Tunable polarized photon source based on perovskite quantum dots and preparation method thereof

Abstract

The present invention relates to the technical field of molecular optoelectronic devices, and specifically discloses a tunable polarized photon source based on perovskite quantum dots and a preparation method thereof, the method comprising the following steps: transferring a graphene-PMMA structure to a silicon wafer surface and marking a pattern; making an external electrode on the graphene according to the pattern; making a graphene electrode pair; preparing a chiral molecule with adjustable chirality: condensing the chiral molecule with graphene electrode amide, then adding a perovskite quantum dot precursor solution to react, and in-situ assembling the quantum dots between the graphene electrode pairs to obtain a tunable polarized photon source. The present invention is based on a graphene electrode single-molecule device of a dotted line etching method, constructs a circularly polarized photon source, connects chiral molecules at the edge of a graphene electrode, and introduces a chiral site to in-situ assemble quantum dots, constructs high-quality, morphology-controllable quantum dots, greatly improves the molecular connection success rate, and shortens the molecular connection cycle.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular optoelectronic devices, and in particular to a tunable polarized photon source based on perovskite quantum dots and a preparation method thereof. Background Art

[0002] Quantum systems are fundamentally different from traditional classical systems in terms of working principles and operation methods, and require the support of new hardware and new modules. Among them, circularly polarized photon sources play an important role in quantum computing, quantum communication, and information processing. Since the spin angular momentum of photons is associated with the circular polarization state, circularly polarized single photon sources can be used as carriers for manipulating and transmitting quantum information in quantum computing. In particular, in certain quantum computing models, the polarization state of a single photon can be directly mapped to the state of a quantum bit. By precisely controlling circularly polarized light, quantum bits can be operated and quantum logic gates can be triggered to perform complex quantum logic operations and quantum algorithms. In quantum information processing, circularly polarized single photon sources can be used to realize the transmission of quantum information and build quantum communication networks. In quantum communication protocols such as quantum key distribution, circularly polarized light can be used to encode information. By connecting static bits with flying quantum bits, information transmission in quantum networks and interaction between nodes can be realized, thereby achieving long-distance quantum information transmission while maintaining information security.

[0003] At present, the main technologies for preparing single-photon sources include parametric down-conversion triggered single-photon sources, high-quality factor low-mode volume microring resonant optical microcavities, and single-photon sources based on quantum dots. In comparison, single-photon sources based on quantum dots have attracted much attention due to their unique advantages such as small size, tunable emission wavelength, high efficiency, and high purity of emitted photons. Among them, CsPbX 3 Perovskite quantum dots are a good candidate for the preparation of single-photon sources because of their low chemical synthesis cost, controllable size and morphology, adjustable composition, long coherence time and fast radiation lifetime. However, the quantum dot single-photon source devices reported so far are difficult to integrate with existing optical and electronic systems, making it difficult to achieve more complex quantum information processing functions. At the same time, how to achieve high-efficiency and high-purity controllable emission of circularly polarized light in single-photon sources is also a major difficulty.

[0004] Graphene-based single-molecule devices are an important method for constructing stable single-molecule nanodevices. Graphene, a carbon material with a unique two-dimensional structure, has attracted much attention since its discovery in 2004 due to its excellent electron mobility, thermal conductivity, mechanical strength, and transparency. Graphene-based single-molecule devices take advantage of these excellent properties of graphene. By preparing graphene into electrodes, it is possible to construct stable and interface-controllable single-molecule-level electronic devices. With the development of nano-processing technology, the preparation of graphene-based single-molecule devices has become more and more sophisticated, and more precise atomic-level manipulation can be achieved to form the required electrode structure edge configuration and a certain nanogap. At present, graphene-based single-molecule devices have successfully constructed a variety of molecular electronic devices including field-effect transistors, switches, rectifiers, memristors, and light-emitting diodes. These devices not only show broad application prospects in chip miniaturization, integration, and multifunctionality, but also their unique physical and chemical properties bring new opportunities to quantum information technology, biosensing, energy conversion, and other fields.

[0005] By constructing a circularly polarized photon source on a graphene base and then designing a bridge-connected chiral molecule, a light-controlled tunable polarized photon source can be realized. It can control the emission of different polarized photons, including linearly polarized and circularly polarized photons, by light-controlling the spiral chiral structure. At the same time, the self-assembly method of synthesizing quantum dots in situ in the gap between graphene electrodes defined with atomic-level precision has the natural advantages of miniaturization, high connection rate, easy integration, and convenient functional design. It can overcome the problem that quantum dot single-photon source devices are difficult to integrate with existing optoelectronic systems and difficult to control single-photon emission. However, the connection rate of this method is only 30-50%, and the low connection rate brings problems of difficulty in integration and long preparation cycle. Summary of the invention

[0006] The present invention aims to solve the problems of integration difficulties and long preparation cycle caused by the low connection rate of tunable polarized photon sources. To this end, the present invention provides a tunable polarized photon source based on perovskite quantum dots and a preparation method thereof, a graphene electrode single-molecule device based on the dotted line etching method, a circularly polarized photon source is constructed, and a method of connecting chiral molecules at the edge of the graphene electrode, introducing chiral sites and then assembling quantum dots in situ is adopted to construct quantum dots with high quality and controllable morphology, so that the molecular connection success rate is greatly improved while shortening the molecular connection cycle. The chirality of the chiral molecule spiral can be tuned by light of different wavelengths, thereby controlling the polarization state of the electrons injected into the core of the quantum dot, and then realizing the polarization state of the photons emitted by the optical wavelength control device, making polarization-controlled luminescence possible, and using different polarized light illumination of the corresponding band for photoexcitation, as well as polarized photon statistical counting, to verify its controllable polarized luminescence performance.

[0007] The present invention provides a method for preparing a tunable polarized photon source based on perovskite quantum dots, and the technical scheme adopted is as follows: comprising the following steps:

[0008] S1: fabricate graphene-PMMA structure, transfer graphene-PMMA structure to silicon wafer surface and mark the pattern;

[0009] S2: making external electrodes on graphene according to the pattern;

[0010] S3: fabricating graphene electrode pairs according to the pattern;

[0011] S4: Preparation of chiral molecules with tunable chirality:

[0012] S5: Condensation of chiral molecules with graphene electrode amide, and then adding perovskite quantum dot precursor solution to react, assembling quantum dots in situ between graphene electrode pairs to obtain a tunable polarized photon source.

[0013] Furthermore, S3 includes the following steps:

[0014] S31: Spin-coating photoresist on the silicon wafer according to the dotted lines of the pattern, and performing electron beam exposure on the silicon wafer with the photoresist spun on, so that the graphene is exposed at the pattern exposure position, and the other parts are covered and protected by the photoresist, and after development, a dotted line is formed between the electrode pairs;

[0015] S32: Etching the silicon wafer using a plasma etcher according to the dotted lines between the electrode pairs to produce graphene electrode pairs. During the etching process, the preparation of the electrode pairs is evaluated by monitoring the magnitude of the current between the electrode pairs and the shape of the curve.

[0016] Furthermore, in S32, the graphene electrode pair is a triangular electrode pair with a gap of 5 nm.

[0017] Furthermore, the chiral molecule has a chiral site on its molecular skeleton, and the chiral site is tunable. The first end of the chiral molecule has a group for connecting to a carboxyl group formed by oxidation of a graphene electrode, and the second end of the chiral molecule has a group for supporting a nucleation site required for assembling a quantum dot core.

[0018] Furthermore, the structure of the chiral molecule is as follows:

[0019] .

[0020] Further, S5 includes the following steps:

[0021] S51: connecting the chiral molecule to the edge of the graphene electrode through amide condensation of the chiral molecule and the graphene electrode, thereby obtaining a graphene electrode connected with the chiral molecule;

[0022] S52: By adding a perovskite quantum dot precursor solution, the quantum dot core is in situ assembled at the nucleation site of the graphene electrode connected to the chiral molecule, and a PMMA solution is dripped thereon to form a protective layer to obtain a tunable polarized photon source.

[0023] Further, S51 includes the following steps:

[0024] The chiral molecule and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride are placed in a pyridine solution to obtain a mixed solution; a graphene electrode pair is placed in the mixed solution to react in a dark nitrogen atmosphere, and then PbI is added 2 The reaction was continued, and finally the graphene electrode connected to the chiral molecule was obtained by washing with acetone and ultrapure water and drying.

[0025] Further, S52 includes the following steps:

[0026] Perovskite quantum dot precursor solution includes PbI 2 Precursor solution and Cs-DOPA precursor solution;

[0027] In a nitrogen environment, the graphene electrode connected to the chiral molecule is first immersed in PbI 2 The precursor solution was allowed to react, then immersed in an ice-water bath of Cs-DOPA precursor solution, and then PbI was added to its surface. 2 The precursor solution is then rinsed with HEX, and the above steps are repeated many times; then the graphene electrode connected to the chiral molecule is immersed in the Cs-DOPA precursor solution and heated, taken out and blown dry after the reaction, and then PMMA solution is dripped on its surface and rotated to form a PMMA protective layer to obtain a tunable polarized photon source.

[0028] The present invention also provides a tunable polarized photon source based on perovskite quantum dots, which is prepared by using the above-mentioned method for preparing a tunable polarized photon source based on perovskite quantum dots.

[0029] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0030] 1. The present invention can design the electrode position and hole position by itself through in-situ drawing of external electrodes and electron beam exposure etching process, and has strong integrated design at the nanoscale. A row of equidistant dotted lines is designed between an electrode pair, and finally an array structure can be obtained.

[0031] 2. The present invention prepares the graphene electrode gap by monitoring the tunneling current and using plasma etching, introduces chiral molecules and terminal nucleation sites, and assembles quantum dots in situ, which has the advantages of high connection rate and connection efficiency. The connection rate is increased from 30-50% to more than 90%. 20 devices are randomly selected from the prepared multiple devices to test their connection rate, overcoming the integration difficulties and long preparation cycle caused by the low connection rate. The current of tens of nanoamperes and the volt-ampere characteristic curve with semiconductor characteristics indicate that quantum dots are successfully assembled between the graphene electrode pairs. At the same time, the quantum dots defined by the graphene gap have better size dispersity than the molecular devices formed by solution phase synthesis and reconnection. By testing and comparing the normalized fluorescence emission curves of the solution phase and in situ self-assembled devices, it can be seen that both can be fitted with Gaussian curves, but the in situ self-assembled quantum dots defined by the graphene nano-gap have narrower fluorescence emission peaks, indicating that their size is more uniform and controllable and of higher quality.

[0032] 3. The present invention assembles quantum dots by defining the nano-gap of graphene electrodes and coating them with PMMA as a protective layer, thereby making the device more stable while maintaining its miniaturization. The device still maintains an 85% survival rate after being left at room temperature for 2 months, and basically no degradation occurs.

[0033] 4. The present invention introduces tunable chiral molecules, injects spin-polarized electron holes, and makes them compound to emit polarized light in the central perovskite quantum dot. It can control the switch of the spiral chiral structure by irradiating light of different wavelengths, and then control the polarization state of the emitted photons, and use polarized light of the corresponding band for photoexcitation, thereby obtaining the light polarization-dependent photoconductivity phenomenon and photon polarization state statistics.

[0034] 5. The present invention provides a prerequisite for the functional introduction of connecting molecules by electrically defining in-situ self-assembled quantum dots through controllable gap graphene, while also improving the quality and stability of the quantum dot core, reducing the broadening of the fluorescence emission peak caused by uneven size and the interference of ligand exchange randomness on its polarized luminescence, and providing a basis for the preparation of a photon source with controllable polarization state. At the same time, the self-assembly method increases the connection success rate to more than 90%, and shortens the preparation cycle by 24 hours, providing a basis for circuit integration design. Finally, by introducing chiral molecules with special structures to form a light-controlled chiral switch, a polarization-controllable photon source centered on perovskite quantum dots is realized, providing a new idea for the construction of a controllable polarization photon source.

[0035] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 It is a flow chart of the method provided by the present invention.

[0038] Figure 2 This is a parallel integrated graphene electrode diagram provided by the present invention.

[0039] Figure 3 It is a synthesis flow chart of the chiral molecule provided by the present invention.

[0040] Figure 4 It is a schematic diagram of the structure of the tunable polarization photon source provided by the present invention.

[0041] Figure 5 It is a schematic diagram of the three-dimensional structure of the tunable polarization photon source provided by the present invention.

[0042] Figure 6 It is a comparison diagram between the Gaussian fitting curve of this method and the Gaussian fitting curve of solution phase synthesis.

[0043] Figure 7 It is a normalized photon polarization state count diagram of the tunable polarized photon source in the circular polarization mode after irradiation with 600nm visible light provided by the present invention.

[0044] Figure 8 It is a curve diagram of conductivity change under circularly polarized light of the tunable polarized photon source provided by the present invention.

[0045] Fig. 9 It is a normalized photon polarization state count diagram in the linear polarization mode of the tunable polarized photon source after irradiation with 400nm visible light provided by the present invention.

[0046] Reference numerals:

[0047] 1. Graphene electrode; 2. Quantum dots; 3. Silicon wafer; 4. PMMA protective layer; 5. Chiral molecules. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are 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.

[0049] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0050] Combine the following Figures 1 to 9 The present invention is further described in detail, and a tunable polarized photon source based on perovskite quantum dots and a preparation method thereof are described as follows:

[0051] In this embodiment, Figure 1 As shown, a method for preparing a tunable polarized photon source based on perovskite quantum dots is provided, comprising the following steps:

[0052] S1: Prepare graphene-PMMA structure, transfer the graphene-PMMA structure to the silicon wafer surface and mark the pattern.

[0053] The specific process is: soak and clean the silicon wafer with 110°C piranha solution for 2-4 hours, then use acetone, anhydrous ethanol, and ultrapure water for ultrasonic cleaning, and blow dry with nitrogen for later use.

[0054] Take a section of copper foil and soak it in 36% acetic acid for 10-15 minutes to remove the copper oxide on the surface, rinse it with ethanol and ultrapure water, and blow it dry for later use. Grow graphene on the surface of copper foil using chemical vapor deposition. Spin-coat PMMAA5950 photoresist on the graphene and cut it into the size of a silicon wafer to form a copper foil-graphene-PMMA structure.

[0055] The back of the copper foil was cleaned by plasma etching and then transferred to a ferric chloride solution and left to stand for 1-2 hours. After the copper foil was completely corroded, the graphene-PMMA was transferred to 5mmol / L dilute hydrochloric acid solution, 3mmol / L dilute hydrochloric acid solution, 1mmol / L dilute hydrochloric acid solution, ultrapure water, 1mmol / L potassium hydroxide solution, ultrapure water, 1mmol / L dilute hydrochloric acid solution, 0.5mmol / L dilute hydrochloric acid solution, and ultrapure water respectively. It was left to stand and clean for 0.5 hours and finally transferred to the clean silicon wafer surface to dry. The pattern was made by ultraviolet exposure, and 8nm of chromium and 50nm of gold were evaporated by thermal resistance evaporation coating instrument, and the pattern was formed after removing the glue for subsequent photolithography alignment.

[0056] S2: Make external electrodes on graphene according to the pattern.

[0057] The specific process is: according to the pattern, the graphene is photoetched into a suitable size by plasma etching. Then, the external electrode is photoetched on the graphene according to the pattern, and 8nm of chromium and 80nm of gold are evaporated to produce the external electrode.

[0058] S3: Fabricate graphene electrode pairs according to the pattern.

[0059] The specific steps include:

[0060] S31: According to the dotted lines of the pattern, PMMA A5 950 photoresist is spin-coated on the silicon wafer, and the silicon wafer with the PMMA A5 950 photoresist spin-coated is subjected to electron beam exposure, where the graphene is exposed at the pattern exposure position, and other parts are covered and protected by the photoresist, and dotted lines are formed between the electrode pairs after development.

[0061] S32: According to the dotted lines between the electrode pairs, the silicon wafer is etched with a plasma etcher to produce a graphene electrode pair. During the etching process, the preparation of the electrode pair is evaluated by monitoring the current between the electrode pairs and the shape of the curve. Usually, under a bias voltage of 1V, a microampere current and a linear volt-ampere characteristic curve represent that the graphene is not disconnected. When the current magnitude gradually decreases with the increase of etching time, it means that the holes on the graphene are gradually expanding, causing the graphene conductive channel between the electrode pairs to slowly narrow, and the electrode gap is about to form. When the current magnitude reaches a few nanoamperes and the volt-ampere characteristic curve is nonlinear, specifically manifested as having a certain turn-on voltage, it represents the formation of a graphene gap. The gap size can be evaluated by the tunneling current size, and finally a triangular electrode pair with a gap size of about 5nm is obtained, that is, a graphene electrode pair is produced, and the emission wavelength is about 700nm under the quantum dot size defined by the gap of about 5nm.

[0062] In this step, parallel integrated graphene electrodes are produced on silicon wafers, such as Figure 2 shown. Figure 2 The arrows in the figure indicate the nanogap formed between the graphene electrode pairs.

[0063] S4: Preparation of chiral molecules with tunable chirality.

[0064] Specifically, the chiral molecule needs to have a chiral site on its molecular skeleton, the chiral site is tunable, the first end of the chiral molecule needs to have a group for connecting with the carboxyl group formed by oxidation of the graphene electrode, and the second end of the chiral molecule needs to have a group for supporting the nucleation site required for assembling the quantum dot core. The chiral molecule has two-handed chiral sites and can be chirally separated.

[0065] This example provides a specific chiral molecule, the structure of which is shown below:

[0066] .

[0067] After being irradiated with light at about 600nm, the ring-closed structure of the chiral molecule is as follows:

[0068] .

[0069] like Figure 3 As shown, the specific synthesis steps of the above chiral molecule are:

[0070] S41: Synthesis of compound 2.

[0071] Compound 1 (100.0 mmol) was dissolved in 200 mL of acetic acid (AcOH) and added to a dry round-bottom flask. NBS (200.0 mmol) was slowly added to the solution and stirred at room temperature (rt) for 4-5 h. The mixture was quenched with 2 M NaOH solution. After extraction with DCM to the organic layer, the organic layer was washed with saturated sodium bicarbonate solution and then dried over anhydrous sodium sulfate. After removing the solvent, it was purified by silica gel column chromatography to obtain compound 2. 1HNMR (500 MHz, CDCl 3 )δ9.82(s,1H),7.57(s,1H),3.82(s,1H),-0.68(s,1H).13CNMR(125MHz,CDCl 3 )δ135.87,131.27,110.72,109.97,14.71.HRMS(TOF-ESI+)(m / z)C 5 H 4 Br 2 S255.84.

[0072] S42: Synthesis of compound 3.

[0073] Under nitrogen, compound 2 (20.0 mmol) was dissolved in 75 ml of redistilled THF (dryTHF) in a 250 ml dry two-necked flask. After cooling to -78 °C, n-BuLi (10 ml 2.0 M) was added dropwise to the mixture. After stirring at -78 °C for 1 h, 10 ml of THF solution containing TMSCl (20.0 mmol) was added dropwise to the system. After stirring at -78 °C for 1 h, the reaction was gradually warmed to room temperature, and then saturated ammonium chloride solution was added for quenching. Concentration, followed by extraction with ethyl acetate, drying the organic phase with anhydrous sodium sulfate, spin drying, and purification by silica gel column chromatography gave compound 3. 1HNMR (500 MHz, CDCl 3 )δ7.17(s,1H),2.27(s,3H),0.39(s,9H).13CNMR(125MHz,CDCl 3 )δ139.72,138.68,131.15,110.41,14.71.HRMS(TOF-ESI+)(m / z)C 8 H 13 BrSSi249.97.

[0074] S43: Synthesis of compound 4.

[0075] Under nitrogen, compound 3 (20.0 mmol) and 75 ml of redistilled THF were added to a dry two-necked flask and cooled to -78 °C. At -78 °C, n-BuLi (10 ml of 2.0 M) was added dropwise to the reactant and stirred for 1 h. A solution of THF (10 ml) containing compound 10 (10.0 mmol) was added dropwise to the system and stirred for 1 h. The reaction temperature was then raised to room temperature. The reaction was quenched with saturated ammonium chloride solution and extracted with ethyl acetate. The combined organic phases were dried over anhydrous sodium sulfate and purified by silica gel column chromatography to obtain compound 4. 1HNMR (500 MHz, CDCl 3 )δ8.86(dd,J=4.0,2.0Hz,1H),8.30(dd,J=7.5,2.0Hz,1H),7.56(dd,J=7.5,4.1Hz,1H),7.38(s,1H),0.39(s,7H).13CNMR(125MHz,CDCl 3 )δ149.71,144.86,140.52,137.16,134.53,133.08,131.29,129.48,128.74,121.52,15.03.HRMS(TOF-ESI+)(m / z)C 28 H 32 N 2 S 2 Si2 516.87.

[0076] S44: Synthesis of compound 5.

[0077] Under nitrogen atmosphere, compound 4 (10.0 mmol) and 100 ml THF were added to a 250 ml dry round-bottom flask. The reactant was covered with aluminum foil and placed in an ice-water bath, followed by dropwise addition of NBS (22.0 mmol). After stirring at 0 °C for 3 h, the mixture was warmed to room temperature and reacted for 24 h. 20 mL of acetone was added to quench the reaction, and the mixture was rotary evaporated, extracted with dichloromethane / water, and the organic layer was dried over anhydrous sodium sulfate and purified by silica gel column chromatography to obtain compound 5. 1HNMR (500 MHz, CDCl 3 )δ8.86(dd,J=4.0,2.0Hz,1H),8.30(dd,J=7.5,2.0Hz,1H),7.56(dd,J=7.5,4.0Hz,1H),7.31(s,1H).13CNMR(125MHz,CDCl 3 )δ151.67,149.71,138.57,134.43,133.45,131.29,128.74,128.05,121.52,109.72,15.13.HRMS(TOF-ESI+)(m / z)C 22 H 14 Br 2 N 2 S 2 530.30.

[0078] S45: Synthesis of compound 6.

[0079] Under nitrogen atmosphere, compound 5 (5.0 mmol), compound 11 (5.0 mmol), Na 2 CO 3 (5.0mmol), Pd(PPh 3 ) 4 (0.05mmol). 20ml of a mixture of toluene: water = 5:1 (volume ratio) was added via a syringe, and the mixture was refluxed for 30h in an oil bath at 110°C. After cooling, the reaction mixture was poured into water and extracted three times with dichloromethane (50ml), the organic layer was dried, and the solvent was removed. The crude product was purified by silica gel column chromatography to obtain compound 6. 1HNMR (500MHz, CDCl 3)δ8.86(dd,J=4.0,2.0Hz,1H),8.30(dd,J=7.6,2.0Hz,1H),7.59–7.46(m,3H),7.18(dt,J=7.6,1.0Hz,1H),5.20(t,J=4.9Hz,0H), 3.17(td,J=5.6,4.8Hz,1H),2.65(tt,J=7.9,1.1Hz,1H),2.35(d,J=9.3Hz,3H),1.82(tt,J=7.9,5.7Hz,1H).13CNMR(125MHz,CDCl 3 )δ156.39,151.85,151.65,149.74,149.71,142.32,139.44,138.86,1 38.57,136.51,135.63,134.44,133.43,133.23,131.31,131.29,128.7 8,128.74,128.57,128.05,127.06,124.17,121.58,121.52,109.72,79 .54,40.36,33.59,29.99,28.30,15.39,15.13.HRMS(TOF-ESI+)(m / z)C 36 H 34 Bn 3 O 2 S 2 684.71.

[0080] S46: Synthesis of compound 7.

[0081] Under nitrogen atmosphere, compound 6 (2.0 mmol), compound 12 (2.0 mmol), Na 2 CO 3 (2.0 mmol), Pd(PPh 3 ) 4 (0.05mmol). 20ml of a mixture of toluene: water = 5:1 (volume ratio) was added via a syringe, and the mixture was refluxed for 30h in an oil bath at 110°C. After cooling, the reaction mixture was poured into water and extracted three times with dichloromethane (50ml), the organic layer was dried, and the solvent was removed. The crude product was purified by silica gel column chromatography to obtain compound 7. 1HNMR (500MHz, CDCl 3)δ8.86(dd,J=4.0,2.0Hz,2H),8.30(dd,J=7.6,2.0Hz,2H),7.56(dd,J=7.6,4. 1Hz,2H),7.53–7.46(m,6H),7.18(dq,J=7.5,0.9Hz,4H),5.20(t,J=4.9Hz,1H) ,3.66(q,J=5.9Hz,2H),3.17(td,J=5.6,4.8Hz,2H),2.79(t,J=5.7Hz,1H),2.6 5(tt,J=8.0,1.0Hz,4H),2.34(s,5H),1.91–1.78(m,4H).13CNMR(125MHz,CDCl 3 )δ156.39,151.85,149.74,149.71,142.32,142.15,139.45,139.44,138.89,138.86,1 36.55,136.51,135.66,135.62,133.06,133.02,131.31,131.29,128.78,128.74,128. 66,128.64,128.57,127.09,127.07,127.06,124.20,124.17,121.58,121.52,79.54,6 0.47,40.36,34.11,33.59,30.82,29.99,28.30,15.39,15.35.HRMS(TOF-ESI+)(m / z)C 45 H 45 N 3 O 3 S 2 739.99.

[0082] S47: Synthesis of compound 8.

[0083] Under nitrogen atmosphere, compound 7 (2.0 mmol), carbon tetrabromide (2.1 mmol), and 50 mL of dichloromethane were added to a two-necked flask. The reactant was covered with aluminum foil and placed in an ice-water bath. Triphenylphosphine (2.0 mmol) was added dropwise. The resulting mixture was stirred for 24 h. The solvent was removed in vacuo and purified by silica gel column chromatography to obtain compound 8. 1HNMR (500 MHz, CDCl 3)δ8.86(dd,J=4.0,2.0Hz,1H),8.30(dd,J=7.6,2.0Hz,1H),7.56(dd,J=7.6,4.1Hz,1H),7. 53–7.46(m,3H),7.18(ddq,J=7.6,2.3,1.4Hz,2H),5.20(t,J=4.9Hz,0H),3.41(t,J=4.8Hz, 1H),3.17(td,J=5.6,4.8Hz,1H),2.72(tt,J=7.4,1.1Hz,1H),2.65(tt,J=7.9,1.1Hz,1H), 2.34(s,2H),2.11(tt,J=7.3,4.7Hz,1H),1.82(tt,J=7.9,5.8Hz,1H).13CNMR(125MHz,CDCl 3 )δ13CNMR(125MHz,CommonNMRSolvents)δ156.39,151.85,149.74,149.71,142.32,141.84,139. 45,139.44,138.89,138.86,136.55,136.51,135.66,135.63,133.06,133.02,131.31,131.29,1 28.78,128.74,128.62,128.60,128.57,127.09,127.07,127.06,124.20,124.17,121.58,121.5 2,79.54,40.36,34.67,33.86,33.59,32.41,29.99,28.30,15.39,15.35.HRMS(TOF-ESI+)(m / z)C 45 H 44 Bn 3 O 2 S 2 802.89.

[0084] S48: Synthesis of compound 9 (chiral molecule).

[0085] Under nitrogen atmosphere, compound 8 (2.0 mmol) dissolved in 95% ethanol was added to 50 mL of refluxing thiourea (10 mmol) in 95% ethanol solution, refluxed for 24 h, and then 25 mL of 10% sodium hydroxide solution was added and refluxed for 2 h. After cooling to room temperature, the mixture was extracted with ethyl acetate, dried, concentrated to remove the solvent, and purified by silica gel column chromatography to obtain compound 9, which was finally separated by chiral column. 1HNMR (500 MHz, CDCl 3)δ8.86(dd,J=4.0,2.0Hz,2H),8.30(dd,J=7.6,2.0Hz,2H),7.56(dd,J=7.6,4.1 Hz,2H),7.53–7.46(m,6H),7.18(ddt,J=7.6,2.4,1.1Hz,4H),5.20(t,J=4.9Hz, 1H),3.17(td,J=5.6,4.8Hz,2H),2.72–2.65(m,2H),2.69–2.61(m,4H),2.34(s, 4H),1.87–1.78(m,4H),1.42(s,7H),1.38(t,J=6.8Hz,1H).13CNMR(125MHz,CDCl 3 )δ156.39,151.85,149.74,149.71,142.32,141.88,139.45,139.44,138.89,138.86, 136.55,136.51,135.66,135.63,133.06,133.02,131.31,131.29,128.78,128.74,12 8.62,128.60,128.57,127.09,127.07,127.06,124.20,124.17,121.58,121.52,79.5 4,40.36,34.31,33.59,32.58,29.99,28.30,25.58,15.39,15.35.(TOF-ESI+)(m / z)C 45 H 45 N 3 O 2 S 3 756.05. Finally, the chiral molecule was obtained after column separation and acid deprotection.

[0086] S5: Condensation of chiral molecules with graphene electrode amide, and then adding perovskite quantum dot precursor solution to react, assembling quantum dots in situ between graphene electrode pairs to obtain a tunable polarized photon source.

[0087] The specific steps include:

[0088] S51: The chiral molecule is connected to the edge of the graphene electrode through amide condensation of the chiral molecule and the graphene electrode, thereby obtaining a graphene electrode connected to the chiral molecule.

[0089] The specific operation process is as follows: 1mmol of chiral molecule and 6mmol of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride are placed in 10ml of pyridine solution to obtain a mixed solution, wherein the purity of trifluoroacetic acid is ≥99% and the purity of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride is ≥99%. The silicon wafer with graphene electrode prepared by S3 is placed in the mixed solution, reacted in a dark nitrogen atmosphere for 48h, and then an appropriate amount of PbI 2 (0.001mmol), continue the reaction for 24h, then wash with acetone and ultrapure water and dry to obtain a graphene electrode connected to the chiral molecule.

[0090] S52: By adding a perovskite quantum dot precursor solution, the quantum dot core is assembled in situ at the nucleation site of the graphene electrode connected to the chiral molecule, and a PMMA solution is dripped thereon to form a protective layer to obtain a tunable polarized photon source. The perovskite quantum dot precursor solution includes PbI 2 Precursor solution and Cs-DOPA precursor solution.

[0091] PbI 2 The concentration of the precursor solution is about 0.04 mol / L. By mixing 1 mmol (0.4610 g) PbI 2 The solid and 5 mmol (1.9332 g) TOPO solid were added to a 50 ml glass bottle. 5 ml OCT (octane) was injected and a 6×10 mm A-type magnet was added. The temperature was raised to 120°C with a magnetic stirrer and stirred to dissolve. Once the solid was observed to be completely dissolved, the magnetic stirrer was turned off and allowed to stand. After cooling to room temperature, 20 ml HEX was added and the bottle was sealed and stored in the refrigerator.

[0092] The concentration of the Cs-DOPA precursor solution used was about 0.02 mol / L. 2 CO 3 The solid was added to a 50ml glass bottle, and 1ml DOPA and 2ml OCT were injected. After adding type A magnet, the temperature was raised to 120℃ using a magnetic stirrer to stir and dissolve. Once the solid was observed to be completely dissolved, the magnetic stirrer was turned off and allowed to stand. After cooling to room temperature, 27ml HEX was added and sealed for storage. Among them, OCT is n-octane, HEX is n-hexane, TOPO is trioctylphosphine oxide, purity ≥99%, and DOPA is diisooctylphosphinic acid, purity ≥90%.

[0093] The specific operation process is: in a nitrogen environment, immerse the graphene electrode connected to the chiral molecule into the PbI 2 The precursor solution was allowed to react for 30 minutes, and then immersed in an ice-water bath of Cs-DOPA precursor solution. After 5 minutes, the silicon wafer was taken out and 20uLPbI 2The precursor solution is dripped onto the surface of the graphene electrode connected to the chiral molecule, and then rinsed with HEX. The above steps are repeated multiple times, and in this embodiment, they are repeated three times. Then, the graphene electrode connected to the chiral molecule is immersed in the Cs-DOPA precursor solution and heated at 150°C for 30 minutes, taken out and blown dry, and a PMMA solution is dripped onto its surface and pre-spun at 500rpm for 6s and then at 4000rpm for 40s to form a 200-400nm PMMA protective layer to obtain a tunable polarized photon source. Among them, the PMMA solution is prepared by dissolving PMMA solid in acetone and stirring with a magnetic pole for 24h, and the concentration is 0.1mol / L.

[0094] The structure of a single tunable polarization photon source is as follows: Figure 4 and Figure 5 As shown, the triangular graphene electrode 1 is located on the silicon wafer 3, the perovskite quantum dot 2 is assembled between two graphene electrodes 1 with a certain gap at the end site of the chiral molecule 5, and a PMMA protective layer 4 is spin-coated thereon. The graphene electrode 1 can be freely designed for circuit integration on the silicon wafer 3 through etching pattern design.

[0095] In the reaction process of step 5, the chiral molecule condenses with the graphene electrode amide and then reacts with PbI 2 The combination provides nucleation sites for quantum dot assembly. The Cs source and PbI 2 The source is assembled in situ to form a quantum dot light-emitting core (perovskite quantum dot) defined by the graphene gap with atomic-level precision, which greatly improves the connection efficiency and success rate, and can easily realize the connection of quantum dot cores in different circuit structures to achieve integration.

[0096] The present embodiment adopts the above method to make 20 tunable polarization photon sources on the same silicon wafer, and the graphene electrode gap is etched to 5nm, and a connection test is performed. The test results show that the connection success rate reaches 90%. The in-situ self-assembly method defined by the graphene nanogap adopted in this method has a huge improvement in the connection success rate compared to the previous connection method in the form of ligand exchange, and the integrated connection process greatly improves the connection efficiency. After the tunable polarization photon source is placed in an aluminum box and stored at room temperature for 2 months, 3 of the 20 tunable polarization photon sources have increased signal instability. It is speculated that improper preparation or storage leads to oxidation of the graphene electrode or poor contact of the surface protective layer of the quantum dot, which leads to deterioration of the quantum dot core or impurities entering to increase the additional conductive channel, but the survival rate still reaches 85%, showing the good stability of the tunable polarization photon source.

[0097] In situ self-assembled quantum dots defined by the gap between graphene electrodes exhibit improved uniformity, providing a basis for polarization-controllable single-photon emission. Figure 6As shown in the figure, compared with quantum dots synthesized in solution phase, in situ self-assembled quantum dots have narrower fluorescence emission half-peak width. Since the size of quantum dots is defined by the gap, its emission wavelength is also closer to 700nm, showing better controllability. A well-preserved tunable polarized photon source was selected for optical testing. Figure 7 It can be seen that after irradiation with 600nm visible light, the tunable polarized photon source is in circular polarization emission mode, and the photon counts in all directions are roughly the same, but the number of photons in a specific direction is slightly reduced, which preliminarily shows that the photons emitted by the tunable polarized photon source are completely unpolarized or circularly polarized and partially linearly polarized. Figure 8 The I / V curve test shows that the tunable polarization photon source has different conductances under different circularly polarized light irradiation, which indicates that the polarization state of the light field has a regulatory effect on the tunable polarization photon source. Electrons excited by different polarized photons show different conductances due to the spin selection effect of chiral molecules, which indirectly proves that the electroluminescence of the tunable polarization photon source can generate circularly polarized photons. At the same time, the tunable polarization photon source can also be used to study the interaction mechanism between the spin selection effect and polarized light. Fig. 9 It can be seen that after irradiation with 400nm visible light, the tunable polarized photon source is in a linearly polarized emission mode, and the emitted photons pass in a specific direction.

[0098] In summary, the self-assembled perovskite quantum dots defined by graphene nanogaps have the advantages of good stability, high quality, strong integration and great design potential. By condensing chiral molecular amides to the edge of the graphene electrode and then controlling the assembly of quantum dots by forming nucleation sites, the quality of the grown quantum dots is higher and the size and morphology are more controllable. The problems of uneven size distribution and uncontrollable distortion of quantum dots synthesized in the solution phase and reconnection are overcome. The problems of unstable thiol groups, large steric hindrance and low connection rate caused by long-chain ligands in the ligand exchange method are overcome. Not only is the connection success rate and efficiency greatly improved, but also the integrated preparation of quantum dot core circuits is possible. At the same time, the advantages of controllable size and less mutual interference between quantum dots are used to further introduce specific molecular wires, and the electrons injected into the core of the quantum dots are controlled by chirality. The electrons are transmitted to the light-emitting center of the quantum dots through the chiral molecular wires, and the properties of the quantum dot light source can be regulated by regulating the chirality, so that the output photon polarization can be changed, realizing a tunable polarized photon source.

[0099] In this embodiment, a tunable polarized photon source based on perovskite quantum dots is also provided, which is prepared using the above-mentioned method for preparing a tunable polarized photon source based on perovskite quantum dots.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a tunable polarized photon source based on perovskite quantum dots, characterized in that: The following steps are involved: S1: fabricate graphene-PMMA structure, transfer graphene-PMMA structure to silicon wafer surface and mark the pattern; S2: making external electrodes on graphene according to the pattern; S3: fabricating graphene electrode pairs according to the pattern; S4: Preparation of chiral molecules with tunable chirality: S5: Condensation of chiral molecules with graphene electrode amide, and then adding perovskite quantum dot precursor solution to react, assembling quantum dots in situ between graphene electrode pairs to obtain a tunable polarized photon source.

2. The method for preparing a tunable polarized photon source based on perovskite quantum dots according to claim 1, characterized in that: S3 includes the following steps: S31: Spin-coating photoresist on the silicon wafer according to the dotted lines of the pattern, and performing electron beam exposure on the silicon wafer with the photoresist spun on, so that the graphene is exposed at the pattern exposure position, and the other parts are covered and protected by the photoresist, and after development, a dotted line is formed between the electrode pairs; S32: Etching the silicon wafer using a plasma etcher according to the dotted lines between the electrode pairs to produce graphene electrode pairs. During the etching process, the preparation of the electrode pairs is evaluated by monitoring the magnitude of the current between the electrode pairs and the shape of the curve.

3. The method for preparing a tunable polarized photon source based on perovskite quantum dots according to claim 1, characterized in that: In S32, the graphene electrode pair is a triangular electrode pair with a gap of 5 nm.

4. The method for preparing a tunable polarized photon source based on perovskite quantum dots according to claim 1, characterized in that: The chiral molecule has a chiral site on its molecular skeleton, and the chiral site is tunable. The first end of the chiral molecule has a group for connecting with a carboxyl group formed by oxidation of a graphene electrode, and the second end of the chiral molecule has a group for supporting a nucleation site required for assembling a quantum dot core.

5. The method for preparing a tunable polarized photon source based on perovskite quantum dots according to claim 4, characterized in that: The structure of the chiral molecule is shown below: 。 6. The method for preparing a tunable polarized photon source based on perovskite quantum dots according to claim 1, characterized in that: S5 includes the following steps: S51: connecting the chiral molecule to the edge of the graphene electrode through amide condensation of the chiral molecule and the graphene electrode, thereby obtaining a graphene electrode connected with the chiral molecule; S52: By adding a perovskite quantum dot precursor solution, the quantum dot core is in situ assembled at the nucleation site of the graphene electrode connected to the chiral molecule, and a PMMA solution is dripped thereon to form a protective layer to obtain a tunable polarized photon source.

7. The method for preparing a tunable polarized photon source based on perovskite quantum dots according to claim 6, characterized in that: S51 includes the following steps: A chiral molecule and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride are placed in a pyridine solution to obtain a mixed solution; a graphene electrode pair is placed in the mixed solution and reacted in a dark nitrogen atmosphere, and then PbI2 is added to continue the reaction, and finally the mixture is cleaned with acetone and ultrapure water and dried to obtain a graphene electrode connected to the chiral molecule.

8. The method for preparing a tunable polarized photon source based on perovskite quantum dots according to claim 6, characterized in that: S52 includes the following steps: The perovskite quantum dot precursor solution includes a PbI2 precursor solution and a Cs-DOPA precursor solution; In a nitrogen environment, the graphene electrode connected to the chiral molecule is first immersed in a PbI2 precursor solution for a static reaction, and then immersed in a Cs-DOPA precursor solution in an ice water bath for a reaction. After being taken out, the PbI2 precursor solution is dripped on its surface, followed by rinsing with HEX, and the above steps are repeated many times; then the graphene electrode connected to the chiral molecule is immersed in a Cs-DOPA precursor solution and heated, taken out after the reaction and blown dry, and then a PMMA solution is dripped on its surface and rotated to form a PMMA protective layer to obtain a tunable polarized photon source.

9. A tunable polarized photon source based on perovskite quantum dots, characterized in that: The tunable polarized photon source is prepared by the method for preparing a perovskite quantum dot-based tunable polarized photon source as described in any one of claims 1 to 8.

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