Preparation and surface control method of high-uniformity infrared colloidal quantum dots and application

Abstract

The application relates to a preparation and surface control method of high-uniformity infrared colloidal quantum dots and application. The application belongs to the infrared colloidal quantum dot field. The application aims to solve the technical problems that the size uniformity of the existing infrared colloidal quantum dots and the quality of the thin film based on the colloidal quantum dots need to be further improved. First, a high-reaction-rate tellurium-containing precursor solution is used to make the colloidal quantum dots nucleate rapidly, then a low-reaction-rate tellurium-containing precursor solution is used to make the colloidal quantum dots grow stably, the nucleation and growth are separated, and the uniformity of the colloidal quantum dots is further improved. In addition, in order to more finely control the surface properties of the colloidal quantum dots, while avoiding unnecessary damage to the colloidal quantum dot film, the application adopts gas phase treatment and small molecule solution treatment in sequence, and the overall performance of the infrared photoelectric device, such as the carrier transport property and the conductivity, is further improved.

Description

Technical Field

[0001] This invention belongs to the field of infrared colloidal quantum dots, specifically relating to a method for preparing and controlling the surface of highly uniform infrared colloidal quantum dots and their applications. Background Technology

[0002] Colloidal quantum dots, as an emerging semiconductor material, have been gradually applied in the field of infrared photoelectric detection. Among them, mercury telluride (HgTe) infrared colloidal quantum dots, as an important branch, possess excellent photoelectric properties. Since the development of colloidal quantum dots, liquid-phase synthesis technology has been mainly used. Through continuous improvement and optimization, the control of the size and yield of colloidal quantum dots has been significantly improved. However, the synthesis of HgTe colloidal quantum dots is a complex process controlled by multiple interdependent variables. Due to its high specific surface energy, HgTe colloidal quantum dots are thermodynamically unstable and prone to aggregation, leading to a decrease in their photoelectric properties. To solve the problem of quantum dot aggregation, it is necessary to optimize the quantum dot synthesis method and perform surface modification treatment. Moreover, the reproducibility and uniformity of existing synthesis methods have always been a focus; therefore, the optimization of colloidal quantum dot synthesis methods has been a continuous area of ​​exploration. Currently, the size uniformity of infrared colloidal quantum dots is mainly controlled by optimizing the substituent groups of quantum dot precursors. However, the size uniformity of quantum dots synthesized from currently disclosed trisubstituted quantum dot precursors still needs further improvement.

[0003] Furthermore, to further improve the carrier transport capability of colloidal quantum dots, more precise control over their surface properties is needed to ensure that carriers can be rapidly transported to the electrodes and generate electrical signals, thereby improving the stability of colloidal quantum dots and providing a more effective way to enhance the performance of colloidal quantum dot optoelectronic devices. Ligand exchange is a commonly used method for modifying quantum dots. After synthesis, quantum dots typically have long-chain strong ligands on their surface to improve the stability of the quantum dot solution. However, these long-chain ligands may hinder the effective transport of carriers after the formation of a solid film. Traditionally, the surface ligand treatment method for colloidal quantum dots has been solid-state ligand exchange. This method involves washing away the original long-chain ligands on the surface of the colloidal quantum dot film with a short-chain ligand solution after film formation to achieve surface re-modification. However, this solid-state ligand exchange method easily damages the colloidal quantum dot film, which reduces its quality and affects its structural integrity, thereby reducing device performance and stability. Especially in the later stages of thin film preparation, rinsing can cause problems such as film peeling and cracking. At the same time, these methods cannot replace the internal ligands, which will affect properties such as charge carrier transport and lead to a decrease in the performance of optoelectronic devices. Summary of the Invention

[0004] The purpose of this invention is to address the technical problems of size uniformity of existing infrared colloidal quantum dots and the need to further improve the quality of films based on colloidal quantum dots, and to provide a method for preparing and surface-modulating highly uniform infrared colloidal quantum dots and its applications.

[0005] One of the objectives of this invention is to provide a highly uniform infrared colloidal quantum dot, which is prepared by a two-step method using mercury salt and tellurium precursors shown in Formulas 1 and 2.

[0006]

[0007] In the formula, R 1 R 3 Each is independently selected from one of the following: a substituted or unsubstituted C1-12 alkyl chain, a substituted or unsubstituted C3-12 cycloalkyl chain, or a substituted or unsubstituted C2-12 olefin chain; R 2 Selected from one of the following: substituted or unsubstituted C1-12 alkyl chains, substituted or unsubstituted C3-12 cycloalkyl chains, or substituted or unsubstituted C2-12 olefin chains, R 2＇ Selected from substituted or unsubstituted aryl groups.

[0008] Preferably, the substituted aryl group is a halogen-substituted aryl group or an alkoxy-substituted aryl group.

[0009] The second objective of this invention is to provide a method for preparing highly uniform infrared colloidal quantum dots, the method comprising the following steps:

[0010] S1: Dissolve the tellurium precursors shown in Formula 1 and Formula 2 in oleylamine (OAm) respectively to obtain a tellurium precursor solution with a high reaction rate and a tellurium precursor solution with a low reaction rate.

[0011] S2: Under heating conditions, a high-reaction-rate tellurium precursor solution is first injected into a mercury salt / oleylamine solution for nucleation for 20-40 seconds, then a low-reaction-rate tellurium precursor solution is injected, and the reaction continues for a certain time. The reaction is then stopped by cooling with ice water, and finally washed to obtain highly uniform infrared colloidal quantum dots.

[0012] Preferably, the molar ratio of the high-reaction-rate tellurium-containing precursor to the low-reaction-rate tellurium-containing precursor in S2 is 1:(0.8-1.2).

[0013] Preferably, the heating temperature in S2 is 90-110℃.

[0014] Preferably, S2 is cleaned using 1-dodecylthiol (DDT), bis(dodecyl)dimethylammonium bromide (DDAB), and isopropanol (IPA).

[0015] The third objective of this invention is to provide a method for surface manipulation of highly uniform infrared colloidal quantum dots, the method comprising the following steps:

[0016] Step 1: First, introduce AsH3 or Cl2 into the synthesized colloidal quantum dot solution and react for 10-20 seconds;

[0017] Step 2: Under nitrogen atmosphere, spin-coat the colloidal quantum dot ink treated in Step 1 onto the substrate, remove excess ligands by rinsing with IPA to form a colloidal quantum dot film, then drop in a 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone (F4-TCNQ) solution, let stand for 5-15 seconds, rinse with IPA and spin dry.

[0018] Preferably, the flow rate of AsH3 or Cl2 in step 1 is 2.24-22.4 mL / min.

[0019] Preferably, the concentration of the F4-TCNQ solution in step 2 is 3-4 mM.

[0020] Preferably, the solvent for the F4-TCNQ solution in step 2 is IPA, acetone, or chloroform.

[0021] The fourth objective of this invention is to provide an infrared colloidal quantum dot thin film with high carrier transport and conductivity obtained by the above method.

[0022] The fifth objective of this invention is to provide an application of the above-mentioned infrared colloidal quantum dot thin film with high carrier transport and conductivity in infrared photodetectors.

[0023] The significant advantages of this invention compared to existing technologies are:

[0024] This invention proposes a method for regulating the activity of tellurium-containing precursors, enabling effective control over the precursors and consequently, the size and size distribution of the final colloidal quantum dots. This results in highly uniform infrared colloidal quantum dots, and this novel method promises to provide a more effective approach to improving the performance of colloidal quantum dot optoelectronic devices. Through more precise surface manipulation, this invention can achieve comprehensive performance optimization of colloidal quantum dot films, including improving carrier transport characteristics and conductivity, thereby optimizing the doping control and optoelectronic performance of infrared colloidal quantum dots. Specific advantages are as follows:

[0025] (1) To further improve the size uniformity of colloidal quantum dots, this invention controls the number and type of substituents in the tellurium-containing precursor. More importantly, it uses a two-step synthesis method. First, a high-reaction-rate tellurium-containing precursor solution is used to rapidly nucleate the colloidal quantum dots. Then, a low-reaction-rate trisubstituted tellurium-containing precursor solution is used to stably grow the colloidal quantum dots. Through the separation of nucleation and growth, the uniformity of the colloidal quantum dots is further improved, enabling the formation of superlattices.

[0026] (2) This invention employs a vapor-phase treatment method to modulate the surface ligands of HgTe colloidal quantum dots. This achieves doping control of HgTe colloidal quantum dots, improving their stability and photoelectric properties. Compared to the traditional solid-state ligand exchange method, this method is gentler, reducing the risk of damage to the colloidal quantum dot film and providing a more reliable foundation for the fabrication of infrared optoelectronic devices. Simultaneously, small-molecule solutions are further used to control the doping of the HgTe colloidal quantum dot film. By using specific small-molecule solutions in the treatment of the HgTe colloidal quantum dot film, optical properties are optimized. This technique makes the doping of HgTe colloidal quantum dot films more precise and controllable, laying the foundation for further improving the capabilities of infrared optoelectronic devices. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the preparation process of the highly uniform HgTe colloidal quantum dots of the present invention.

[0028] Figure 2 This is a diagram of the AsH3 gas phase processing procedure;

[0029] Figure 3 This is a diagram of the Cl2 gas phase processing;

[0030] Figure 4 The absorption spectra of HgTe colloidal quantum dots obtained in Example 1 and Comparative Examples 1-2 are shown below.

[0031] Figure 5 The images show TEM images and size distribution diagrams of the HgTe colloidal quantum dots obtained in Example 1 and Comparative Examples 1-2; where A-Example 1, B-Comparative Example 1, and C-Comparative Example 2.

[0032] Figure 6 This is a schematic diagram of the field-effect transistor structure of the present invention;

[0033] Figure 7 The image shows the doping effect of HgTe quantum dots after treatment in Example 2; where A-AsH3 treatment, B-AsH3 + 3mM small molecule solution treatment, and C-AsH3 + 4mM small molecule solution treatment are shown.

[0034] Figure 8The image shows the doping effect of HgTe quantum dots after treatment in Example 2; where A-Cl2 treatment, B-Cl2 + 3mM small molecule solution treatment, and C-Cl2 + 4mM small molecule solution treatment are shown. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below.

[0036] A specific embodiment of the present invention provides a tellurium precursor as shown in Formula 1 and Formula 2, the general structural formula of which is as follows:

[0037]

[0038] In the formula, R 1 R 3 Each is independently selected from one of the following: a substituted or unsubstituted C1-12 alkyl chain, a substituted or unsubstituted C3-12 cycloalkyl chain, or a substituted or unsubstituted C2-12 olefin chain; R 2 Selected from one of the following: substituted or unsubstituted C1-12 alkyl chains, substituted or unsubstituted C3-12 cycloalkyl chains, or substituted or unsubstituted C2-12 olefin chains, R 2＇ Selected from substituted or unsubstituted aryl groups. Preferably, the substituted aryl group is a halogen-substituted aryl group or an alkoxy-substituted aryl group.

[0039] The present invention preferably synthesizes tellurium precursors having the substituents shown in Table 1, and obtains the relative conversion rates of tellurium-containing precursors with other structures using the conversion rate of scheme 2-2 as the unit "1".

[0040] Table 1. Tellurium precursor schemes with different substituents

[0041]

[0042]

[0043] A second specific embodiment of the present invention provides a method for synthesizing a tellurium precursor, the reaction equation and specific steps of which are as follows:

[0044]

[0045] Among them, R 1 R 3 R 2 R 2＇ The definition of R in tellurium precursor is shown in Equations 1 and 2. 1 R 3 R 2 R 2＇ As shown.

[0046] In a nitrogen atmosphere, tellurium powder, amine, and isocyanate are added to toluene in a 1:1:1 molar ratio, and the mixture is heated to 90-110°C in an oil bath with constant stirring. During this process, all the tellurium powder is consumed, and the reaction mixture becomes colorless or yellow. The resulting mixture is filtered, and volatiles are removed under vacuum. Recrystallization is performed by adding pentane to a saturated toluene solution to obtain a recrystallized solid tellurium-containing precursor, which is then separated by filtration using a glass frit funnel and dried under vacuum. The final separated tellurium-containing precursor powder can be stored long-term in a glove box under a nitrogen atmosphere.

[0047] A third specific embodiment of the present invention provides a method for preparing highly uniform infrared colloidal quantum dots, the reaction equation and specific steps of which are as follows:

[0048]

[0049] (1) In a nitrogen atmosphere, weigh mercuric chloride (HgCl2) and dissolve it in oleylamine (OAm) at a concentration of 0.02-0.03M. Place the solution in a sample bottle and heat it at 90-110℃ for 0.5-1.5h to obtain HgCl2 / OAm solution.

[0050] (2) Dissolve the tellurium precursor shown in Formula 1 in OAm at a concentration of 0.08-0.12M, place it in a sample bottle, and heat it at 150-200℃ for 1.5-2.5h to finally generate a transparent liquid, namely a high reaction rate tellurium precursor solution.

[0051] (3) Dissolve the tellurium precursor shown in Formula 2 in OAm at a concentration of 0.08-0.12M, place it in a sample bottle, and heat it at 150-200℃ for 1.5-2.5h to finally generate a transparent liquid, namely a low reaction rate tellurium precursor solution.

[0052] (4) Inject 500 μL of high-reaction-rate tellurium-containing precursor solution into 4 mL of HgCl2 / OAm solution, nucleate at 90-110℃ for 20-40 s, then inject 500 μL of low-reaction-rate tellurium-containing precursor solution, react at 90-110℃ for 4-6 min. Then cool with cold water to end the reaction.

[0053] (5) Take the HgTe colloidal quantum dot solution after the reaction is complete into a centrifuge tube, add 1-dodecylthiol (DDT), bis(dodecyldimethylammonium bromide) (DDAB), and then add isopropanol (IPA). Centrifuge at 7500 rpm for 6 min. After centrifugation, discard the supernatant, dissolve the precipitate with chlorobenzene (CBZ), and filter using a disposable filter. The filtered colloidal quantum dot ink can be used to manufacture devices. If storage is required, DDT should be added to the colloidal quantum dot ink for long-term storage. The HgTe colloidal quantum dot synthesis and cleaning flowchart is shown below. Figure 1 As shown.

[0054] A fourth embodiment of the present invention provides a method for surface manipulation of highly uniform infrared colloidal quantum dots, the method comprising the following steps:

[0055] Step 1: First, introduce AsH3 or Cl2 into the synthesized colloidal quantum dot solution and react for 10-20 seconds; the introduction rate of AsH3 or Cl2 is 2.24-22.4 mL / min.

[0056] AsH3 is prepared by reacting Zn3As2 with 4 mol / L dilute hydrochloric acid or dilute sulfuric acid in a molar ratio of 1:(6-12); the AsH3 gas phase treatment process is shown in the figure below. Figure 2 As shown. 3－ The injection caused it to aggregate on the surface of HgTe colloidal quantum dots, forming a structure with Hg 2 + The opposite surface dipole electric field indicates a change in the surface charge of the quantum dot, achieving p-type doping of the HgTe colloidal quantum dot.

[0057] Cl2 is prepared by reacting hydrochloric acid and sodium hypochlorite (6 wt%), followed by drying with calcium chloride (CaCl2) and bubbling with carbon tetrachloride (CCl4); the Cl2 gas phase treatment process is shown in the figure below. Figure 3 As shown. Cl - The introduction of HgTe colloidal quantum dots will increase the surface Hg content. 2+ The enrichment level of Cl is utilized to stabilize electrons in HgTe colloidal quantum dots using the localized electric field of the surface dipoles generated therein, thus achieving n-type doping of HgTe colloidal quantum dots. In this way, negative charge carriers (electrons) are successfully introduced, altering the conductivity properties of HgTe colloidal quantum dots and providing new possibilities for their application in electronic devices. Meanwhile, Cl... - The introduction of chlorination effectively prevents oxidation of HgTe colloidal quantum dots caused by long-term exposure to air, passivates surface traps, and improves the photoelectric properties of HgTe colloidal quantum dots. This dual effect gives n-type doped HgTe colloidal quantum dots achieved through chlorination excellent stability and performance advantages.

[0058] Step 2: Under nitrogen atmosphere, spin-coat the HgTe colloidal quantum dot ink treated in Step 1 onto the substrate. Specifically, control the spin speed at 3000 r / s, spin-coat for 30 s, stop for 10 s to allow the HgTe colloidal quantum dots to wet the substrate, and then spin-coat with IPA for 30 s to remove excess ligands from the HgTe colloidal quantum dots, forming an HgTe colloidal quantum dot film. After film formation, dissolve F4-TCNQ solution in IPA, acetone, or chloroform to prepare a 3.6 mM F4-TCNQ solution. Drop the F4-TCNQ solution onto the HgTe colloidal quantum dot film, treat for 10 s, then rinse with IPA and spin-dry. 2,3,5,6-Tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone (F4-TCNQ) was selected as a small molecule, which allows it to effectively accept electrons and introduce holes into the colloidal quantum dot film, achieving p-type doping of the semiconductor film. The interaction between F4-TCNQ and HgTe colloidal quantum dot films is not limited to doping effects but also involves charge transfer and electronic structure modulation. Introducing F4-TCNQ via a small-molecule solution method allows for the simultaneous modulation of electrical properties in HgTe colloidal quantum dot films, providing an efficient and controllable material optimization technique for infrared optical devices.

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0060] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0061] Tellurium precursor preparation:

[0062] Preparation Example 1: Taking schemes 1-5 as examples, the specific structural formulas and preparation methods of the N,N-dibutyl-N'-cyclohexyl tellurium precursor are given:

[0063]

[0064] Dibutylamine (387.7 mg, 3 mmol), tellurium powder (382.8 mg, 3 mmol), and cyclohexyl isocyanate (327.5 mg, 3 mmol) were mixed in toluene (2.6 mL) and heated to 100 °C with constant stirring. During this process, all the tellurium powder was consumed. The resulting mixture was filtered, and volatiles were removed under vacuum. The mixture was recrystallized from a saturated toluene solution. The tellurium-containing precursor solid was obtained by filtration through a glass funnel, followed by washing with pentane and drying under vacuum for 3 h. A white powder was finally obtained in 76% yield.

[0065] Preparation Example 2: The structural formula of the N,N-diisopropyl-N'-cyclohexyl tellurium precursor in Scheme 1-1 is as follows:

[0066]

[0067] The preparation steps were the same as in Preparation Example 1, and colorless crystals were finally obtained with a yield of 57%.

[0068] Preparation Example 3: The structural formula of the N'-cyclohexyl-N-ethyl-N-isopropyl tellurium precursor in schemes 1-2 is as follows:

[0069]

[0070] The preparation steps were the same as in Preparation Example 1, and a white crystalline solid was finally obtained with a yield of 79%. It was obtained by recrystallization from a saturated solution of dichloromethane and toluene in a 2:3 ratio.

[0071] Preparation Example 4: The structural formula of the N'-cyclohexyl-N-isopropyl-N-methyl tellurium precursor in schemes 1-3 is as follows:

[0072]

[0073] The preparation steps were the same as in Preparation Example 1, and a white powder was finally obtained with a yield of 90%, which was obtained by recrystallization from a saturated solution of 2:3 dichloromethane:toluene.

[0074] Preparation Example 5: The structural formula of the N-cyclohexylpiperidine-1-carbon telluramide-containing precursor in schemes 1-4 is as follows:

[0075]

[0076] The preparation steps were the same as in Preparation Example 1, and a white powder was finally obtained with a yield of 82%, which was obtained by recrystallization from a saturated solution of dichloromethane:toluene by evaporation.

[0077] Preparation Example 6: The structural formula of the N,N-diethyl-N'-butyl tellurium precursor in schemes 1-6 is as follows:

[0078]

[0079] The preparation steps were the same as in Preparation Example 1, and a pale yellow oily substance was finally obtained with a yield of 97%.

[0080] Preparation Example 7: Taking scheme 2-1 as an example, the specific structural formula of the N'-butyl-N-(4-methoxyphenyl)-N-methyl tellurium-containing precursor and its preparation method are given:

[0081]

[0082] Under nitrogen atmosphere, 566.4 mg of methoxyaniline (3 mmol), 382.8 mg of tellurium powder (3 mmol), and 249.4 mg of butylisocyanate (3 mmol) were mixed in 2.6 mL of toluene and heated to 100 °C with constant stirring. During this process, all the tellurium powder was consumed. The resulting mixture was filtered, and volatiles were removed under vacuum. The mixture was recrystallized from a saturated toluene solution. The tellurium-containing precursor solid was obtained by filtration through a glass funnel, followed by washing with pentane and drying under vacuum for 3 h. A white crystalline powder was finally obtained. The yield was 72%.

[0083] Preparation Example 8: The structural formula of the 1-(4-chlorophenyl)-3-cyclohexyl-1-methyl tellurium precursor in Scheme 2-2 is as follows:

[0084]

[0085] The preparation steps were the same as in Preparation Example 7, and a pale yellow powder was finally obtained with a yield of 27%. It was obtained by recrystallization from a saturated toluene solution with the addition of pentane, and then stored overnight at -40°C.

[0086] Example 1: Preparation of HgTe colloidal quantum dots

[0087] (1) In a nitrogen atmosphere, 27.2 mg of HgCl2 was weighed and dissolved in 4 mL of OAM, placed in a 40 mL sample bottle, and heated at 100 °C for 1 h to obtain an HgCl2 / OAm solution. 317.4 mg of N,N-dibutyl-N'-cyclohexyl tellurium precursor powder (numbers 1-5) prepared in Preparation Example 1 (1 mmol) was dissolved in 10 mL of OAM, placed in a 40 mL sample bottle, and heated at 180 °C for 2 h to finally generate a transparent liquid, namely a high-reaction-rate tellurium precursor solution. 299.3 mg of N'-butyl-N-(4-methoxyphenyl)-N-methyl tellurium precursor (serial number 2-1) powder (1 mmol) prepared in Preparation Example 7 was dissolved in 10 mL of OAM, placed in a 40 mL sample vial, and heated at 180 °C for 2 h to finally generate a transparent liquid, namely a low-reaction-rate tellurium precursor solution.

[0088] (2) Inject 500 μL of high-reaction-rate tellurium-containing precursor solution (numbers 1-5) into 4 mL of HgCl2 / OAm solution, nucleate at 100 °C for 30 s, then inject 500 μL of low-reaction-rate tellurium-containing precursor solution (numbers 2-1), react at 100 °C for 5 min. Then cool with cold water to end the reaction.

[0089] (3) Take the HgTe colloidal quantum dot solution after the reaction is complete into a centrifuge tube, add 1 mL of DDT, 20 drops of DDAB, and then add 15 mL of IPA. Centrifuge at 7500 rpm for 6 min. After centrifugation, discard the supernatant, dissolve the precipitate with 2 mL of CBZ, and filter using a disposable filter. The filtered colloidal quantum dot ink can be used to manufacture devices. If storage is required, add 5 drops of DDT to the HgTe colloidal quantum dot ink for long-term storage.

[0090] Comparative Example 1:

[0091] (1) In a nitrogen atmosphere, 27.2 mg of HgCl2 was weighed and dissolved in 4 mL of OAM, placed in a 40 mL sample bottle, and heated at 100 °C for 1 h to obtain an HgCl2 / OAm solution. 317.4 mg of N,N-dibutyl-N'-cyclohexyl tellurium precursor powder (numbers 1-5) prepared in Preparation Example 1 (1 mmol) was dissolved in 10 mL of OAM, placed in a 40 mL sample bottle, and heated at 180 °C for 2 h to finally generate a transparent liquid, i.e., a tellurium precursor solution.

[0092] (2) Inject 500 μL of high-reaction-rate tellurium precursor solution (serial number 1-5) into 4 mL of HgCl2 / OAm solution, nucleate at 100 °C for 5 min, and then cool with cold water to end the reaction.

[0093] (3) Take the HgTe colloidal quantum dot solution after the reaction is complete into a centrifuge tube, add 1 mL of DDT, 20 drops of DDAB, and then add 15 mL of IPA. Centrifuge at 7500 rpm for 6 min. After centrifugation, discard the supernatant, dissolve the precipitate with 2 mL of CBZ, and filter using a disposable filter. The filtered colloidal quantum dot ink can be used to manufacture devices. If storage is required, add 5 drops of DDT to the HgTe colloidal quantum dot ink for long-term storage.

[0094] Comparative Example 2:

[0095] The preparation process was the same as that of Comparative Example 1, except that the N,N-dibutyl-N'-cyclohexyl tellurium precursor powders (numbers 1-5) obtained in Preparation Example 1 were replaced with the existing (TMS)2Te precursor.

[0096] Appendix Figure 4 The absorption spectra of the HgTe colloidal quantum dots obtained in Example 1 and Comparative Examples 1-2 are shown below. Figure 4 It can be seen that quantum dots with similar cutoff wavelengths were obtained in Example 1 and Comparative Examples 1-2. Among them, the quantum dots obtained in Example 1 have the smallest cutoff wavelength absorption broadening, that is, the highest uniformity; Comparative Example 1 has obvious energy level broadening at longer wavenumbers, and its uniformity is second; Comparative Example 2 has the largest cutoff wavelength absorption broadening and the worst uniformity.

[0097] Figure 5 Figures A and B show the TEM (transmission electron microscopy) images and size distribution diagrams obtained by normal fitting of the HgTe colloidal quantum dots obtained in Example 1 and Comparative Examples 1-2. Figure A shows that the average particle size of the HgTe colloidal quantum dots prepared in Example 1 is 4.96 nm, with high size uniformity, and it can form a superlattice. Figures B and C show that the size uniformity of the HgTe colloidal quantum dots prepared in Comparative Examples 1-2 is poor, and they cannot form a superlattice.

[0098] Example 2: Surface control method of HgTe infrared colloidal quantum dots

[0099] Step (1): Place 102 mg Zn3As2 (0.3 mmol) in a reaction flask, inject 0.9 mL of 4 mol / L hydrochloric acid, and pass the AsH3 gas generated by the reaction into the HgTe colloidal quantum dot solution synthesized in Example 1. The reaction time is 15 s. Then add 15 mL of methanol and centrifuge at 7500 rpm for 6 min. After centrifugation, discard the supernatant and dissolve the precipitate with 2 mL of n-hexane to obtain a p-type doped HgTe colloidal quantum dot solution.

[0100] Alternatively, under nitrogen atmosphere, 10 mL of hydrochloric acid and 5 mL of sodium hypochlorite (6 wt% in water) are reacted. The released gas is dried over anhydrous CaCl2 and then bubbled through CCl4 at room temperature to prepare Cl2. The Cl2 is then passed into a HgTe colloidal quantum dot solution for 15 seconds. Then, 15 mL of methanol is added, and the solution is centrifuged at 7500 rpm for 6 minutes. After centrifugation, the supernatant is discarded, and the precipitate is dissolved in 2 mL of n-hexane to obtain an n-type doped HgTe colloidal quantum dot solution.

[0101] Step (2): Under nitrogen atmosphere, take 50 μL of p-type doped HgTe colloidal quantum dot solution ink treated with AsH3 gas in step (1) and n-type doped HgTe colloidal quantum dot solution ink treated with Cl2 gas in step (1), and spin-coat them onto the substrate. Specifically, control the rotation speed to 3000 r / s, spin-coat for 30 seconds, stop for 10 seconds to allow the HgTe colloidal quantum dots to wet the substrate, and then take 3 mL of IPA to rinse for 30 seconds to remove excess ligands in the HgTe colloidal quantum dots, forming an HgTe colloidal quantum dot film. After the film is formed, take 100 μL of F4-TCNQ / IPA solution with concentrations of 3 mM and 4 mM respectively and drop it onto the HgTe colloidal quantum dot film, treat for 10 seconds, then rinse with 3 mL of IPA for 30 seconds and spin dry to complete the small molecule solution, and obtain an infrared colloidal quantum dot film with high carrier transport and conductivity.

[0102] To further determine the doping status of the HgTe colloidal quantum dots after the vapor phase treatment in step (1), a field-effect transistor (FET) was constructed to measure the HgTe colloidal quantum dot film. A schematic diagram of the FET structure is shown below. Figure 6 As shown. The substrate is composed of SiO2 (300nm) / Si, with gold interdigitated electrodes photolithographically etched on it. The HgTe colloidal quantum dot solution treated in step 1 was spin-coated to form a film. The spin speed was controlled at 3000 r / s, and the spin-coating process lasted 30 s, followed by a 10 s pause to allow the HgTe colloidal quantum dots to wet the substrate. Then, an IPA was used to spin-coat for 30 s to remove excess ligands from the HgTe colloidal quantum dots. This process was repeated until the resulting HgTe colloidal quantum dot film was approximately 200 nm thick. A layer of polymethyl methacrylate (PMMA) was then spin-coated to prevent the influence of external air. The doping status of the HgTe colloidal quantum dots before and after vapor phase treatment was then tested using a field-effect transistor method, thereby precisely controlling the doping effect of the vapor phase treatment method on the HgTe colloidal quantum dots. The results are as follows. Figure 7-8 As shown, by Figure 7 As shown in A, the HgTe colloidal quantum dots treated with AsH3 gas exhibit a p-type structure. Figure 8 As can be seen from A, the HgTe colloidal quantum dots treated with Cl2 gas exhibit an n-type structure. Furthermore, the mobility of the HgTe colloidal quantum dot film is calculated using the following field-effect transistor calculation formula (1):

[0103]

[0104] In the above mathematical relation (1), C i The capacitance of 300nm SiO2 is 1.15 × 10⁻⁶. -4 F / m 2 The gap L = 10 μm, the total channel width W = 5 μm, and the drain voltage VD =1V, The slope of the source / drain current versus the gate voltage.

[0105] Calculations show that the mobility of HgTe colloidal quantum dots treated with AsH3 gas is 8 cm⁻¹. 2 / Vs, The mobility of HgTe colloidal quantum dots treated with Cl2 was 10.6 cm⁻¹ 2 / Vs.

[0106] To further investigate the performance of HgTe colloidal quantum dot films after step (1) AsH3 gas treatment + step (2) small molecule solution treatment and after step (1) Cl2 gas treatment + step (2) small molecule solution treatment, a field-effect transistor (FET) was used. Figure 6 The experiment measured the HgTe colloidal quantum dot film regulated by F4-TCNQ, and the measurement results are as follows: Figure 7 BC and Figure 8 As shown in BC, the F4-TCNQ doping method can further control quantum doping. 3 mM F4-TCNQ enhances the p-type of HgTe colloidal quantum dots treated with AsH3 gas, and 4 mM F4-TCNQ further enhances the p-type without compromising carrier mobility. 3 mM F4-TCNQ changes HgTe colloidal quantum dots treated with Cl2 gas from N-type to intrinsic type, and 4 mM F4-TCNQ further changes the quantum dots from intrinsic to p-type without compromising carrier mobility.

[0107] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for surface regulation of high-uniformity infrared colloidal quantum dots, characterized in that, The method described: Step 1: First, introduce AsH3 or Cl2 into the synthesized colloidal quantum dot solution and react for 10-20 seconds; Step 2: Under nitrogen atmosphere, spin-coat the colloidal quantum dot ink treated in Step 1 onto the substrate, remove excess ligands by rinsing with IPA to form a colloidal quantum dot film, then add F4-TCNQ solution, let stand for 5-15 seconds, rinse with IPA and spin dry. The infrared colloidal quantum dots are prepared according to the following steps: S1: Dissolve the tellurium precursors shown in Formula 1 and Formula 2 in OAm respectively to obtain a tellurium precursor solution with a high reaction rate and a tellurium precursor solution with a low reaction rate. S2: Under heating conditions, a high-reaction-rate tellurium precursor solution is first injected into a mercury salt / oleylamine solution for nucleation for 20-40 seconds, then a low-reaction-rate tellurium precursor solution is injected, and the reaction continues for a certain time. The reaction is then stopped by cooling with ice water. Finally, after washing, highly uniform infrared colloidal quantum dots are obtained. Highly uniform infrared colloidal quantum dots are prepared by a two-step method using mercury salt and tellurium precursors as shown in Formulas 1 and 2. wherein R 1 , R 3 are each independently selected from one of a substituted or unsubstituted C1-12alkyl chain, a substituted or unsubstituted C3-12cycloalkyl, a substituted or unsubstituted C2-12alkene chain, R 2 is selected from one of a substituted or unsubstituted C1-12alkyl chain, a substituted or unsubstituted C3-12cycloalkyl, a substituted or unsubstituted C2-12alkene chain, R 2＇ is selected from a substituted or unsubstituted aryl.

2. The method of claim 1, wherein, In step 1, the flow rate of AsH3 or Cl2 is 2.24-22.4 mL / min.

3. The method of claim 1, wherein, In step 2, the concentration of the F4-TCNQ solution is 3-4 mM, and the solvent is IPA, acetone, or chloroform.

4. The method of claim 1, wherein, The substituted aryl group is either a halogen-substituted aryl group or an alkoxy-substituted aryl group.

5. The method of claim 1, wherein, The molar ratio of the high-reaction-rate tellurium-containing precursor to the low-reaction-rate tellurium-containing precursor in S2 is 1:(0.8-1.2), and the heating temperature is 90-110℃.

6. The method of claim 2, wherein, S2 uses DDT, DDAB, and IPA for cleaning.

7. The infrared colloidal quantum dot thin film with high carrier transport and conductivity obtained by the method according to any one of claims 1-6.

8. The application of the infrared colloidal quantum dot thin film with high carrier transport and conductivity as described in claim 7 in infrared photodetectors.

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