PbS-EDT quantum dot hole transport layer and preparation method and application thereof

Abstract

The invention discloses a PbS-EDT quantum dot hole transport layer and a preparation method and application thereof, and the preparation method comprises the following steps: (1) preparing PbS-OA quantum dots into a PbS-OA quantum dot solution; the preparation method comprises the following steps: dissolving 1, 2-ethanedithiol in a mixed solvent composed of dichloromethane, isopropanol and acetonitrile to obtain a solution 1, dissolving PbCl2 in N, N-dimethylformamide (DMF) to obtain a solution 2, and adding the solution 2 into the solution 1 to obtain an exchange solution; (2) coating the PbS-OA quantum dot solution on a substrate to obtain a PbS-OA quantum dot layer; the PbS-OA quantum dot layer is coated with the PbS-EDT quantum dot hole transport layer, the PbS-OA quantum dot layer is fully paved with the exchange liquid, cleaning is carried out after ligand exchange is carried out, then the steps of PbS-OA quantum dot coating, full paving of the exchange liquid, ligand exchange and cleaning are repeated, and the PbS-EDT quantum dot hole transport layer is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of quantum dot films, and particularly relates to a PbS-EDT quantum dot hole transport layer and a preparation method and application thereof. BACKGROUND

[0002] Colloidal quantum dots (CQDs) have low cost and surface-dominant doping characteristics, and can be widely applied to thin film optoelectronic devices such as light-emitting diodes, lasers, solar cells and infrared photodetectors. In the past decade, lead sulfide (PbS) CQDs have become one of the most promising materials in the field of infrared photodetectors and solar cells. At present, a large number of researches mainly focus on the optimization of PbS CQD synthesis, surface modification and device structure optimization, and few people pay attention to the hole transport layer (HTL) as one of the most critical parts of the PbS-CQD thin film optoelectronic device. The P-type HTL usually performs the key function of separating photo-generated carriers, and generally adopts a PbS-OA quantum dot layer as the HTL, but defects are prone to occur in the HTL. The PbS-OA quantum dot has a long-chain insulating ligand, which generally needs to be replaced by a short-chain conductive ligand (such as 1,2-ethanedithiol, EDT) to improve the carrier mobility, but the existing short-chain conductive ligand generally uses a high-polarity solvent (such as acetonitrile, polarity 6.2), which will cause the exchange rate of the ligand to be too fast, causing quantum dot aggregation and internal stress of the film, and micro-cracks are formed during the drying process, which seriously reduces the device efficiency. In addition, after the EDT exchange is completed, the HTL layer needs to be oxidized, so water will inevitably erode, and the water will leave hydroxyl groups on the surface of the quantum dots, which will capture carriers and cause energy loss during device operation. In addition, in the preparation of the EDT layer, the traditional method only prepares two layers of PbS-EDT layers with the same concentration, which will cause the bottom layer of the PbS-EDT layer to fail to fully contact O2 during oxidation, resulting in fewer holes and poor P performance. SUMMARY

[0003] In view of this, the purpose of the present application is to provide a PbS-EDT quantum dot hole transport layer and a preparation method and application thereof.

[0004] In a first aspect, the present application provides a preparation method of a PbS-EDT quantum dot hole transport layer, comprising the following steps: (1) PbS-OA quantum dots are prepared into a PbS-OA quantum dot solution; 1,2-ethanedithiol is dissolved in a mixed solvent composed of dichloromethane, isopropyl alcohol and acetonitrile to obtain solution 1, and PbCl2 is dissolved in N,N-dimethylformamide (DMF) to obtain solution 2; solution 2 is added to solution 1 to obtain an exchange solution; (2) coating PbS-OA quantum dot solution on the substrate to obtain PbS-OA quantum dot layer; spreading exchange solution on the PbS-OA quantum dot layer, carrying out ligand exchange, cleaning, then repeating the coating of PbS-OA quantum dot, spreading exchange solution, ligand exchange and cleaning to obtain PbS-EDT quantum dot hole transport layer.

[0005] Preferably, in the step (1), the concentration of PbS-OA quantum dot solution is 20-25 mg / mL.

[0006] Preferably, in the step (1), in solution 1, the volume ratio of dichloromethane, isopropyl alcohol and acetonitrile is (1.5-2.5):(2.5-3.5):(4.5-5.5); the concentration of 1,2-ethanedithiol in solution 1 is 0.01-0.02wt%. Preferably, in the step (1), the concentration of lead chloride in solution 2 is 0.05-0.1M; the volume ratio of solution 1 to solution 2 is 100:(0.8-1.2).

[0007] Preferably, in the step (2), the ligand exchange time is 20-30s.

[0008] Preferably, in the step (2), the cleaning is carried out by using a mixed solvent composed of dichloromethane, isopropyl alcohol and acetonitrile for 3-4 times.

[0009] Preferably, in the step (2), the number of times of repeating the coating of PbS-OA quantum dot, spreading exchange solution, ligand exchange and cleaning is 1-2 times.

[0010] Preferably, in the step (2), the thickness of PbS-EDT quantum dot hole transport layer is 35-55nm.

[0011] In the second aspect, the application provides a PbS-EDT quantum dot hole transport layer prepared by the aforementioned preparation method.

[0012] In the third aspect, the application provides an application of PbS-EDT quantum dot hole transport layer in solar cell and photoelectric detector.

[0013] In the fourth aspect, the application provides a PbS quantum dot solar cell, from bottom to top, comprising lower electrode layer, electron transport layer, PbS-PbX2 quantum dot active layer, the aforementioned PbS-EDT hole transport layer and upper electrode layer; wherein: X is I and / or Br.

[0014] Preferably, the lower electrode layer is an ITO thin film layer, the electron transport layer is one or more of a zinc oxide layer, a tin dioxide layer, a magnesium-doped zinc oxide layer, and an aluminum-doped zinc oxide layer, and the upper electrode layer is one or more of an Au electrode layer, a silver electrode layer, and an aluminum electrode layer.

[0015] Preferably, the thickness of the electron transport layer is 130-160 nm, and the thickness of the PbS-PbX2 quantum dot thin film layer is 300-380 nm.

[0016] In a fifth aspect, the present application provides a method for preparing a PbS quantum dot solar cell, comprising the following steps: A layer of an electron transport layer is prepared on the lower electrode layer by a coating method; a layer of a PbS-PbX2 quantum dot layer is coated on the electron transport layer, and after annealing treatment, a PbS-PbX2 quantum dot active layer is obtained; the PbS-EDT hole transport layer is prepared according to the method described above with the PbS-PbX2 quantum dot active layer as a substrate, and finally, an upper electrode layer is prepared on the PbS-EDT hole transport layer to obtain a PbS quantum dot solar cell.

[0017] Preferably, the annealing temperature is 70-85℃, and the annealing treatment time is 10-20 min.

[0018] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: In the method of the present application, the solvent of the exchange solution is an acetonitrile-dichloromethane-isopropanol system; the solvent system inhibits unnecessary ionization of ligand molecules by regulating the dielectric environment, changes the surface coordination process from random adsorption to directional and ordered assembly, not only reduces the defect state density such as surface dangling bonds, but also significantly improves the carrier mobility and device stability. At the same time, the addition of PbCl2 in the exchange solution can make up for the slow exchange rate of EDT caused by the change of the solvent, and the Cl - The advantages of the PbS-EDT hole transport layer are that it can quickly occupy sites and compete with hydroxyl groups for sites to form a hydrophobic barrier, thereby enhancing the water resistance of the PbS-EDT hole transport layer. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Mechanism diagram of the exchange solution passivating the PbS-OA quantum dot layer.

[0020] Figure 2 The PbS-EDT hole transport layer prepared for Example 1 and Comparative Example 1 was subjected to PL testing.

[0021] Figure 3 SCLC testing diagram of the PbS-EDT hole transport layer prepared for Example 1 and Comparative Example 1.

[0022] Figure 4PCE test chart of the solar cell prepared for Example 1 and Comparative Example 1.

[0023] Figure 5 EQE test chart of the solar cell prepared for Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the present application, the present application will be described in more detail below in conjunction with the drawings of the specification and the preferred embodiments, but the protection scope of the present application is not limited to the following specific embodiments. Unless otherwise defined, all the professional terms used herein have the same meaning as generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing the specific embodiments and are not intended to limit the protection scope of the present application.

[0025] As described previously, in the first aspect, a preparation method of a PbS-EDT quantum dot hole transport layer includes the following steps: (1) PbS-OA quantum dots are prepared into a PbS-OA quantum dot solution; 1,2-ethanedithiol is dissolved in a mixed solvent composed of dichloromethane, isopropyl alcohol and acetonitrile to obtain solution 1, PbCl2 is dissolved in N,N-dimethylformamide (DMF) to obtain solution 2, and solution 2 is added to solution 1 to obtain an exchange solution; (2) The PbS-OA quantum dot solution is coated on a substrate to obtain a PbS-OA quantum dot layer; the exchange solution is spread over the PbS-OA quantum dot layer, and after ligand exchange, cleaning, and then repeating the steps of coating PbS-OA quantum dots, spreading the exchange solution, ligand exchange and cleaning, a PbS-EDT quantum dot hole transport layer is obtained.

[0026] The conventional EDT directly uses pure acetonitrile for dissolution. Since the polarity of acetonitrile and EDT is large, the rate of replacing the oleic acid ligand on the surface of the quantum dots is too fast, which can cause the local shrinkage force of the quantum dot film to be too large, thereby causing the film to crack and produce microcracks. The mechanism diagram of the ligand exchange process in the preparation process of the PbS-EDT quantum dot hole transport layer in the present application is shown in FIG. 1. Figure 1 As can be seen from FIG. 1, in the present application, dichloromethane (DCM), isopropyl alcohol (IPA) and acetonitrile are blended to form a low-polarity solvent system, so that the polarity of the exchange solution and the critical polarity of the desorption of the oleic acid ligand are highly matched, thereby reducing the replacement rate and releasing the internal stress of the film, avoiding the local stress concentration of the quantum dots due to rapid agglomeration, and further improving the transmission speed of the carriers. In addition, in the present application, PbCl2 is introduced into the exchange solution to passivate the surface of the quantum dots, and Cl -The ions can occupy the defect sites and anchor the active sites of the surface, compete with the hydroxyl in water for the active sites, on one hand, compensate for the decrease of ligand exchange efficiency caused by the decrease of exchange reaction rate, on the other hand, block the erosion path of the environmental hydroxyl, thereby hindering the erosion of the environmental moisture to the greatest extent. In addition, due to the presence of PbCl2, the PbS-OA quantum dot film can be oxidized for a longer time, so that a lower concentration of PbS-OA quantum dot solution can be used to prepare a multilayer composite PbS-EDT hole transport layer, so that the hole transport performance is stronger, and the performance is further improved. Therefore, the preparation of the PbS-EDT hole transport layer in the application can allow the single-layer film to have more time to accept oxidation, and the step is linked with the low-concentration PbS-EDT layer, thereby solving the problem of insufficient internal oxidation of the multilayer hole transport layer.

[0027] Preferably, in the step (1), the concentration of the PbS-OA quantum dot solution is 20-25 mg / mL, including but not limited to 20 mg / mL, 21 mg / mL, 22 mg / mL, 23 mg / mL, 24 mg / mL, 25 mg / mL, etc.

[0028] Preferably, in the step (1), in the solution 1, the volume ratio of dichloromethane, isopropyl alcohol and acetonitrile is (1.5-2.5):(2.5-3.5):(4.5-5.5), including but not limited to 1.5:2.5:4.5, 1.5:3:4.5, 1.5:3.5:4.5, 1.5:3:4.5, 1.5:3:5, 1.5:3.5:5.5, 2:2.5:4.5, 2:3:4.5, 2:3.5:4.5, 2:3:4.5, 2:3:5, 2:3.5:5.5, 3:2.5:4.5, 3:3:5, 3:3.5:4.5, 3:3.5:4.5, 3:2.5:5.5, 3:3.5:5, etc.

[0029] In the application, by controlling the volume ratio of dichloromethane, isopropyl alcohol and acetonitrile, the exchange speed can be ensured while effectively avoiding the occurrence of microcracks in the PbS-EDT quantum dot hole transport layer.

[0030] Preferably, in the step (1), the concentration of 1,2-ethanedithiol in the solution 1 is 0.01-0.02wt%, including but not limited to 0.01wt%, 0.012wt%, 0.015wt%, 0.018wt%, 0.02wt%, etc.

[0031] Preferably, in the step (1), the concentration of lead chloride in solution 2 is 0.05-0.1 M, including but not limited to 0.05 M, 0.06 M, 0.07 M, 0.08 M, 0.09 M, 0.1 M, etc.; the volume ratio of solution 1 to solution 2 is 100:(0.8-1.2), including but not limited to 100:0.8, 100:0.9, 100:1, 100:1.1, 100:1.2, etc.

[0032] In the present application, by controlling the concentration of lead chloride, the performance of the PbS-EDT hole transport layer is improved while avoiding affecting the main ligand exchange process of the quantum dots.

[0033] Preferably, in the step (2), the thickness of the PbS-EDT quantum dot hole transport layer is 35-55 nm, including but not limited to 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, etc.

[0034] Preferably, in the step (2), the ligand exchange time is 20-30 s, including but not limited to 20 s, 22 s, 25 s, 28 s, 30 s, etc.

[0035] Preferably, in the step (2), the cleaning uses a mixed solvent composed of dichloromethane, isopropyl alcohol and acetonitrile for 3-4 times of cleaning.

[0036] Preferably, in the step (2), the number of times of repeating the steps of coating quantum dots, spreading exchange solution, ligand exchange and cleaning is 1-2 times.

[0037] In a second aspect, the present application provides a PbS-EDT quantum dot hole transport layer prepared by the above preparation method.

[0038] In a third aspect, the present application provides a PbS-EDT quantum dot hole transport layer for use in solar cells and photodetectors.

[0039] In a fourth aspect, the present application provides a PbS quantum dot solar cell, which comprises, from bottom to top, a lower electrode layer, an electron transport layer, a PbS-PbX2 quantum dot active layer, the above-mentioned PbS-EDT hole transport layer and an upper electrode layer; wherein X is I and / or Br.

[0040] Preferably, the lower electrode layer is an ITO thin film layer, the electron transport layer is one or more of a zinc oxide layer, a tin dioxide layer, a magnesium-doped zinc oxide layer and an aluminum-doped zinc oxide layer, and the upper electrode layer is one or more of an Au electrode layer, a silver electrode layer and an aluminum electrode layer.

[0041] Preferably, the thickness of the electron transport layer is 130-160 nm, and the thickness of the PbS-PbX2 quantum dot active layer is 300-380 nm.

[0042] In a fifth aspect, the present application provides a method for preparing a PbS quantum dot solar cell, comprising the following steps: A layer of electron transport layer is prepared on the lower electrode layer by coating method; a layer of PbS-PbX2 quantum dot layer is coated on the electron transport layer, and after annealing treatment, a PbS-PbX2 quantum dot active layer is obtained; the PbS-PbX2 quantum dot film layer is used as a substrate, and the PbS-EDT hole transport layer is prepared according to the preparation method described above, and finally the upper electrode layer is prepared on the PbS-EDT hole transport layer to obtain the PbS quantum dot solar cell.

[0043] Preferably, the annealing treatment temperature is 70-85℃, and the annealing treatment time is 10-20min.

[0044] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0045] Preparation Example 1 Preparation of PbS-OA quantum dots 4.5g of PbO, 16mL of OA (oleic acid) and 40mL of ODE (octadecene) were mixed and then added to a reactor, followed by heating to 80℃ under vacuum, and maintaining the temperature for 1h; after the end of the incubation, nitrogen was continuously introduced into the flask for 8min; after the end of the aeration, vacuum was applied, and the temperature was raised to 120℃ under vacuum, and the reaction was carried out for 40min; then 11.4mL of (TMS)2M (bis (trimethylsilyl) sulfide) ODE solution (1.4mL of (TMS)2M was dissolved in 10mL of ODE and deoxygenated and dehydrated) was injected into the reaction solution, and the reaction was quenched by injecting 40mL of n-hexane, and the reaction solution was cooled to 0-2℃ using an ice bath, and then the solution was allowed to stand at a temperature of 0-2℃ for 12h, and then centrifuged at a speed of 6000rpm for 5min, and then the upper layer of the centrifuged solution was added with a washing solution (the washing solution was a mixture of ethyl acetate and ethanol in a volume ratio of 1:2), and then shaken for 30min, and then centrifuged at a speed of 4000rpm for 5min, and then the PbS-OA quantum dots were precipitated, and the upper liquid was poured out, and then the washing solution was added again, and then the washing operation was repeated for 3 times to obtain wet PbS-OA quantum dots; the wet PbS-OA quantum dots were vacuum dried for 4h to obtain PbS-OA quantum dots (the absorption peak of the quantum dots was 885nm).

[0046] Preparation Example 2 After 5.5 g of PbO, 30 mL of OA (oleic acid), and 40 mL of ODE (octadecene) were mixed, they were added to a reactor, which was then heated to 110°C under vacuum and kept at this temperature for 1 h; after the incubation period, nitrogen was continuously introduced into the flask for 8 min; after the gas was introduced, the vacuum was re-applied and the temperature was raised to 135°C under vacuum, and the reaction was allowed to proceed for 40 min; 12.1 mL of a (TMS)2M (bis (trimethylsilyl) sulfide) solution in ODE (2.1 mL of (TMS)2M was dissolved in 10 mL of ODE and deoxygenated and dehydrated) was then injected into the reaction solution, and the reaction was allowed to proceed rapidly for 2 min; the reaction was then quenched by injecting 40 mL of n-hexane, and the reaction solution was cooled to 0-2°C using an ice bath, and then allowed to stand at 0-2°C for 12 h, after which it was centrifuged at 6000 rpm for 5 min; a washing solution (a 1:2 mixture by volume of ethyl acetate and ethanol) was then added to the supernatant, and the mixture was shaken for 30 min and then centrifuged at 4000 rpm for 5 min; the PbS-OA quantum dots were then precipitated, the supernatant was poured out, and the washing solution was added again; this washing operation was repeated three times to obtain wet PbS-OA quantum dots; the wet PbS-OA quantum dots were then vacuum-dried for 4 h to obtain PbS-OA quantum dots (the absorption peak of the quantum dots was 1330 nm) Preparation of PbS-PbX2quantum dots After 0.922 g of PbI2, 0.294 g of PbBr2, and 0.0617 g of ammonium acetate were added to 20 mL of DMF, the solute was allowed to dissolve completely by shaking the solution at 50°C for 3 h using a shaking instrument, and then the solution was filtered using a polytetrafluoroethylene (PTFE) filter head with a pore size of 0.22 μm to obtain a lead halide precursor solution. The PbS-OA quantum dots prepared in Preparation Example 1 were dispersed in n-hexane to prepare a 7 mg / mL PbS-OA quantum dot solution. 20 mL of the PbS-OA quantum dot solution was added to 20 mL of the lead halide precursor solution, and after shaking at 50°C for 3 min, the upper layer of the solution became colorless and the lower layer became black; at this point, the upper layer was poured out, and n-hexane was then added to the lower layer to wash it; after the solution was washed five times, toluene was added, and the resulting mixture was centrifuged; the solid obtained after centrifugation was vacuum-dried to obtain PbS-PbX2quantum dots.

[0047] Preparation of PbS-PbX2quantum dots The preparation was basically the same as in Preparation Example 3, except that the PbS-OA quantum dots used were those prepared in Preparation Example 2.

[0048] Preparation of PbS quantum dot solar cells The PbS quantum dot solar cell in the embodiment includes, from bottom to top, ITO lower electrode layer, ZnO electron transport layer, PbS-PbX2 quantum dot active layer, PbS-EDT hole transport layer, and Au upper electrode layer in sequence. The specific preparation method is as follows: 1) The PbS quantum dots prepared in Preparation Example 1 were dispersed in n-hexane to prepare a PbS quantum dot solution with a concentration of 22 mg / mL; the PbS-PbX2 quantum dots prepared in Preparation Example 3 were dissolved in n-butylamine (BTA) to prepare a PbS-PbX2 quantum dot solution with a concentration of 320 mg / mL; 1,2-ethanedithiol was dissolved in a mixed solvent composed of dichloromethane, isopropyl alcohol and acetonitrile in a volume ratio of 2:3:5 to obtain solution 1 (1,2-ethanedithiol concentration of 0.015 wt%); lead chloride was dissolved in DMF to obtain solution 2 (lead chloride concentration of 0.075 M); solution 1 and solution 2 were mixed in a volume ratio of 100:1 to obtain an exchange solution.

[0049] 2) After the transparent conductive substrate ITO was subjected to ultrasonic cleaning and plasma cleaning in sequence, a pretreated ITO electrode was obtained; a layer of ZnO electron transport layer (thickness of 150 nm) was prepared on the pretreated ITO electrode by spin coating; then the PbS-PbX2 quantum dot solution (prepared in step 1) was immediately spin-coated on the ZnO electron transport layer at a rotation speed of 1800 rpm after centrifugation at a rotation speed of 12000 rpm for 1 min, and then annealed at 80℃ for 15 min to obtain a PbS-PbX2 quantum dot layer (thickness of 350 nm); the PbS-OA quantum dot solution (prepared in step 1) was spin-coated on the PbS-PbX2 quantum dot layer, and then a PbS-OA quantum dot layer was obtained; after the PbS quantum dot layer was spread with the exchange solution, the reaction was carried out for 25 s, and then the film was washed with a mixed solution composed of dichloromethane, isopropyl alcohol and acetonitrile in a volume ratio of 2:3:5 for three times; the steps of spin-coating PbS-OA quantum dots, spreading with the exchange solution and washing were repeated once (the spin-coating of PbS-OA quantum dots, the spreading with the exchange solution and the washing were carried out for two times in total) to obtain a PbS-EDT hole transport layer (thickness of 40 nm); a layer of Au upper electrode (thickness of 80 nm) was prepared on the EDT hole transport layer by vacuum evaporation to obtain a PbS quantum dot solar cell.

[0050] Comparative Example 1 The same as Example 1, except that the preparation method of the exchange solution in step (1) is as follows: 1,2-ethanedithiol was dissolved in a mixed solvent composed of dichloromethane, isopropyl alcohol and acetonitrile in a volume ratio of 2:3:5 to obtain solution 1 (1,2-ethanedithiol concentration of 0.015 wt%); solution 1 and DMF were mixed in a volume ratio of 100:1 to obtain the exchange solution.

[0051] The PbS-EDT hole transport layer prepared in Example 1 and Comparative Example 1 was subjected to PL test, and the results are shown in Figure 2 It can be seen that the absorption peak position of the hole transport layer in Example 1 is red-shifted from 1048 nm to 1051 nm, i.e. Example 1 has a red shift of 3 nm, which can be attributed to the enhanced coupling between the quantum dots in Example 1, thus faster energy transfer.

[0052] The SCLC test chart of the PbS-EDT hole transport layer prepared in Example 1 and Comparative Example 1 is shown in Figure 3 It can be found that the V TFL of Comparative Example 1 is 0.29 V, and the V TFL of Example 1 is 0.22 V, indicating that the limiting filling voltage of Example 1 is greater than that of Comparative Example 1, which shows that the overall defects of the hole transport layer of Example 1 are less and the quality is better.

[0053] In addition, the solar cell prepared in Example 1 and Comparative Example 1 was subjected to PCE test and EQE test, and the test results are shown in Figure 4 and Figure 5 , and the specific data are shown in Table 1. It can be seen that the PCE of the device of Comparative Example 1 is 10.20%, and the PCE of the device of Example 1 is 11.06%; which shows that the photoelectric conversion efficiency of Example 1 is higher, which can be mainly attributed to the optimization of the PbS-EDT hole transport layer. The EQE of Example 1 has higher quantum efficiency, and the defects inside the solar cell are less, which is more conducive to the separation of excitons and the transport of carriers.

[0054] Comparative Example 2 is basically the same as Example 1, except that in step (1), the solvent of solution 1 is single acetonitrile as the solvent.

[0055] Comparative Example 3 is basically the same as Example 1, except that in step (1), the solvent of solution 1 is dichloromethane and acetonitrile in a volume ratio of 5:5.

[0056] Comparative Example 4 is basically the same as Example 1, except that in step (1), the solvent of solution 1 is isopropanol and acetonitrile in a volume ratio of 5:5.

[0057] Example 2 is basically the same as Example 1, except that in step (1), the concentration of lead chloride in solution 2 is 0.05 M, and solution 1 and solution 2 are mixed in a volume ratio of 100:0.8.

[0058] Example 3 The preparation method of Example 1 is basically the same, except that in step (1), the concentration of lead chloride in solution 2 is 0.1M, and solution 1 and solution 2 are mixed in a volume ratio of 100:1.2.

[0059] The solar cells prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to J-V testing and EQE testing, and the test data are shown in Table 1; it can be seen that in Comparative Example 1, no lead chloride is added to the exchange solution, and the performance of the solar cell is poor, and in Example 1, the addition of lead chloride significantly improves the overall performance of the solar cell. In Example 2, the content of lead chloride added is less, and the overall performance of the solar cell is lower than that of Example 1, which may be because the amount added is too small, and the passivation effect and exchange speed relief effect are limited. In Example 3, the content of lead chloride added is more, and the overall performance of the solar cell is lower than that of Example 1, which may be because the amount of PbCl2 added is too much, and Cl ions and EDT form too many site competitions, resulting in a decrease in P property of the hole transport layer, affecting the charge transport. However, the overall performance of the solar cell in Example 2 and Example 3 is still better than that in Comparative Example 1. Comparative Examples 2-4 mainly use different solvents in solution 1 compared with Example 1, and the solvent of solution 1 in Comparative Example 2 is only acetonitrile, the solvent of solution 1 in Comparative Example 3 is a volume ratio of 5:5 dichloromethane and acetonitrile, and the solvent of solution 1 in Comparative Example 4 is a volume ratio of 5:5 isopropanol and acetonitrile; the overall performance of the solar cells obtained in Comparative Examples 2-4 is significantly lower than that of Example 1, which may be because the solvents in Comparative Examples 2-4 easily cause microcracks in the PbS-EDT hole transport layer, thereby affecting the performance of the solar cell.

[0060] Table 1 Preparation of a PbS quantum dot solar cell in Example 4 The PbS quantum dot solar cell in this example includes, from bottom to top, an ITO lower electrode layer, a ZnO electron transport layer, a PbS-PbX2 quantum dot active layer, a PbS-EDT hole transport layer, and an Au upper electrode layer; the specific preparation method is as follows: 1) The PbS-OA quantum dots prepared in Preparation Example 1 were dispersed in n-hexane to prepare a PbS-OA quantum dot solution with a concentration of 20 mg / mL; the PbS-PbX2 quantum dots prepared in Preparation Example 2 were dissolved in n-butylamine (BTA) to prepare a PbS-PbX2 quantum dot solution with a concentration of 310 mg / mL; 1,2-ethanedithiol was dissolved in a mixed solvent composed of dichloromethane, isopropyl alcohol and acetonitrile in a volume ratio of 1.5:3.5:4.5 to obtain solution 1 (the concentration of 1,2-ethanedithiol was 0.01 wt%); lead chloride was dissolved in DMF to obtain solution 2 (the concentration of lead chloride was 0.085 M); solution 1 and solution 2 were mixed in a volume ratio of 100:1 to obtain an exchange solution.

[0061] 2) The transparent conductive substrate ITO was subjected to ultrasonic cleaning and plasma cleaning in sequence to obtain a pretreated ITO electrode; a ZnO electron transport layer (130 nm in thickness) was prepared on the pretreated ITO electrode by a spin coating method; then the PbS-PbX2 quantum dot solution (prepared in step 1) was immediately spin-coated on the ZnO electron transport layer at a rotation speed of 12000 rpm, and after spin coating, the sample was annealed at 70°C for 20 min to obtain a PbS-PbX2 quantum dot layer (300 nm in thickness); the PbS-OA quantum dot solution (prepared in step 1) was spin-coated on the PbS-PbX2 quantum dot layer, and after spin coating, a PbS-OA quantum dot layer was obtained; the exchange solution was spread on the PbS-OA quantum dot layer, and after reaction for 30 s, the film was washed with a mixed solution composed of dichloromethane, isopropyl alcohol and acetonitrile in a volume ratio of 1.5:3.5:4.5 for three times; the spin-coating of the PbS-OA quantum dots, the spreading of the exchange solution and the washing were repeated once (the spin-coating of the PbS-OA quantum dots, the spreading of the exchange solution and the washing were performed twice in total) to obtain a PbS-EDT hole transport layer (35 nm in thickness); an Au upper electrode layer (80 nm in thickness) was prepared on the EDT hole transport layer by a vacuum evaporation method to obtain a PbS quantum dot solar cell.

[0062] The solar cell prepared in Example 4 was subjected to J-V testing and EQE testing, and the test data are shown in Table 2.

[0063] Table 2 Example 5 Quantum dot detector The PbS quantum dot detector in this example comprises, from bottom to top, an ITO lower electrode layer, a ZnO electron transport layer, a PbS-PbX2 quantum dot active layer, a PbS-EDT hole transport layer and an Au upper electrode layer in sequence; the specific preparation method is as follows: 1) PbS-OA quantum dots prepared in Preparation Example 2 were dispersed in n-hexane to prepare a PbS quantum dot solution of 25 mg / mL; PbS-PbX2 quantum dots prepared in Preparation Example 4 were dissolved in n-butylamine (BTA) to prepare a PbS-PbX2 quantum dot solution of 340 mg / mL; 1,2-ethanedithiol was dissolved in a mixed solvent of dichloromethane, isopropyl alcohol and acetonitrile in a volume ratio of 2.5:2.5:5.5 to obtain solution 1 (1,2-ethanedithiol concentration of 0.02 wt%); lead chloride was dissolved in DMF to obtain solution 2 (lead chloride concentration of 0.065 M); solution 1 and solution 2 were mixed in a volume ratio of 100:1 to obtain an exchange solution.

[0064] 2) After the transparent conductive substrate ITO was subjected to ultrasonic cleaning and plasma cleaning in sequence, a pretreated ITO electrode was obtained; a ZnO electron transport layer (thickness of 160 nm) was prepared on the pretreated ITO electrode by a spin coating method; then the PbS-PbX2 quantum dot solution (prepared in step 1) was immediately spin-coated on the ZnO electron transport layer at a rotation speed of 12000 rpm, and after spin coating, the PbS-PbX2 quantum dot layer (thickness of 380 nm) was obtained by annealing at 85°C for 10 min; the PbS-OA quantum dot solution (prepared in step 1) was spin-coated on the PbS-PbX2 quantum dot layer, and after spin coating, the PbS-OA quantum dot layer was obtained; after the PbS-OA quantum dot layer was spread with the exchange solution, the reaction was carried out for 20 s, then the film was washed with a mixed solution of dichloromethane, isopropyl alcohol and acetonitrile in a volume ratio of 2.5:2.5:5.5 for three times, and the spin-coating of the PbS-OA quantum dot, the spreading with the exchange solution and the washing were repeated twice (the spin-coating of the PbS-OA quantum dot, the spreading with the exchange solution and the washing were carried out for three times in total), and a PbS-EDT hole transport layer (thickness of 55 nm) was obtained; an Au upper electrode (thickness of 80 nm) was prepared on the EDT hole transport layer by a vacuum evaporation method, and a PbS quantum dot detector was obtained.

[0065] Comparative Example 5 The same as Example 5, except that the exchange solution was prepared as follows: 1,2-ethanedithiol was dissolved in a mixed solvent of dichloromethane, isopropyl alcohol and acetonitrile in a volume ratio of 2.5:2.5:5.5 to obtain solution 1 (1,2-ethanedithiol concentration of 0.02 wt%), and solution 1 and DMF were mixed in a volume ratio of 100:1 to obtain the exchange solution.

[0066] The quantum dot detectors prepared in Example 5 and Comparative Example 5 were tested for wavelength response range, responsivity, detectivity and dark current density, and the test results are shown in Table 3, and the specific test methods are as follows: (1) Wavelength response range: can be directly tested by using Fourier transform infrared spectrometer or tunable laser.

[0067] (2) Responsivity: the responsivity test is to use a standard halogen lamp and a monochromator to output monochromatic light of a specific wavelength, calibrate the light power by a power meter, measure the photocurrent I ph under the bias voltage of the detector with a picoammeter.

[0068] Responsivity calculation formula: R = I ph / P opt (A / W) (3) Dark current density: the dark current density test is to place the detector in a full black shielding box to eliminate the interference of ambient light, and measure the dark current I dark with the change of bias voltage.

[0069] Dark current density calculation formula: J dark = I dark / A (A / cm²), wherein A is the effective area of a single pixel.

[0070] (4) Specific detectivity: the specific detectivity (D*) is a core parameter representing the sensitivity of the photodetector, defined as the signal-to-noise ratio corresponding to the unit incident radiation power when the sensitive element area of the detector is 1 cm² and the measurement bandwidth is 1 Hz.

[0071] Specific detectivity calculation formula: D* = I Table 3 As can be seen from Table 3, the introduction of lead chloride in the exchange solution in Example 5 can increase the performance of quantum dot detection responsivity, specific detectivity, dark current density, etc. compared with Comparative Example 5.

[0072] The above examples are only for illustrating the technical concept and characteristics of the present application, the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A method for preparing a PbS-EDT quantum dot hole transport layer, characterized in that, Includes the following steps: (1) PbS-OA quantum dots were prepared into PbS-OA quantum dot solution; 1,2-ethanedithiol was dissolved in a mixed solvent composed of dichloromethane, isopropanol and acetonitrile to obtain solution 1; PbCl2 was dissolved in N,N-dimethylformamide to obtain solution 2. Solution 2 is added to solution 1 to obtain the exchange solution; (2) The PbS-OA quantum dot solution was coated onto the substrate to obtain a PbS-OA quantum dot layer; The PbS-OA quantum dot layer was coated with an exchange solution, and after ligand exchange, it was washed. Then, the steps of coating PbS-OA quantum dots, coating with exchange solution, ligand exchange, and washing were repeated to obtain the PbS-EDT quantum dot hole transport layer.

2. The method for preparing the PbS-EDT quantum dot hole transport layer according to claim 1, characterized in that, In step (1), the concentration of the PbS-OA quantum dot solution is 20~25 mg / mL; In solution 1, the volume ratio of dichloromethane, isopropanol, and acetonitrile is (1.5~2.5):(2.5~3.5):(4.5~5.5); The concentration of 1,2-ethylenedithiol in solution 1 is 0.01~0.02 wt%; The concentration of lead chloride in solution 2 is 0.05~0.01M; The volume ratio of solution 1 to solution 2 is 100:(0.8~1.2).

3. The method for preparing the PbS-EDT quantum dot hole transport layer according to claim 1, characterized in that, In step (2), the ligand exchange time is 20~30s; The cleaning process involves 3-4 cycles of cleaning with a mixed solvent consisting of dichloromethane, isopropanol, and acetonitrile.

4. The method for preparing the PbS-EDT quantum dot hole transport layer according to claim 1 or 3, characterized in that, The process of coating PbS-OA quantum dots, spreading the exchange solution, ligand exchange, and washing is repeated 1 to 2 times.

5. The method for preparing the PbS-EDT quantum dot hole transport layer according to claim 1 or 3, characterized in that, In step (2), the thickness of the PbS-EDT quantum dot hole transport layer is 35~55nm.

6. A PbS-EDT quantum dot hole transport layer, prepared by any of the preparation methods described in claims 1 to 5.

7. The PbS-EDT quantum dot hole transport layer according to claim 6 is used in solar cells and photodetectors.

8. A PbS quantum dot solar cell, characterized in that, From bottom to top, it includes a lower electrode layer, an electron transport layer, a PbS-PbX2 quantum dot active layer, a PbS-EDT hole transport layer as described in claim 5, and an upper electrode layer; wherein: X is I and / or Br.

9. The PbS quantum dot solar cell according to claim 8, characterized in that, The lower electrode layer is an ITO thin film layer, the electron transport layer is one or more of zinc oxide layer, tin dioxide layer, magnesium-doped zinc oxide layer, and aluminum-doped zinc oxide layer, and the upper electrode layer is one or more of Au electrode layer, silver electrode layer, and aluminum electrode layer.

10. The PbS quantum dot solar cell according to claim 8, characterized in that, The thickness of the electron transport layer is 130~160nm; the thickness of the PbS-PbX2 quantum dot thin film layer is 300~380nm.

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