing processing system: the substrate with graphene oxide is fixed on the piezoelectric platform; the software control system sends instructions to control the On and off to control the opening and closing of the laser beam; the software control system drives the three-dimensional precision moving system according to the programmed patterned graphene electrode micro-nano structure, and then makes the focused laser spot scan point by point in the graphene oxide , the graphene oxide at the laser scanning site is reduced to graphene, so that the micro-nano structure of graphene is obtained according to a pre-designed program, and a patterned graphene electrode is obtained. the

The femtosecond laser conditions used are: laser wavelength 700-800nm, repetition frequency 70-80MHz, energy of a single pulse 15-20nJ, and pulse width about 100-120fs. The selected objective lens has a magnification of 100 and an aperture of 1.4. When reducing graphene, the selected laser power range is about 5-13mW, and the single-point exposure time selection interval is between 500-2000μs. The patterned graphene electrode is a ladder-type electrode or a bow-tie-type electrode. The area of the ladder-type electrode is 4000-5000 μm ² , and the area of the bow-tie-type electrode is 1000-2500 μm ² , as shown in Figure 5 and Figure 6 respectively. The area of the electrode area Belongs to the micron level.

In addition to femtosecond lasers, pulsed lasers with high transient power such as picoseconds and nanoseconds, as well as continuous lasers, can be used for reduction. The wavelength range of the picosecond pulse laser is 200-2600nm, the pulse width range is 10ps-800ps, the repetition frequency range is 1Hz-80MHz; the wavelength range of the nanosecond pulse laser system is 200-2000nm, the pulse width range is 10ns-900ns, the repetition The frequency range is 1Hz ~ 10KHz. the

The hole injection layer material in the device is star-shaped explosive triphenylamine, star-shaped polyamine, polyaniline, copper phthalocyanine, preferably 4,4', 4 "-tris(3-methylphenylphenylamino)triphenylamine (m -MTDATA) to improve hole injection capability. 

The material of the hole transport layer is an aromatic amine compound. According to the molecular structure type and combined with the topological structure, it can be divided into: pair-coupled diamine compounds, star-shaped triphenylamine compounds, triphenylamine compounds with a spiral structure, branched Triphenylamine compounds, triarylamine polymers, carbazole compounds, organosilicon and organometallic complexes, etc., typically such as N, N'-diphenyl-N, N'-bis(1,1'-biphenyl)-4 , 4'-diamine(NPB), N,N'-Bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine(TPD), N,N'-Bis(naphthalene-1-yl)- N, N'-bis(phenyl)-2,2'-dimethylbenzidine (α-NPD), etc., preferably NPB here. the

The light-emitting layer is mainly electroluminescent materials of organic small molecules, including pure organic small molecule blue light-emitting materials, green light materials, red light materials and electroluminescent materials of metal complexes. Here, the green light-emitting material tris-(8-hydroxyquinoline)aluminum (Alq ₃ ) with carrier transport properties is preferred, and also serves as an electron transport material.

The cathode generally uses metals with low work functions such as lithium, magnesium, calcium, strontium, indium, and aluminum, or their alloys with copper, gold, and silver, or a composite type composed of a thin insulating layer (such as LiF) and them. The cathode is preferably a composite cathode LiF/Al here. the

The organic electroluminescent device provided by this solution has the following innovations and advantages:

Using laser processing technology to reduce graphene oxide and realize the patterning of reduced graphene at the same time, introducing graphene electrodes with a micron-scale area into organic electroluminescent devices makes the light-emitting area of the device a specific pattern, and the pattern can be determined according to Arbitrary processing is required to realize patterned organic electroluminescent devices. The prepared graphene material has good electrical conductivity and a relatively smooth surface, which plays an excellent role as an electrode in the device. Moreover, the device of the prepared OLED has high luminous uniformity. the

Description of drawings

Figure 1: Schematic diagram of laser micro-nano processing optical path

101 laser, 102 shutter, 103 attenuator, 104 rotating mirror, 105CCD camera, 106 lens, 107 dielectric mirror, 108 objective lens, 109 piezoelectric platform, 110 graphene oxide electrode and substrate, 111 lens, 112CCD camera. the

Figure 2: Schematic diagram of the device structure of the present invention

(a) Device structure diagram: 1 cover glass substrate, 2 patterned graphene electrode (as anode), 3 hole injection layer, 4 hole transport layer, 5 light emitting layer and electron transport layer, 6 cathode. the

(b) Structural diagram of the electrode part of the device;

Figure 3: AFM image of the surface of the patterned graphene electrode;

Figure 4: Atomic force microscope pictures of graphene electrode thickness (a) Atomic force topography at the interface between graphene and substrate, (b) Thickness distribution curve of the area marked by the oblique line in the left figure;

Fig. 5: Fluorescence micrographs of the ladder electrode device in Example 1 of the present invention under different voltages (a) voltage 0V, (b) voltage 9V, (c) voltage 10V, (d) voltage 11V;

Fig. 6: Fluorescent micrographs of the tie-shaped electrode device in Example 1 of the present invention under different voltages (a) voltage 0V, (b) voltage 6V, (c) voltage 7V, (d) voltage 8V. the

Detailed ways

The specific implementation will be given below and the technical solution of the present invention will be explained in conjunction with the accompanying drawings, and it should be noted that the following implementation is only for helping understanding, rather than limiting the present invention. the

Example 1:

Fabrication of organic electroluminescent devices with ladder-shaped patterned graphene electrodes. The device structure is: Graphene (graphene, ~20nm)/m-MTDATA(30nm)/NPB(20nm)/Alq ₃ (50nm)/LiF(1nm)/Al(100nm), as shown in Figure 2(a). Proceed as follows:

(1) On the cleaned substrate, a metal deposition system is used to grow a gold electrode as an extraction electrode. During the growth process, the vacuum degree of the system is controlled at 1×10 ^-3 Pa, and a copper wire mask is left in the middle of the gold electrode. The channel width is about 90 μm, the thickness of the gold electrode is 18 nm, the electrode length is 17 mm, and the width is 5 mm.

(2) Graphene oxide is spin-coated on the gold electrode, and the gold electrode and the channel in the middle are completely covered. The spin-coating speed is 1000rpm, and the spin-coating time is 18s. In a vacuum oven at 40°C, the film is Carry out drying treatment, the time is 60min. the

(3) Using laser to reduce graphene oxide. As shown in Figure 1, the femtosecond pulsed laser 101 output wavelength is 800nm, pulse width is 150fs, the laser light that repetition frequency is 80MHz reaches rotating mirror 104 after optical gate 102, attenuation plate 103 (attenuation is 50% of original light intensity) , and then enter the objective lens 108 through the dielectric mirror 107, and focus on the graphene oxide 110 on the substrate on the piezoelectric platform 109. There is a leaky position on the piezoelectric platform through which light can pass. The spot diameter focused in the graphene oxide film is about 400nm, and the spot energy is about 120uJ. The visible light emitted by the visible light source 112 is focused in the graphene oxide film by the lens 111 , and then focused by the lens 106 to form an image in the CCD 105 . the

The ladder pattern model is designed by the CAD program, and saved as a DXF or STL file; then read with VB conversion software or Geomagic Studio software, and processed into point cloud data; then read the point cloud data with the control program written in VB, and then communicate with the computer The connected serial port drives the three-dimensional precision movement system. All programs are written from point to line and then to surface. The program written in the involute and micro-broken program starts from the starting point on the left, follows the direction of the line, and ends at the end point on the right to obtain a complete structure. Place the substrate with graphene oxide on the piezoelectric platform, the above-mentioned femtosecond pulsed laser is focused inside the graphene oxide through the optical path in Figure 1, and the program is pre-designed according to the ladder pattern, and the laser spot is on the graphene. The interior of the oxide is scanned point by point, and the scanned points are photoinduced to reduce the graphene oxide to graphene to obtain a graphene micro-nano structure. the

The selected laser power is 8mW, and the single-point exposure time is 1500μs. At the same time, the light spot is controlled by a graphics program to process a ladder-shaped graphene electrode. The contact mode between the restored electrode and the gold electrode channel is shown in Figure 2(b) , the thickness of the electrode is about 20nm, and the area of the ladder electrode is about: 90×45μm ² .

(4) Finally, in a multi-source organic molecule vapor deposition system, a hole injection layer, a hole transport layer, and a light-emitting layer are sequentially grown on the ladder-type graphene electrode, which also serves as an electron transport layer and a cathode. The luminescence phenomenon of the device was observed with a fluorescence microscope. the

Fig. 3 is the surface morphology of the laser processed graphene electrode of the present invention. It can be seen from the figure that the average surface roughness of the processed graphene is 5.45nm. the

Fig. 4 is an atomic force microscope image for measuring the thickness of a graphene electrode according to the present invention. It can be seen from the figure that the measured thickness is about 20nm. the

Fig. 5 is the luminescent image of the ladder-type electrode device prepared by the present invention observed by a fluorescence microscope. The area of the luminescent region is about 90×45 μm ² , and it can be seen that the luminescence uniformity of the device is relatively high.

Example 2:

Fabrication of organic electroluminescent devices with bow-tie patterned graphene electrodes. The device structure is: Graphene (graphene, ~20nm)/m-MTDATA(30nm)/NPB(20nm)/Alq ₃ (50nm)/LiF(1nm)/Al(100nm), as shown in Figure 2(a).

On the cleaned substrate, a metal deposition system is used to grow a gold electrode as an extraction electrode. During the growth process, the vacuum degree of the system is controlled at 1×10 ^-3 Pa, and a copper wire mask is left in the middle of the gold electrode with a width of about 50 μm channel, the thickness of the gold electrode is 15nm; then the graphene oxide is spin-coated on the gold electrode to completely cover the gold electrode and the channel in the middle, the spin-coating speed is 1200rpm, and the spin-coating time is 20s. In a vacuum oven at 40°C, the film was dried for 50 minutes; then the graphene oxide was reduced by laser, the processing process was the same as that described in Example 1, the selected laser power was 6mW, and single-point exposure The time is 2000μs. At the same time, graphene electrodes with bow-tie patterns were prepared through the control program. The contact mode between the reduced electrodes and the gold electrode channel is shown in Figure 2(b). The area of the bow-tie electrodes is about: 50× 25 μm ² ; Finally, in a multi-source organic molecule vapor deposition system, a hole injection layer, a hole transport layer, and a light-emitting layer are sequentially grown on the bow-tie graphene electrode as an electron transport layer and a cathode. The luminescence phenomenon of the device was observed with a fluorescence microscope.

Fig. 6 is the luminescent image of the bowtie electrode device prepared by the present invention observed by a fluorescence microscope. The area of the luminescent region is about 50×25 μm ² , and the device also shows a good luminous effect.

Claims (4)

1. A method for preparing an organic electroluminescent device based on laser reduction patterned graphene electrodes, characterized in that: first on a cleaned cover glass substrate, a metal deposition system is used to grow a gold electrode with a channel structure As the extraction electrode, the vacuum degree of the system is controlled at 1×10 ^-3 ~ 3×10 ^-3 Pa during the growth process, and a channel with a width of 50 ~ 120 μm is left in the middle of the gold electrode through a copper wire mask. The thickness is 15-20nm; then the suspension of graphene oxide is spin-coated on the gold electrode to completely cover the gold electrode and the channel in the middle position, the spin-coating speed is 1000-3000rpm, and the spin-coating time is 15- 20s, the thickness of graphene oxide is 80-100nm, put the spin-coated graphene oxide substrate into a vacuum oven, and dry it in a vacuum environment of 35-40°C for 40-60min; then use The point-by-point scanning laser direct writing processing system reduces the graphene oxide, and at the same time prepares a ladder-shaped or bow-tie patterned graphene electrode on the graphene oxide, and makes the graphene electrode overlap the channel On the gold electrodes on both sides, the thickness of the graphene electrode is 15-30nm, the lateral length is 20-150μm, and the vertical length is 40-300μm; finally, in the multi-source organic molecule vapor deposition system, holes are sequentially grown on the graphene electrode The injection layer, the hole transport layer, and the light-emitting layer are also used as the electron transport layer and the cathode, thereby preparing an organic electroluminescent device with patterned graphene as an electrode. 2. a kind of preparation method based on the organic electroluminescence device of laser reduction patterned graphene electrode as claimed in claim 1, it is characterized in that: the preparation of the suspension of graphene oxide is to mix 1～2g, average size It is a mixture of 500-600μm flake graphite, 1-2g sodium nitrate, 48-96mL concentrated sulfuric acid, 6-12g potassium permanganate, stir in a water bath at 0°C for 60-90min, and then heat up to 25-35°C Then continue to stir for 2 to 3 hours; then slowly add 40 to 80 mL of ultrapure water to the mixed solution within 30 minutes, and then add 100 to 200 mL of ultrapure water and 5 to 10 mL of hydrogen peroxide with a mass concentration of 30%; The precipitate after graphite oxidation is extracted by centrifugation, the centrifugal speed is 9000-12000r/s, the centrifugation time is 10-15min, and then the precipitate is washed repeatedly with ultra-pure water, so that the acidity is greatly weakened, so that the pH value is close to 7. Finally, ultrasonically treat the near-neutral precipitate for 5-10 minutes, thereby peeling off the graphite layer by layer to obtain a suspension of graphene oxide. 3. the preparation method of a kind of organic electroluminescent device based on laser reduction patterned graphene electrode as claimed in claim 1, it is characterized in that: the thickness of hole injection layer is 20～40nm, the thickness of hole transport layer 15-40nm, and the thickness of the light-emitting layer also serving as the electron transport layer is 40-60nm. 4. a kind of preparation method based on the organic electroluminescence device of laser reduction patterned graphene electrode as claimed in claim 1, is characterized in that: substrate is cover glass; Hole injection layer is m-MTDATA; The hole transport layer is NPB; the light-emitting layer is Alq ₃ , which is also used as an electron transport material; the cathode is a composite cathode LiF/Al.