A lead-free perovskite hemispherical photodetector, a preparation method and application thereof in single-pixel lensless color imaging

Abstract

A kind of lead-free perovskite hemispherical photodetector, preparation method and its application in single-pixel lensless color imaging belong to the field of image processing technology.The detector is composed of chromium electrode layer, electron transport layer, perovskite layer, hole transport layer and metal electrode layer from inside to outside on the spherical surface of hemispherical transparent substrate.The perovskite obtained by the application has strong lead-free and excellent stability, outstanding charge carrier transport capacity, high collection efficiency and strong weak light sensing ability.The application uses perovskite for color imaging, directly converts optical signal into electrical signal, has high sensitivity, shows excellent performance with linear dynamic response range of 146dB, and has the advantages of uniform response capacity and uniform thickness.The halide perovskite used by the application has low cost, short preparation time, does not contain toxic element lead, improves the application range of perovskite detector, and reduces the manufacturing cost and time cost of perovskite detector.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of image processing, and particularly relates to a lead-free perovskite hemispherical photodetector, a preparation method and application thereof in single-pixel lensless color imaging. BACKGROUND

[0002] With the rapid development of the Internet of Things and artificial intelligence technology, the way of information acquisition and processing is undergoing profound changes. In this context, optical information processing technology, especially photodetector technology, has become particularly important due to its wide application in optical imaging, biological detection, optical communication, and military security. Photodetectors can convert optical signals into electrical signals, which is the primary step of information acquisition, and its performance directly affects the accuracy and efficiency of subsequent information processing.

[0003] Traditional optical imaging technology relies on a complex filter system and multi-pixel array. This complexity not only increases the cost and maintenance difficulty of the system, but also limits its flexibility and efficiency in specific application scenarios. Especially in applications that require fast response and high-resolution imaging, such as night monitoring and biomedical imaging, existing technology is difficult to meet the demand. In addition, the integration of multi-pixel arrays also increases the volume and energy consumption of the system, which is not conducive to application in portable devices.

[0004] In extreme environments such as low light and high temperature, the performance of existing photodetectors often suffers significant impact. In particular, silicon photomultipliers (SiPMs) may experience a sharp decline in imaging quality under these harsh conditions, which greatly limits their potential use in a wider range of application scenarios. The main reason is that the thermal noise of semiconductor materials will increase significantly in high-temperature environments. The rise of this noise not only leads to an increase in device noise, but also causes fluctuations in dark current. These factors work together to ultimately affect the clarity and reliability of imaging. Therefore, improving the performance of photodetectors in complex environments has become a pressing technical problem to ensure that they can work stably and reliably under various conditions.

[0005] In recent years, perovskite photodetectors have attracted much attention due to their outstanding performance. These detectors not only have high sensitivity, wide spectral response range, fast response rate, low noise, and other characteristics, but also have the advantages of simple preparation process, low cost, strong environmental adaptability, and scalability and multifunctionality. These characteristics make perovskite photodetectors have great application potential in the field of photoelectric imaging. However, many high-performance photodetectors currently rely on lead-containing perovskite materials. Although these materials perform excellently in photoelectric performance, the toxicity of lead limits their use in certain application scenarios. In addition, traditional planar photodetectors also have certain limitations in wide-angle detection and light signal collection efficiency. When receiving scattered light, the planar structure of the detector is limited by its receiving area and angle, making it difficult to effectively capture light signals from different directions, thereby reducing the collection efficiency of light signals. In view of this, it is particularly urgent to develop a new type of lead-free perovskite hemispherical photodetector. This detector can realize color imaging in complex environments, not only solving the problem of lead pollution, but also improving the collection efficiency of light signals and widening the application range of photodetectors. SUMMARY

[0006] In view of the above problems and deficiencies, the present application provides a lead-free perovskite hemispherical photodetector, a preparation method and its application in single-pixel lensless color imaging. The present application breaks through the limitations of existing photodetectors in imaging technology and provides a solution for high-quality, high-resolution lensless color imaging in complex environments.

[0007] The present application provides a lead-free perovskite hemispherical photodetector, which is composed of a chromium electrode layer, an electron transport layer, a perovskite layer, a hole transport layer and a metal electrode layer from inside to outside on the spherical surface of a hemispherical transparent substrate (such as glass);

[0008] The electron transport layer material is tin dioxide;

[0009] The perovskite layer material is CsBi3I 10 ;

[0010] The hole transport layer material is poly[bis(4-phenyl)(2,4,6-trimethylphenyl) amine];

[0011] The metal electrode layer material is chromium and gold.

[0012] Preferably, the thickness ratio of the chromium electrode layer, the electron transport layer, the perovskite layer, the hole transport layer and the metal electrode layer is 100-200 nm: 100-200 nm: 1000-1500 nm: 25-30 nm: 10-20 nm.

[0013] The application further provides a preparation method of the lead-free perovskite hemispherical photodetector.

[0014] (1) depositing a chromium electrode layer on the spherical surface of the hemispherical glass substrate treated by ultraviolet ozone for 15-30 minutes through vacuum thermal evaporation deposition, the rate of vacuum thermal evaporation deposition being 0.1-0.3 A / s;

[0015] (2) treating the hemispherical glass substrate obtained in step (1) by ultraviolet ozone for 15-30 minutes, and then transferring it to a plasma treatment chamber for treatment for 3-8 minutes; raising the treated substrate to 90-110 DEG C, and then spraying an electron transport layer solution on the surface of the chromium electrode layer, annealing at 140-160 DEG C for 20-40 minutes after the spraying is completed, and obtaining an electron transport layer on the surface of the chromium electrode layer; the electron transport layer solution is a tin dioxide aqueous solution with a concentration of 1.0-2.0 wt.%;

[0016] (3) raising the hemispherical glass substrate obtained in step (2) to 90-110 DEG C, and then spraying a perovskite precursor solution on the surface of the electron transport layer, annealing at 115-135 DEG C for 20-40 minutes after the spraying is completed, and obtaining a perovskite layer on the surface of the electron transport layer; the perovskite precursor solution is a mixed aqueous solution of CsBi3I 10 and guanidine thiocyanate, the concentration of CsBi3I 10 is 0.2-0.4 mol / L, and the concentration of guanidine thiocyanate is 0.5-3 mol%;

[0017] (4) raising the hemispherical glass substrate obtained in step (3) to 80-100 DEG C, and then spraying a hole transport layer solution on the surface of the perovskite layer, annealing at 100-120 DEG C for 8-15 minutes after the spraying is completed, and obtaining a hole transport layer on the surface of the perovskite layer; the hole transport layer solution is a toluene solution of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] with a concentration of 0.3-0.8 mg / mL;

[0018] (5) vacuum thermal evaporation deposition of a metal electrode layer on the surface of the hole transport layer obtained in step (4), thereby obtaining the lead-free perovskite hemispherical photodetector; the rate of thermal evaporation deposition of the metal electrode layer is 0.1-0.3 A / s; The metal electrode material is chromium and gold.

[0019] The spraying equipment in steps (2)-(4) is a spray gun, the nozzle diameter of the spray gun is 0.2 mm, the pressure of the spray gun is 1-1.1 bar, and the spraying distance is 3-4 cm.

[0020] The application also provides a process for color imaging of the above-mentioned lead-free perovskite hemispherical photodetector. A color Fourier basis pattern is generated by using a digital projector and illuminating the target imaging object. The color Fourier basis pattern is generated by a computer and the projector is controlled to project the pattern onto the target object. The reflected light of the object under the structured light pattern illumination is collected by the perovskite hemispherical photodetector and converted into an electrical signal. The amplified electrical signal is collected by a digital signal power meter and transmitted to a computer for numerical calculation.

[0021] The perovskite obtained by the application has the advantages of lead-free, excellent stability, outstanding charge carrier transport capacity, high collection efficiency, strong weak light sensing ability, etc. The application uses the perovskite for color imaging, directly converts the optical signal into an electrical signal, has high sensitivity, and exhibits excellent performance with a linear dynamic response range of 146 dB, uniform response capacity, uniform thickness, etc. In addition, the halide perovskite used in the application has low cost, short preparation time, and does not contain toxic lead, thereby improving the application range of the perovskite detector and reducing the manufacturing cost and time cost of the perovskite detector.

[0022] The lead-free perovskite hemispherical detector described in the application can maintain excellent stability under complex environments, such as high temperature conditions.

[0023] The application uses a semiconductor material for single-pixel lensless color imaging, avoids the complex pixel array structure and various lens equipment required by the commonly used imaging method, and greatly reduces the imaging cost.

[0024] The application obtains a perovskite layer with large crystal grains and uniform thickness by a spraying method, so that the hemispherical photodetector has good stability and excellent uniformity. The preparation method provided by the application has the advantages of simple steps, high efficiency, time saving, good operability, and prospect of large-scale production.

[0025] The application also provides a lensless hemispherical color imaging method. The core part of the imaging scheme provided by the application is a hemispherical perovskite photodetector. The hemispherical photodetector of the application is a single-pixel photodetector, which is responsible for receiving the signal of diffuse reflection light and converting it into a readable electrical signal. The application uses a Fourier basis combined with a Bayer template to obtain a colorful Fourier basis pattern. The computer-generated colorful Fourier basis pattern is projected onto the surface of the object to be imaged using a projector, and the current value converted by the light intensity of the diffuse reflection light of the imaging object is recorded using a data acquisition device. By calculating the current value obtained by the perovskite hemispherical photodetector, the Fourier coefficients of the image of the target object can be obtained. Then, using the inverse Fourier transform, these spectral coefficients can be converted back to the spatial domain, thereby reconstructing the grayscale image of the object. Finally, using the traditional color imaging demosaicing algorithm for color restoration, the color image of the object is reconstructed from the grayscale image, thereby realizing the application of the lead-free perovskite hemispherical photodetector in single-pixel lensless color imaging.

[0026] Therefore, the application applies lead-free perovskite to perovskite single-pixel color imaging, fully utilizes the performance of perovskite, and makes a high-performance single-pixel perovskite hemispherical photodetector capable of lensless color imaging.

[0027] The perovskite hemispherical photodetector provided by the application is sensitive to weak changes in light and has excellent low-light imaging capability. The perovskite hemispherical photodetector provided by the application has uniform thickness, uniform response capability, high linearity and good stability, so that the instrument provided by the application can accurately capture and represent the current values of different Fourier bases, which is crucial for color imaging.

[0028] The perovskite hemispherical photodetector provided by the application can receive diffuse reflection light at different angles and has excellent imaging capability at multiple angles. The color imaging effect of the perovskite hemispherical photodetector provided by the application is obviously improved relative to that of a planar photodetector at different angles.

[0029] The perovskite hemispherical photodetector provided by the application can still maintain good photoelectric efficiency at high temperatures, and the current still maintains good stability at 100 DEG C. Color imaging can be realized at 25 DEG C to 100 DEG C, and the imaging effect at high temperatures is better than that of a traditional silicon photomultiplier. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0031] Figure 1 Structure diagram of a perovskite hemispherical photoelectric detector prepared in Embodiment 1 of the present application;

[0032] Figure 2 Diagram of color imaging of a perovskite hemispherical photoelectric detector prepared in Embodiment 1 of the present application;

[0033] Figure 3 XRD spectrum of a perovskite layer prepared in Embodiments 1-4 of the present application;

[0034] Figure 4 Cross-sectional SEM image of a perovskite layer of a perovskite hemispherical photoelectric detector prepared in Embodiment 1 of the present application;

[0035] Figure 5 Linear dynamic diagram of a perovskite photoelectric detector prepared in Embodiment 1 of the present application;

[0036] Figure 6 Responsivity and detectivity diagram of a perovskite photoelectric detector prepared in Embodiment 1 of the present application;

[0037] Figure 7 Long-term stability diagram of a perovskite hemispherical photoelectric detector prepared in Embodiment 1 of the present application;

[0038] Figure 8 XRD diagram of a perovskite layer prepared in Embodiment 1 of the present application at different temperatures;

[0039] Figure 9 High-temperature current stability diagram of a perovskite photoelectric detector prepared in Embodiment 1 of the present application;

[0040] Figure 10 High-resolution color imaging diagram of a perovskite hemispherical photoelectric detector prepared in Embodiment 1 of the present application;

[0041] Figure 11 Color imaging diagram of a perovskite hemispherical photoelectric detector prepared in Embodiment 1 of the present application under weak light.

[0042] Figure 12 Color imaging diagram of a perovskite hemispherical photoelectric detector prepared in Embodiment 1 of the present application under high temperature. DETAILED DESCRIPTION

[0043] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations to the present application.

[0044] Embodiment 1

[0045] Preparation of lead-free perovskite hemispherical photodetector and color imaging, as follows:

[0046] (a) Preparation of CsBi3I 10 - Guanidinium thiocyanate perovskite precursor solution: Cesium iodide and bismuth iodide powders were dissolved in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (volume ratio of DMF and DMSO was 9:1) at a molar ratio of 1:3, and 1 mol% of guanidinium thiocyanate (GTC) was added to form CsBi3I 10 - Guanidinium thiocyanate perovskite precursor solution (CsBi3I 10 - GTC-1).

[0047] (b) Manufacturing of hemispherical device: First, a hemispherical glass substrate with a radius of 5 mm was treated with ultraviolet ozone for 20 minutes, and then a 100 nm chromium electrode layer was deposited on the spherical surface by vacuum thermal evaporation at a deposition rate of 0.1 A / s. After the deposition of the chromium electrode layer was completed, the substrate was treated with ultraviolet ozone for 20 minutes, and then transferred to a plasma treatment chamber (radio frequency power of 200 W, working gas of nitrogen) for 5 minutes. Next, the treated hemispherical glass substrate was fixed on a stainless steel plate and heated to 100°C. At the same time, a tin dioxide solution was dissolved in deionized water at a volume ratio of 1:12 to obtain a 1.5wt% tin dioxide aqueous solution, and a spray gun with a nozzle diameter of 2 mm was used to uniformly spray the heated hemispherical substrate to obtain an electron transport layer with a thickness of 100 nm. After spraying the tin dioxide aqueous solution, the chromium / tin dioxide substrate was heat annealed at 150°C for 30 minutes. Then, the treated substrate was re-fixed and heated to 100°C, and a spray gun with a nozzle diameter of 2 mm was used to uniformly spray the CsBi3I 10 - Guanidinium thiocyanate perovskite precursor solution on the treated chromium / tin dioxide substrate to obtain a perovskite layer with a thickness of 1.5 μm. After spraying, the entire device was heat annealed at 125°C for 30 minutes. Then, the hemispherical glass substrate obtained in step (2) was heated to 100°C, and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] was dissolved in toluene, with a concentration of 0.5 mg mL -1 -1, and a spray gun with a nozzle diameter of 2 mm was used to uniformly spray it on the heated substrate and heat annealed at 110°C for 10 minutes to obtain a hole transport layer with a thickness of 30 nm. Finally, 10 nm of chromium and 10 nm of gold were directly deposited on the device by vacuum thermal evaporation at a deposition rate of 0.1 A / s. The schematic structure of the obtained lead-free perovskite hemispherical photodetector is shown in Figure 1 .

[0048] (c) Perform color imaging and detection of the target object: The color imaging process is as follows Figure 2 As shown, a colored Fourier basis pattern is first generated using a digital projector to illuminate the target object. The colored Fourier basis pattern is generated by a computer, and the projector is controlled to project the pattern onto the target object. The intensity of the diffuse light is approximately 30 μW cm⁻¹. -2 The reflected light from the object under structured light pattern illumination is collected by a perovskite hemispherical photodetector and converted into an electrical signal. The converted electrical signal is then collected by a power meter as a digital signal and transmitted to a computer for storage and recording.

[0049] (d) Calculating and processing to obtain the color image of the target object: The core of Fourier single-pixel imaging lies in decomposing the image information of the target object into the frequency domain through Fourier transform, that is, obtaining the Fourier spectrum of the image. This process is usually achieved by projecting a series of Fourier basis patterns onto the target object, and using a single-pixel detector to measure the light intensity values ​​reflected from these patterns on the object and converting them into current values ​​for recording. The coefficients of the image in the Fourier domain, i.e., the Fourier spectrum, can be calculated using the recorded current values. By calculating the current values ​​obtained from the perovskite hemispherical photodetector in step (c), the Fourier coefficients of the target object image can be obtained. Then, using inverse Fourier transform, these spectral coefficients can be converted back to the spatial domain, thereby reconstructing the grayscale image of the object. Since the illumination is achieved using a colored Fourier basis pattern, the reconstructed object image is identical to the original pattern acquired by a monochrome image sensor in traditional color imaging. Therefore, the color image of the object can be reconstructed from the grayscale image using the same demosaic algorithm used for color restoration in traditional color imaging.

[0050] Example 2

[0051] The fabrication and color imaging of a lead-free perovskite hemispherical photodetector are detailed below:

[0052] (a) Preparation of CsBi3I 10 Perovskite precursor solution: Cesium iodide and bismuth iodide powders were dissolved in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a molar ratio of 1:3 (DMF to DMSO volume ratio of 9:1) to form CsBi3I. 10 Perovskite precursor solution (CsBi3I) 10 -GTC-0).

[0053] (b) Fabrication of the hemispherical device: First, a hemispherical glass substrate with a radius of 5 mm was treated with ultraviolet ozone for 20 minutes. Then, a 100 nm chromium electrode was deposited on the spherical surface of the hemispherical glass substrate by vacuum thermal evaporation. After the chromium electrode deposition, the substrate was treated with ultraviolet ozone for 20 minutes, and then transferred to a plasma treatment chamber (RF power 200 W, working gas nitrogen) for 5 minutes. Next, the treated hemispherical glass substrate was fixed on a stainless steel plate and heated to 100 °C. Simultaneously, a tin dioxide solution was dissolved in deionized water at a volume ratio of 1:12 to obtain a 1.5 wt% tin dioxide aqueous solution, which was uniformly sprayed onto the heated hemispherical substrate using a spray gun with a nozzle diameter of 2 mm, resulting in an electron transport layer thickness of 100 nm. After spraying the tin dioxide aqueous solution, the chromium / tin dioxide substrate was thermally annealed at 150 °C for 30 minutes. Then, the treated substrate was refixed and heated to 100 °C. Then, CsBi3I was sprayed onto the substrate using a spray gun with a nozzle diameter of 2 mm. 10 Perovskite precursor (CsBi3I) 10 The GTC-0 solution was uniformly sprayed onto the treated chromium / tin dioxide substrate, resulting in a perovskite layer with a thickness of 1.5 μm. After spraying, the entire device was thermally annealed at 125 °C for 30 minutes. Then, the hemispherical glass substrate obtained in step (2) was heated to 100 °C, and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] was dissolved in toluene at a concentration of 0.5 mg / mL. -1 The hole transport layer was uniformly sprayed onto a heated substrate using a spray gun with a nozzle diameter of 2 mm and then thermally annealed at 110°C for 10 minutes, resulting in a hole transport layer thickness of 30 nm. Finally, 10 nm of chromium and 10 nm of gold were directly deposited on the device via vacuum thermal evaporation at a deposition rate of [missing information]. The structural schematic diagram of the obtained lead-free perovskite hemispherical photodetector is shown below. Figure 1 As shown.

[0054] (c) Perform color imaging and detection of the target object: The color imaging process is as follows Figure 2 As shown, a colored Fourier basis pattern is first generated using a digital projector to illuminate the target object. The colored Fourier basis pattern is generated by a computer, and the projector is controlled to project the pattern onto the target object. The intensity of the diffuse light is approximately 30 μW cm⁻¹. -2 The reflected light from the object under structured light pattern illumination is collected by a perovskite hemispherical photodetector and converted into an electrical signal. The converted electrical signal is then collected by a power meter as a digital signal and transmitted to a computer for storage and recording.

[0055] (d) Calculating the color image of the target object: The core of Fourier ptychographic imaging is to decompose the image information of the target object into the frequency domain through Fourier transform, that is, to obtain the Fourier spectrum of the image. This process is usually achieved by projecting a series of Fourier basis patterns onto the target object, and using a single-pixel detector to measure the light intensity values of the reflected patterns on the object and convert them into current values for recording. Through the recorded current values, the coefficients of the image in the Fourier domain, that is, the Fourier spectrum, can be calculated. By calculating the current values obtained by the perovskite hemispherical photodetector in step (c), the Fourier coefficients of the image of the target object can be obtained. Then, using the inverse Fourier transform, these spectral coefficients can be converted back to the spatial domain, thereby reconstructing the gray-scale image of the object. Since the color Fourier basis patterns are used for illumination, the reconstructed image of the object is the same as the original pattern captured by the monochrome image sensor in traditional color imaging. Therefore, the same de-mosaicing algorithm for color restoration in traditional color imaging can be used to reconstruct the color image of the object from the gray-scale image.

[0056] Example 3

[0057] Preparation of a lead-free perovskite hemispherical photodetector and color imaging, as follows:

[0058] (a) Preparation of CsBi3I 10 - Guanidinium thiocyanate perovskite precursor solution: Dissolve cesium iodide and bismuth iodide powders in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a volume ratio of 9:1 (DMF and DMSO) at a molar ratio of 1:3, and add 0.5 mol% of guanidinium thiocyanate (GTC) to form a CsBi3I 10 - Guanidinium thiocyanate perovskite precursor solution (CsBi3I 10 - GTC-0.5).

[0059] (b) Fabrication of the hemispherical device: First, a hemispherical glass substrate with a radius of 5 mm was treated with ultraviolet ozone for 20 minutes. Then, a 100 nm chromium electrode was deposited on the spherical surface of the hemispherical glass substrate by vacuum thermal evaporation. After the chromium electrode deposition, the substrate was treated with ultraviolet ozone for 20 minutes, and then transferred to a plasma treatment chamber (RF power 200 W, working gas nitrogen) for 5 minutes. Next, the treated hemispherical glass substrate was fixed on a stainless steel plate and heated to 100 °C. Simultaneously, a tin dioxide solution was dissolved in deionized water at a volume ratio of 1:12 to obtain a 1.5 wt% tin dioxide aqueous solution, which was uniformly sprayed onto the heated hemispherical substrate using a spray gun with a nozzle diameter of 2 mm, resulting in an electron transport layer thickness of 100 nm. After spraying the tin dioxide aqueous solution, the chromium / tin dioxide substrate was thermally annealed at 150 °C for 30 minutes. Then, the treated substrate was refixed and heated to 100 °C. Then, CsBi3I was sprayed onto the substrate using a spray gun with a nozzle diameter of 2 mm. 10 - Guanidinium thiocyanate perovskite precursor (CsBi3I) 10 A 0.5 μm thick perovskite layer was uniformly sprayed onto the treated chromium / tin dioxide substrate using a GTC-0.5 solution. After spraying, the entire device was thermally annealed at 125 °C for 30 minutes. Then, the hemispherical glass substrate obtained in step (2) was heated to 100 °C, and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] was dissolved in toluene at a concentration of 0.5 mg / mL. -1 The hole transport layer was uniformly sprayed onto a heated substrate using a spray gun with a nozzle diameter of 2 mm and then thermally annealed at 110°C for 10 minutes, resulting in a hole transport layer thickness of 30 nm. Finally, 10 nm of chromium and 10 nm of gold were directly deposited on the device via vacuum thermal evaporation at a deposition rate of [missing information]. The structural schematic diagram of the obtained lead-free perovskite hemispherical photodetector is shown below. Figure 1 As shown.

[0060] (c) Perform color imaging and detection of the target object: The color imaging process is as follows Figure 2 As shown, a colored Fourier basis pattern is first generated using a digital projector to illuminate the target object. The colored Fourier basis pattern is generated by a computer, and the projector is controlled to project the pattern onto the target object. The intensity of the diffuse light is approximately 30 μW cm⁻¹. -2 The reflected light from the object under structured light pattern illumination is collected by a perovskite hemispherical photodetector and converted into an electrical signal. The converted electrical signal is then collected by a power meter as a digital signal and transmitted to a computer for storage and recording.

[0061] (d) Calculating the color image of the target object: The core of Fourier ptychographic imaging is to decompose the image information of the target object into the frequency domain through Fourier transform, that is, to obtain the Fourier spectrum of the image. This process is usually achieved by projecting a series of Fourier basis patterns onto the target object, and using a single-pixel detector to measure the light intensity values of the reflected patterns on the object and convert them into current values for recording. Through the recorded current values, the coefficients of the image in the Fourier domain, that is, the Fourier spectrum, can be calculated. By calculating the current values obtained by the perovskite hemispherical photodetector in step (c), the Fourier coefficients of the image of the target object can be obtained. Then, using the inverse Fourier transform, these spectral coefficients can be converted back to the spatial domain, thereby reconstructing the gray-scale image of the object. Since the color Fourier basis patterns are used for illumination, the reconstructed image of the object is the same as the original pattern captured by the monochrome image sensor in traditional color imaging. Therefore, the same de-mosaicing algorithm for color restoration in traditional color imaging can be used to reconstruct the color image of the object from the gray-scale image.

[0062] Example 4

[0063] Preparation of lead-free perovskite hemispherical photodetector and color imaging, as follows:

[0064] (a) Preparation of CsBi3I 10 - Guanidinium thiocyanate perovskite precursor solution: Dissolve cesium iodide and bismuth iodide powders in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a volume ratio of 9:1 (DMF and DMSO) at a molar ratio of 1:3, add 3 mol% guanidinium thiocyanate (GTC) to form a CsBi3I 10 - Guanidinium thiocyanate perovskite precursor solution (CsBi3I 10 - GTC-3).

[0065] (b) Fabrication of the hemispherical device: First, a hemispherical glass substrate with a radius of 5 mm was treated with ultraviolet ozone for 20 minutes. Then, a 100 nm chromium electrode was deposited on the spherical surface of the hemispherical glass substrate by vacuum thermal evaporation. After the chromium electrode deposition, the substrate was treated with ultraviolet ozone for 20 minutes, and then transferred to a plasma treatment chamber (RF power 200 W, working gas nitrogen) for 5 minutes. Next, the treated hemispherical glass substrate was fixed on a stainless steel plate and heated to 100 °C. Simultaneously, a tin dioxide solution was dissolved in deionized water at a volume ratio of 1:12 to obtain a 1.5 wt% tin dioxide aqueous solution, which was uniformly sprayed onto the heated hemispherical substrate using a spray gun with a nozzle diameter of 2 mm, resulting in an electron transport layer thickness of 100 nm. After spraying the tin dioxide aqueous solution, the chromium / tin dioxide substrate was thermally annealed at 150 °C for 30 minutes. Then, the treated substrate was refixed and heated to 100 °C. Then, CsBi3I was sprayed onto the substrate using a spray gun with a nozzle diameter of 2 mm. 10 - Guanidinium thiocyanate perovskite precursor (CsBi3I) 10 The GTC-3 solution was uniformly sprayed onto the treated chromium / tin dioxide substrate, resulting in a perovskite layer with a thickness of 1.5 μm. After spraying, the entire device was thermally annealed at 125 °C for 30 minutes. Then, the hemispherical glass substrate obtained in step (2) was heated to 100 °C, and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] was dissolved in toluene at a concentration of 0.5 mg / mL. -1 The hole transport layer was uniformly sprayed onto a heated substrate using a spray gun with a nozzle diameter of 2 mm and then thermally annealed at 110°C for 10 minutes, resulting in a hole transport layer thickness of 30 nm. Finally, 10 nm of chromium and 10 nm of gold were directly deposited on the device via vacuum thermal evaporation at a deposition rate of [missing information]. The structural schematic diagram of the obtained lead-free perovskite hemispherical photodetector is shown below. Figure 1 As shown.

[0066] (c) Perform color imaging and detection of the target object: The color imaging process is as follows Figure 2 As shown, a colored Fourier basis pattern is first generated using a digital projector to illuminate the target object. The colored Fourier basis pattern is generated by a computer, and the projector is controlled to project the pattern onto the target object. The intensity of the diffuse light is approximately 30 μW cm⁻¹. -2 The reflected light from the object under structured light pattern illumination is collected by a perovskite hemispherical photodetector and converted into an electrical signal. The converted electrical signal is then collected by a power meter as a digital signal and transmitted to a computer for storage and recording.

[0067] (d) Calculating and processing to obtain the color image of the target object: The core of Fourier single-pixel imaging lies in decomposing the image information of the target object into the frequency domain through Fourier transform, that is, obtaining the Fourier spectrum of the image. This process is usually achieved by projecting a series of Fourier basis patterns onto the target object, and using a single-pixel detector to measure the light intensity values ​​reflected from these patterns on the object and converting them into current values ​​for recording. The coefficients of the image in the Fourier domain, i.e., the Fourier spectrum, can be calculated using the recorded current values. By calculating the current values ​​obtained from the perovskite hemispherical photodetector in step (c), the Fourier coefficients of the target object image can be obtained. Then, using inverse Fourier transform, these spectral coefficients can be converted back to the spatial domain, thereby reconstructing the grayscale image of the object. Since the illumination is achieved using a colored Fourier basis pattern, the reconstructed object image is identical to the original pattern acquired by a monochrome image sensor in traditional color imaging. Therefore, the color image of the object can be reconstructed from the grayscale image using the same demosaic algorithm used in traditional color imaging for color restoration.

[0068] Test Example 1

[0069] Crystal structure: This invention relates to CsBi3I 10 Guanidine thiocyanate (GTC) was introduced into the perovskite layer as an additive. The guanidine cation can passivate cation vacancy defects and Bi-I antisite defects on the bottom surface of the perovskite layer through hydrogen bonding and electrostatic interactions between the amino groups in the guanidine. Secondly, the anion thiocyanate (SCN-) has a similar effect to I... - Similar chemical behavior (SCN) - Ionic radius (217 pm) and I - (220m) equivalent) Lone pairs in the linear structure can be related to Bi 3+ Coordination, thereby controlling CsBi3I 10 It participates in the nucleation and growth of perovskites. It can form hydrogen bonds with cations in the material and anchor at grain boundaries, enhancing the structural stability of the perovskite layer.

[0070] The perovskite materials prepared in Examples 1-4 with different concentrations of guanidine thiocyanate (GTC) were characterized by XRD. The characterization results are as follows: Figure 3 The XRD test results are shown. Figure 3 The x-axis is twice the incident angle of the X-rays, usually represented by the symbol "2θ", and the y-axis is the intensity after diffraction. Adding different concentrations of guanidine thiocyanate affects the CsBi3I... 10 Perovskites serve different purposes. From Figure 3 As can be seen from the data, when the concentration of guanidine thiocyanate (GTC) is 1 mol%, (CsBi3I) 10 -GTC-1), with the best effect. CsBi3I 10The guanidinium thiocyanate perovskite layer exhibits significantly suppressed (006) peak intensity and enhanced (003) peak intensity, indicating a significant improvement in phase purity and crystallinity. This demonstrates that the perovskite material obtained in Example 1 is optimal.

[0071] Test Example 2

[0072] Appearance and Morphology: The cross-sectional morphology of the perovskite layer was observed using SEM. In this invention, the perovskite layer is prepared using a spray coating method. The uniformity of the thickness is crucial for device performance. The cross-sectional SEM results of the hemispherical perovskite layer prepared in Example 1 are shown below. Figure 4 As shown. According to Figure 4 It can be seen that the perovskite layer exhibits uniform thickness and density, indicating that the perovskite layer prepared by spraying has good performance. The above tests demonstrate that the hemispherical perovskite photodetector prepared by this invention possesses excellent crystallinity and uniform thickness.

[0073] Test Example 3

[0074] Photoelectric performance of the hemispherical photodetector: The linear dynamic range, responsivity, and specific detectivity of the lead-free perovskite hemispherical photodetector prepared in Example 1 were tested. The results are as follows: Figure 5 and Figure 6 As shown, linear dynamic range is a key parameter for diffuse reflection imaging. Linear dynamic range describes the detector's linear response to different light intensities, and is obtained by fitting a linear relationship between light intensity and photocurrent density. The current density of the hemispherical photodetector under different light intensities is recorded using a current source meter; the light intensity variation is provided by a nanosecond laser. Figure 5 The horizontal axis represents light intensity, and the vertical axis represents photocurrent density. According to... Figure 5 As can be seen, the linear dynamic range is 146 dB, indicating that the hemispherical photodetector performs excellently in low-light detection. The responsivity and specific detectivity of the lead-free perovskite hemispherical photodetector were tested as follows: Figure 6 As shown. Figure 6 The x-axis represents light intensity, the left y-axis represents responsivity, and the right y-axis represents specific detectivity. Responsivity (R) is defined as the ratio of the device's photocurrent to the light irradiance. It describes the magnitude of the current generated by illumination. Specific detectivity (D*) is a parameter that comprehensively evaluates the device's response capability, defined by noise current and responsivity. Its specific detectivity (D*) and responsivity (R) reach 1.47 × 10⁻⁶. 13 Jones and 188.6mAW -1 This further demonstrates the superior performance of hemispherical photodetectors in low-light detection, which is crucial for color imaging in low light conditions.

[0075] Test Example 4

[0076] Stability of the hemispherical photodetector: The CsBi3I prepared in Example 1 10 Long-term stability testing was conducted on the guanidinium thiocyanate perovskite layer. The stability of the photodetector is crucial for color imaging because it directly affects the accuracy of the Fourier coefficients obtained in the reconstructed image. The stability of CsBi3I was determined using a UV-Vis-NIR spectrophotometer. 10 The absorption intensity curves of the device at different wavelengths are shown below after the guanidinium thiocyanate perovskite layer has been exposed to air (50% relative humidity (RH), 25°C) for 30 days. Figure 7 As shown. Figure 7 The horizontal axis represents the wavelength of light, and the vertical axis represents the intensity of light absorption by the material. According to... Figure 7 Based on the light absorption curve, around 30 days later, CsBi3I 10 The absorption curves of the guanidine thiocyanate perovskite layer almost overlap, indicating that CsBi3I 10 - The guanidine thiocyanate perovskite layer exhibits good stability.

[0077] CsBi3I prepared in Example 1 10 High-temperature stability tests were conducted on the guanidine thiocyanate perovskite layer. CsBi3I layers were subjected to different ambient temperatures. 10 XRD analysis of the guanidinium thiocyanate perovskite layer is as follows: Figure 8 As shown. At a temperature of 150℃, CsBi3I 10 The intensity of the characteristic peak (003) of the guanidine thiocyanate perovskite layer does not change significantly. This indicates that CsBi3I 10 The lattice and structure of the guanidine thiocyanate perovskite layer did not undergo significant changes at high temperatures, indicating that CsBi3I 10 - Guanidocyanate perovskite layers are suitable for fabricating lead-free perovskite hemispherical photodetectors for high-temperature applications.

[0078] CsBi3I prepared in Example 1 10 High-temperature stability tests were conducted on the guanidinium thiocyanate perovskite photodetector. The current-time variation curve of the lead-free perovskite photodetector was recorded using a current source meter when placed on a 100°C thermal stage. The results are as follows: Figure 9 As shown. Figure 9 The horizontal axis represents time, and the vertical axis represents current intensity. This displays CsBi3I. 10 The guanidinium thiocyanate perovskite photodetector exhibited minimal photocurrent change over 3600 seconds, verifying the performance of CsBi3I. 10 Devices fabricated from guanidine thiocyanate perovskite materials exhibit good thermal stability. (CsBi3I) 10 - Guanidine thiocyanate perovskite photodetectors can meet imaging requirements at high temperatures.

[0079] Test Example 5

[0080] Color imaging: Color imaging was performed using the lead-free perovskite hemispherical photodetector prepared in Example 1, and the results are as follows. Figure 10 As shown, a hemispherical perovskite photodetector is used to record the intensity of diffuse reflected light generated by the Fourier substrate projection onto the object surface. The hemispherical photodetector converts the light signal into an electrical signal and records it. Then, a color image is generated through inverse Fourier transform calculation and a demosaicing algorithm.

[0081] Color imaging under low light was performed using the lead-free perovskite hemispherical photodetector prepared in Example 1, and the results are as follows: Figure 11 As shown. At 5.5 μW cm -2 Under low-light conditions, a hemispherical perovskite photodetector is used to record the intensity of diffuse reflected light generated by the Fourier substrate projection onto the object. The hemispherical photodetector converts the light signal into an electrical signal and records it. Based on... Figure 11 The imaging results show that even under low light conditions, CsBi3I 10 - Guanidinium thiocyanate perovskite hemispherical photodetectors can still produce color imaging (with slightly lower resolution). Figure 10 This is beneficial for expanding the application range of lead-free perovskite hemispherical photodetectors for imaging.

[0082] High-temperature color imaging was performed using the lead-free perovskite hemispherical photodetector prepared in Example 1, and the results are as follows: Figure 12 As shown. Under high-temperature conditions of 100℃, a hemispherical perovskite photodetector is used to record the intensity of diffuse reflected light generated by the Fourier substrate projection onto the object. The hemispherical photodetector converts the light signal into an electrical signal and records it. According to... Figure 12 The imaging results show that even under high temperature conditions of 100℃, CsBi3I 10 - Guanidine thiocyanate perovskite hemispherical photodetectors can still perform color imaging, which shows that lead-free perovskite hemispherical photodetectors can perform color imaging in complex environments ranging from 25°C to 100°C.

[0083] As can be seen from the above embodiments, the present invention provides a hemispherical single-pixel photodetector based on a lead-free perovskite layer, which enables filter-free single-pixel color imaging in complex environments. This detector exhibits excellent stability, superior low-light response, and a hemispherical device structure that allows it to collect more diffuse light, thereby improving image quality. This simple design not only saves the space and cost required to construct complex detector arrays but also promotes the development of filter-free color imaging technology.

[0084] Although the above embodiments have been described in detail, it should be understood that these are only some embodiments of the present application, but not all embodiments, and other embodiments can be obtained without creativity on the basis of the above embodiments, and these embodiments all belong to the protection scope of the present application.

Claims

1. A method for preparing a lead-free perovskite hemispherical photodetector, comprising the following steps: (1) depositing a chromium electrode layer on the spherical surface of a hemispherical glass substrate treated by ultraviolet ozone for 15-30 minutes through vacuum thermal evaporation; (2) treating the hemispherical glass substrate obtained in step (1) by ultraviolet ozone for 15-30 minutes, and then transferring it to a plasma treatment chamber for 3-8 minutes; heating the treated substrate to 90-110℃, and then spraying an electron transport layer solution on the surface of the chromium electrode layer; after the spraying, annealing at 140-160℃ for 20-40 minutes to obtain an electron transport layer on the surface of the chromium electrode layer; (3) heating the hemispherical glass substrate obtained in step (2) to 90-110℃, and then spraying a perovskite precursor solution on the surface of the electron transport layer; after the spraying, annealing at 115-135℃ for 20-40 minutes to obtain a perovskite layer on the surface of the electron transport layer; (4) heating the hemispherical glass substrate obtained in step (3) to 80-100℃, and then spraying a hole transport layer solution on the surface of the perovskite layer; after the spraying, annealing at 100-120℃ for 8-15 minutes to obtain a hole transport layer on the surface of the perovskite layer; (5) depositing a metal electrode layer on the surface of the hole transport layer obtained in step (4) through vacuum thermal evaporation, thereby obtaining the lead-free perovskite hemispherical photodetector.

2. The method of claim 1, wherein the method further comprises: In step (2), the electron transport layer solution is a tin dioxide aqueous solution with a concentration of 1.0-2.0wt%.

3. The method of claim 1, wherein the method further comprises: The perovskite precursor solution in step (3) is CsBi3I 10 and a guanidine thiocyanate aqueous solution, the concentration of CsBi3I 10 is 0.2-0.4 mol / L, and the concentration of guanidine thiocyanate is 0.5-3 mol%.

4. The method of claim 1, wherein the method further comprises: In step (4), the hole transport layer solution is a toluene solution of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] with a concentration of 0.3-0.8mg / mL.

5. The method of claim 1, wherein the method further comprises: The thermal evaporation deposition rate of the metal electrode layer in step (5) is The metal electrode material is chromium and gold.

6. The method of claim 1, wherein the method further comprises: In steps (2)-(4), the spraying equipment is a spray gun with a nozzle diameter of 0.2mm, a pressure of 1-1.1bar, and a spraying distance of 3-4cm.

7. The method of claim 1, wherein the method further comprises: depositing a first layer of a first material on the substrate; depositing a second layer of a second material on the first layer; and depositing a third layer of a third material on the second layer, wherein the first material, the second material, and the third material form the perovskite material. In steps (1) and (5), the rate of vacuum thermal evaporation deposition is 8. A lead-free perovskite hemispherical photoelectric detector, characterized in that: The lead-free perovskite hemispherical photodetector is prepared by the method of any one of claims 1-7.

9. A lead-free perovskite hemispherical photoelectric detector according to claim 8, wherein: The thickness ratio of the chromium electrode layer, the electron transport layer, the perovskite layer, the hole transport layer, and the metal electrode layer is 100-200nm: 100-200nm: 1000-1500nm: 25-30nm: 10-20nm.

10. The use of the lead-free perovskite hemispherical photodetector of claim 8 or 9 in single-pixel lensless color imaging.

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