Lead sulfide infrared photoelectric detector and preparation method and application thereof
By introducing a bilayer LiF/C60 interface structure into a PbS infrared photodetector, the carrier recombination problem caused by interface defects was solved, improving quantum efficiency, response speed and stability, and broadening the response wavelength range.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-28
- Publication Date
- 2026-03-27
AI Technical Summary
Traditional PbS infrared photodetectors suffer from increased carrier recombination due to interface defects, resulting in low quantum efficiency, slow response speed, and poor stability.
A bilayer LiF/C60 interface structure was designed, with the LiF film serving as the initial interface modification layer to reduce the interface state density, and the C60 film enhancing the electron transport capability. The uniformity and stability of the layers were ensured by strictly controlling the deposition conditions.
It effectively reduces carrier recombination, improves quantum efficiency and response speed, enhances the long-term stability of the device, and broadens the wavelength range for efficient response.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of optoelectronics, and in particular to a lead sulfide infrared photodetector and a preparation method and application thereof. BACKGROUND
[0002] Lead sulfide (PbS) infrared photodetectors are important devices in the field of photodetection, with good photoelectric performance. However, conventional PbS infrared photodetectors have significant problems in interface defects, which can cause an increase in carrier recombination, thereby reducing quantum efficiency and response speed. In addition, interface defects can also cause a decrease in the stability of the device, affecting the reliability and stability of long-term use.
[0003] In related technologies, the above problems are generally improved by optimizing the material preparation process or introducing an interface modification layer. However, the current material preparation process optimization has limited effect; and the introduction of an interface modification layer is also difficult to comprehensively improve the performance of the device, and the problem of how to effectively combine the newly introduced material with the original structure to form a stable interface structure needs to be solved.
[0004] Therefore, it is of great significance to effectively solve the problem of carrier recombination caused by the interface defects of the current PbS infrared photodetector, and to improve the quantum efficiency and response speed of the detector, as well as the stability of long-term use of the device. SUMMARY
[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a lead sulfide infrared photodetector and a preparation method and application thereof, aiming to solve the problem of carrier recombination caused by the interface defects of the current PbS infrared photodetector, and to improve the quantum efficiency and response speed of the detector, as well as the stability of long-term use of the device.
[0006] Embodiments of the first aspect of the present application provide a lead sulfide infrared photodetector, comprising a transparent electrode, a hole transport layer, a lead sulfide infrared light absorption layer, a functional layer, an electron transport layer, and a top electrode which are sequentially stacked from bottom to top; the functional layer comprises a LiF thin film and a C 60 thin film on the surface of the LiF thin film.
[0007] The lead sulfide infrared photodetector according to the embodiments of the first aspect of the present application has at least the following beneficial effects: the lead sulfide (PbS) infrared photodetector provided by the present application designs a double-layer LiF / C 60 interface structure as a functional layer: a LiF (lithium fluoride) thin film is used as an initial interface modification layer to reduce interface state density and reduce carrier recombination; a C 60The thin film layer enhances the electron transmission capacity, thereby improving the quantum efficiency and response speed of the device. 60 The deposition conditions are strictly controlled to ensure the uniformity and stability of the LiF and C 60 layers. The photoelectric performance and stability of the experimental device are evaluated to verify the application effect of the device in the PbS detector. The PbS infrared photodetector with the above-mentioned double-layer LiF / C 60 interface structure effectively reduces the carrier recombination caused by the interface defects of the lead sulfide detector, thereby improving the quantum efficiency; the response speed is improved by enhancing the electron transmission capacity; and the long-term use stability of the device is improved by the stable interface structure.
[0008] C 60 is a member of the fullerene family, which is composed of 60 carbon atoms and has a shape similar to a football, so it is also called "fullerene". The unique structure of fullerene endows it with excellent electron transmission performance, and LiF can effectively reduce the interface state density. Both of them have the potential to be used as interface modification materials, which can theoretically improve the performance of the device. However, how to effectively combine these two materials to form a stable interface structure is still a problem to be solved. Based on this, the present application designs a double-layer LiF / C 60 interface structure, adopts LiF as the initial interface modification layer to reduce the interface state density and reduce carrier recombination; and deposits C 60 layer to enhance the electron transmission capacity, thereby improving the quantum efficiency and response speed of the device. The present application first deposits the LiF layer to reduce the interface state density, and then deposits the C 60 layer to enhance the electron transmission capacity. At the same time, the deposition conditions (temperature, pressure, time, etc.) are strictly controlled during the deposition process to ensure the uniformity and stability of the LiF and C 60 layers. Finally, the photoelectric performance test is carried out to evaluate the quantum efficiency, response speed and stability of the device, and to verify the application effect of the device in the PbS detector. It is finally found that the above-mentioned double-layer LiF / C 60 interface structure of the lead sulfide infrared photodetector effectively reduces the carrier recombination caused by the interface defects of the lead sulfide detector, thereby improving the quantum efficiency; the response speed is improved by enhancing the electron transmission capacity; and the long-term use stability of the device is improved by the stable interface structure.
[0009] The core function of a PbS infrared photodetector is to realize the conversion of "optical signal to electrical signal", and its core requirements include low dark current, high detection rate and fast response speed, which are suitable for infrared spectral detection, biomedical and other weak light scenes. However, the PbS infrared photodetector has a core defect, specifically, there is a high interface state density between the PbS light absorption layer and the electron transport layer, and the carrier recombination is serious, which leads to low quantum efficiency, slow response speed and poor stability. To solve the above-mentioned key problem of interface defect of PbS detector, the present application focuses on the device structure, and a functional layer (LiF / C 60 ) is designed. Among them, the LiF thin film can reduce the interface state density and inhibit the carrier recombination; the C 60 thin film can enhance the electron transport capacity. The synergistic effect of the two can effectively improve the quantum efficiency, response speed and long-term stability of the detector. Although there are reports that LiF and fullerene are used as an electron transport layer, the electron transport layer also includes other modification layers or buffer layers. In this structure, LiF is only used as a "starting passivation layer", which needs to rely on the modification layer to provide nucleophilic groups to assist the nucleation of the buffer layer, and its core function is to isolate fullerene from the buffer layer precursor, which cannot solve the above-mentioned key problem of interface defect of PbS detector. Unlike the above, the present application adopts an independent double-layer functional layer (LiF+C 60 ), which is directly arranged between the PbS light absorption layer and the electron transport layer without additional auxiliary layers. Among them, the LiF thin film is not a "starting layer", but can directly passivate the defects on the surface of PbS, which can directly fill the defect sites on the surface of PbS quantum dots, effectively reduce the interface state density, and inhibit the recombination of carriers from the root; and the C 60 thin film plays a role of close connection, which closely connects the LiF layer and the electron transport layer, and by virtue of the high electron mobility of C 60 , the photo-generated electrons can be quickly guided out to avoid their retention at the interface, and the electron transport capacity is enhanced, thereby forming a synergistic effect with the LiF layer; the two form a "passivation-transport" synergistic effect, which can solve the interface recombination problem of the PbS system.
[0010] In some embodiments of the present application, the LiF (lithium fluoride) thin film is located on the surface of the lead sulfide infrared light absorption layer, and the C 60 thin film is located on the surface of the LiF thin film. LiF modification not only improves the "efficiency limit" of photoelectric conversion, but also widens the wavelength range of high-efficiency response, and shows more excellent weak light adaptability.
[0011] In some embodiments of the present application, the thickness of the LiF thin film ranges from 0.5 nm to 3 nm, preferably from 1 nm to 3 nm, and more preferably about 1 nm. Exemplarily, it can be 0.5 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, or within a range between any two of the above values. As an electron transport layer or an interface modification layer, the thickness of the LiF layer directly affects the carrier transport, interface state and light response characteristics. The effective range of the thickness of the LiF thin film is 0.5 nm to 3 nm, and the optimal thickness is about 1 nm. Within this range, the device has high EQE and low dark current, and the photoelectric performance is optimal. In the actual process, the deposition thickness of LiF needs to be strictly controlled. The deposition rate and thickness can be monitored in real time to ensure that the key parameters fall within the effective range, thereby obtaining a high-performance device. If the LiF is too thin, it cannot cover the defects; if it is too thick, it will form a transport barrier. The present application proves that when the thickness of LiF is 1 nm, the collection efficiency of photo-generated carriers in a wide spectral range is excellent; from the dark current-voltage curve, the dark current density is extremely low, the leakage current under reverse bias is small, and the turn-on characteristics under forward bias are good, indicating that the device has few interface defects and good carrier transport barrier matching. This shows that when the thickness of LiF is 1 nm, the interface modification effect is moderate, which effectively promotes electron transport without introducing too many defects due to excessive thickness, and is one of the optimal parameter selections.
[0012] In some embodiments of the present application, the C 60 The thickness of the thin film ranges from 10 nm to 15 nm, and preferably is about 10 nm. Exemplarily, it can be 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, or within a range between any two of the above values. The present application optimizes the C 60 thin film for the infrared detection scene. If the C 60 thin film is too thin (<10 nm), the transport channel is insufficient; if it is too thick (>15 nm), the resistance will increase. Only within the thickness range of 10 nm to 15 nm, the C 60 thin film can not only tightly connect the LiF layer and the electron transport layer, but also quickly guide the photo-generated electrons out to avoid their retention at the interface, thereby enhancing the electron transport capacity and forming a synergistic effect with the LiF layer to solve the interface recombination problem of the PbS system.
[0013] In some embodiments of the present application, the lead sulfide infrared photoelectric detector comprises at least one of (a1) to (a7):
[0014] (a1) the transparent electrode comprises at least one of an ITO electrode, an FTO electrode, or an AZO electrode; (a2) the hole transport layer comprises a NiO x thin film, and a NiO xa ligand of PbS quantum dots in the PbS-EDT quantum dot film is 1,2-ethanedithiol (EDT); (a3) when (a2) is included, an exciton absorption peak of the PbS-EDT quantum dots in the PbS-EDT quantum dot film is 850-880 nm; (a4) the PbS infrared light absorption layer includes a PbS-ink quantum dot film, and a ligand of PbS quantum dots in the PbS-ink quantum dot film is lead iodide and lead bromide; (a5) when (a4) is included, an exciton absorption peak of the PbS quantum dots in the PbS-ink quantum dot film is 1200-1350 nm; (a6) the electron transport layer includes a PCBM film and a BCP film on a surface of the PCBM film; (a7) the top electrode includes an Ag electrode.
[0015] In some embodiments of the present application, at least one of (b1)-(b7) is included: (b1) the transparent electrode has a thickness of 130-170 nm; (b2) the NiO x a thickness of the film is 10-20 nm; (b3) the PbS-EDT quantum dot film has a thickness of 30-80 nm; (b4) the PbS-ink quantum dot film has a thickness of 300-500 nm; (b5) the PCBM film has a thickness of 10-20 nm; (b6) the BCP film has a thickness of 10-20 nm; (b7) the top electrode has a thickness of 80-120 nm.
[0016] In some embodiments of the present application, the transparent electrode includes at least one of an ITO (indium tin oxide) electrode, an FTO (fluorine-doped tin oxide) electrode, or an AZO (aluminum-doped zinc oxide) electrode, but is not limited thereto. The above-mentioned substances have a large band gap and thus absorb only ultraviolet light and not visible light, and are thus called "transparent electrodes". Any transparent electrode commonly used in the art can be reasonably applied.
[0017] In some embodiments of the present application, the transparent electrode has a thickness of 130-170 nm; preferably, about 150 nm. Exemplarily, it can be 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, or within a range between any two of the above-mentioned values.
[0018] In some embodiments of the present application, the hole transport layer comprises NiO x The thin film, and a PbS-EDT quantum dot film on the surface of the NiO x thin film, the ligand of the PbS quantum dot in the PbS-EDT quantum dot film is 1,2-ethanedithiol (EDT).
[0019] In some embodiments of the present application, the exciton absorption peak of the PbS quantum dot in the PbS-EDT quantum dot film is 850-880 nm.
[0020] In some embodiments of the present application, the thickness of the hole transport layer is 40-100 nm; preferably about 65 nm. Exemplarily, it can be 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or within a range between any two of the above values.
[0021] In some embodiments of the present application, the thickness of the NiO x thin film is 10-20 nm; preferably about 15 nm. Exemplarily, it can be 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, or within a range between any two of the above values.
[0022] In some embodiments of the present application, the thickness of the PbS-EDT quantum dot film is 30-80 nm; preferably about 50 nm. Exemplarily, it can be 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, or within a range between any two of the above values.
[0023] In some embodiments of the present application, the PbS-ink quantum dot film on the surface of the PbS-EDT quantum dot film uses mixed halogen ions iodine ion I - , bromine ion Br - as ligand treatment.
[0024] In some embodiments of the present application, the exciton absorption peak of the PbS quantum dot in the PbS-ink quantum dot film is 1200-1350 nm; preferably about 1240 nm.
[0025] In some embodiments of the present application, the thickness of the PbS-ink quantum dot film is 300-500 nm; preferably about 400 nm. Exemplarily, it can be 300 nm, 320 nm, 340 nm, 360 nm, 380 nm, 400 nm, 520 nm, 440 nm, 460 nm, 480 nm, 500 nm, or within a range between any two of the above values.
[0026] In some embodiments of the present application, the electron transport layer comprises a PCBM film and a BCP film on the surface of the PCBM film.
[0027] In some embodiments of the present application, the thickness of the PCBM film is 10-20 nm; exemplarily, it can be 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, or within a range between any two of the above values.
[0028] In some embodiments of the present application, the thickness of the BCP film is 10-20 nm; exemplarily, it can be 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, or within a range between any two of the above values.
[0029] In some embodiments of the present application, the top electrode comprises an Ag electrode.
[0030] In some embodiments of the present application, the thickness of the top electrode is 80-120 nm. Preferably, it is about 100 nm. Exemplarily, it can be 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, or within a range between any two of the above values.
[0031] In a specific embodiment of the present application, a double-layer LiF / C 60 interface structure PbS infrared photodetector is provided, the structure of the detector comprising: an indium tin oxide (ITO) transparent electrode, a nickel oxide (NiO x ) film on the surface of the ITO transparent electrode, a lead sulfide (PbS-EDT) quantum dot film on the surface of the NiO x film, which is exchanged with 1,2-ethanedithiol (EDT) ligand, a halogen ion (iodine ion I - , bromine ion Br -) PbS-ink quantum dot film after ligand exchange, lithium fluoride (LiF) film on the surface of PbS-ink quantum dot film, C 60 film on the surface of LiF film, PCBM film on the surface of C 60 film, BCP film on the surface of PCMB film and silver metal electrode on the BCP film, as shown in the structural schematic diagram Figure 1 The photoelectric detector of the present application is a p-i-n structure, more specifically, the device structure is sequentially from bottom to top: ITO (150 nm) / NiO x (15 nm) / PbS-EDT (50 nm) / PbS-ink (400 nm) / LiF (1 nm) / C 60 (10 nm) / PCBM (15 nm) / BCP (15 nm) / Ag (100 nm).
[0032] The device energy level diagram of the double-layer interface structure lead sulfide infrared photoelectric detector provided by the present application is shown in Figure 2 As can be seen from the figure, the inverted structure of the lead sulfide quantum dot short wave infrared (PbS QD SWIR) photoelectric detector generally adopts a p-i-n stacking order, in which light is incident from the top transparent electrode, and then passes through the hole transport layer (HTL), PbS QD active layer and electron transport layer (ETL) in turn, and finally reaches the bottom electrode. After the short wave infrared photons penetrate the top electrode, they are absorbed by the PbS QD active layer. Due to the size-adjustable band gap of the quantum dots, the absorption peak of the QD can be controlled to cover the SWIR band. When the photon energy is greater than the QD band gap, an electron-hole pair (exciton) is excited. Under the action of the built-in electric field, the exciton rapidly separates: the electron drifts to the electron transport layer, and the hole drifts to the hole transport layer. The separated carriers form a photocurrent in the external circuit.
[0033] In the embodiments of the second aspect of the present application, a preparation method of the above-mentioned lead sulfide infrared photoelectric detector is provided, comprising the steps of: S100, providing a substrate and preparing a transparent electrode on the substrate; S200, preparing a hole transport layer on the surface of the transparent electrode; S300, preparing a lead sulfide infrared light absorbing layer on the surface of the hole transport layer; S400, preparing a functional layer on the surface of the lead sulfide infrared light absorbing layer, the functional layer comprising a LiF film and a C 60 film on the surface of the LiF film; S500, preparing an electron transport layer on the surface of the functional layer; S600, preparing a top electrode on the surface of the electron transport layer.
[0034] In some embodiments of the present application, the LiF thin film and the C 60 film are prepared by vacuum thermal evaporation method. During the deposition process, the deposition conditions (temperature, pressure, time, etc.) are strictly controlled to ensure the uniformity and stability of the LiF and C 60 layers.
[0035] In some embodiments of the present application, the LiF thin film and the C 60 film are both thermally evaporated at a pressure lower than 5*10 -4 Pa, and the substrate rotation rate of the evaporation equipment is 25 rpm.
[0036] In some embodiments of the present application, the LiF thin film is evaporated at a power of 16% W and a rate of 0.1-0.2 Å / S.
[0037] In some embodiments of the present application, the C 60 film is evaporated at a power of 14% W and a rate of 0.2-0.3 Å / S.
[0038] In some embodiments of the present application, the transparent electrode is prepared by physical deposition method.
[0039] In some embodiments of the present application, the hole transport layer, the PbS infrared light absorbing layer, and the electron transport layer are prepared by chemical spin coating method.
[0040] In some embodiments of the present application, the top electrode is prepared by vacuum thermal evaporation method, the Ag evaporation is performed at a power of 25% W and a rate of 0.5-0.7 Å / S.
[0041] The PbS infrared photodetector with double-layer LiF / C 60 interface structure of the present application, the transparent bottom electrode (ITO electrode) is prepared by physical deposition thin film method, the hole transport layer (NiO x film and PbS-EDT quantum dot film), the infrared light absorbing layer PbS-ink quantum dot film, and the electron transport layer (PCBM film and BCP film) are prepared by chemical spin coating method, and the LiF thin film, the C 60 film, and the top electrode (Ag electrode) are prepared by vacuum thermal evaporation method. The above-mentioned methods are all conventional preparation schemes in the field, which are mature in process and not harsh in conditions, and are convenient for industrial production; meanwhile, the conditions (temperature, pressure, time, etc.) can be strictly controlled during the preparation process to ensure the uniformity and stability of each layer.
[0042] In some embodiments of the present application, step S100 specifically comprises: providing a substrate, and preparing a transparent ITO electrode on the substrate, then sequentially performing ultrasonic cleaning with deionized water, isopropanol, acetone and ethanol for 15-20 minutes, and then performing oxygen plasma treatment for 15-20 minutes to enhance the hydrophilicity of the ITO electrode surface.
[0043] In some embodiments of the present application, step S200 specifically comprises: taking NiO x nanoparticles into deionized water to prepare a 15-20 mg / ml NiO x solution, and spin-coating the NiO x solution on the ITO electrode treated by oxygen plasma at a speed of 2000 rpm for 30 seconds, and then annealing in an air environment at 150°C for about 30 minutes to obtain a NiO x thin film; a PbS-EDT quantum dot thin film is prepared by a layer-by-layer method: depositing oleic acid-capped PbS CQDs (40-60 mg / ml, solution is n-octane) by spin-coating at a speed of 3000 rpm for 30 seconds, then treating with a 0.01-0.02% volume concentration EDT-acetonitrile solution for 30 seconds, then spin-coating at a speed of 4000 rpm for 10 seconds, and cleaning the thin film with acetonitrile three times, and repeating the process twice to obtain a PbS-EDT quantum dot thin film with a thickness of about 50 nm.
[0044] In some embodiments of the present application, step S300 specifically comprises: using I - / Br - capped quantum dot ink (solution is DMF: butylamine is 1:4), spin-coating at a speed of 1200 rpm for 4 seconds, then spin-coating at a speed of 2500 rpm for 40 seconds, and then annealing at 85°C for 10 minutes to prepare a PbS-ink quantum dot absorption layer with a thickness of about 400 nm.
[0045] In some embodiments of the present application, step S400 specifically comprises: depositing LiF and C 60 on a substrate by thermal evaporation under a pressure of less than 5×10 -4 Pa: the power of LiF evaporation is about 16% W, the film thickness display rate is 0.1-0.2 Å / S, and the film thickness display is 1 nm to stop; the power of C 60 evaporation is about 14% W, the film thickness display rate is 0.2-0.3 Å / S, and the film thickness display is 10 nm to stop (the substrate rotation rate of the evaporation equipment is 25 rpm).
[0046] In some embodiments of the present application, step S500 specifically comprises: preparing the PCBM layer by spin coating at 2000 rpm for 30 seconds, and preparing the BCP layer by spin coating at 4000 rpm for 30 seconds after standing for 10 minutes.
[0047] In some embodiments of the present application, step S600 specifically comprises: the Ag is deposited by thermal evaporation at a pressure of 5x10 -4 The Ag is deposited by thermal evaporation at a pressure of 5x10 Pa: the power of Ag evaporation is about 25% W, the rate displayed by the film thickness meter is 0.5-0.7 Å / S, and the film thickness meter thickness display of 100 nm can stop (the substrate rotation rate of the evaporation equipment is 25 rpm).
[0048] The application provides an application of the PbS infrared photodetector or the PbS infrared photodetector prepared by the method to infrared spectrum detection, wireless communication, biomedicine or environmental detection.
[0049] Additional features and advantages of the application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The objectives and other advantages of the application will be realized and attained by the structure particularly pointed out in the description and claims. BRIEF DESCRIPTION OF DRAWINGS
[0050] Figure 1 A double-layer LiF / C 60 A device structure schematic diagram of the PbS infrared photodetector with a double-layer LiF / C Figure 2 A double-layer LiF / C 60 A device energy level diagram of the PbS infrared photodetector with a double-layer LiF / C Figure 3 A double-layer LiF / C 60 interface infrared photodetector prepared by the example 1 of the present application and a single-layer C 60 An external quantum efficiency (EQE) curve diagram of the infrared photodetector with a double-layer LiF / C Figure 4 A double-layer LiF / C 60 interface infrared photodetector prepared by the example 1 of the present application and a single-layer C 60 A specific detectivity curve diagram of the infrared photodetector with a double-layer LiF / C Figure 5 A double-layer LiF / C 60 interface infrared photodetector prepared by the example 1 of the present application and a single-layer C 60Schematic diagram of dark current density of infrared photodetector of interface; Figure 6 Double-layer LiF / C with different thickness of LiF layer prepared for the present application embodiment 1-3 60 Schematic diagram of dark state current-voltage characteristic test result of infrared photodetector of interface; Figure 7 Double-layer LiF / C with different thickness of LiF layer prepared for the present application embodiment 1-3 60 Schematic diagram of external quantum efficiency (EQE) curve of infrared photodetector of interface with wavelength. DETAILED DESCRIPTION
[0051] The concept and technical effects of the present application will be described below in combination with embodiments, so as to fully understand the purpose, features and effects of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.
[0052] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are contained in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.
[0053] In the description of the present application, unless otherwise specified, the numerical range "a~b" represents a shorthand representation of any real combination between a and b, where a and b are real numbers. Unless otherwise specified, each reaction or operation step can be carried out in sequence or not in sequence. Preferably, the reaction method in the present application is carried out in sequence.
[0054] The experimental methods in the following examples not specified in the specific conditions are usually carried out according to the conventional conditions, or according to the conditions recommended by the manufacturer. The materials, reagents and the like used in the present embodiment are commercially available reagents and materials, unless otherwise specified.
[0055] Example 1 Double-layer LiF / C 60 Interface structure PbS photodetector The present embodiment provides a double-layer LiF / C 60 Interface structure PbS photodetector, the schematic diagram of its structure is as Figure 1The structure of the PbS photodetector includes: a transparent glass substrate, an indium tin oxide (ITO) electrode on the surface of the transparent glass substrate, a nickel oxide (NiO x ) film on the surface of the ITO electrode, a lead sulfide (PbS-EDT) quantum dot film on the surface of the NiO x film using 1,2-ethanedithiol (EDT) ligand exchange, a lead sulfide (PbS-ink) quantum dot film on the surface of the PbS-EDT quantum dot film using halogen ion (iodine ion I - , bromine ion Br - ) ligand exchange, a lithium fluoride (LiF) film on the surface of the PbS-ink quantum dot film, a C 60 film on the surface of the LiF film, a PCBM film on the surface of the C 60 film, a BCP film on the surface of the PCMB film, and a silver electrode above the BCP film.
[0056] 1. Preparation of transparent electrode film: ITO film was sputtered and deposited on the transparent glass using a magnetron sputtering device to obtain TIO conductive glass with a thickness of about 150 nm (the TIO conductive glass in this embodiment was directly purchased from Optimal Technology). The ITO conductive glass was subjected to 15 minutes of oxygen plasma treatment to enhance the surface hydrophilicity.
[0057] 2. Preparation of hole transport layer film: NiO x film and PbS-EDT quantum dot film were prepared on the transparent glass with deposited ITO film using chemical spin coating method. The thickness of the NiO x film was about 15 nm, and the thickness of the PbS-EDT quantum dot film was about 50 nm.
[0058] The specific steps of spin coating the NiO x film are as follows: 1) Take an appropriate amount of NiO x nanoparticles (purchased from Optimal Technology, purity 99.999%), dissolve the NiO x nanoparticles in deionized water to prepare a solution of 20 mg / ml, then seal the bottle with sealing film to prevent the solution from permeating out, and place it in an ultrasonic device for at least 30 minutes before use. 2) Screen the ultrasonically treated NiO x aqueous solution to prevent large molecular particles from dissolving, and also to prevent large particles from affecting the overall performance of the device on the device; 3) Screen the NiO xThe aqueous solution was spin-coated on the ITO thin film after oxygen plasma treatment at a rotation speed of 2000 rpm for 30 seconds and annealed in air at 150°C for 30 minutes, finally obtaining a NiO thin film with a thickness of about 15 nm x thin film.
[0059] The specific steps of spin-coating PbS-EDT quantum dot thin film are as follows: 1) First, synthesize PbS quantum dots: PbS quantum dots are synthesized by a typical hot injection method. The entire preparation process of PbS quantum dots is carried out in a fume hood. 0.45 grams of lead oxide (PbO; 99.9%, Aldrich), 8 milliliters of oleic acid (OA; 90%, Sigma-Aldrich), and 12 milliliters of octadecene (ODE; 90%, J&K Scientific) are mixed in a 100-milliliter three-necked flask. Nitrogen is introduced into the three-necked flask at 40°C, and a lead precursor is prepared by stable vacuum extraction at 120°C for 3 hours. 1 milliliter of hexamethyldisilane ((TMS)2S; 99%, Aldrich) and 9 milliliters of ODE are uniformly mixed to prepare a sulfur source. To synthesize quantum dots, the temperature of the lead precursor is reduced to 100°C. After nitrogen is introduced, 2 milliliters of the sulfur source are injected and reacted for 30-40 seconds, and then cooled to room temperature. Next, centrifuged at 7000 rpm for 3 minutes in a test tube, purified with n-hexane and acetone three times, and the precipitate is retained as the final quantum dot product.
[0060] 2) Take the oleic acid-capped PbS quantum dots (exciton absorption peak of 850-880 nm) and dissolve them in n-octane to prepare a PbS quantum dot solution with a concentration of 50 mg / ml. Shake well to dissolve completely, then sieve three times to prevent large particles of PbS quantum dots from not dissolving completely, thereby affecting the performance of the entire device. 3) Prepare at least 20 milliliters of anhydrous acetonitrile, and take 10 milliliters of anhydrous acetonitrile to prepare an EDT-acetonitrile solution with a volume ratio of 0.02% EDT by adding 2 microliters of EDT (1,2-ethanedithiol). 4) The PbS quantum dot solution of step 2) is spin-coated on the NiO x thin film at a rotation speed of 3000 rpm for 30 seconds, then treated with the EDT-acetonitrile solution with a volume ratio of 0.02% for 30 seconds, spin-coated at a rotation speed of 4000 rpm for 10 seconds, and washed with acetonitrile two to three times; this process is repeated twice, and finally a PbS-EDT quantum dot thin film with a thickness of about 50 nm is obtained; finally, oxidize for 12-17 hours, and the device performance is best.
[0061] 3. Infrared light-absorbing layer thin film preparation: A PbS-ink quantum dot thin film (using mixed halogen ions iodine ion I- Br - Ligand treatment, the exciton absorption peak is about 1240 nm), the steps are as follows: 1) Configuration of ligand solution: 1.844 g of PbI2 and 0.64 g of PbBr2 are dissolved in a centrifuge tube containing 15 ml of N, N-dimethylformamide (DMF), the centrifuge tube is sealed and shaken for 10-15 minutes to fully dissolve the mixture, then the mixed solution is filtered with a filter head and placed in a clean glass bottle, sealed for use; 2) Dissolve the oleic acid-coated PbS quantum dots (PbS quantum dot synthesis method as above) in n-octane to prepare a 10 mg / ml PbS quantum dot solution, filter the PbS quantum dot solution three times with a filter head, then take 15 ml of the filtered solution and slowly inject it along the wall of the clean glass bottle containing the ligand solution in step 1) (do not drop into it), shake vigorously for 5-10 minutes, and the solution in the glass bottle will separate into layers, indicating that the quantum dots have transferred from the non-polar solvent to the polar solvent DMF, indicating that the I - and Br - Ligand successfully replaces the long-chain oleic acid ligand; 3) Discard the supernatant in the glass bottle with a dropper, then add n-octane to the glass bottle and wash three times to ensure that the oleic acid ligand in the solution is completely removed; then add about 1-2 ml of n-octane to the glass bottle, then place it in a centrifuge; discard the colorless liquid and yellow liquid in the middle after centrifugation, and leave the black powder at the bottom; vacuum dry the black powder for 40 minutes to obtain PbS quantum dot powder coated with halide ion ligand; 4) Prepare 1 mL of mixed solvent (n-butylamine: DMF = 4:1), dissolve the PbS quantum dot powder vacuum-dried in the previous step in the mixed solvent to prepare a 350-380 mg / ml solution, shake for two minutes with a shaker to obtain a quantum dot solution, then centrifuge the quantum dot solution for 10-30 seconds with a centrifuge (the quantum dot solution needs to be centrifuged before each spin coating); drop the centrifuged quantum dot solution on the ITO electrode on which the NiO x thin film and PbS-EDT quantum dot thin film, spin coat at 1200 rpm for 4 seconds, then spin coat at 2500 rpm for 40 seconds, and anneal at 85°C for 10 minutes to prepare a PbS-ink quantum dot thin film with a thickness of about 400 nm.
[0062] 4. Functional layer thin film preparation: The LiF thin film on the surface of the PbS-ink quantum dot thin film and the C 60 thin film on the surface of the LiF thin film are prepared by vacuum thermal evaporation (equipment model F type coating machine, FS-1044), the steps are as follows: 1) Put appropriate amount of LiF (purchased from Aladdin, purity 99.99%, CAS number 7789-24-4) into heating source 1, then put appropriate amount of C 60 (purchased from Opt. Tech, purity 99.9%, CAS number 99685-96-8) into heating source 2, and put the device prepared with PbS-ink quantum dot film into the evaporation cavity of the evaporation chamber, and close the hatch; 2) Open the mechanical pump, front valve, molecular pump, etc. respectively, and wait for the vacuum in the evaporation cavity of the evaporation chamber to be less than 5x10 - 4 Pa, and then start to add power; the power of LiF evaporation is about 16%W, the film thickness instrument shows a rate of 0.1Å / S, and the film thickness instrument shows 1nm to stop, that is, a LiF film with a thickness of 1 nm is prepared; the power of C 60 evaporation is about 14%W, the film thickness instrument shows a rate of 0.2Å / S, and the film thickness instrument shows 10nm to stop, that is, a C 60 film with a thickness of 10 nm is prepared.
[0063] 5, electron transport layer film preparation: PCBM film on the surface of C 60 film and BCP film on the surface of PCMB film, the specific steps are as follows: 1) Take appropriate amount of PCBM nanoparticles (purchased from Opt. Tech, purity 99.99%), dissolve the PCBM nanoparticles in chlorobenzene to prepare a PCBM solution of 20 mg / ml, then seal the bottle with sealing film to prevent the solution from penetrating out, and put it into the ultrasonic device for at least 30 min before use.
[0064] 2) At the same time, take appropriate amount of BCP nanoparticles (purchased from Opt. Tech, purity 99.5%), dissolve the BCP nanoparticles in isopropanol to prepare a BCP solution of 0.5 mg / ml, then seal the bottle with sealing film to prevent the solution from penetrating out.
[0065] 3) Screen the ultrasonic PCBM solution, then drop the screened PCBM solution on the surface of the device prepared with C 60 film, and spin coat at a speed of 2000 rpm for 30 seconds to prepare a PCBM film with a thickness of 15 nm; after standing for 10 min, spin coat the BCP solution, drop the BCP solution on the surface of the device prepared with PCBM film, and spin coat at a speed of 4000 rpm for 30 seconds to prepare a BCP film with a thickness of 15 nm.
[0066] 6, top electrode silver film preparation: The top electrode is prepared by vacuum thermal evaporation (the equipment model is F-type coating machine, FS-1044).
[0067] An appropriate amount of silver is placed in a heating source, and the device prepared with the multilayer film is fixed on a tray and placed in an evaporation chamber. -4 Pa, and then the silver evaporation power is controlled at about 24 %W, and the evaporation is stopped when the crystal oscillator shows that the evaporation thickness is 100 nm, so that a silver electrode with a thickness of 100 nm is prepared.
[0068] Example 2: A double-layer LiF / C 60 Interface structure PbS photoelectric detector The difference between this embodiment and example 1 is that, in the preparation of the functional layer film, the LiF evaporation power is about 16 %W, the film thickness instrument shows a rate of 0.1 Å / S, and the film thickness instrument shows a thickness of 3 nm to stop, so that a LiF film with a thickness of 3 nm is prepared. The remaining steps are the same as those in example 1, and will not be repeated here.
[0069] Example 3: A double-layer LiF / C 60 Interface structure PbS photoelectric detector The difference between this embodiment and example 1 is that, in the preparation of the functional layer film, the LiF evaporation power is about 16 %W, the film thickness instrument shows a rate of 0.1 Å / S, and the film thickness instrument shows a thickness of 5 nm to stop, so that a LiF film with a thickness of 5 nm is prepared.
[0070] The remaining steps are the same as those in example 1, and will not be repeated here.
[0071] Comparative Example 1: A single-layer C 60 Interface structure PbS photoelectric detector The difference between this comparative example and example 1 is that this comparative example is a single-layer C 60 Interface structure PbS photoelectric detector, which comprises: a transparent glass substrate, an indium tin oxide (ITO) electrode on the surface of the transparent glass substrate, a nickel oxide (NiO x ) film on the surface of the ITO electrode, a lead sulfide (PbS-EDT) quantum dot film on the surface of the NiO x film, a lead sulfide (PbS-ink) quantum dot film on the surface of the PbS-EDT quantum dot film after ligand exchange with halogen ions (iodine ions I - , bromine ions Br - ), a C 60 film on the surface of the PbS-ink quantum dot film, and a C 60The PCBM thin film on the surface of the thin film, the BCP thin film on the surface of the PCMB thin film, and the silver electrode above the BCP thin film.
[0072] In the preparation steps, the LiF thin film is not prepared when the functional layer thin film is prepared, and only the C 60 thin film is prepared. 60 The thin film is on the surface of the PbS-ink quantum dot thin film.
[0073] The remaining steps are the same as those in Example 1 and will not be repeated here.
[0074] Test Example 1. External quantum efficiency (EQE) test The device used is APD-QE (RR12231001), and the external quantum efficiency of the PbS quantum dot thin film photodetector prepared is detected at a bias voltage of -0.1.
[0075] 2. Specific detectivity test The calculation formula of specific detectivity is:
[0076] wherein, A is the area of the working region of the detector, A = 0.045, Delta F is the measurement bandwidth (Hz), R is the responsivity, which is measured at the same time as the external quantum effect EQE, i n is the noise current density read from the noise spectral density at 1 Hz.
[0077] 3. Dark current-voltage characteristic test The dark current-voltage characteristic test is the dark current density measured at the same time in a dark environment by using the APD-QE (RR12231001) device.
[0078] The double-layer LiF / C 60 interface infrared photodetector prepared in Example 1 and the single-layer C 60 interface infrared photodetector prepared in Comparative Example 1. The external quantum efficiency (EQE) of the infrared photodetector with the double-layer LiF / C Figure 3The external quantum efficiency (EQE) reflects the proportion of "incident photons converted into carriers in the external circuit", directly reflecting the photoelectric conversion efficiency of the device. As can be seen from the figure, under a bias of-0.1, the device without LiF modification: EQE continuously decreases with increasing wavelength, about 45% at 400 nm, and decreases to below 15% at 1200 nm, and the photoelectric conversion capability under weak light decays obviously; the device with LiF modification: EQE shows more excellent wavelength stability: EQE at 400 nm is more than 55% (higher than that of the device without LiF); EQE at 1200 nm still maintains more than 25%, and the local peak value of EQE is significantly higher than that of the device without LiF.
[0079] It can be seen that the LiF modification not only improves the "efficiency limit" of photoelectric conversion, but also widens the wavelength range of high-efficiency response, and shows more excellent weak light adaptability.
[0080] The double-layer LiF / C 60 interface infrared photodetector prepared in Example 1 and the single-layer C 60 interface infrared photodetector prepared in Comparative Example 1 is as shown in Figure 4 The specific detectivity (D ) is a core index for measuring the weak light detection capability of a photodetector, and the higher the value is, the more sensitive the device is to weak light signals. As can be seen from the figure, the device without LiF modification: the specific detectivity is maintained at 10 11 Jones order in the full wavelength range (400-1600 nm), and reaches a local peak value of 1.33x10 11 Jones near 1240 nm; the device with LiF modification: the specific detectivity is significantly improved, and the peak value near 1240 nm is as high as 8.47x10 11 Jones, which is about 6 times that of the device without LiF.
[0081] The double-layer LiF / C 60 interface infrared photodetector prepared in Example 1 and the single-layer C 60 interface infrared photodetector prepared in Comparative Example 1 is as shown in Figure 5 It can be seen that after adding a layer of LiF modification, the dark current of the device is lower, and the specific detectivity is 8.47x10 11 Jones, and the weak light detection capability is significantly enhanced.
[0082] This difference shows that: the LiF modification effectively suppresses the dark current of the device (the dark current is a key factor limiting the specific detectivity), and at the same time, enhances the separation / transport efficiency of photo-generated carriers, and finally greatly improves the detection sensitivity of the device to weak light signals.
[0083] Bilayer LiF / C prepared in Examples 1-3 60 The external quantum efficiency (EQE) and dark-state current-voltage characteristics of the interface infrared photodetector are as follows: Figures 6-7 As shown in the figure, the performance of Example 1 (LiF layer thickness = 1 nm) is as follows: The EQE spectrum shows a high peak value (>30%) in the 400–1000 nm band, with a significant response near 1200 nm, indicating excellent photogenerated carrier collection efficiency over a wide spectral range. The dark-state current-voltage curve shows extremely low dark current density, small leakage current under reverse bias, and good turn-on characteristics under forward bias, indicating few interface defects and good carrier transport barrier matching. This demonstrates that a LiF thickness of 1 nm provides a moderate interface modification effect, effectively promoting electron transport without introducing excessive defects due to excessive thickness, making it one of the optimal parameter choices for performance.
[0084] Example 2 (LiF layer thickness = 3nm) Performance: In the EQE spectrum, the EQE across the entire wavelength range is significantly lower than that at 1nm, especially the peak EQE at 400-1000nm, which drops to ~20%. The response near 1200nm also weakens significantly, indicating that carrier collection efficiency decreases with increasing LiF thickness. In the dark-state current-voltage curve, when the dark current density is higher than 1nm, the reverse leakage current increases, indicating that increasing the LiF thickness introduces more interface defects or carrier transport barriers. This shows that when the LiF thickness increases to 3nm, the intralayer resistance increases or the interface state density rises, leading to impaired photogenerated carrier transport and increased dark current, resulting in performance inferior to the 1nm example.
[0085] Example 3 (LiF layer thickness = 5nm) Performance: In the EQE spectrum, the full-band EQE is at its lowest level, with a peak EQE of only ~5%, and the spectral response range is significantly narrowed, indicating that most photogenerated carriers cannot be effectively collected due to the excessive LiF thickness. In the dark-state current-voltage curve, the dark current density is significantly higher than that at 1nm and 3nm, the leakage current under reverse bias is large, and the forward turn-on characteristics deteriorate, indicating that the excessive LiF thickness severely hinders carrier transport and leads to a large accumulation of interface defects. This shows that when the LiF thickness reaches 5nm, it exceeds the effective operating range. The excessively thick LiF layer becomes a "barrier" for carrier transport and introduces a large number of defects, causing a sharp deterioration in the device's optoelectronic performance.
[0086] In summary, the above embodiments can derive the effective range of key parameters and performance correlation: the thickness of LiF layer as the electron transport layer or interface modification layer directly affects the carrier transport, interface state and light response characteristics. The effective range of LiF layer thickness is 0.5-3 nm, and the optimal thickness is about 1 nm. Within this range, the device has high EQE and low dark current, and the photoelectric performance is optimal. When the thickness increases to 5 nm (invalid range), the performance continues to decline, and when the thickness is 5 nm, the device performance cannot meet the practical requirements. In the actual process, the deposition thickness of LiF needs to be strictly controlled to about 1 nm (for example, 0.5-3 nm), and the deposition rate and thickness can be monitored in real time to ensure that the key parameters fall within the effective range, so as to obtain high-performance devices.
[0087] The above is a specific description of the preferred embodiments of the present application, but the present application is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.
Claims
1. A lead sulfide infrared photodetector, characterized in that, The structure comprises, from bottom to top, a transparent electrode, a hole transport layer, a lead sulfide infrared light-absorbing layer, a functional layer, an electron transport layer, and a top electrode; the functional layer includes a LiF thin film and C atoms located on the surface of the LiF thin film. 60 film.
2. The lead sulfide infrared photodetector according to claim 1, characterized in that, The thickness of the LiF thin film ranges from 0.5 to 3 nm.
3. The lead sulfide infrared photodetector according to claim 1, characterized in that, The C 60 The thickness of the thin film ranges from 10 to 15 nm.
4. The lead sulfide infrared photodetector according to claim 1, 2, or 3, characterized in that, Including at least one of (a1) to (a7): (a1) The transparent electrode includes at least one of ITO electrode, FTO electrode, or AZO electrode; (a2) The hole transport layer includes NiO x Thin film, and located in the NiO x A PbS-EDT quantum dot film on the surface of a thin film, wherein the ligand of the PbS quantum dots in the PbS-EDT quantum dot film is 1,2-ethylenedithiol. (a3) When (a2) is included, the exciton absorption peak of PbS quantum dots in the PbS-EDT quantum dot film is 850~880nm; (a4) The lead sulfide infrared light absorbing layer includes a PbS-ink quantum dot film, wherein the ligands of the PbS quantum dots in the PbS-ink quantum dot film are lead iodide and lead bromide. (a5) When (a4) is included, the exciton absorption peak of the PbS quantum dots in the PbS-ink quantum dot film is 1200~1350nm; (a6) The electron transport layer includes a PCBM film and a BCP film located on the surface of the PCMB film; (a7) The top electrode includes an Ag electrode.
5. The lead sulfide infrared photodetector according to claim 4, characterized in that, Including at least one of (b1) to (b7): (b1) The thickness of the transparent electrode is 130~170nm; (b2) The NiO x The thickness of the thin film is 10~20nm; (b3) The thickness of the PbS-EDT quantum dot film is 30~80nm; (b4) The thickness of the PbS-ink quantum dot film is 300~500nm; (b5) The thickness of the PCBM film is 10~20nm; (b6) The thickness of the BCP film is 10~20nm; (b7) The thickness of the top electrode is 80~120nm.
6. A method for preparing a lead sulfide infrared photodetector as described in any one of claims 1-5, characterized in that, Including the following steps: A substrate is provided, and a transparent electrode is fabricated on the substrate; A hole transport layer is prepared on the surface of the transparent electrode; A lead sulfide infrared light-absorbing layer is prepared on the surface of the hole transport layer; A functional layer is fabricated on the surface of the lead sulfide infrared light-absorbing layer. The functional layer includes a LiF thin film and a C layer located on the surface of the LiF thin film. 60 film; An electron transport layer is fabricated on the surface of the functional layer; A top electrode is fabricated on the surface of the electron transport layer.
7. The preparation method according to claim 6, characterized in that, The LiF thin film and the C were prepared by vacuum thermal evaporation. 60 film.
8. The preparation method according to claim 7, characterized in that, The LiF thin film and the C 60 The films are all below 5×10 -4 Thermal evaporation under Pa pressure: the LiF thin film is deposited at a power of 16% W and a rate of 0.1~0.2 Å / s; and / or, the C 60 The power of the thin film evaporation was 14% W, and the rate was 0.2~0.3 Å / S.
9. The preparation method according to claim 6, characterized in that, The transparent electrode was prepared by physical deposition. The hole transport layer, the lead sulfide infrared light-absorbing layer, and the electron transport layer are prepared by chemical spin coating; the top electrode is prepared by vacuum thermal evaporation.
10. The application of the lead sulfide infrared photodetector as described in any one of claims 1-5 or the lead sulfide infrared photodetector prepared by the method described in any one of claims 6-9 in infrared spectroscopy detection, wireless communication, biomedicine, or environmental monitoring.