AlQDs@Ga2O3 solar-blind photodetectors based on quantum size effect: fabrication method and application

Abstract

This invention discloses an AlQDs@Ga2O3 solar-blind photodetector based on quantum size effects, its fabrication method, and its applications, belonging to the field of photoelectric detection technology. The solar-blind photodetector of this invention includes a substrate, a Ga2O3 layer, a quantum dot material layer, and electrodes. The Ga2O3 layer is disposed on the surface of the substrate, and the quantum dot material layer is disposed on the surface of the Ga2O3 layer, but does not completely cover the Ga2O3 layer. The electrodes include electrode I and electrode II; electrode I and electrode II are disposed on either the Ga2O3 layer or the quantum dot material layer; and electrode I and electrode II are not simultaneously located on the same material layer; the quantum dot material layer includes aluminum quantum dots (AlQDs). This invention combines AlQDs with continuously tunable optical bandgap in the solar-blind band with Ga2O3 with a compatible bandgap value in the solar-blind band to fabricate a solar-blind detector. This detector exhibits excellent wavelength selectivity, providing new ideas for high-resolution single-pixel imaging, ultra-low-power remote sensing, and ultraviolet multispectral photoelectric detection applications, and can also be used for deep ultraviolet anti-interference imaging.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, and particularly relates to an AlQDs@Ga2O3 solar-blind photodetector based on quantum size effect, its preparation method and application. Background Technology

[0002] Because the ozone layer in the atmosphere strongly absorbs UVC-band ultraviolet radiation, photons in this band typically cannot penetrate the atmosphere, hence the term "solar blind zone." This characteristic ensures that deep ultraviolet solar blind detection is free from interference from the solar background, offering significant advantages such as high precision and high signal-to-noise ratio. Therefore, solar blind ultraviolet photodetectors are indispensable key components in civilian fields such as sterilization, water purification, environmental monitoring, and ultraviolet curing technology; scientific research fields such as medicine and biology; and military fields such as covert battlefield communications.

[0003] Commercial ultraviolet (UV) detection primarily relies on photomultiplier tubes (PMTs) or UV-enhanced silicon photodiodes (SPDs), but these technologies are limited by low-temperature operation requirements, high power consumption, low sensitivity, and the need for optical filtering systems. Third-generation wide-bandgap semiconductors (WBSs), such as AlN, GaN, SiC, Ga₂O₃, ZnO, and diamond, offer a promising alternative for deep UV detection due to their stability, high thermal conductivity, and suitable cutoff wavelengths. Among these, monoclinic gallium oxide (β-Ga₂O₃) has been extensively studied; however, its performance is limited by high dark current and slow response time caused by neutral oxygen vacancy photoionization. To overcome these problems, epitaxial semiconductor thin films, organic conductive polymers, and transition metal dichalcogenides (TMDs) have been used in heterojunction fabrication. However, these methods still encounter obstacles, including complex fabrication processes, high dark current density, and poor spectral selectivity. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an AlQDs@Ga2O3 solar-blind photodetector based on quantum size effects, its fabrication method, and applications. This invention fabricates AlQDs with continuously tunable optical bandgap in the solar-blind band and combines them with Ga2O3, which has a compatible bandgap value in the solar-blind band, to create an AlQDs@Ga2O3 heterojunction solar-blind photodetector. The detector's ultra-narrow band optical response in the solar-blind band enables its application in deep ultraviolet interference-resistant imaging. Furthermore, by changing the relative molar ratio of the metal precursor and reducing agent, AlQDs of different particle sizes can be fabricated. The quantum confinement effect allows for continuous tunability of the optical bandgap in the deep ultraviolet solar-blind band, achieving the fabrication of a heterojunction with a cascaded bandgap structure. The ultra-sensitive AlQDs@Ga2O3 heterojunction solar-blind photodetector fabricated by this invention based on quantum size effects provides a new approach for high-resolution single-pixel imaging, ultra-low-power remote sensing, and ultraviolet multispectral photoelectric detection applications.

[0005] The technical solution of the present invention is as follows:

[0006] The first aspect of this invention provides an ultrasensitive AlQDs@Ga2O3 heterojunction solar-blind photodetector based on quantum size effects, comprising a substrate, a Ga2O3 layer, a quantum dot material layer, and electrodes; the Ga2O3 layer is disposed on the surface of the substrate, and the quantum dot material layer is disposed on the surface of the Ga2O3 layer, but does not completely cover the Ga2O3 layer; the electrodes include electrode I and electrode II; electrode I and electrode II are disposed on either the Ga2O3 layer or the quantum dot material layer, and electrode I and electrode II are not located on the same material layer; the quantum dot material layer comprises AlQDs quantum dots.

[0007] Preferably, the Ga2O3 includes at least one of β-Ga2O3, α-Ga2O3, γ-Ga2O3, δ-Ga2O3, and ε-Ga2O3; the quantum dot material layer includes at least one quantum dot material layer.

[0008] Preferably, the quantum dot material layer comprises two or more AlQDs quantum dot material layers with different particle sizes.

[0009] Preferably, electrode I includes at least one of a Ti electrode and an Au electrode; electrode II includes at least one of a Ti electrode and an Au electrode.

[0010] A second aspect of the present invention provides a method for fabricating the AlQDs@Ga2O3 heterojunction solar-blind photodetector described in the first aspect above, comprising the following steps:

[0011] S1: Prepare colloidal AlQDs solution and prepare a substrate containing a Ga2O3 layer.

[0012] S2: The colloidal AlQDs solution is deposited layer by layer on the surface of the Ga2O3 layer of the substrate containing the Ga2O3 layer to form an AlQDs@Ga2O3 heterojunction, thus obtaining a material containing both the Ga2O3 layer and the AlQDs layer.

[0013] S3: Electrode I and electrode II are deposited on the Ga2O3 layer and AlQDs layer respectively by mask evaporation to obtain the AlQDs@Ga2O3 heterojunction solar-blind photodetector.

[0014] In step S2, the AlQDs layer partially covers the Ga2O3 layer.

[0015] Preferably, in step S1, the concentration of the colloidal AlQDs solution is 10-20 mg / mL.

[0016] Preferably, in step S1, the colloidal AlQDs solution is prepared by:

[0017] S1-1: Add aluminum halide and surfactant to solvent I, sonicate, and the solution color changes from pale yellow to colorless to obtain the precursor solution.

[0018] S1-2: After the precursor solution is degassed by argon, it is heated under anhydrous and oxygen-free conditions, and then a reducing agent solution is added. The mixture is stirred and reacted, and then solvent II is added and stirred for 5 minutes. The white precipitate is removed by centrifugation, and solvent I is removed by rotary evaporation of the supernatant to obtain crude AlQDs. After ultrasonic dispersion with solvent III, colloidal AlQDs solution is obtained.

[0019] Preferably, in step S1-1, the aluminum halide includes at least one of aluminum chloride and aluminum bromide.

[0020] The surfactant includes a quaternary ammonium cationic surfactant; preferably, the surfactant includes at least one of tetraoctylammonium bromide, tetramethylammonium fluoride, and dialkyldimethylammonium chloride; the molar ratio of the aluminum halide to the surfactant is 1:1-32; the solvent I includes at least one of anhydrous xylene and oleylamine.

[0021] Preferably, in steps S1-2, the heating refers to heating to 110-120℃; the reducing agent solution is lithium aluminum hydride solution or ammonia ethanol solution; the reducing agent solution is 2M; the addition rate of the reducing agent solution is 1-4 mL / h; the molar ratio of aluminum halide to the reducing agent is 2:1-1:4; the stirring reaction speed is 700-900 r / min, the reaction temperature is 110-130℃, and the time is 3-8 h; preferably, the stirring reaction is carried out under an argon atmosphere; solvent II includes methanol; solvent III includes at least one of ethanol and dimethylformamide.

[0022] Preferably, in step S2, the Ga2O3 includes at least one of β-Ga2O3, α-Ga2O3, γ-Ga2O3, δ-Ga2O3, and ε-Ga2O3; the step of depositing the colloidal AlQDs solution layer by layer on the surface of the Ga2O3 layer of the substrate containing the Ga2O3 layer involves spin-coating the colloidal AlQDs solution onto a portion of the surface of the Ga2O3 substrate, annealing, repeating the spin-coating and annealing process to form a multilayer AlQDs layer; the number of repetitions is greater than or equal to 0; the spin-coating is first done at 500 rpm for 10 s, then at 2000 rpm for 30 s; the annealing temperature is 90°C and the time is 10 min.

[0023] Preferably, in step S3, electrode I is disposed on the surface of AlQDs; electrode II is disposed on the surface of Ga2O3 that is not coated with AlQDs solution; electrode I includes at least one of Ti electrode and Au electrode; electrode II includes at least one of Ti electrode and Au electrode; the electrode materials of electrode I and electrode II may be the same or different.

[0024] A third aspect of the present invention provides an imaging device, comprising the ultrasensitive AlQDs@Ga2O3 heterojunction solar-blind photodetector based on quantum size effect as described in the first aspect above, or the AlQDs@Ga2O3 heterojunction solar-blind photodetector prepared by the preparation method described in the second aspect above.

[0025] The beneficial technical effects of this invention are as follows:

[0026] (1) The AlQDs quantum dot material with continuously tunable optical bandgap prepared in this invention can be combined with Ga2O3, especially β-Ga2O3, and by the characteristic absorption of the deep ultraviolet solar blind light band, a heterojunction solar blind detector with ultra-narrow band response in the deep ultraviolet band can be prepared, which is conducive to its wide application in the field of solar blind band feature recognition.

[0027] (2) The present invention further achieves the preparation of AlQDs with different particle sizes by changing the relative molar ratio of metal precursor and reducing agent, and realizes the continuous tunability of its optical bandgap in the deep ultraviolet solar blind band by utilizing the quantum confinement effect, which helps to realize the preparation of heterojunctions with cascaded band structure distribution.

[0028] (3) Compared with the current photodetector structure with cascade structure mainly in the mid-infrared band, the present invention innovatively utilizes the quantum confinement effect of quantum dots to prepare a cascade heterojunction solar-blind photodetector. Due to its cascaded band structure arrangement and the presence of built-in electric field, the dark current of the device is effectively suppressed to achieve ultra-sensitive photodetection. At the same time, its narrow-band response in the solar-blind band can be used to realize anti-interference deep ultraviolet solar-blind imaging applications.

[0029] (4) The synthesis route of AlQDs quantum dots in this invention has the advantages of simple and readily available raw materials, simple and easy reaction conditions, simple operation, and high product quality. The heterojunction solar-blind ultraviolet photodetector with cascaded band structure prepared has excellent anti-interference solar-blind imaging capability and has broad application prospects in ultraviolet missile early warning, ground-based air defense, and battlefield non-line-of-sight optical communication. Attached Figure Description

[0030] Figure 1The images shown are transmission electron microscope (TEM) images of colloidal aluminum quantum dots with different size distributions prepared in Examples 1-5 of this invention. The quantum dots prepared according to the relative molar ratio of precursor to reducing agent of 1:0.5, 1:1, 1:2, 1:3, and 1:4 are labeled as AlQDs-0.5, AlQDs-1, AlQDs-2, AlQDs-3, and AlQDs-4, respectively.

[0031] In the figure: a) is the TEM image of AlQDs-0.5; b) is the ACTEM image of AlQDs-0.5; c) is the TEM image of AlQDs-1; d) is the ACTEM image of AlQDs-1; e) is the TEM image of AlQDs-2; f) is the ACTEM image of AlQDs-2; g) is the TEM image of AlQDs-3; h) is the ACTEM image of AlQDs-3; i) is the TEM image of AlQDs-4; j) is the ACTEM image of AlQDs-4.

[0032] Figure 2 The images show the UV absorption and fluorescence emission spectra of colloidal aluminum quantum dots with different size distributions prepared in Examples 1-5 of this invention.

[0033] In the figure: a) Ultraviolet absorption spectrum; b) Fluorescence emission spectrum.

[0034] Figure 3 The IV and It diagrams of the AlQDs@β-Ga2O3 heterojunction solar-blind photodetector with cascaded band structure prepared in Example 6 of this invention, as well as the comparison diagram between Example 6 and Example 7.

[0035] In the figure: a is a comparison diagram of the It diagram of the detector of Example 6; b is the IV diagram of Example 6; c is a comparison diagram of Example 6 and Example 7.

[0036] Figure 4 The images show ultrasensitive solar-blind images of the cascaded band structure AlQDs@β-Ga2O3 heterojunction solar-blind photodetector prepared in Example 6 of this invention under different optical power densities.

[0037] In the figure: (1) is 23 nW / cm 2 (2) is 1.2 μW / cm 2 (3) is 60 μW / cm 2 (4) is 233 μW / cm 2 (5) is 6.0 mW / cm 2 .

[0038] Figure 5 The AlQDs@β-Ga2O3 heterojunction solar-blind photodetector with a cascaded band structure prepared in Example 6 of this invention corresponds to... Figure 4Photocurrent corresponding to different optical power densities.

[0039] Figure 6 Anti-interference solar-blind imaging tests were conducted on the cascaded band structure AlQDs@β-Ga2O3 heterojunction solar-blind photodetector and a commercial silicon detector prepared in Example 6 of this invention under different hybrid light sources.

[0040] In the figure: a) Solar-blind image of the solar-blind photodetector with cascaded band structure prepared in Example 6 under different mixed light sources; b) Solar-blind image of a commercial silicon detector under different mixed light sources.

[0041] Figure 7 This is a schematic diagram of the cascaded band structure AlQDs@β-Ga2O3 heterojunction solar-blind photodetector prepared in this invention.

[0042] In the figure: 1. Substrate; 2. Ga2O3 layer; 3. First colloidal AlQDs layer; 4. Second colloidal AlQDs layer; 5. Electrode. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0044] Based on the problems of existing technologies, there is an urgent need to provide a new solar-blind detector that can suppress dark current and achieve ultra-sensitive photoelectric detection. The confinement of charge carriers (holes and electrons) in three dimensions of III-V group quantum dots (QDs) leads to a strong quantum confinement effect. Compared with bulk materials, they offer advantages such as low-cost solution-processability, bandgap tuning through size control, surface chemical engineering, and metal co-doping, and high stress and strain resistance, making them easy to integrate into crystalline or flexible substrates. Furthermore, improving the external quantum dot efficiency (EQE) of the detector through system bandgap engineering can achieve better photoelectric conversion and suppress the device's dark current (Ig). d This invention provides a method for fabricating and applying an ultrasensitive AlQDs@Ga2O3 heterojunction solar-blind photodetector based on quantum size effects to further enhance the sensitivity of the device.

[0045] The first aspect of this invention provides a solar-blind photodetector based on quantum size effects, such as... Figure 7 As shown, it includes a substrate 1, a Ga2O3 layer 2, a quantum dot material layer, and an electrode 5. The quantum dot material layer has one or more layers, for example, such as... Figure 7As shown, it includes a first layer of colloidal AlQDs 3 and a second layer of colloidal AlQDs 4; the Ga2O3 layer is disposed on the surface of the substrate 1, and the quantum dot material layer is disposed on the surface of the Ga2O3 layer 2, but does not completely cover the Ga2O3 layer 2; the electrode 5 includes electrode I and electrode II.

[0046] In some embodiments, electrode I and electrode II are disposed on a Ga2O3 layer or a quantum dot material layer; and electrode I and electrode II are not located in the same material layer at the same time.

[0047] In some embodiments, electrode I and electrode II are disposed on the Ga2O3 layer; the quantum dot material layer includes AlQDs quantum dots.

[0048] It is understood that the present invention combines AlQDs with continuously tunable optical bandgap with Ga2O3, especially β-Ga2O3, and prepares a heterojunction solar-blind detector with ultra-narrow band response in the deep ultraviolet band by characteristic absorption of the deep ultraviolet solar-blind light band.

[0049] In some embodiments, the Ga2O3 includes at least one of β-Ga2O3, α-Ga2O3, γ-Ga2O3, δ-Ga2O3, and ε-Ga2O3; preferably β-Ga2O3. The quantum dot material layer is disposed on all or part of the surface of the Ga2O3 layer; the quantum dot material layer includes at least one quantum dot material layer; preferably, the quantum dot material layer includes two or more AlQDs quantum dot material layers with different particle sizes. The different particle sizes of the quantum dot materials can be achieved by changing the ratio of the metal precursor to the reducing agent.

[0050] It is understandable that when the quantum dot material layer comprises two or more AlQDs quantum dot layers with different particle sizes (constructing AlQDs quantum dots with different band gaps), a cascaded band arrangement can be formed. The Fermi level difference promotes the effective separation of photogenerated carriers, leading to band bending and the formation of an internal electric field. This internal electric field promotes the transport of photogenerated electrons from the Ga2O3 side to the gradient AlQDs side while suppressing radiative recombination, thereby improving photodetection efficiency and extending carrier diffusion length. Furthermore, the band shift between different layers reduces electron tunneling, helping to suppress dark current and achieve ultrasensitive photodetection.

[0051] It is understood that the cascaded heterojunction solar-blind photodetector fabricated in this invention utilizes the quantum confinement effect of quantum dots. Due to its cascaded band structure arrangement and the presence of a built-in electric field, the dark current of the device is effectively suppressed, achieving ultra-sensitive photoelectric detection. Simultaneously, its narrowband response in the solar-blind band enables interference-resistant deep ultraviolet solar-blind imaging applications. The fabricated heterojunction solar-blind ultraviolet photodetector exhibits excellent interference-resistant solar-blind imaging capabilities and has broad application prospects in ultraviolet missile early warning, ground-based air defense, and battlefield non-line-of-sight optical communication.

[0052] Electrode I includes at least one of Ti electrode and Au electrode; Electrode II includes at least one of Ti electrode and Au electrode.

[0053] A second aspect of the present invention provides a method for fabricating the AlQDs@Ga2O3 heterojunction solar-blind photodetector described in the first aspect above, comprising the following steps:

[0054] S1: Prepare colloidal AlQDs solution and prepare a substrate containing a Ga2O3 layer.

[0055] S2: The colloidal AlQDs solution is deposited layer by layer on the surface of the Ga2O3 layer of the substrate containing the Ga2O3 layer to form an AlQDs@Ga2O3 heterojunction, thus obtaining a material containing both the Ga2O3 layer and the AlQDs layer.

[0056] S3: Electrode I and electrode II are then deposited on the Ga2O3 layer and AlQDs layer respectively by mask evaporation to obtain the AlQDs@Ga2O3 heterojunction solar-blind photodetector.

[0057] In some embodiments, in step S1, the concentration of the colloidal AlQDs solution is 10-20 mg / mL.

[0058] In some embodiments, the preparation method of the colloidal AlQDs solution in step S1 is as follows:

[0059] S1-1: Add aluminum halide and surfactant to solvent I, sonicate, and the solution color changes from pale yellow to colorless to obtain the precursor solution.

[0060] S1-2: After the precursor solution is degassed by argon, it is heated under anhydrous and oxygen-free conditions, and then a reducing agent solution is added. The mixture is stirred and reacted, and then solvent II is added and stirred for 5 minutes. The white precipitate is removed by centrifugation, and solvent I is removed by rotary evaporation of the supernatant to obtain crude AlQDs. After ultrasonic dispersion with solvent III, colloidal AlQDs solution is obtained.

[0061] In some embodiments, in step S1-1, the aluminum halide includes at least one of aluminum chloride and aluminum bromide; the surfactant includes a quaternary ammonium cationic surfactant. Preferably, the surfactant includes at least one of tetraoctylammonium bromide, tetramethylammonium fluoride, and dialkyldimethylammonium chloride.

[0062] In some embodiments, the molar ratio of the aluminum halide to the surfactant is 1:1-3; the solvent I includes at least one of anhydrous xylene and oleylamine.

[0063] In some implementations, in steps S1-2, the heating refers to heating to 110-120°C.

[0064] Understandably, heating the temperature too high will exceed the boiling point of the solvent, while heating the temperature too low will affect the quality of the crystallization.

[0065] In some embodiments, in steps S1-2, the reducing agent solution is ammonia-ethanol or lithium aluminum hydride solution, preferably lithium aluminum hydride solution; the concentration of the reducing agent solution is 2M; the addition rate of the reducing agent solution is 1-4 mL / h; the molar ratio of aluminum halide to the reducing agent is 2:1-1:4. The molar volume ratio of aluminum chloride to solvent I is 1 mol: 100 mL.

[0066] It is understood that this invention achieves the preparation of AlQDs with different particle sizes by changing the relative molar ratio of the metal precursor and the reducing agent, and utilizes the quantum confinement effect to achieve continuous tunability of their optical bandgap in the deep ultraviolet solar blind band, which helps to realize the preparation of heterojunctions with cascaded band structure distribution.

[0067] In some embodiments, in steps S1-2, the stirring reaction rate is 700-900 r / min, the reaction temperature is 110-120℃, and the time is 3-8 h; preferably, the stirring reaction is carried out under an argon atmosphere.

[0068] In some embodiments, in steps S1-2, solvent I includes at least one of xylene and oleylamine; solvent II includes methanol; and solvent III includes at least one of ethanol and dimethylformamide.

[0069] In some embodiments, in step S2, the Ga2O3 includes at least one of β-Ga2O3, α-Ga2O3, γ-Ga2O3, δ-Ga2O3, and ε-Ga2O3; preferably β-Ga2O3.

[0070] In some embodiments, the step of depositing the colloidal AlQDs solution layer by layer onto the surface of the Ga2O3 layer of the substrate containing the Ga2O3 layer involves spin-coating the colloidal AlQDs solution onto a portion of the surface of the Ga2O3 substrate, annealing, repeating the spin-coating and annealing process to form a multilayer AlQDs layer; the number of repetitions is greater than or equal to 0.

[0071] In some embodiments, the spin coating is performed by first spin coating at 500 rpm for 10 seconds, and then spin coating at 2000 rpm for 30 seconds.

[0072] In some embodiments, the annealing temperature is 90°C and the time is 10 minutes.

[0073] In some embodiments, step S3, depositing electrode I and electrode II in the Ga2O3 layer and AlQDs layer respectively by mask evaporation, includes depositing electrode I in the Ga2O3 layer and electrode II in the AlQDs layer, or depositing electrode I in the AlQDs layer and electrode II in the Ga2O3 layer.

[0074] In some embodiments, in step S3, electrode I is disposed on the surface of AlQDs; electrode II is disposed on the surface of Ga2O3 that is not coated with AlQDs solution.

[0075] Electrode I includes at least one of Ti electrode and Au electrode; Electrode II includes at least one of Ti electrode and Au electrode; Electrode I and Electrode II may be made of the same or different electrode materials.

[0076] In some embodiments, the layer thickness of electrode I is 10 nm; the layer thickness of electrode II is 100 nm.

[0077] A third aspect of the present invention provides an imaging device, comprising the ultrasensitive AlQDs@Ga2O3 heterojunction solar-blind photodetector based on quantum size effect as described in the first aspect above, or the AlQDs@Ga2O3 heterojunction solar-blind photodetector prepared by the preparation method described in the second aspect above.

[0078] It is understood that, in the embodiments of the present invention, before the experiment begins, all glassware used must be placed in an oven to dry at high temperature to remove moisture, and then naturally cooled to room temperature before use.

[0079] The present invention will be further described below through examples and other means.

[0080] Example 1:

[0081] A colloidal AlQDs with a continuously tunable optical bandgap is synthesized by the following steps:

[0082] (1) Weigh 2 mmol of tetraoctane ammonium bromide and 1 mmol of aluminum chloride using an electronic analytical balance, add them to 100 mL of anhydrous xylene and sonicate. The solution color gradually changes from pale yellow to clear and transparent colorless solution to obtain the precursor solution required for the reaction.

[0083] (2) The prepared precursor solution was transferred to a dehydrated and deoxygenated double-row tube reaction system, and then the reaction system was degassed with argon for 20 minutes. The degassed solution was then gradually heated to 120°C, and lithium aluminum hydride solution was slowly added to the solution at a rate of 1 mL / h using a microfluidic injection pump so that the molar ratio of aluminum chloride to lithium aluminum hydride was 1:1.

[0084] (3) After the reducing agent lithium aluminum hydride solution is injected, the reaction solution is continuously stirred magnetically at 800 r / min for 4 hours at a high temperature of 120℃. The entire experiment is carried out under the protection of argon atmosphere.

[0085] (4) Add 3 mL of low-temperature methanol solvent to the reaction solution in step (3) to disrupt the reverse micelle synthesis system, and then add 10 mL of deionized water to separate the excess surfactant. Centrifuge the reaction solution and store the supernatant.

[0086] (5) The organic solvent xylene was removed by rotary evaporation of the supernatant from step (4) to obtain the initial product of AlQDs quantum dots. Then, dimethylformamide was added and ultrasonically dispersed to obtain a colloidal AlQDs solution, which was stored for subsequent research.

[0087] Example 2:

[0088] A colloidal AlQDs with a continuously tunable optical bandgap is synthesized using a method essentially the same as in Example 1. The only difference is that in step (2), the molar ratio of aluminum chloride to lithium aluminum hydride is 1:2.

[0089] Example 3:

[0090] A colloidal AlQDs with a continuously tunable optical bandgap was synthesized using a method essentially the same as in Example 1. The only difference was that in step (2), the molar ratio of aluminum chloride to lithium aluminum hydride was 1:3.

[0091] Example 4:

[0092] A colloidal AlQDs with a continuously tunable optical bandgap was synthesized using a method essentially the same as in Example 1. The only difference was that in step (2), the molar ratio of aluminum chloride to lithium aluminum hydride was 1:4.

[0093] Example 5

[0094] A colloidal AlQDs with a continuously tunable optical bandgap was synthesized using the same method as in Example 1. The only difference was that in step (2), the molar ratio of aluminum chloride to lithium aluminum hydride was 1:0.5.

[0095] Example 6

[0096] A schematic diagram of a solar-blind photodetector based on quantum size effect and cascaded AlQDs@β-Ga2O3 heterojunction is shown below. Figure 7 As shown, the preparation method includes the following steps:

[0097] (1) Specifically, the commercial β-Ga2O3 substrate used was first ultrasonically treated for 5 min in acetone, isopropanol and deionized water to remove organic matter and contaminants from the substrate surface.

[0098] (2) The colloidal AlQDs solutions prepared in Examples 2 and 4 were spin-coated layer by layer onto a β-Ga2O3 substrate, with the colloidal AlQDs solution not completely covering the β-Ga2O3 layer. The specific spin-coating parameters were 500 rpm for 10 s and 2000 rpm for 30 s. To ensure uniform quantum dot film formation, annealing was performed after each AlQDs spin-coating, specifically annealing at 90°C for 10 min before proceeding to the next spin-coating operation. That is, the colloidal AlQDs solution from Example 2 was spin-coated first, followed by annealing, and then the colloidal AlQDs solution prepared in Example 4 was spin-coated again and annealed once more to form a multilayer colloidal AlQDs quantum dot layer.

[0099] (4) A custom-designed shadow mask was used to cover the transfer onto a heterojunction solar-blind detector with a semi-covered structure. The surface dust was removed by blowing with a nitrogen gun for 30 seconds. Then, Ti / Au electrodes were deposited using a magnetron sputtering machine. The Ti layer was deposited on the surface of the β-Ga2O3 layer with a thickness of 10 nm, and the Au layer was deposited on the surface of the AlQDs quantum dot layer with a thickness of 100 nm. After the evaporation was completed, the shadow mask was removed to obtain an AlQDs@β-Ga2O3 heterojunction solar-blind photodetector with a cascaded band structure.

[0100] Example 7

[0101] A solar-blind photodetector based on quantum size effect and cascaded AlQDs@β-Ga2O3 heterojunction is presented, with its structure and preparation method being basically the same as in Example 6. The only difference is that in step (2), the colloidal AlQDs solution prepared in Example 2 is deposited only on β-Ga2O3, followed by annealing to obtain a monolayer AlQDs thin film. Experiments show that the detector with the cascaded heterojunction structure exhibits enhanced performance compared to the detector in this example.

[0102] Application test case:

[0103] (1) Performance characterization of colloidal AlQDs

[0104] Surface morphology analysis was performed on the TEM and ACTEM of the colloidal AlQDs quantum dots with different optical band gaps synthesized in Examples 1-5. The results are as follows: Figure 1 As shown in the figure, the particle size of AlQDs gradually decreases with increasing reducing agent concentration. Considering the quantum confinement effect of quantum dots, their absorption and photoluminescence spectra also undergo a significant blue shift.

[0105] The colloidal AlQDs quantum dots with different optical band gaps synthesized in Examples 1-5 were analyzed by UV-Vis absorption and photoluminescence fluorescence spectroscopy. The results are as follows: Figure 2 As shown in the figure, AlQDs-0.5, AlQDs-1, AlQDs-2, AlQDs-3, and AlQDs-4 represent the quantum dots prepared in Examples 5, 1, 2, 3, and 4, respectively, i.e., colloidal aluminum quantum dots prepared when the relative molar ratio of precursor to reducing agent is 1:0.5, 1:1, 1:2, 1:3, and 1:4. Figure 2 It can be seen that the prepared AlQDs have continuously adjustable optical bandgap values ​​and exhibit strong photoluminescence in the UVB-UVA band.

[0106] (2) Detector performance characterization

[0107] The detectors prepared in Examples 6 and 7 were connected to a Keithley 2602B, respectively, and the photoelectric response was measured at different wavelengths of 254 nm. Figure 3 Figure a shows a comparison of the photocurrent (It) of the detector in Example 6 under different bias voltages. It can be seen that, under the same conditions, the photocurrent of the photodetector with the cascaded bandgap structure is three times that of the single-layer detector. Figure b shows the I-V diagram of the photodetector in Example 6; it can be seen from the figure that the detector of this embodiment exhibits ultra-low dark current under reverse bias voltage, which is beneficial for achieving ultra-sensitive solar-blind detection. Figure c shows a comparison between Example 6 and Example 7. It can be seen from the figure that the device has excellent linear response and stability in optical power.

[0108] (3) Testing of detectors for anti-interference imaging

[0109] An imaging system was constructed using the AlQDs@β-Ga2O3 heterojunction solar-blind photodetector with a cascaded band structure prepared in Example 6, and the anti-interference imaging performance of the detector was measured.

[0110] The imaging system places a solar-blind detector on the focal plane and then uses a two-axis displacement platform to gradually scan the mask under test to obtain imaging images at different light power densities. Further testing and research on detection-based anti-interference imaging are conducted using this imaging system.

[0111] In the specific imaging experiment, the detector’s ultra-sensitive solar-blind detection under low light conditions was first verified, and then its great potential for anti-interference solar-blind imaging in the solar-blind band was verified by using a hybrid light source.

[0112] A. Solar-blind detection in low light conditions:

[0113] The specific method is as follows: Construct a transmission scanning imaging system according to the above method, adjust the optical power of the 254nm LED, and verify its ultra-sensitive solar-blind detection under different light intensities, such as... Figure 4 As shown in the figure, (1)-(5) represent images under different light intensities. Combined with... Figure 5 It is known that solar-blind detectors with cascaded band structures can operate at energy levels as low as 23 nW / cm². -2 Even under certain lighting conditions, clear imaging in day-blind conditions can still be achieved.

[0114] B. Solar-blind detection under mixed light sources:

[0115] The specific method is as follows: Construct a transmission scanning imaging system according to the above method, using different light sources, specifically as follows... Figure 6 As shown, the anti-interference experiment in the deep ultraviolet band was verified under conditions including a hybrid light source using 254nm and 365nm light sources, a hybrid light source using 254nm and 395nm light sources, and a 254nm LED and white light source. The results were compared with those of a commercial silicon detector. Figure 6 As shown in the figure, Figure a illustrates solar-blind imaging achieved by a solar-blind photodetector with a cascaded band structure, while Figure b illustrates solar-blind imaging achieved by a commercial silicon detector. The comparison reveals that the solar-blind detector with a cascaded band structure proposed in this invention can achieve highly selective solar-blind imaging, and has broad application prospects in both military and civilian fields.

[0116] This invention constructs a heterojunction-type solar-blind detector with an ultra-narrowband response by fabricating Al quantum dots (QDs) with continuously tunable optical bandgap and combining them with β-Ga₂O₃. The cascaded band structure and built-in electric field of this detector not only effectively suppress dark current but also significantly improve photoelectric detection sensitivity, making it particularly suitable for high-precision imaging in the deep ultraviolet band. Its narrowband response characteristics demonstrate great potential for interference-resistant deep ultraviolet solar-blind imaging.

[0117] The method described in this invention is expected to have wide applications in multiple fields, including high-sensitivity ultraviolet imaging in space exploration and solar activity monitoring. Furthermore, in defense and industrial inspection, systems relying on deep ultraviolet light detection can leverage the solar-blindness of this technology to improve imaging quality and anti-interference capabilities in complex environments. In environmental monitoring, the high selectivity of deep ultraviolet light detection can help identify specific gas components, and it holds promise for the detection and analysis of atmospheric pollutants. Further technological optimization may also drive the application of this detector in medical spectral analysis and high-precision optical sensors.

[0118] The above description is merely a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that are directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A solar-blind photodetector based on quantum size effect and realizing ultrasensitive AlQDs@Ga2O3 heterojunction, characterized in that, Includes a substrate, a Ga2O3 layer, a quantum dot material layer, and electrodes; The Ga2O3 layer is disposed on the surface of the substrate, and the quantum dot material layer is disposed on the surface of the Ga2O3 layer, but does not completely cover the Ga2O3 layer; The electrodes include electrode I and electrode II; Electrode I and electrode II are disposed on a Ga2O3 layer or a quantum dot material layer, and electrode I and electrode II are not located on the same material layer; The quantum dot material layer includes AlQDs quantum dots; The quantum dot material layer comprises two or more AlQDs quantum dot material layers with different particle sizes.

2. The AlQDs@Ga2O3 heterojunction solar-blind photodetector according to claim 1, characterized in that, The Ga2O3 includes at least one of β-Ga2O3, α-Ga2O3, γ-Ga2O3, δ-Ga2O3, and ε-Ga2O3; Electrode I includes at least one of Ti electrode and Au electrode; Electrode II includes at least one of Ti electrode and Au electrode.

3. A method for fabricating an AlQDs@Ga2O3 heterojunction solar-blind photodetector according to any one of claims 1-2, characterized in that, The preparation method includes the following steps: S1: Prepare colloidal AlQDs solution and prepare a substrate containing a Ga2O3 layer; S2: The colloidal AlQDs solution is deposited layer by layer on the surface of the Ga2O3 layer of the substrate containing the Ga2O3 layer to form an AlQDs@Ga2O3 heterojunction, thus obtaining a material containing both the Ga2O3 layer and the AlQDs layer. S3: Electrode I and electrode II were deposited on the Ga2O3 layer and AlQDs layer respectively by mask evaporation to obtain an AlQDs@Ga2O3 heterojunction solar-blind photodetector; In step S2, the AlQDs layer partially covers the Ga2O3 layer.

4. The preparation method according to claim 3, characterized in that, In step S1, the concentration of the colloidal AlQDs solution is 10-20 mg / mL.

5. The preparation method according to claim 3, characterized in that, In step S1, the colloidal AlQDs solution is prepared as follows: S1-1: Add aluminum halide and surfactant to solvent I, sonicate, and the solution color changes from pale yellow to colorless to obtain the precursor solution; S1-2: After the precursor solution is degassed by argon, it is heated under anhydrous and oxygen-free conditions, and then a reducing agent solution is added. The mixture is stirred and reacted, and then solvent II is added and stirred for 5 minutes. The white precipitate is removed by centrifugation, and solvent I is removed by rotary evaporation of the supernatant to obtain crude AlQDs. After ultrasonic dispersion with solvent III, colloidal AlQDs solution is obtained.

6. The preparation method according to claim 5, characterized in that, In step S1-1, the aluminum halide includes at least one of aluminum chloride and aluminum bromide; The surfactant includes at least one of tetraoctylammonium bromide, tetramethylammonium fluoride, and dialkyldimethylammonium chloride; The molar ratio of the aluminum halide to the surfactant is 1:1-3; Solvent I includes at least one of anhydrous xylene and oleylamine.

7. The preparation method according to claim 5, characterized in that, In steps S1-2, the heating refers to raising the temperature to 110-120℃; The reducing agent solution is an ammonia ethanol solution or a lithium aluminum hydride solution; the concentration of the reducing agent solution is 2 M. The reducing agent solution is added at a rate of 1-4 mL / h; The molar ratio of the aluminum halide to the reducing agent is 2:1 to 1:4; The stirring reaction is carried out at a speed of 700-900 r / min, a reaction temperature of 110-130 ℃, and a time of 3-8 h; the stirring reaction is carried out under an argon atmosphere. Solvent II includes methanol; Solvent III includes at least one of ethanol and dimethylformamide.

8. The preparation method according to claim 3, characterized in that, In step S2, the Ga2O3 includes at least one of β-Ga2O3, α-Ga2O3, γ-Ga2O3, δ-Ga2O3, and ε-Ga2O3; The process of depositing colloidal AlQDs solution layer by layer onto the surface of Ga2O3 layer of substrate containing Ga2O3 layer involves spin-coating colloidal AlQDs solution onto a portion of the surface of Ga2O3 substrate, annealing, repeating spin-coating and annealing to form a multilayer AlQDs layer. The spin coating process involves first spin coating at 500 rpm for 10 seconds, and then spin coating at 2000 rpm for 30 seconds. The annealing temperature was 90°C and the time was 10 minutes.

9. The preparation method according to claim 3, characterized in that, In step S3, electrode I is disposed on the AlQDs surface; electrode II is disposed on the Ga2O3 surface that is not coated with AlQDs solution. Electrode I includes at least one of a Ti electrode and an Au electrode; Electrode II includes at least one of Ti electrode and Au electrode; The electrode materials of electrode I and electrode II may be the same or different.

10. An imaging device, characterized in that, This includes the ultrasensitive AlQDs@Ga2O3 heterojunction solar-blind photodetector based on quantum size effect as described in any one of claims 1-2, or the AlQDs@Ga2O3 heterojunction solar-blind photodetector prepared by the preparation method described in any one of claims 3-9.

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