Quantum dot infrared detector and preparation method thereof

Abstract

The present invention discloses a quantum dot infrared detector and a preparation method thereof, and belongs to the technical field of semiconductor infrared detection materials. The infrared detector comprises, from bottom to top, a bottom electrode, an electron transport layer, a quantum dot light absorbing layer, a hole transport layer and a top electrode, wherein the electron transport layer is a bismuth-based chalcogenide film, and the bismuth-based chalcogenide film, the quantum dot light absorbing layer and the hole transport layer form an N-I-P type heterojunction. The quantum dot infrared detector of the present invention makes up for the problem that the quantum dot infrared detector with a detection cutoff wavelength ≥ 2um does not have a suitable electron transport layer, and the prepared infrared detector has a simple structure, high performance, strong repeatability and simple equipment requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor infrared detection materials, and more specifically, relates to a quantum dot infrared detector and a preparation method thereof. Background Art

[0002] Infrared light usually refers to electromagnetic waves with a wavelength range of 0.76μm to 100μm. According to the blackbody radiation theory, any object with an absolute temperature higher than 0K spontaneously radiates infrared light. The human eye cannot directly observe infrared light, so infrared detection technology is needed. Among various infrared detectors, photovoltaic infrared detectors are the most mature detector device structure in the current business due to their excellent performance such as low noise and fast response speed.

[0003] The mainstream photovoltaic infrared detectors are mainly indium gallium arsenide infrared detectors, mercury cadmium telluride infrared detectors, indium antimonide infrared detectors, etc., which are mainly III-V and II-VI crystal materials. Although the above detectors have excellent performance and occupy most of the photovoltaic infrared detector market on the market, they are subject to the requirements of MOCVD, MBE, LPE and other high-precision epitaxial technologies for preparation, and they cannot be directly integrated with silicon-based readout circuits. Therefore, their high prices have hindered the application of infrared detectors in the civilian field.

[0004] Quantum dot infrared detector is an emerging infrared detector. Its unique advantage is that quantum dots can be synthesized in solution and prepared as quantum dot light absorption layer in solution. Its process is simple and low cost, and it can be directly integrated with silicon-based readout circuit. At present, quantum dot infrared detector technology cannot achieve the high performance of III-V detectors, but through chemical passivation of quantum dot surface and construction of detector band engineering, it is still expected to achieve high-performance and low-cost infrared detectors.

[0005] At present, the commonly used electron transport layers in quantum dot infrared detectors are usually inorganic materials such as zinc oxide, tin oxide, titanium oxide, and cadmium sulfide, but these electron transport layers are only suitable for near-infrared quantum dot infrared detectors (0.76μm-1.7μm). As the size of quantum dots increases, the detection cutoff wavelength of quantum dots extends to the long-wave infrared direction, and the conduction band of quantum dots will gradually move down. Especially for quantum dot light-absorbing layers with detection cutoff wavelengths above 2μm, the existing electron transport layer does not match its conduction band, that is, the conduction band of the electron transport layer is higher than the conduction band of the quantum dot light-absorbing layer. This mismatch will form a serious electron potential barrier at the heterojunction interface, resulting in the inability of the photogenerated electrons of the quantum dot light-absorbing layer to be effectively extracted by the electron transport layer, which greatly affects the performance of quantum dot infrared detectors. Therefore, there is currently no suitable electron transport layer in quantum dot infrared detectors with detection cutoff wavelengths above 2μm, which seriously restricts the exploration and research of quantum dot infrared detectors in the long-wave direction. Therefore, exploring an electron transport layer that is more suitable for infrared detectors and developing a new infrared detector structure are of great significance for the further development and wide application of quantum dot infrared detectors. Summary of the invention

[0006] In view of the defects of the prior art and the need for improvement, the present invention provides a quantum dot infrared detector and a method for preparing the same, which aims to solve the problem of conduction band mismatch between the electron transport layer and the quantum dot absorption layer when the detection cutoff wavelength is ≥2μm.

[0007] To achieve the above-mentioned purpose, according to one aspect of the present invention, a quantum dot infrared detector is provided, which includes, from bottom to top, a bottom electrode, an electron transport layer, a quantum dot light absorbing layer, a hole transport layer and a top electrode, wherein the electron transport layer is a bismuth-based chalcogenide compound film, and the bismuth-based chalcogenide compound film, the quantum dot light absorbing layer and the hole transport layer form a NIP type heterojunction.

[0008] Furthermore, the bismuth-based chalcogenide compound is Bi2X3 or Bi2(X m Y 1-m )3, wherein X, Y are any two different element combinations of S, Se or Te; 0<m<1.

[0009] Furthermore, the bismuth-based chalcogenide is bismuth sulfide Bi2S3, bismuth sulfide selenide Bi2(S m Se 1-m )3 or bismuth telluride Bi2(S m Te 1-m )3.

[0010] Furthermore, the materials of the bottom electrode and the top electrode are infrared transparent conductive materials or metal conductive materials, and at least one of the bottom electrode and the top electrode is made of infrared transparent conductive materials.

[0011] Furthermore, the infrared transparent conductive material is ITO, FTO or AZO; the metal conductive material is gold, silver, copper or aluminum.

[0012] Furthermore, the material of the quantum dot light-absorbing layer is mercury telluride, lead sulfide, lead selenide, cadmium sulfide, cadmium selenide or zinc sulfide quantum dots.

[0013] Furthermore, the hole transport layer material is nickel oxide, molybdenum oxide, PEDOT, Spiro-MeTAD, silver telluride quantum dots or P-type doped quantum dots corresponding to the quantum dot light absorbing layer material.

[0014] According to another aspect of the present invention, there is provided a method for preparing a quantum dot infrared detector as described in any one of the first aspects, comprising:

[0015] S1, depositing a bismuth-based chalcogenide thin film on the bottom electrode by a rapid thermal evaporation method to form an electron transport layer;

[0016] S2, preparing a quantum dot light absorbing layer on the electron transport layer;

[0017] S3, preparing a hole transport layer on the quantum dot light absorbing layer;

[0018] S4. Prepare a top electrode on the prepared hole transport layer.

[0019] Furthermore, the rapid thermal evaporation method is implemented as follows: the bottom electrode is inverted 0.1 cm-2 cm above the bismuth-based chalcogenide powder, the temperature of the bottom electrode is set to 30-400°C, the evaporation temperature is 500-800°C, the evaporation time is 10s-100s, and the vacuum is evacuated to a vacuum degree not higher than 0.1 Torr.

[0020] Furthermore, in step S2, the quantum dot light absorbing layer is prepared by coating, printing, spin coating, drip coating, scraping, spraying or printing.

[0021] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0022] (1) The present invention applies bismuth-based chalcogenide compounds as electron transport layers in the field of quantum dot infrared detectors. Through the heterojunction formed between the bismuth-based chalcogenide compound film and the quantum dot light absorbing layer, conduction band matching between the electron transport layer and the quantum dot light absorbing layer with a detection cutoff wavelength ≥ 2 μm is achieved (the conduction band of the electron transport layer is not higher than the conduction band of the quantum dot light absorbing layer, and the conduction band difference between the two is less than 0.2 electron volts), thereby increasing the ability of the electron transport layer to extract photogenerated electrons in the quantum dot light absorbing layer; and because the band gap width of the bismuth-based chalcogenide compound is at least twice that of the quantum dot light absorbing layer, its valence band position is lower than the valence band of the quantum dot light absorbing layer, and there is a large valence band difference, it can prevent the reverse transmission of photogenerated holes in the quantum dot light absorbing layer, further enhancing the signal collection capability of the quantum dot infrared detector and improving the detector's responsiveness.

[0023] (2) At the same time, a heterojunction is formed between the bismuth-based chalcogenide film and the quantum dot light-absorbing layer, so that the bismuth-based chalcogenide film has a positive contribution to the built-in electric field of the quantum dot infrared detector, effectively suppressing the dark current noise, and reducing the dark current noise by several times to multiple orders of magnitude.

[0024] (3) As a preference, in addition to commonly used metals, the top electrode material may also be made of infrared transparent conductive materials such as ITO, FTO, AZO, etc. as a light-transmitting window, thereby realizing the detection signal light incident from the top.

[0025] (4) The present invention introduces the rapid thermal evaporation method into the field of quantum dot infrared detectors, and the prepared bismuth-based chalcogenide compound film has better flatness and wettability, and is more suitable for the preparation of quantum dot absorption layers with a detection cutoff wavelength ≥ 2 μm.

[0026] (5) Compared with the magnetron sputtering process used in traditional electron transport layers (such as zinc oxide, tin oxide, etc.), the epitaxially grown bismuth-based sulfide compound film prepared by rapid thermal evaporation requires simple equipment and concise steps, and can achieve fully automated production.

[0027] In summary, the quantum dot infrared detector of the present invention makes up for the problem that the quantum dot infrared detector with a detection cutoff wavelength ≥ 2μm has no suitable electron transport layer; and the prepared infrared detector has a simple structure, high performance, strong repeatability, and simple equipment requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the infrared detector of the present invention.

[0029] Figure 2 This is a surface SEM image of the bismuth sulfide film prepared in Example 1 of the present invention.

[0030] Figure 3This is a surface AFM image of the bismuth sulfide film prepared in Example 1 of the present invention.

[0031] Figure 4 It is a schematic diagram of the energy band relationship between the bismuth sulfide film and the mercury telluride quantum dot light-absorbing layer in Example 1 of the present invention.

[0032] Figure 5 This is a cross-sectional SEM image of the infrared detector in Example 1 of the present invention.

[0033] Figure 6 It is a schematic diagram of infrared detection in an embodiment of the present invention.

[0034] Figure 7 This is a photoelectric conversion performance diagram of the infrared detector in Example 1 of the present invention.

[0035] Figure 8 It is a schematic diagram of the energy band relationship between the bismuth selenide film and the lead sulfide quantum dot light absorbing layer in Example 2 of the present invention.

[0036] Fig. 9 This is a photoelectric conversion performance diagram of the infrared detector in Example 2 of the present invention.

[0037] Fig.10 Schematic diagram of the energy band relationship between the bismuth telluride sulfide film and the lead selenide quantum dot light absorbing layer in Example 3 of the present invention.

[0038] Fig.11 This is a photoelectric conversion performance diagram of the infrared detector in Example 3 of the present invention.

[0039] In all drawings, the same reference numerals are used to represent the same elements or structures, wherein 1 is a substrate, 2 is a bottom electrode, 3 is an electron transport layer, 4 is a quantum dot absorption layer, 5 is a hole transport layer, and 6 is a top electrode. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] like Figure 1As shown, a quantum dot infrared detector includes, from bottom to top, a bottom electrode 2, an electron transport layer 3, a quantum dot light absorbing layer 4, a hole transport layer 5 and a top electrode 6; wherein the bottom electrode serves as a cathode, the top electrode serves as an anode, the electron transport layer is a bismuth-based chalcogenide film, and the detection cutoff wavelength of the quantum dot light absorbing layer is ≥2μm. The bismuth-based chalcogenide film, the quantum dot light absorbing layer and the hole transport layer form a NIP type heterojunction, so that the infrared detector is a photovoltaic structure. The bismuth-based chalcogenide film serves as an electron transport layer to extract photogenerated electrons in the quantum dot light absorbing layer; the quantum dot light absorbing layer serves as an absorption layer for infrared light, and is used to convert infrared light less than the detection cutoff wavelength into an electrical signal to detect infrared light; the hole transport layer serves to extract photogenerated holes in the quantum dot light absorbing layer.

[0042] The bismuth-based chalcogenide compound is Bi2X3 or Bi2(X m Y 1-m )3, wherein X, Y are any two different elements of S, Se or Te; 0<m<1. For example, the bismuth-based chalcogenide is but not limited to bismuth sulfide Bi2S3, bismuth sulfide selenide Bi2(S m Se 1-m )3 or bismuth telluride Bi2(S m Te 1-m )3.

[0043] The material of the bottom electrode is infrared transparent conductive electrode materials such as ITO, FTO, AZO, or common conductive metal materials such as gold, silver, copper, and aluminum; the materials in the quantum dot light absorbing layer include but are not limited to quantum dots such as mercury telluride, lead sulfide, lead selenide, cadmium sulfide, cadmium selenide, and zinc sulfide; the hole transport layer material includes but is not limited to silver telluride quantum dots and P-type doped quantum dots corresponding to the quantum dot light absorbing layer material (i.e., P-type mercury telluride, P-type lead sulfide, and P-type lead selenide quantum dots), etc., and can also be inorganic or organic materials such as nickel oxide, molybdenum oxide, PEDOT, and Spiro-MeTAD; the top electrode material is common conductive metal materials such as gold, silver, copper, and aluminum, or infrared transparent conductive electrode materials such as ITO, FTO, and AZO; however, at least one of the bottom electrode and the top electrode is prepared using infrared transparent conductive electrode material to serve as an infrared detection window.

[0044] The conduction band of the bismuth-based chalcogenide film of the present invention is much lower than the conduction band of the currently common electron transport layer materials (titanium oxide, zinc oxide, cadmium sulfide, etc.), and matches the conduction band of the quantum dot light absorption layer with a detection cutoff wavelength of ≥2μm, that is, the conduction band of the electron transport layer can be made not higher than the conduction band of the quantum dot light absorption layer, and the conduction band difference △E CLess than 0.2 electron volts; a heterojunction is formed between the bismuth-based chalcogenide and the quantum dot light-absorbing layer, which enhances the ability to extract photogenerated electrons from the quantum dots. In addition, the bismuth-based chalcogenide does not absorb infrared light with a wavelength greater than 1 μm, and will not affect the acquisition of signals from the quantum dot light-absorbing layer.

[0045] Furthermore, since the band gap width of the bismuth-based chalcogenide compound is at least twice that of the quantum dot light absorbing layer, and its valence band position is lower than the valence band of the quantum dot light absorbing layer, there is a large valence band difference ΔEv between the bismuth-based chalcogenide compound film and the quantum dot light absorbing layer, thereby preventing the reverse transmission of photogenerated holes in the quantum dot light absorbing layer, that is, the transmission from the quantum dot light absorbing layer to the bismuth-based chalcogenide compound film.

[0046] In the present invention, the preparation method of the above quantum dot infrared detector is as follows:

[0047] (1) A bismuth-based sulfide compound film is deposited on the bottom electrode by rapid thermal evaporation.

[0048] Specifically, weigh 0.1-10g of bismuth-based sulfide compound powder, sprinkle the weighed bismuth-based sulfide compound powder evenly on white glass with a 50-mesh sieve, and place it in a tube furnace; the substrate 1 and the bottom electrode form a conductive substrate, and the cleaned and dried conductive substrate is placed upside down 0.1-2cm above the bismuth-based sulfide compound powder, and the substrate is kept warm; evacuate to a vacuum degree not higher than 0.1Torr, and set the program of the corresponding equipment for rapid thermal evaporation, set the substrate temperature to 30-400℃, keep warm for 5-30 minutes, evaporation temperature 500-800℃, and evaporation time 10-100s. After the evaporation is completed and the temperature is lowered and then released, the prepared bismuth-based sulfide compound film is obtained. Among them, the material of the substrate is generally glass, sapphire and other infrared transparent materials, flexible materials such as polyimide, or silicon-based readout circuits.

[0049] Specifically, during the preparation process, the thickness, crystallinity, doping concentration and other properties of the bismuth-based chalcogenide film are adjusted by adjusting the evaporation temperature, substrate temperature, evaporation time and the distance from the substrate to the evaporation source, so as to construct a more efficient quantum dot infrared detector.

[0050] (2) Prepare a quantum dot absorption layer on a bismuth-based sulfide compound film.

[0051] Specifically, the quantum dot solution is prepared, the bismuth-based chalcogenide film prepared in step (1) is placed horizontally, and the prepared quantum dot solution is coated or printed on the epitaxially grown bismuth-based chalcogenide film to form a quantum dot light absorption layer. In addition to coating or printing, the preparation method of the quantum dot light absorption layer can also be spin coating, drip coating, scraping, spraying or printing. The thickness of the quantum dot light absorption layer is in the range of 100nm-5000nm.

[0052] The materials in the quantum dot light-absorbing layer include, but are not limited to, quantum dots such as mercury telluride, lead sulfide, lead selenide, cadmium sulfide, cadmium selenide and zinc sulfide. By selecting a suitable quantum dot material system and changing the synthesis method, synthesis time, synthesis temperature and other conditions of the quantum dots, the absorption range of the quantum dot light-absorbing layer can be adjusted to achieve infrared detection of different wavelengths.

[0053] (3) preparing a hole transport layer on the quantum dot light absorbing layer;

[0054] The thickness of the prepared hole transport layer is 20-200 nm, and the preparation materials of the hole transport layer include but are not limited to nickel oxide, molybdenum oxide, silver telluride quantum dots, and P-type doped quantum dots corresponding to the preparation materials of the aforementioned quantum dot light absorbing layer.

[0055] (4) Prepare a top electrode on the prepared hole transport layer.

[0056] Specifically, the preparation method of the top electrode includes but is not limited to thermal evaporation, magnetron sputtering, electron beam evaporation, etc. The top electrode material includes but is not limited to gold, silver, copper, aluminum, ITO, FTO, etc.

[0057] The present invention will be further described below in conjunction with specific embodiments.

[0058] Example 1

[0059] In this embodiment, a mercury telluride quantum dot infrared detector based on bismuth sulfide film is prepared:

[0060] (1) Weigh 0.5g of bismuth sulfide powder, sprinkle the bismuth sulfide powder evenly on white glass with a 50-mesh sieve, and place it in a tube furnace; the substrate and the prepared ITO bottom electrode form an ITO conductive substrate, and the cleaned and dried ITO conductive substrate is placed upside down 1cm above the bismuth sulfide powder, and covered with a graphite block to keep the substrate warm; evacuate to a vacuum degree of 0.002Torr, and set the rapid thermal evaporation program, set the substrate temperature to 100°C, the insulation time to 10 minutes, the heating rate to 10°C / s, the evaporation temperature to 600°C, and the evaporation time to 50s. Start the rapid thermal evaporation process, and after the evaporation is completed and the temperature is lowered, vent and take it out, place the bismuth sulfide film in a vacuum environment, anneal at 400°C for 10 minutes, and then take it out to obtain the prepared bismuth sulfide film. In this embodiment, the thickness of the prepared bismuth sulfide film is 50nm.

[0061] (2) The bismuth sulfide film is placed horizontally, and the mercury telluride quantum dot solution is dropped on the bismuth sulfide film prepared in step (1), and the solution is spin-coated at a speed of 2000 rpm for 30 seconds, soaked in ethanedithiol for 10 seconds, and spin-coated for 30 seconds, and repeated 10 times to finally form a quantum dot light absorption layer. The thickness of the mercury telluride quantum dot light absorption layer is 400 nm, and the detection cutoff wavelength is 2.5 μm.

[0062] (3) The film prepared in step (2) was placed horizontally, and the silver telluride quantum dot solution was dropped onto the mercury telluride quantum dot light-absorbing layer, and the solution was spin-coated at a speed of 2000 rpm for 30 seconds, and the solution was soaked in ethanedithiol for 30 seconds, and the solution was spin-coated for 30 seconds, and the process was repeated twice to obtain a prepared hole transport layer with a thickness of 20 nm.

[0063] (4) On the thin film prepared in step (3), gold is deposited by thermal evaporation as a top electrode. The vacuum degree of the evaporator is 0.005 Pa, the evaporation current is 128 A, and the thickness of the prepared gold conductive electrode is 50 nm.

[0064] like Figure 2 The surface SEM image of the bismuth sulfide film prepared in this example is shown in FIG.

[0065] like Figure 3 The figure is the surface AFM current potential diagram of the bismuth sulfide film prepared in this embodiment. It can be seen that the surface leakage of the prepared bismuth sulfide film is very small, which meets the requirements of the electron transport layer of the infrared detector.

[0066] like Figure 4 As shown, it is the energy band relationship between the bismuth sulfide film and the mercury telluride quantum dot light absorbing layer in this embodiment. It can be seen from the figure that the conduction bands of the bismuth sulfide film and the mercury telluride quantum dot light absorbing layer are both -4.43eV, and their conduction band difference △Ec=0eV; compared with the conduction band of traditional electron transport layer materials (the conduction bands of materials such as zinc oxide, tin oxide, titanium oxide, and cadmium sulfide are between -3.8eV and -4.2eV, where eV is electron volts), the energy bands of the bismuth sulfide film and the mercury telluride quantum dot light absorbing layer in the embodiment of the present invention are completely matched, and more efficient photogenerated electron extraction can be achieved. At the same time, the valence band of the bismuth sulfide film is lower than the valence band of the mercury telluride quantum dot light absorbing layer, and the valence band difference between the two is △Ev=0.67eV, which can better prevent the photogenerated holes in the quantum dot light absorbing layer from being transmitted to the bismuth sulfide film. That is, while achieving efficient photogenerated electron extraction, the reverse transmission of photogenerated holes can be blocked.

[0067] like Figure 5 , which is a cross-sectional SEM image of the infrared detector in this embodiment. It can be seen from the figure that the bismuth sulfide film in this embodiment has good flatness and wettability, and is more suitable for the preparation of quantum dot light absorbing layers with a detection cutoff wavelength ≥ 2 μm.

[0068] like Figure 6The figure shows the basic application principle diagram of the quantum dot infrared detector of the present invention (bottom-incident detection type, top-incident only requires the light source to be placed on the top electrode, and the bias voltage is reversed). Infrared light is incident on the detector from the bottom electrode, the quantum dot light-absorbing layer absorbs the light signal and converts it into a current signal, a signal acquisition instrument is connected to the bottom electrode and the top electrode, the current loop is connected, and the photogenerated current signal is collected by the instrument to realize the detection of infrared light. It usually works in a zero bias voltage or negative bias voltage mode (the bottom electrode is connected to a positive voltage, and the top electrode is connected to a negative voltage).

[0069] like Figure 7 As shown in FIG. 1 , it is an infrared conversion performance diagram of the infrared detector in this embodiment. It can be seen that the photocurrent of the mercury telluride quantum dot infrared detector in this embodiment using bismuth sulfide film as the electron transport layer is 2.5 times that of the mercury telluride quantum dot infrared detector without bismuth sulfide film as the electron transport layer under the same wavelength, the same power and the same distance of illumination, indicating that the detection capability of infrared signal light under the same conditions is significantly improved. Among them, w / o bismuth sulfide in the figure means that the electron transport layer does not contain bismuth sulfide.

[0070] Example 2

[0071] In this embodiment, a lead sulfide quantum dot infrared detector based on bismuth sulfide selenide film is prepared.

[0072] (1) Weigh 0.5g of bismuth sulfide powder and 0.3g of bismuth selenide powder to form a mixed powder, sprinkle the mixed powder evenly on white glass with a 50-mesh sieve, place it in a tube furnace, place the washed and dried ITO conductive substrate upside down 1cm above the mixed powder, and cover it with a graphite block to keep the substrate warm. Evacuate to a vacuum degree of 0.002Torr, set the substrate temperature to 100°C, the evaporation temperature to 640°C, the evaporation time to 60s, start the rapid thermal evaporation process, and after the evaporation is completed and the temperature is lowered, release the gas and take it out to obtain the prepared bismuth selenide sulfide film. In this embodiment, the thickness of the prepared bismuth selenide sulfide film is 80nm.

[0073] (2) The bismuth sulfide selenide film is placed horizontally, and the lead sulfide quantum dot solution is dripped onto the surface of the epitaxially grown bismuth sulfide selenide film, and the film is spin-coated at a speed of 2000 rpm for 30 seconds, and annealed at 85° C. for 10 minutes to form a lead sulfide quantum dot light-absorbing layer. The thickness of the lead sulfide quantum dot light-absorbing layer is 350 nm.

[0074] (3) The lead sulfide quantum dot solution was dropped onto the lead sulfide quantum dot light absorbing layer, and the solution was spin-coated at a speed of 2000 rpm for 30 s, and then soaked in ethanedithiol for 10 s, and spin-coated for 30 s, and the process was repeated twice to obtain a prepared hole transport layer with a thickness of 50 nm and a detection cutoff wavelength of 2 μm.

[0075] (4) Using thermal evaporation to deposit gold as a top electrode on the thin film prepared in step (3). The vacuum degree of the evaporator is 0.005 Pa, the evaporation current is 128 A, and the thickness of the prepared gold conductive electrode is 50 nm.

[0076] like Figure 8 As shown, it is the energy band relationship between the bismuth sulfide selenide film and the lead sulfide quantum dot light absorption layer in this embodiment. It can be found that the conduction band of the bismuth sulfide selenide film is lower than that of the lead sulfide quantum dot light absorption layer, and the two are close, and their conduction band difference △Ec=0.1eV. The energy bands of the two can be well matched, and efficient photogenerated electron extraction can be achieved. At the same time, the valence band of the bismuth sulfide selenide film is lower than the valence band of the lead sulfide quantum dot light absorption layer, and their valence band difference △Ev=0.48eV, which can effectively prevent the photogenerated holes in the quantum dot light absorption layer from being transmitted to the bismuth sulfide selenide film.

[0077] like Fig. 9 , which is the infrared conversion performance diagram of the infrared detector in this embodiment. It can be seen that the lead sulfide quantum dot infrared detector in this embodiment using bismuth sulfide selenide film as the electron transport layer is 3.09 times the lead sulfide quantum dot infrared detector without bismuth sulfide selenide film as the electron transport layer under the same wavelength, power and distance of light, indicating that the detection capability of infrared signal light under the same conditions is significantly improved.

[0078] Example 3

[0079] In this embodiment, a lead selenide quantum dot infrared detector based on bismuth telluride sulfide film is prepared.

[0080] (1) Weigh 1g of bismuth sulfide powder and 0.1g of bismuth telluride to form a mixed powder. Use a 50-mesh sieve to evenly sprinkle the mixed powder on white glass, place it in a tube furnace, and place the washed and dried ITO conductive substrate upside down 1cm above the mixed powder. Cover it with a graphite block to keep the substrate warm. Evacuate to a vacuum degree of 0.002Torr, set the substrate temperature to 30°C, the evaporation temperature to 600°C, and the evaporation time to 30s. Start the rapid thermal evaporation process. After the evaporation is completed and the temperature is lowered, release the gas and take it out. The bismuth telluride sulfide film is prepared. In this embodiment, the thickness of the prepared bismuth telluride sulfide film is 20nm.

[0081] (2) Place the bismuth telluride sulfide film horizontally, drip the lead selenide quantum dot solution onto the surface of the epitaxially grown bismuth sulfide film, spin-coat at 2500 rpm for 30 seconds, soak in tetrabutylammonium iodide solution for 30 seconds, spin-coat at 2500 rpm for 30 seconds, repeat the above steps 8 times, and finally form a lead selenide quantum dot light-absorbing layer. The thickness of the lead selenide quantum dot light-absorbing layer is 300 nm, and the detection cutoff wavelength is 2.1 μm.

[0082] (3) Drop the lead selenide quantum dot solution on the lead selenide quantum dot light absorbing layer, spin-coat at 2500 rpm for 30 seconds, soak in ethanedithiol for 10 seconds, spin-coat for 30 seconds, and repeat twice to obtain a prepared hole transport layer with a thickness of 50 nm.

[0083] (4) Using thermal evaporation to deposit silver as a top electrode on the film prepared in step (3). The vacuum degree of the evaporator is 0.005 Pa, the evaporation current is 115 A, and the thickness of the prepared silver conductive electrode is 80 nm.

[0084] like Fig.10 As shown, it is the energy band relationship between the bismuth telluride sulfide film and the lead selenide quantum dot light absorbing layer in this embodiment. It can be found that the conduction band of the bismuth telluride sulfide film is lower than that of the lead selenide quantum dot light absorbing layer, and the two are close, and their conduction band difference △Ec=0.15eV. The energy bands of the two can be well matched, and efficient photogenerated electron extraction can be achieved. At the same time, the valence band of the bismuth telluride sulfide film is lower than the valence band of the lead sulfide quantum dot light absorbing layer, and their valence band difference △Ev=0.45eV, which can effectively prevent the photogenerated holes in the quantum dot light absorbing layer from being transmitted to the bismuth telluride sulfide film.

[0085] like Fig.11 , which is the infrared conversion performance diagram of the infrared detector in this embodiment. It can be seen that the lead selenide quantum dot infrared detector in this embodiment using sulfur telluride film as the electron transport layer is 2.75 times the photocurrent of the lead selenide quantum dot infrared detector without using sulfur telluride film as the electron transport layer under the same wavelength, power and distance of light, indicating that the detection capability of infrared signal light under the same conditions is significantly improved.

[0086] The quantum dot infrared detector of the present invention is preferably applied to the detection cutoff wavelength of the quantum dot light absorbing layer ≥ 2μm. The conduction band of the bismuth-based chalcogenide film is much lower than the currently common electron transport layer, and matches the conduction band of the quantum dot light absorbing layer with a detection cutoff wavelength ≥ 2μm, thereby solving the problem of the lack of a suitable electron transport layer in the quantum dot infrared detector with a detection cutoff wavelength ≥ 2μm, which is of great significance to the future development of quantum dot infrared detectors.

[0087] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A quantum dot infrared detector, comprising, from bottom to top: A bottom electrode (2), an electron transport layer (3), a quantum dot light absorbing layer (4), a hole transport layer (5) and a top electrode (6), characterized in that the electron transport layer (3) is a bismuth-based chalcogenide compound film, and the bismuth-based chalcogenide compound film, the quantum dot light absorbing layer and the hole transport layer form a NIP type heterojunction, so that the conduction band of the electron transport layer (3) is not higher than the conduction band of the quantum dot light absorbing layer (4), and the conduction band difference between the two is less than 0.2 electron volts; The bismuth-based chalcogenide compound thin film is deposited on the bottom electrode (2) by adopting a rapid thermal evaporation method; and the rapid thermal evaporation method is implemented by: placing the bottom electrode (2) upside down 0.1 cm-2 cm above the bismuth-based chalcogenide compound powder, setting the temperature of the bottom electrode (2) to 30-400° C., the evaporation temperature to 500-800° C., the evaporation time to 10s-100s, and evacuating to a vacuum degree not higher than 0.1 Torr.

2. The quantum dot infrared detector according to claim 1, characterized in that: The bismuth-based chalcogenide compound is Bi2X3 or Bi2(X m Y 1-m )3, wherein X, Y are any two different element combinations of S, Se or Te; 0<m<1.

3. The quantum dot infrared detector according to claim 2, characterized in that: The bismuth-based chalcogenide compound is bismuth sulfide Bi2S3, bismuth sulfide selenide Bi2(S m Se 1-m )3 or bismuth telluride Bi2(S m Te 1-m )3.

4. The quantum dot infrared detector according to claim 3, characterized in that: The bottom electrode and the top electrode are made of infrared transparent conductive material or metal conductive material, and at least one of the bottom electrode and the top electrode is made of infrared transparent conductive material.

5. The quantum dot infrared detector according to claim 4, characterized in that: The infrared transparent conductive material is ITO, FTO or AZO; the metal conductive material is gold, silver, copper or aluminum.

6. The quantum dot infrared detector according to claim 5, characterized in that: The material of the quantum dot light-absorbing layer is mercury telluride, lead sulfide, lead selenide, cadmium sulfide, cadmium selenide or zinc sulfide quantum dots.

7. The quantum dot infrared detector according to claim 6, characterized in that: The hole transport layer material is nickel oxide, molybdenum oxide, PEDOT, Spiro-MeTAD, silver telluride quantum dots or P-type doped quantum dots corresponding to the quantum dot light absorption layer material.

8. A method for preparing a quantum dot infrared detector according to any one of claims 1 to 7, characterized in that: include: S1, depositing a bismuth-based chalcogenide thin film on the bottom electrode by a rapid thermal evaporation method to form an electron transport layer; S2, preparing a quantum dot light absorbing layer on the electron transport layer; S3, preparing a hole transport layer on the quantum dot light absorbing layer; S4. Prepare a top electrode on the prepared hole transport layer.

9. The preparation method according to claim 8, characterized in that: The rapid thermal evaporation method is implemented as follows: the bottom electrode is inverted 0.1 cm-2 cm above the bismuth-based chalcogenide powder, the temperature of the bottom electrode is set to 30-400°C, the evaporation temperature is 500-800°C, the evaporation time is 10s-100s, and the vacuum is evacuated to a vacuum degree not higher than 0.1 Torr.

10. The preparation method according to claim 9, characterized in that: In step S2, the quantum dot light absorbing layer is prepared by coating, printing, spin coating, drip coating, scraping, spraying or printing.

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