Colloidal quantum dot dual-mode detector and method of making

Abstract

This invention discloses a colloidal quantum dot dual-mode detector and its fabrication method. The colloidal quantum dot dual-mode detector comprises, from bottom to top, a substrate, a bottom electrode, a photodiode layer, an electric field modulation layer, a gain device layer, and a top electrode, stacked sequentially. Through an innovative vertically stacked bandgap design, this invention integrates a colloidal quantum dot photodiode and a multi-junction gain structure within a single device for the first time. The device intelligently modulates the direction of the internal electric field using an external bias voltage, achieving precise and rapid switching between high-gain weak-light detection and high-linearity strong-light detection modes. It also fundamentally suppresses dark current, solving the problems of excessive noise and poor stability in traditional gain devices. Furthermore, the device maintains high response speed and excellent stability while possessing a compact structure and high compatibility with existing planar processes, demonstrating excellent process compatibility and large-scale fabrication potential, providing a stable and reliable technical foundation for the development of high-resolution infrared imaging devices.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detector technology, and more specifically, relates to a colloidal quantum dot dual-mode detector and its preparation method. Background Technology

[0002] Colloidal quantum dots, due to their advantages such as tunable bandgap, solution-processable nature, and compatibility with flexible substrates, have shown great research and application potential in the field of infrared photodetectors. Photodiode devices based on quantum dot materials possess advantages such as low dark current, fast response speed, and wide linear dynamic range, and have been widely used in high-resolution infrared imaging.

[0003] However, the response capability of traditional single-junction quantum dot photodiodes under extremely weak illumination conditions is still limited by their low external quantum efficiency and limited photoelectric gain, resulting in poor detection capability in weak light. Gain-type structures based on the photoconductivity effect extend the lifetime of photogenerated carriers and induce repeated injection of another type of carrier, thereby forming a multiplied signal output in the circuit. These photoconductivity-type gain devices exhibit high responsivity and high gain under weak light conditions, but the response is nonlinear and faces problems such as slow response speed, high dark current, and difficulty in structural integration. Gain-type structures based on the avalanche multiplication effect achieve gain through the impact ionization effect of photogenerated carriers in the multiplication layer, but face problems such as high bias voltage required to achieve gain, high power consumption, and large dark current.

[0004] The human eye, due to the presence of rod and cone cells, naturally possesses a high dynamic range, enabling excellent perception of both weak and strong light. Based on the biomimetic concept of the human eye, a quantum dot detector can be constructed that exhibits high gain in weak light and high linear dynamic range in strong light. Changyong L and Chun L et al. proposed a device combining single-crystal silicon and a silicon-chromium heterojunction. Under positive bias, it utilizes the photoconductivity of single-crystal silicon for weak light detection, and under negative bias, it relies on the silicon-chromium heterojunction for high-linearity strong light detection. However, the two detectors are horizontally distributed, meaning half of a pixel is used for weak light detection and half for strong light detection, resulting in a pixel duty cycle of only 50%, which is detrimental to subsequent high-resolution applications. Currently, existing multi-mode quantum dot detectors mainly achieve multi-band detection, i.e., controlling the junction depth by adjusting the bias voltage to detect different wavelengths of light in different regions. There are no publicly available examples of combining gain-type devices with high dynamic range devices. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a colloidal quantum dot dual-mode detector and its fabrication method. Through an innovative vertically stacked bandgap design, it integrates a colloidal quantum dot photodiode and a multi-junction gain structure within a single device for the first time. The device intelligently controls the direction of the internal electric field using an external bias voltage, achieving precise and rapid switching between high-gain weak-light detection and high-linearity strong-light detection modes. It also fundamentally suppresses dark current, solving the problems of excessive noise and poor stability in traditional gain devices. Furthermore, the device maintains high response speed and excellent stability while possessing a compact structure and high compatibility with existing planar processes, demonstrating excellent process compatibility and scalable fabrication potential, providing a stable and reliable technical foundation for the development of high-resolution infrared imaging devices.

[0006] To achieve the above objectives, the present invention employs the following technical solution: A colloidal quantum dot dual-mode detector, characterized in that it comprises a substrate, a bottom electrode, a photodiode layer, an electric field modulation layer, a gain device layer, and a top electrode, which are stacked sequentially from bottom to top. The detector can achieve a weak light high gain detection state when a forward bias is applied, or a photodiode working state when a reverse bias is applied. The electric field modulation layer is used to regulate the built-in electric field and band structure at the interface between the photodiode layer and the gain device layer, and to achieve dual working mode switching of the detector when applying positive and reverse voltages. The photodiode layer comprises, from bottom to top, an electron transport layer, a first quantum dot absorption layer, and a second quantum dot absorption layer, and the gain device layer is composed of alternating stacks of the first quantum dot absorption layer and the second quantum dot absorption layer.

[0007] Preferably, the electron transport layer material is zinc oxide or tin oxide; the ligand of the first quantum dot absorption layer is any one or a combination of PbI2 and PbBr2; the ligand of the second quantum dot absorption layer is EDT; and the electric field modulation layer material is gold. Preferably, the substrate material includes, but is not limited to, glass, quartz, silicon oxide wafer, polyimide, polyethylene naphthalate, and polyethylene terephthalate; the bottom electrode material is ITO; and the top electrode includes, but is not limited to, gold, silver, aluminum, or ITO.

[0008] Preferably, the absorption peak of the first quantum dot absorption layer is 1300~1550 nm, and the absorption peak of the second quantum dot absorption layer is 850~950 nm.

[0009] Preferably, the forward bias voltage is 1 to 2 V and the reverse bias voltage is -0.1 to -1 V.

[0010] This invention also provides a method for preparing a colloidal quantum dot dual-mode detector, characterized by comprising the following steps: S100: A bottom electrode and an electron transport layer are formed on the substrate; S200: On the electron transport layer, a first quantum dot absorption layer and a second quantum dot absorption layer are sequentially formed using a spin coating method to prepare a photodiode layer; an electric field control layer is formed on the photodiode layer using a thermal evaporation process; the first quantum dot absorption layer and the second quantum dot absorption layer are alternately stacked and spin-coated onto the electric field control layer using a spin coating method, which is completed a total of 5 times, with the stacking order from bottom to top being second / first / second / first / second quantum dot absorption layers, to prepare a gain device layer; S300: Prepare the top electrode for the substrate of the device obtained above, and finally obtain the colloidal quantum dot dual-mode detector device.

[0011] Preferably, in step S100, the bottom electrode material is ITO, the electron transport layer material is zinc oxide or tin oxide, and the fabrication process is radio frequency magnetron sputtering or atomic layer deposition.

[0012] Preferably, in step S200, the first quantum dot layer is formed by ligand exchange using a solution containing either PbI2 or PbBr2 or a combination thereof, followed by annealing; the second quantum dot layer is formed by ligand exchange using a solution containing EDT; the electric field modulation layer material is gold, and a thermal evaporation process is employed, with a thickness of 1 nm.

[0013] Preferably, in step S300, the top electrode material is gold, silver, aluminum or ITO, the preparation process is thermal evaporation technology or magnetron sputtering technology, and the thickness is 60~80 nm.

[0014] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: 1. This invention, for the first time, successfully integrates a colloidal quantum dot photodiode and a quantum dot multi-junction cascaded gain structure within a single device through a vertically stacked bandgap engineering design, simultaneously overcoming the core performance contradiction between high gain and wide dynamic range. By utilizing external bias switching to achieve directional control of the electric field within the electric field modulation layer, not only is precise and rapid switching between two operating modes—high-gain weak-light detection and high-linearity strong-light detection—achieved, but the directional modulation of the bandgap by the electric field fundamentally suppresses carrier injection, significantly reducing dark current and solving the problems of excessive noise and unstable performance in traditional gain devices.

[0015] 2. The dual-mode detector fabricated in this invention achieves a comprehensive performance improvement in high sensitivity, wide dynamic range, fast response, and high stability while maintaining high response speed and excellent stability. Utilizing a single device structure, it exhibits excellent characteristics of high-gain weak-light detection and high-linearity strong-light detection under forward and reverse bias, respectively, demonstrating superior adaptive sensing and signal fidelity capabilities in complex, wide-range illumination environments. Furthermore, this device exhibits excellent process compatibility and scalable fabrication potential. Its compact structure is highly compatible with existing planar processes, providing a stable and scalable core device and process foundation for the development of next-generation adaptive intelligent sensing systems. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a colloidal quantum dot dual-mode detector according to an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the working principle of the colloidal quantum dot dual-mode detector in Embodiment 1 of the present invention. Figure 2 (a) is a schematic diagram of the energy band and photogenerated carrier transport of the device when a +1 V bias voltage is applied and illumination is applied. Figure 2 (b) is a schematic diagram of the energy band and photogenerated carrier transport of the device when a -1 V bias voltage is applied and illumination is applied; Figure 3 This is a schematic diagram illustrating the overall performance of the colloidal quantum dot dual-mode detector according to Embodiment 1 of the present invention. Figure 3 (a) shows the external quantum efficiency-optical power density curve of the device. Figure 3 (b) shows the photodiode mode response time curve of the device. Figure 3 (c) is the gain mode response time curve of the device; Figure 4 This is a schematic diagram comparing the performance of the colloidal quantum dot dual-mode detectors in Embodiments 1 and 2 of the present invention. Figure 4 (a) Current-voltage curves of devices with and without an electric field modulation layer. Figure 4 (b) External quantum efficiency-optical power curves for devices with and without an electric field modulation layer; Figure 5 This is a schematic diagram of the charge transport mechanism of the colloidal quantum dot dual-mode detector according to an embodiment of the present invention. Figure 5 (a) is a schematic diagram of the charge transport mode of the colloidal quantum dot dual-mode detector in Example 2. Figure 5 (b) is a schematic diagram of the charge transport mode of the colloidal quantum dot dual-mode detector in Example 1; Figure 6 This is a schematic diagram comparing the dynamic range of the detectors in Embodiment 1 and Comparative Example 1 of the present invention. Figure 6 (a) is a schematic diagram of the dynamic range of a colloidal quantum dot single-mode detector. Figure 6(b) is a schematic diagram of the dynamic range of the colloidal quantum dot dual-mode detector.

[0017] Reference numerals: 101-substrate; 102-bottom electrode; 103-electron transport layer; 104-first quantum dot absorption layer; 105-second quantum dot absorption layer; 106-electron modulation layer; 107-top electrode. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0019] An embodiment of the present invention is a colloidal quantum dot dual-mode detector and its preparation method, comprising the following steps: Example 1 This embodiment provides a colloidal quantum dot dual-mode detector, the preparation method of which includes the following steps: (1) Preparation of bottom electrode and electron transport layer: The ITO glass substrate was cleaned sequentially with glass cleaner, deionized water, isopropanol, and ethanol using ultrasonic cleaning. After cleaning, it was dried with a nitrogen gun and set aside for later use. A zinc oxide hole transport layer was prepared on the ITO glass substrate. The cleaned ITO glass was attached to the substrate of the magnetron sputtering equipment and placed in the magnetron sputtering equipment. The zinc oxide target was installed, and the chamber was evacuated using a mechanical pump and a molecular pump. Argon gas was introduced, and sputtering was performed using a 100 W radio frequency power supply for 30 minutes.

[0020] (2) PbS-PbI x / PbBr xLayer preparation: A PbS quantum dot solution with an absorption peak at 1300 nm and a concentration of 10 mg / mL was prepared; a mixed solution of PbI2 and PbBr2 ligands was prepared using DMF as the solvent; equal volumes of the quantum dot solution and ligand solution were placed in a glass bottle, shaken and mixed for 1.5 min to perform liquid-phase ligand exchange, and allowed to stand for layering. The upper clear liquid layer was removed, and 10 mL of n-octane was added and shaken and mixed for 30 s for washing. After layering, the upper clear liquid layer was removed again, and the n-octane washing process was repeated once. The quantum dot solution after ligand exchange was centrifuged at 9000 rpm for 5 min, and the liquid was removed to obtain quantum dot solids. The quantum dot solids were then vacuum dried. A dispersant consisting of BTA and DMF was prepared to disperse the quantum dot solids to obtain colloidal quantum dots with a concentration of 300 mg / mL. The substrate prepared in step (1) was placed on a spin coater, and 80 μL of colloidal quantum dots were spin-coated at 2500 rpm for 40 s, and then annealed on a hot plate at 90 ℃ for 5 min.

[0021] (3) Preparation of PbS-EDT layer: Prepare a quantum dot solution with an absorption peak at 880 nm at 20 mg / ml and centrifuge at 8000 rpm for 1.5 min for later use; prepare a 0.01% EDT acetonitrile solution for later use; adsorb the substrate prepared in step (2) onto the spin coater chuck, add the quantum dot solution to the substrate, and spin coat at 4000 rpm for 20 s; add a 0.01% EDT acetonitrile solution to the substrate after spin coating of quantum dots to completely cover the substrate, let it stand for 30 s, and then spin coat at 4000 rpm for 20 s to remove the EDT acetonitrile solution; continue to add acetonitrile solution to the obtained substrate, and repeat the spin coating and cleaning process twice. Repeat the spin coating and cleaning process of quantum dot layer once more. The entire process is carried out in a dry fume hood. The prepared PbS-EDT substrate was placed in a drying tower containing color-changing silica gel for 12 hours to oxidize, thus obtaining the photodiode layer.

[0022] (4) Preparation of the electric field control layer: The PbS-EDT substrate prepared in step (3) is attached to the thermal evaporation substrate and placed in the evaporation chamber. 0.4 g of gold particles are placed on a clean tungsten boat, the chamber door is closed, and the vacuum is evacuated to 5 × 10⁻⁶. -4 Turn on the evaporation power supply, slowly increase the evaporation current to 90 A, control the evaporation rate at 0.02 A / s, evaporate to a thickness of 1 nm, turn off the baffle and vacuum power supply, fill the chamber with gas and take out the prepared substrate.

[0023] (5) Take the substrate prepared in step (4) and place it on a spin coater. Repeat steps (2) and (3) alternately for a total of 5 times. The stacking order from bottom to top is (3) / (2) / (3) / (2) / (3) to prepare a gain device layer. This whole process is carried out in a glove box in a nitrogen atmosphere.

[0024] (6) After attaching the metal mask to the substrate prepared in step (5), prepare an 80 nm thick Au electrode.

[0025] Example 2 This embodiment provides a colloidal quantum dot dual-mode detector without an electric field modulation layer, the fabrication method of which includes the following steps: (1) Preparation of bottom electrode and electron transport layer: The ITO glass substrate was cleaned sequentially with glass cleaner, deionized water, isopropanol, and ethanol using ultrasonic cleaning. After cleaning, it was dried with a nitrogen gun and set aside for later use. A zinc oxide hole transport layer was prepared on the ITO glass substrate. The cleaned ITO glass was attached to the substrate of the magnetron sputtering equipment and placed in the magnetron sputtering equipment. The zinc oxide target was installed, and the chamber was evacuated using a mechanical pump and a molecular pump. Argon gas was introduced, and sputtering was performed using a 100 W radio frequency power supply for 30 minutes.

[0026] (2) Preparation of PbS-PbIx / PbBrx layer: A PbS quantum dot solution with an absorption peak at 1300 nm and a concentration of 10 mg / mL was prepared; a mixed solution of PbI2 and PbBr2 ligands was prepared using DMF as the solvent; equal volumes of the quantum dot solution and ligand solution were placed in a glass bottle, shaken and mixed for 1.5 min to perform liquid-phase ligand exchange, and allowed to stand for layering. The upper clear and transparent liquid was removed, and 10 mL of n-octane was added and shaken and mixed for 30 s for washing. After layering, the upper clear and transparent liquid was removed again, and the n-octane washing process was repeated once. The quantum dot solution after ligand exchange was centrifuged at 9000 rpm for 5 min to remove the liquid and obtain quantum dot solids. The quantum dot solids were vacuum dried. A dispersant consisting of BTA and DMF was prepared to disperse the quantum dot solids to obtain colloidal quantum dots with a concentration of 300 mg / mL. The substrate prepared in step (1) was placed on a spin coater, and 80 μL of colloidal quantum dots were spin-coated at 2500 rpm for 40 s, and then annealed on a hot plate at 90 ℃ for 5 min.

[0027] (3) Preparation of PbS-EDT layer: Prepare a quantum dot solution with an absorption peak at 880 nm at 20 mg / ml and centrifuge at 8000 rpm for 1.5 min for later use; prepare a 0.01% EDT acetonitrile solution for later use; adsorb the substrate prepared in step (2) onto the spin coater chuck, add the quantum dot solution to the substrate, and spin coat at 4000 rpm for 20 s; add a 0.01% EDT acetonitrile solution to the substrate after spin coating of quantum dots to completely cover the substrate, let it stand for 30 s, and then spin coat at 4000 rpm for 20 s to remove the EDT acetonitrile solution; continue to add acetonitrile solution to the obtained substrate, and repeat the spin coating and cleaning process twice. Repeat the spin coating and cleaning process of quantum dot layer once more. The entire process is carried out in a dry fume hood. The prepared PbS-EDT substrate was placed in a drying tower containing color-changing silica gel for 12 hours to oxidize, thus obtaining the photodiode layer.

[0028] (4) Take the substrate prepared in step (3) and place it on a spin coater. Repeat steps (2) and (3) alternately for a total of 5 times. The stacking order from bottom to top is (3) / (2) / (3) / (2) / (3) to form a gain device layer. This whole process is carried out in a glove box in a nitrogen atmosphere.

[0029] (5) After attaching the metal mask to the substrate prepared in step (4), prepare an 80 nm thick Au electrode.

[0030] Comparative Example 1 This comparative example provides a colloidal quantum dot single-mode detector, the preparation method of which includes the following steps: (1) Preparation of bottom electrode and electron transport layer: The ITO glass substrate was cleaned sequentially with glass cleaner, deionized water, isopropanol, and ethanol using ultrasonic cleaning. After cleaning, it was dried with a nitrogen gun and set aside for later use. A zinc oxide hole transport layer was prepared on the ITO glass substrate. The cleaned ITO glass was attached to the substrate of the magnetron sputtering equipment and placed in the magnetron sputtering equipment. The zinc oxide target was installed, and the chamber was evacuated using a mechanical pump and a molecular pump. Argon gas was introduced, and sputtering was performed using a 100 W radio frequency power supply for 30 minutes.

[0031] (2) Preparation of PbS-PbIx / PbBrx layer: A PbS quantum dot solution with an absorption peak at 1300 nm and a concentration of 10 mg / mL was prepared; a mixed solution of PbI2 and PbBr2 ligands was prepared using DMF as the solvent; equal volumes of the quantum dot solution and ligand solution were placed in a glass bottle, shaken and mixed for 1.5 min to perform liquid-phase ligand exchange, and allowed to stand for layering. The upper clear and transparent liquid was removed, and 10 mL of n-octane was added and shaken and mixed for 30 s for washing. After layering, the upper clear and transparent liquid was removed again, and the n-octane washing process was repeated once. The quantum dot solution after ligand exchange was centrifuged at 9000 rpm for 5 min to remove the liquid and obtain quantum dot solids. The quantum dot solids were vacuum dried. A dispersant consisting of BTA and DMF was prepared to disperse the quantum dot solids to obtain colloidal quantum dots with a concentration of 300 mg / mL. The substrate prepared in step (1) was placed on a spin coater, and 80 μL of colloidal quantum dots were spin-coated at 2500 rpm for 40 s, and then annealed on a hot plate at 90 ℃ for 5 min.

[0032] (3) Preparation of PbS-EDT layer: Prepare a quantum dot solution with an absorption peak at 880 nm at 20 mg / ml and centrifuge at 8000 rpm for 1.5 min for later use; prepare a 0.01% EDT acetonitrile solution for later use; adsorb the substrate prepared in step (2) onto the spin coater chuck, add the quantum dot solution to the substrate, and spin coat at 4000 rpm for 20 s; add a 0.01% EDT acetonitrile solution to the substrate after spin coating of quantum dots to completely cover the substrate, let it stand for 30 s, and then spin coat at 4000 rpm for 20 s to remove the EDT acetonitrile solution; continue to add acetonitrile solution to the obtained substrate, and repeat the spin coating and cleaning process twice. Repeat the spin coating and cleaning process of quantum dot layer once more. The entire process is carried out in a dry fume hood. The prepared PbS-EDT substrate was placed in a drying tower containing color-changing silica gel for 12 hours to oxidize, thus obtaining the photodiode layer.

[0033] (4) After attaching the metal mask to the substrate prepared in step (3), prepare an 80 nm thick Au electrode.

[0034] Working principle analysis of colloidal quantum dot dual-mode detector Figure 2The working principle of the colloidal quantum dot dual-mode detector prepared in Example 1 was analyzed under both forward and reverse bias conditions. It can be seen that when a +1 V bias is applied to the detector and illumination is applied, the photodiode is in the forward conduction state, becoming a resistor with a small resistance value. At this time, only the gain device is active. Electrons generated by the gain device are blocked by the conduction band, allowing holes to circulate within the device and form gain. The photocurrent of this gain device, as the total photocurrent, contributes to the gain and enables weak light detection. However, when a -1 V bias is applied to the detector and illumination is applied, the photodiode is in the cutoff state, with a very small current value. Since the diode and gain device are connected in series, the current of the gain device is limited. At this time, only the photodiode is active, exhibiting the high linearity of photodiode detection of strong light. This demonstrates that the present invention, through a single device structure and relying solely on external bias switching, can achieve intelligent switching between two distinctly different high-performance working modes. It innovatively solves the core contradiction of traditional detectors, where sensitivity and dynamic range are mutually exclusive, providing a crucial device foundation for the development of adaptive, wide dynamic range intelligent photoelectric detection systems.

[0035] Comprehensive performance testing of colloidal quantum dot dual-mode detector Figure 3 The external quantum efficiency-optical power density, photodiode mode response time, and gain mode response time of the colloidal quantum dot dual-mode detector prepared in Example 1 were tested. When a forward bias was applied, the detector exhibited an external quantum efficiency greater than 10, and an external quantum efficiency greater than 100 under weak light conditions, with a fall time on the order of milliseconds, characteristic of a composite gain device. When a reverse bias was applied, the external quantum efficiency was less than 1, and it exhibited high linearity and fast rise and fall times, displaying typical diode characteristics. This indicates that the dual-mode detector prepared in this invention exhibits ideal and expected core photoelectric performance indicators in both operating states. In gain mode, the detector possesses efficient internal gain capability, suitable for detecting extremely weak light signals; in diode mode, the low external quantum efficiency and high linearity precisely correspond to the wide dynamic range and high fidelity requirements for strong light detection.

[0036] Performance Comparison Test of Colloidal Quantum Dot Dual-Mode Detectors with and without Electric Field Modulation Layer Figure 4The figures show the characterization test results of the core electrical and photoelectric performance of the colloidal quantum dot dual-mode detectors prepared in Examples 1 and 2. It can be seen that when the device lacks the gold electric field modulation layer and operates in gain mode, it exhibits a dark current as high as 2.4 mA, overwhelming the photocurrent and resulting in no photoresponse. After adding the electric field modulation layer, the dark current is significantly reduced, and the photoresponse becomes apparent. This indicates that the electric field modulation layer introduced in this invention is a key structure determining whether the device can function properly. By modulating the direction of the built-in electric field, it effectively suppresses the direct injection of charge carriers, thereby significantly reducing the dark current and significantly improving the signal-to-noise ratio while enabling the high photoresponse in gain mode. Ultimately, this ensures the successful implementation of the dual-mode operation and high performance of the device.

[0037] Analysis of charge transport mechanisms in colloidal quantum dot dual-mode detectors Figure 5 This describes the specific charge transport mechanism during operation of the colloidal quantum dot dual-mode detectors prepared in Examples 1 and 2. It can be seen that without the electric field modulation layer, the conduction and valence bands at +1 V favor carrier injection from the electrodes, resulting in a high dark current that overwhelms the photocurrent, leading to no photoresponse. Adding the electric field modulation layer enhances the built-in electric field, thereby tilting the conduction and valence bands to impede electron-hole injection, reducing the dark current and allowing the photocurrent to be observed. This demonstrates that the electric field modulation layer is a key functional layer for achieving dual-mode operation. By reconstructing and enhancing the band tilt direction within the device, this layer transforms the unfavorable carrier injection path into a carrier blocking barrier, fundamentally solving the high dark current problem.

[0038] Performance Comparison Test of Colloidal Quantum Dot Dual-Mode Detector and Colloidal Quantum Dot Single-Mode Detector Figure 6 This is a comparison chart of the photodiode dynamic range tests for Example 1 and Comparative Example 1. It can be seen that the dynamic range of the photodiode in the single-mode detector is approximately 80 dB, while the dual-mode detector, through the integration of a low-light high-gain mode, possesses better low-light detection capability, capable of detecting nW / cm². 2 The device can operate in low-light conditions, thus achieving a dynamic range exceeding 100 dB. This demonstrates that the present invention, through the integration of dual modes, achieves a substantial improvement over traditional solutions in key device performance, laying the foundation for the development of adaptive intelligent photoelectric detection.

[0039] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. A colloidal quantum dot dual-mode detector, characterized in that: It includes a substrate, a bottom electrode, a photodiode layer, an electric field modulation layer, a gain device layer, and a top electrode, which are stacked sequentially from bottom to top. The detector can achieve a weak light high gain detection state when a forward bias is applied, or a photodiode working state when a reverse bias is applied. The electric field modulation layer is used to regulate the built-in electric field and band structure at the interface between the photodiode layer and the gain device layer, and to achieve dual working mode switching of the detector when applying positive and reverse voltages. The photodiode layer comprises, from bottom to top, an electron transport layer, a first quantum dot absorption layer, and a second quantum dot absorption layer, and the gain device layer is composed of alternating stacks of the first quantum dot absorption layer and the second quantum dot absorption layer.

2. The colloidal quantum dot dual-mode detector according to claim 1, characterized in that, The electron transport layer material is zinc oxide or tin oxide; The ligands of the first quantum dot absorption layer are any one or a combination of PbI2 and PbBr2. The ligand of the second quantum dot absorption layer is EDT; the material of the electric field modulation layer is gold.

3. The colloidal quantum dot dual-mode detector according to claim 2, characterized in that, The substrate materials include, but are not limited to, glass, quartz, silicon dioxide wafers, polyimide, polyethylene naphthalate, and polyethylene terephthalate; The bottom electrode material is ITO; the top electrode includes, but is not limited to, gold, silver, aluminum or ITO.

4. A colloidal quantum dot dual-mode detector according to claim 3, characterized in that, The absorption peak of the first quantum dot absorption layer is 1300~1550 nm, and the absorption peak of the second quantum dot absorption layer is 850~950 nm.

5. A colloidal quantum dot dual-mode detector according to any one of claims 1-4, characterized in that, The forward bias voltage is 1 to 2 V, and the reverse bias voltage is -0.1 to -1 V.

6. A method for preparing a colloidal quantum dot dual-mode detector according to any one of claims 1-5, characterized in that, Includes the following steps: S100: A bottom electrode and an electron transport layer are formed on the substrate; S200: On the electron transport layer, a first quantum dot absorption layer and a second quantum dot absorption layer are sequentially formed by spin coating to prepare a photodiode layer; An electric field modulation layer is formed on the photodiode layer using a thermal evaporation process. The first quantum dot absorption layer and the second quantum dot absorption layer were alternately stacked and spin-coated onto the electric field modulation layer using a spin-coating method. This process was repeated a total of 5 times, with the stacking order from bottom to top being the second / first / second / first / second quantum dot absorption layer, thus forming a gain device layer. S300: Prepare the top electrode for the substrate of the device obtained above, and finally obtain the colloidal quantum dot dual-mode detector device.

7. The method for fabricating a colloidal quantum dot dual-mode detector according to claim 6, characterized in that, In step S100, the bottom electrode material is ITO, the electron transport layer material is zinc oxide or tin oxide, and the preparation process is radio frequency magnetron sputtering or atomic layer deposition.

8. A method for fabricating a colloidal quantum dot dual-mode detector according to claim 6 or 7, characterized in that, In step S200, the formation of the first quantum dot layer involves ligand exchange using a solution containing either PbI2 or PbBr2 or a combination thereof, followed by annealing; the formation of the second quantum dot layer involves ligand exchange using a solution containing EDT.

9. The method for fabricating a colloidal quantum dot dual-mode detector according to claim 8, characterized in that, In step S200, the electric field control layer material is gold, and the thickness is 1 nm, achieved through a thermal evaporation process.

10. A method for fabricating a colloidal quantum dot dual-mode detector according to claim 6 or 7, characterized in that, In step S300, the top electrode material is gold, silver, aluminum or ITO, and the preparation process is thermal evaporation technology or magnetron sputtering technology, with a thickness of 60~80 nm.

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