A single-molecule electroluminescent device based on luminescent free radicals and a preparation method thereof

Abstract

The present invention relates to the technical field of electroluminescent devices, and particularly to a single-molecule electroluminescent device based on luminescent free radicals and a preparation method thereof. The single-molecule electroluminescent device based on luminescent free radicals includes an electroluminescent unit, a graphene dot source terminal electrode, and a graphene dot drain terminal electrode. The left end and the right end of the electroluminescent unit are respectively connected to the graphene dot source terminal electrode and the graphene dot drain terminal electrode through amide bonds or ester bonds to form a single-molecule luminescent free radical molecular field effect transistor. By selecting a single luminescent free radical molecule as the electroluminescent unit, the luminescent center at the molecular level can be precisely controlled, enabling high-efficiency, high-stability, and long-life electroluminescence. Moreover, the luminescent free radical molecule has the characteristic of efficient luminescence from the lowest doublet state to the ground state. The preparation method provided by the present invention has a simple preparation process and easy-to-control conditions, which helps to promote the development of the fields of electroluminescence and emerging quantum technologies.

Description

Technical Field

[0001] The present invention relates to the technical field of electroluminescent devices, and particularly to a single-molecule electroluminescent device based on luminescent radicals and a preparation method thereof. Background Art

[0002] Electroluminescence is a phenomenon in which a material emits photons by applying an electric field. Its basic principle is as follows: under the action of an external electric field, electrons and holes are injected into the material from the cathode and anode respectively. These carriers migrate in the material and finally recombine in the light-emitting layer, releasing energy and emitting it in the form of photons. An electroluminescent device is a display device that utilizes an electroluminescent material to emit light when excited.

[0003] Although traditional light-emitting devices have advantages such as self-luminescence and wide color gamut, they have limitations in terms of luminous efficiency, stability, and service life. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the related art. For this reason, the first object of the present invention is to provide a single-molecule electroluminescent device based on luminescent radicals; the second object of the present invention is to provide a preparation method of a light-emitting device.

[0005] In order to achieve the first object, the technical solution adopted by the present invention is as follows:

[0006] A single-molecule electroluminescent device based on luminescent radicals, comprising an electroluminescent unit, a graphene dot source electrode, and a graphene dot drain electrode. The left end and the right end of the electroluminescent unit are respectively connected to the graphene dot source electrode and the graphene dot drain electrode through an amide bond or an ester bond to form a single-molecule luminescent radical molecular field effect transistor;

[0007] Wherein, the electroluminescent unit is composed of single-molecule luminescent radical molecules, and the structural formula of the luminescent radical molecules is as follows:

[0008]

[0009] Or

[0010] ;

[0011] Wherein, R 1 is , , , and any one of, R 2 is OH or NH 2 .

[0012] Further, both the graphene source-terminal electrode and the graphene drain-terminal electrode are graphene nano-gap point electrodes.

[0013] Further, both the graphene source-terminal electrode and the graphene drain-terminal electrode are graphene array electrodes.

[0014] Further, the graphene source-terminal electrode and the graphene drain-terminal electrode are disposed on the hafnium oxide dielectric layer.

[0015] Further, the single-molecule luminescent free radical molecular field effect transistor is encapsulated with polydimethylsiloxane.

[0016] To achieve the second object, the technical solution adopted by the present invention is as follows:

[0017] A method for preparing a light-emitting device, for preparing the single-molecule electroluminescent device based on luminescent free radicals as described in any one of the above, including the preparation of a single-molecule luminescent free radical molecular field effect transistor, the steps are as follows:

[0018] S100. Prepare a graphene source-terminal electrode and a graphene drain-terminal electrode;

[0019] S200. Connect the left and right ends of the luminescent free radical molecule to the graphene source-terminal electrode and the graphene drain-terminal electrode respectively through an amide bond or an ester bond to obtain a single-molecule luminescent free radical molecular field effect transistor.

[0020] Further, the preparation process of step S200 is as follows: Under the protection of an inert gas, add the graphene source-terminal electrode, the graphene drain-terminal electrode, a carbonyl activating reagent, a luminescent free radical molecule, and anhydrous pyridine into a reaction vessel, react for 36 - 54 h, take out, rinse, and dry to obtain a single-molecule luminescent free radical molecular field effect transistor.

[0021] Further, the carbonyl activating reagent is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride.

[0022] Further, the concentration of the luminescent free radical molecule is 0.5×10 −4 ~1.5×10 −4 mol / L.

[0023] Further, it also includes step S300, and the process is as follows: Encapsulate the single-molecule luminescent free radical molecular field effect transistor in step S200 to obtain a single-molecule electroluminescent device based on luminescent free radicals.

[0024] One or more of the above technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0025] A single-molecule electroluminescent device based on luminescent free radicals provided by the present invention selects a single luminescent free radical molecule as the functional molecule, can precisely control the luminescence center at the molecular level, can achieve high-efficiency, high-stability and long-life electroluminescence, and the luminescent free radical molecule has the characteristic of efficient luminescence from the lowest doublet state to the ground state.

[0026] A preparation method of a light-emitting device provided by the present invention has a simple preparation process and easy-to-control conditions, can achieve single-photon generation with controllable wavelength, high purity and high efficiency, and helps to promote the development of the fields of electroluminescence and emerging quantum technologies.

[0027] Additional aspects and advantages of the present invention will be given in part in the following description, will become apparent in part from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic structural diagram of a single-molecule electroluminescent device based on luminescent free radicals provided in Embodiment 3 of the present invention.

[0029] Figure 2 is the detection result of the electrical characteristics of the single-molecule luminescent free radical molecular field effect transistor provided in Embodiment 3 of the present invention.

[0030] Figure 3 is the detection result of the light-emitting point of a single-molecule electroluminescent device based on luminescent free radicals provided in Embodiment 3 of the present invention.

[0031] REFERENCE SIGNS

[0032] 1. Gate; 2. Dielectric layer; 31. Electroluminescent unit; 32. Graphene dot source terminal electrode; 33. Graphene dot drain terminal electrode. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts fall within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0034] In the following embodiments, the experimental methods used are all conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0035] According to a specific embodiment provided by the present invention, a single-molecule electroluminescent device based on luminescent free radicals, such asFigure 1 As shown, it includes a gate 1, a dielectric layer 2, and a single-molecule light-emitting free radical molecular field effect transistor (not shown in the figure) arranged longitudinally in sequence;

[0036] Among them, the single-molecule light-emitting free radical molecular field effect transistor includes an electroluminescent unit 31, a graphene source electrode 32, and a graphene drain electrode 33. The left end and the right end of the electroluminescent unit 31 are respectively connected to the graphene source electrode 32 and the graphene drain electrode 33 through amide bonds or ester bonds to form a single-molecule light-emitting free radical molecular field effect transistor;

[0037] Among them, the electroluminescent unit is composed of single-molecule light-emitting free radical molecules, and the structural formula of the light-emitting free radical molecules is as follows:

[0038]

[0039] or

[0040] ;

[0041] Among them, R 1 is , , , and any one of, R 2 is OH or NH 2 ;

[0042] The light-emitting free radical molecules can be prepared through any of the following routes:

[0043]

[0044] or

[0045] .

[0046] Example 1

[0047] Preparation , the process is as follows:

[0048] Under a nitrogen atmosphere and in the dark, (0.5 mmol), (0.54 mmol), Pd(PPh 3 ) 4 (0.04 mmol), toluene (10 mL), K 3 PO 4An aqueous solution (6 mL) and ethanol (4 mL) were added to a two-necked flask. After stirring and reacting at 90 °C for 48 h, the reaction mixture was cooled to room temperature, and 5% hydrochloric acid was gradually added until no bubbles were generated. Then, extraction was carried out with dichloromethane, and the organic phase was separated and dried with MgSO 4 . Finally, the crude product was purified by silica gel column chromatography (using a volume ratio of petroleum ether to dichloromethane of 3:1 as the eluent) to obtain .

[0049] Under a nitrogen atmosphere, (0.2 mmol), (0.44 mmol), Pd(PPh 3 ) 4 (0.015 mmol), CuI (0.03 mmol), triethylamine (4 mL) and tetrahydrofuran (30 mL) were added to a two-necked flask. Then, after continuously stirring and reacting at 90 °C for 12 h, the mixture was cooled to room temperature, and extraction was carried out with dichloromethane. The organic phase was collected and dried with Na 2 SO 4 . The crude product was further purified by silica gel column chromatography (using a volume ratio of petroleum ether to ethyl acetate of 3:1 as the eluent) to obtain ;

[0050] 1 1H NMR (500 MHz, chloroform- d ) : δ 8.09 (dd, J = 7.3, 1.6 Hz, 1H), 7.97 – 7.92(m, 1H), 7.92 – 7.88 (m, 1H), 7.88 – 7.81 (m, 3H), 7.61 (dd, J = 7.4, 1.7 Hz,1H), 7.55 – 7.47 (m, 6H), 7.38 (d, J = 1.6 Hz, 1H), 7.36 (s, 4H), 7.31 – 7.25(m, 1H), 7.25 – 7.19 (m, 1H), 5.36 (s, 1H), 2.89 – 2.73 (m, 4H), 2.50 (t, J =6.2 Hz, 4H), 2.47 – 2.35 (m, 4H), 1.79 – 1.60 (m, 4H);

[0051] HRMS (ESI + ) m / z: [M] + C51 H 37 Cl 6 N 3 The calculated value is 901.1113; the actual value is 901.1105.

[0052] Under a nitrogen atmosphere and in the dark, (0.1 mmol), an aqueous solution of tetrabutylammonium hydroxide with a mass concentration of 40% (0.26 mmol), and tetrahydrofuran (30 mL) were added to a two-necked flask. After stirring at room temperature for 12 h, chloranil (0.28 mmol) was added to the reaction system, and the reaction was continued with stirring for 1 h. The crude reaction product was purified using a silica gel column chromatography pretreated with triethylamine (using a volume ratio of petroleum ether to ethyl acetate of 3:1 as the eluent) to obtain ;

[0053] HRMS (ESI + ) m / z: [M] + C 51 H 36 Cl 6 N 3 The calculated value is 900.1035, and the actual value is 900.1022.

[0054] Example 2

[0055] Preparation of , the process is as follows:

[0056] Under a nitrogen atmosphere and in the dark, (0.5 mmol), (0.54 mmol), Pd(PPh 3 ) 4 (0.04 mmol), toluene (9 mL), an aqueous solution of K 2 CO 3 (6 mL), and ethanol (4 mL) were added to a two-necked flask and stirred at 90 °C for 48 h; after the reaction was completed, the reaction mixture was cooled to room temperature, and 5% hydrochloric acid was gradually added until no bubbles were generated, and then extracted with dichloromethane. The organic phase was separated and dried with MgSO 4 . Finally, the crude product was purified by silica gel column chromatography (using a volume ratio of petroleum ether to dichloromethane of 3:1 as the eluent) to obtain .

[0057] Under a nitrogen atmosphere, (0.2 mmol), (0.44 mmol), Pd(PPh 3 ) 4(0.015 mmol), CuI (0.03 mmol), triethylamine (4 mL) and tetrahydrofuran (30 mL) were added to a two-necked flask. Then, after continuously stirring the reaction at 90 °C for 12 h, the mixture was cooled to room temperature and extracted with dichloromethane. Subsequently, the organic phase was collected and dried with Na 2 SO 4 . The crude product was further purified by silica gel column chromatography (using a volume ratio of petroleum ether to ethyl acetate of 10:1 as the eluent) to obtain ;

[0058] 1 1H NMR (500 MHz, chloroform- d ) δ 8.10 (s, 1H), 7.97 – 7.91 (m, 2H), 7.91 –7.81 (m, 3H), 7.65 – 7.58 (m, 2H), 7.56 – 7.45 (m, 3H), 7.38 (dd, J J = 7.4, 1.5Hz, 1H), 7.25 (dtd, J J = 24.9, 7.5, 1.7 Hz, 2H), 5.37 (s, 1H), 4.32 (t, J J = 6.0Hz, 2H), 3.73 – 3.58 (m, 4H), 2.58 – 2.45 (m, 4H), 1.84 – 1.67 (m, 4H);

[0059] HRMS (ESI + ) m / z: [M] + + calculated for C 51 H 29 Cl 12 NO 2 1106.8455, found 1106.8467.

[0060] Under a nitrogen atmosphere and in the dark, (0.1 mmol), an aqueous solution of tetrabutylammonium hydroxide with a mass concentration of 40% (0.26 mmol) and tetrahydrofuran (30 mL) were added to a two-necked flask. After stirring at room temperature for 12 h, chloranil (0.28 mmol) was added to the reaction system, and the reaction was continued with stirring for 1 h. The crude reaction product was purified by silica gel column chromatography pretreated with triethylamine (using a volume ratio of petroleum ether to ethyl acetate of 10:1 as the eluent) to obtain ;

[0061] HRMS (ESI +) m / z: [M] + C 51 H 28 Cl 12 NO 2 The calculated value is 1105.8377, and the actual value is 1105.8367.

[0062] Example 3 Preparation of a single-molecule electroluminescent device based on luminescent radicals.

[0063] I. Preparation of the gate and dielectric layer.

[0064] A silicon wafer with a 300-nm-thick silicon oxide coating on its surface was cut into 1×1 cm 2 squares, placed in a piranha solution (the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 7:3), heated on a hot plate to 110 °C for 4 h, ultrasonically cleaned with ultrapure water for 15 minutes, cleaned three times, dried with nitrogen, and a cleaned silicon wafer was obtained. 8 nm of chromium and 60 nm of gold were thermally evaporated on this silicon wafer;

[0065] According to the positions of the evaporated chromium and gold, a 30-nm-thick aluminum film was deposited on the surface of the silicon wafer using an ion beam sputtering system, the glue was removed with acetone, and a dense aluminum oxide was naturally oxidized on the surface of the aluminum film as the dielectric layer, while the metal aluminum served as the gate, and the gate was connected to the chromium and gold evaporated on the surface of the silicon wafer.

[0066] To prevent leakage in the optoelectronic device, a 5-mm-thick hafnium oxide layer was prepared on the surface of the aluminum oxide dielectric layer by the sol-gel method to obtain a hafnium oxide dielectric layer. The process of preparing the hafnium oxide dielectric layer by the sol-gel method is as follows: A hafnium chloride solution was prepared in a glove box, and the molar ratio of HfCl 4 , EtOH, HNO 3 and H 2 O in this solution was 1:350:10:5. After the prepared hafnium chloride was taken out, it was heated in an oil bath at 50 °C for 3 h; spin-coated on the above-mentioned silicon wafer coated with an aluminum film, and maintained at a rotation speed of 6000 rpm for 35 s; left standing for 1 h and then treated with ultraviolet-ozone radiation (Ultraviolet-Ozone, UVO) for 1 h; then placed in a quartz reactor and treated with ultraviolet (ultraviolet, UV) for 3 h, and then slowly heated to 200 °C in a tube furnace under an atmospheric environment and maintained for 1 h to obtain a hafnium oxide dielectric layer.

[0067] II. Preparation of a single-molecule luminescent radical field-effect transistor.

[0068] (I). Preparation of the graphene source-terminal electrode and the graphene drain-terminal electrode, the process is as follows:

[0069] Soak the cut copper sheet (2 cm wide, 5 cm long, 25 μm thick) in acetic acid for about 15 minutes, rinse it 3 times with ultrapure water and ethanol in sequence, and then dry it at 80 °C. After that, put the dried copper sheet into a chemical vapor deposition (CVD) tube furnace and evacuate it with a mechanical pump until the vacuum degree is less than 1 Pa, then pass hydrogen with a flow rate of 16 cm 3 ·min –1 , open the tube furnace and heat it up to 1030 °C. Calculate the heating time starting from room temperature. After heating for 1 h, adjust the hydrogen flow rate to 8 cm 3 ·min –1 , and at the same time open the carbon source (methane) with a flow rate of 1.6 cm 3 ·min –1 . After maintaining for 25 minutes, close the tube furnace and let it cool down naturally. Adjust the hydrogen flow rate back to 16 cm 3 ·min –1 , and adjust the methane flow rate to 0.8 cm 3 ·min –1 . When the temperature drops to 600 °C, turn off the carbon source, continue to cool down to 200 °C, open the lid of the tube furnace to accelerate cooling, and when the temperature drops to 100 °C, take out the copper sheet with grown graphene;

[0070] Cut the copper sheet with grown graphene into 1×2 cm 2 squares, stick them on a clean quartz sheet with transparent tape, and spin-coat the polymethyl methacrylate (950 PMMA) polymer. Heat it at 180 °C for 2 minutes. Cut off the edges of the copper sheet and the places where the transparent tape has been stuck, and at the same time cut each copper sheet into two equal pieces (each piece is about 0.9×0.9 cm 2 ). Place it with the back side up and the PMMA-coated side down in a clean petri dish, and etch the graphene grown on the back side of the copper sheet with oxygen plasma;

[0071] Among them, during the process of spin-coating 950 PMMA on the spin coater, first spin-coat at a speed of 600 rpm for 6 seconds, and then maintain at a speed of 4000 rpm for 40 seconds;

[0072] During the process of etching the graphene grown on the back side of the copper sheet with oxygen plasma, keep the power at 50 W and etch for 50 seconds;

[0073] Place the etched copper sheet face down in a 2 M ferric chloride solution and soak until the copper sheet is completely corroded; transfer the graphene to dilute hydrochloric acid solutions with concentrations of 10 mM, 5 mM, and 1 mM in sequence using a clean silicon wafer, and soak in each dilute hydrochloric acid solution for 30 minutes; then transfer it to ultrapure water and let it stand for 30 minutes; then wash it clean, transfer the graphene to a 1 M potassium hydroxide solution and let it stand for about 1.5 hours; then transfer it to ultrapure water, ultrapure water, 1 mM dilute hydrochloric acid solution, ultrapure water, and ultrapure water in sequence, and let it stand for 15 minutes each; then transfer the graphene to the above hafnium oxide dielectric layer and let it stand until the surface water evaporates; then put it into hot acetone for 10 minutes to remove PMMA, and dry it with nitrogen to obtain monolayer graphene;

[0074] Lithograph graphene strips with a width of 40 μm and a length of 200 μm, and use oxygen plasma etching to etch away the exposed graphene through oxygen plasma etching. Due to the protection of the photoresist, the required part of the graphene strip is left, and dissolve the photoresist with acetone;

[0075] Lithograph the electrodes, thermally evaporate 8 nm of chromium and 60 nm of gold, and remove the glue with acetone to obtain a graphene array electrode;

[0076] Among them, there are 24 electrodes on each graphene, generating 23 channels for connecting molecules; and there are 9 graphene strips on one silicon wafer, with a total of 207 channels.

[0077] Heat the surface of the graphene array electrode at 180 °C for 2 minutes, spin-coat 950 PMMA. First, spin-coat at a speed of 600 rpm for 6 seconds, and then maintain at a speed of 4000 rpm for 40 seconds; use an electron beam to etch a dotted line with a total length of 60 μm in the middle of each channel. The length of each dotted line is 150 nm, the width is 5 nm, and the interval between the dotted lines is 40 nm; after electron beam etching, soak the graphene array electrode in a solution of methyl isobutyl ketone diluted with isopropyl alcohol (volume ratio: methyl isobutyl ketone / isopropyl alcohol = 1 / 3) for development to obtain a graphene dot electrode, which includes a graphene source-end dot electrode and a graphene drain-end dot electrode;

[0078] Etch the above graphene dot electrode using oxygen plasma, and the graphene at both ends of the channel is interrupted; during the step-by-step etching process, continuously test the current values at both ends of the channel to achieve a channel width at the nanometer level; after etching is completed, remove the PMMA with acetone, and burn off the other channels that are not interrupted with Joule heat in the air to obtain a graphene nano-gap dot electrode.

[0079] (2) Connect the left and right ends of the luminescent radical molecule to the graphene source-end dot electrode and the graphene drain-end dot electrode respectively through amide bonds or ester bonds to obtain a single-molecule luminescent radical molecule field-effect transistor, and its preparation process is as follows:

[0080] Under a nitrogen protection environment, the graphene nano-gap point electrode prepared above, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (60×10 −4 M, 1 ml), the luminescent radical molecule obtained in Example 1 (1×10 −4 M, 1 ml) and anhydrous pyridine (10 mL) were added to a 50 mL two-necked flask. After standing and reacting for 48 hours, it was taken out, rinsed with ultrapure water and acetone respectively, and dried with nitrogen. The left and right ends of the luminescent radical molecule were respectively connected to the graphene source-end electrode and the graphene drain-end electrode through amide bonds to form a single-molecule luminescent radical molecule field-effect transistor; the single-molecule luminescent radical molecule field-effect transistor was detected, and the results are as Figure 2 shown. These results indicate that, under a constant bias voltage, the field-effect transistor exhibits electrical characteristics that vary with the gate voltage, indicating that the luminescent radical molecule has been successfully connected to the graphene nano-gap point electrode and can be regulated by changing the gate voltage.

[0081] III. Encapsulating the single-molecule luminescent radical molecule field-effect transistor, the process is as follows:

[0082] The polydimethylsiloxane precursor and the cross-linking agent were fully mixed and spin-coated on the single-molecule luminescent radical molecule field-effect transistor prepared above for encapsulation to obtain a single-molecule electroluminescent device based on luminescent radicals. The luminescent spots were detected, and the results are as Figure 3 shown.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A single-molecule electroluminescent device based on luminescent free radicals, characterized in that, it includes an electroluminescent unit, a graphene dot source terminal electrode and a graphene dot drain terminal electrode. The left end and the right end of the electroluminescent unit are respectively connected to the graphene dot source terminal electrode and the graphene dot drain terminal electrode through amide bonds or ester bonds to form a single-molecule luminescent free radical molecular field effect transistor; wherein, the electroluminescent unit is composed of single-molecule luminescent free radical molecules, and the structural formula of the luminescent free radical molecules is shown as follows: or ； Among them, R 1 is , R 2 is OH or NH 2 .

2. The single-molecule electroluminescent device based on luminescent free radicals according to claim 1, characterized in that, both the graphene dot source terminal electrode and the graphene dot drain terminal electrode are graphene nano-gap point electrodes.

3. The single-molecule electroluminescent device based on luminescent free radicals according to claim 1, characterized in that, both the graphene dot source terminal electrode and the graphene dot drain terminal electrode are graphene array electrodes.

4. The single-molecule electroluminescent device based on luminescent free radicals according to claim 1, characterized in that, the graphene dot source terminal electrode and the graphene dot drain terminal electrode are disposed on a hafnium oxide dielectric layer.

5. The single-molecule electroluminescent device based on luminescent free radicals according to claim 1, characterized in that, the single-molecule luminescent free radical molecular field effect transistor is encapsulated with polydimethylsiloxane.

6. A preparation method of a light-emitting device, characterized in that, it is used to prepare the single-molecule electroluminescent device based on luminescent free radicals according to any one of claims 1 to 5, including the preparation of a single-molecule luminescent free radical molecular field effect transistor, and the steps are as follows: S100. Prepare the graphene dot source terminal electrode and the graphene dot drain terminal electrode; S200. Connect the left and right ends of the luminescent free radical molecules to the graphene dot source terminal electrode and the graphene dot drain terminal electrode respectively through amide bonds or ester bonds to obtain a single-molecule luminescent free radical molecular field effect transistor.

7. The preparation method of the light-emitting device according to claim 6, characterized in that, the preparation process of step S200 is as follows: under the protection of an inert gas, add the graphene dot source terminal electrode, the graphene dot drain terminal electrode, a carbonyl activating reagent, the luminescent free radical molecules and anhydrous pyridine into a reaction vessel, react for 36 - 54 h, take out, rinse and dry to obtain a single-molecule luminescent free radical molecular field effect transistor.

8. The preparation method of the light-emitting device according to claim 7, characterized in that, the carbonyl activating reagent is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride.

9. The preparation method of the light-emitting device according to claim 7, characterized in that, The concentration of the luminescent free radical molecules is 0.5×10 −4 ~1.5×10 −4 mol / L.

10. The preparation method of the light-emitting device according to claim 6, characterized in that, it further includes step S300, and the process is as follows: encapsulate the single-molecule luminescent free radical molecular field effect transistor in step S200 to obtain a single-molecule electroluminescent device based on luminescent free radicals.

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