Retina-like self-adaptive visual device based on perovskite and hydrogen bond organic framework heterostructure and preparation method of retina-like self-adaptive visual device

Abstract

The invention relates to the technical field of artificial vision and neuromorphic devices, and particularly discloses a retina-like adaptive vision device based on a perovskite and hydrogen bond organic framework material heterostructure and a preparation method of the retina-like adaptive vision device. According to the device, a hydrogen bond organic framework is adopted to regulate and control perovskite crystal lattices, carboxyl and lead ion coordination are utilized to induce crystal lattice strain, defect energy barriers are effectively improved, non-radiative recombination of carriers is inhibited, and dynamic regulation and control of photon-generated carriers are achieved. The device can realize the functions of light adaptation and dark adaptation driven by light intensity without voltage modulation, and shows the Weber's law response characteristic similar to the retina of human eyes. The device shows ultra-low monopulse power consumption, wide spectral response range, response speed close to human eyes and high dynamic range, is obviously superior to a traditional CMOS sensor, and provides a new way for high dynamic range imaging and on-chip neuromorphic calculation.

Description

Technical Field

[0001] This invention relates to the field of novel optoelectronic devices and neuromorphic visual perception technology, specifically to a retina-like adaptive visual device based on a perovskite and hydrogen-bonded organic framework heterostructure (PVK@HOF) and its fabrication method. Background Technology

[0002] With the rapid development of artificial intelligence, autonomous driving, and intelligent sensing systems, information acquisition and processing capabilities are facing unprecedented challenges. Especially in complex, dynamic, and high-dynamic-range environments, achieving efficient and accurate environmental perception and intelligent decision-making has become a critical issue. The human eye, as one of the most efficient visual systems in nature, can maintain stable perception and target recognition capabilities across a light intensity range exceeding 160 dB. Its superior visual adaptability stems primarily from the synergistic effect of rod and cone cells, and the mechanism by which photoreceptors rapidly and adaptively adjust to external light intensity. This capability ensures that the human eye can still efficiently complete environmental recognition and visual processing under conditions ranging from extremely low to high light. In contrast, while traditional silicon-based CMOS image sensors are widely used in modern information processing systems, their dynamic range is typically limited to within 70 dB, making it difficult to simultaneously meet the imaging needs under both low and high light conditions. In high-contrast scenes, these sensors often suffer from overexposure or underexposure, leading to significant loss of image information and thus limiting their application in cutting-edge fields such as autonomous driving, intelligent monitoring, and complex environmental perception. Therefore, developing a new type of visual device that is simple in structure, low in energy consumption, has a wide dynamic response range, and can sense changes in external light intensity in a biological manner has become an important direction for promoting the next generation of intelligent sensing technology.

[0003] Perovskite (PVK) materials, with their broad-spectrum absorption characteristics, high carrier mobility, and low-cost solution processing, have shown great potential in photoelectric detection and imaging devices. However, single perovskite materials still have significant shortcomings: their photogenerated carrier recombination rate is relatively fast, leading to a rapid decay of photocurrent after illumination is removed, a lack of sustained response, and a significant hysteresis effect, making it difficult to achieve neuromorphic or biomimetic functions, and usually only exhibiting traditional photoelectric detection characteristics. Therefore, how to effectively suppress nonradiative recombination and delay the decay process of photogenerated carriers has become a core scientific challenge for the development of perovskite biomimetic vision devices. Hydrogen-bonded organic frameworks (HOFs), as a new class of crystalline porous materials, have attracted much attention due to their flexible two-dimensional framework structure, highly tunable intermolecular interactions, and excellent photoresponse performance. HOFs rely on intermolecular hydrogen bonds to achieve self-assembly, giving them unique interface control capabilities. In particular, the abundant carboxyl functional groups can interact with Pb in the perovskite lattice. 2 The coordination of ⁺ ions induces strain modulation at the interface, thereby effectively passivating lattice defects, optimizing the band structure, and significantly improving carrier dynamics. This property provides a new approach for constructing perovskite heterostructures with long lifetimes, hysteretic responses, and tunable photoelectric properties.

[0004] Therefore, combining perovskite with HOF not only significantly slows down carrier recombination and endows devices with synaptic memory and adaptive functions, but also achieves high-sensitivity photoresponse and low-power signal processing over a wide spectral range. This strategy provides a simple and efficient approach to developing high-performance machine vision devices with human-like visual adaptation capabilities, and is expected to drive breakthroughs in the application of next-generation biomimetic vision systems in fields such as autonomous driving, artificial intelligence, drone navigation, and complex environment monitoring. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a retina-like adaptive vision device based on a perovskite-hydrogen-bonded organic framework heterostructure (PVK@HOF) and its fabrication method. This invention utilizes perovskite (FA)... 0.85 Cs 0.15 Pb(Br) 0.05 I 0.95 )3 is the core photosensitive functional layer, and a hydrogen-bonded organic framework rich in carboxyl functional groups is introduced as an interface regulation layer, utilizing the carboxyl groups and uncoordinated Pb in the perovskite lattice. 2+ The combination induces tensile strain in the perovskite lattice, raising the energy barrier for the transition between Pb-Pb dimer (deep-level defects) and non-dimer (potential-level defects) configurations, thereby enabling the regulation of the behavior of photogenerated carriers and simulating the brightness adaptation function of the human eye.

[0006] The first objective of this invention is to provide a retina-like adaptive vision device based on a perovskite and hydrogen-bonded organic framework heterostructure, comprising a conductive substrate layer, an electrode layer, and a functional thin film layer disposed between the conductive substrate layer and the electrode layer; the functional thin film layer comprises PVK@HOF; The PVK@HOF includes PVK and HOF; The PVK is (FA) 0.85 Cs 0.15 Pb(Br) 0.05 I 0.95 3. The HOF is self-assembled from H4TBAPY monomers via hydrogen bonding; through the carboxyl groups in the monomers and the uncoordinated Pb in PVK. 2+ The combination induces tensile strain in the PVK lattice, forming a PVK@HOF functional thin film layer with adaptive function, where FA represents formamidinium.

[0007] In some embodiments of the present invention, the thickness of the electrode layer is 100-200 nm, and the thickness of the functional thin film layer is 300-500 nm.

[0008] A second objective of this invention is to provide a method for fabricating the aforementioned retina-like adaptive vision device based on a perovskite and hydrogen-bonded organic framework heterostructure, comprising the following steps: An FTO substrate with a fluorine-doped tin oxide conductive layer deposited on its surface is provided; Formamidin iodide (FAI), lead iodide (PbI2) and cesium bromide (CsBr) were dissolved in a mixed solvent and stirred to obtain a PVK precursor solution; 1,3,6,8-tetra(4-carboxyphenyl)pyrene (H4TBAPY) was dispersed in a mixed solvent and ultrasonically dispersed to obtain an H4TBAPY solution. The PVK precursor solution and H4TBAPY solution were mixed and ultrasonically dispersed to obtain a uniform PVK@HOF precursor mixture. In an inert atmosphere, the PVK@HOF precursor mixture was drop-coated onto the surface of the FTO substrate, and a functional thin film layer was prepared by spin coating and annealing. The retina-like adaptive vision device is obtained by fabricating an electrode layer on the surface of a functional thin film layer using magnetron sputtering with a metal mask as a shielding element. No metal is deposited in areas blocked by the mask, while metal electrodes are deposited in the unblocked areas.

[0009] In some embodiments of the present invention, the molar ratio of formamidinium iodide (FAI), lead iodide (PbI2), and cesium bromide (CsBr) is 6:7:1.

[0010] In some embodiments of the present invention, the mixed solvent is a mixture of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), wherein the volume ratio of N,N-dimethylformamide (DMF) to dimethyl sulfoxide (DMSO) is (4:1) to (5:1).

[0011] In some embodiments of the present invention, the concentration of the H4TBAPY solution is 15-20 mg / mL.

[0012] In some embodiments of the present invention, the volume ratio of the PVK precursor solution to the H4TBAPY solution is (2:1) to (1:1).

[0013] In some embodiments of the present invention, spin coating is performed in three stages, as shown below: First stage: Spin coat at 1000~1500 rpm for 10 s~15 s to spread the solution evenly; Second stage: Spin-coating at 4000~5000 rpm for 30~50 s to control the thickness of the film formed by spin-coating. 5~10 s before the end of this step, chlorobenzene (as an anti-solvent) is dropped onto the film surface to back-extract the perovskite crystals; Third stage: Spin coat at 1000~1500 rpm for 10~15 s to remove excess chlorobenzene; Annealing process: Heat to 100~120℃ and anneal for 15~30 minutes.

[0014] In some embodiments of the present invention, the electrode layer is deposited using magnetron sputtering technology, and a lattice electrode array is prepared using a metal mask. The specific parameters for magnetron sputtering are: vacuum degree of (4~5)×10⁻⁶. -2 Deposition was performed at Pa and a current of 30–40 mA for 100–150 s, followed by deposition at a current of 30–40 mA for 150–200 s.

[0015] In some embodiments of the present invention, the metal in the electrode layer includes platinum, gold, graphite, FTO, and ITO.

[0016] A third objective of this invention is to provide the application of the aforementioned adaptive vision device based on a perovskite and hydrogen-bonded organic framework heterostructure in biomimetic vision sensing, high dynamic range (HDR) imaging, photosynaptic neural networks, and intelligent sensing systems.

[0017] The beneficial effects of this invention are: This invention employs a low-temperature solution method, which also allows for the fabrication of transparent and flexible substrates, resulting in a simple fabrication process. Adaptive functionality is achieved through lattice strain; the device has a top-bottom structure, eliminating the need for external gate voltage and complex peripheral compensation circuitry, significantly reducing system complexity.

[0018] This invention achieves the lowest single-peak power consumption (1.8 aJ) of current adaptive neuromorphic devices, obtains an ultra-high dynamic range of 104 dB in a broadband response of 365~800 nm, and exhibits sensing behavior consistent with Weber's Law at the hardware level. It also takes into account both strong light suppression and low light recognition, and the overall sensing quality is superior to similar solutions. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the fabrication process of the PVK@HOF device of the present invention.

[0020] Figure 2 Scanning electron microscope images of the PVK@HOF film and the original PVK film.

[0021] Figure 3 Atomic force microscopy images of the PVK@HOF thin film (a) and the original PVK thin film.

[0022] Figure 4 This is a cross-sectional scanning electron microscope image of the PVK@HOF thin film.

[0023] Figure 5 The energy dispersive X-ray spectrum of the PVK@HOF thin film.

[0024] Figure 6 The Fourier transform infrared spectra are of the original perovskite film and the PVK@HOF film.

[0025] Figure 7 X-ray diffraction patterns of the original perovskite film and the PVK@HOF film.

[0026] Figure 8 X-ray electron spectra of the original perovskite film and the PVK@HOF film.

[0027] Figure 9 A comparison of the photocurrent response curves of the PVK@HOF device with those of the original PVK device and the original HOF device.

[0028] Figure 10 The photocurrent response curves of PVK@HOF under different background light intensities are shown.

[0029] Figure 11 This is a conformance test diagram for the PVK@HOF device.

[0030] Figure 12 This is a scatter plot showing the optical responsivity of the PVK@HOF device as a function of light intensity.

[0031] Figure 13 The photocurrent response of the PVK@HOF device to flash stimuli of different intensities under different background light intensities is shown.

[0032] Figure 14 This is a comparison of the photocurrent response of PVK@HOF devices on flexible and rigid substrates. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0034] Example 1 This embodiment provides a fabrication method for a PVK@HOF device, and the fabrication process is as follows: Figure 1 As shown below: I. The heterostructure was prepared by a solution method, and all the following steps were completed in a nitrogen-filled glove box (O2, H2O < 0.1 ppm): (1) Preparation of perovskite precursor solution: Weigh 0.4386 g of FAI (formamidinium iodide), 1.383 g of PbI2 and 0.0958 g of CsBr, and dissolve them in a mixed solvent of DMF:DMSO=4:1 (volume ratio, DMF 0.8 mL, DMSO 0.2 mL). Stir magnetically at room temperature for about 12 h until completely clear and homogeneous. Filter through a 20 μm PTFE filter membrane for later use to obtain PVK precursor solution.

[0035] (2) Preparation of HOF precursor solution: Weigh 20 mg of H4TBAPY (1,3,6,8-tetra(4-carboxyphenyl)pyrene) and dissolve it in a mixed solvent of DMF:DMSO=4:1 (volume ratio, DMF 0.8 mL, DMSO 0.2 mL). Sonicate for 15 min to obtain a uniform dispersion, i.e. H4TBAPY solution.

[0036] (3) Preparation of PVK@HOF composite film: PVK precursor solution and H4TBAPY solution were mixed in equal volumes (100 μL each) and sonicated for 15 min to obtain PVK@HOF precursor mixture. 70 μL of the mixture was dropped onto a pre-cleaned FTO substrate and spin-coated at 1000 rpm for 10 s and 5000 rpm for 50 s respectively. 5 s before the end of this step, 300 μL of chlorobenzene was rapidly added as an anti-solvent, and spin-coated at 1000 rpm for 10 s. Immediately after film formation, the film was annealed on a 100 °C heating stage for 15 to 30 minutes to form PVK@HOF composite film. Finally, Pt top electrode (approximately 100 nm thick, 67 μm diameter) was deposited by magnetron sputtering through a metal mask to obtain the PVK@HOF device.

[0037] The PVK@HOF film is dark brown-black, and its thickness is as follows: Figure 4 As shown, it is approximately 300-500 nm.

[0038] Comparative Example 1 This comparative example provides a device fabricated based on the original HOF thin film, and the specific fabrication method is shown below: 70 μL of H4TBAPY solution was dropped onto a pre-cleaned FTO substrate, and spin-coated at 500 rpm for 10 s, followed by spin-coating at 1000 rpm for 20 s. Immediately after film formation, the substrate was annealed at 100 °C for 15 to 30 minutes. Finally, using a metal mask, a Pt top electrode (approximately 100 nm thick, 67 μm diameter) was deposited by magnetron sputtering to obtain the HOF device.

[0039] Comparative Example 2 This comparative example provides a device fabricated based on a pristine perovskite thin film, and the specific fabrication method is shown below: 70 μL of the PVK precursor solution was dropped onto a pre-cleaned FTO substrate, and spin-coated sequentially at 1000 rpm for 10 s and 5000 rpm for 50 s. Five s before the end of this step, 300 μL of chlorobenzene was rapidly added as an antisolvent, and spin-coated at 1000 rpm for 10 s. Immediately after film formation, the substrate was annealed at 100 °C for 15 to 30 minutes. Finally, using a metal mask, a Pt top electrode (approximately 100 nm thick, 67 μm in diameter) was deposited by magnetron sputtering to obtain the PVK device.

[0040] Structural characterization The PVK@HOF composite film obtained in Example 1 was structurally characterized, and the results are as follows: Figures 2-8 As shown: like Figure 2 As shown, compared to the original perovskite film (a), the HOF coverage is clearly visible in the image (b) of the PVK@HOF composite film, which reduces the perovskite grain size, demonstrating the regulatory effect of HOF on the perovskite grain size.

[0041] like Figure 3 As shown, compared with the original perovskite film (a) and the PVK@HOF composite film (b), the introduction of HOF reduces the perovskite grain size. Figure 2 The conclusions are consistent with those of the previous studies, showing that the overall roughness of the thin film decreased.

[0042] like Figure 4 As shown, the thickness of PVK@HOF in the PVK@HOF composite film is approximately 200-500 nm.

[0043] like Figure 5As shown, O is a characteristic element of HOF, demonstrating the uniform distribution of HOF in the film. Br and Pb are characteristic elements of perovskite, demonstrating the good uniformity of the composite film.

[0044] like Figure 6 As shown, compared to the original perovskite film, the PVK@HOF composite film sample also exhibits an aromatic ring (1176 cm⁻¹). -1 ) and hydrogen bond interactions (2550-2700 cm) -1 The additional absorption peaks related to this confirm the existence of HOF.

[0045] like Figure 7 As shown, both films crystallize in an orthorhombic phase (Pbnm space group). Notably, in the PVK@HOF composite film, the (100) diffraction peak near 13.9° splits, resulting in two distinct peaks at 13.8° and 14.1°, while the remaining diffraction characteristics remain largely unchanged. This is attributed to interfacial lattice strain induced by HOF, which modulates crystallographic symmetry and lattice periodicity. The slight downward shift of the main peak also indicates tensile strain within the lattice.

[0046] like Figure 8 As shown, X-ray photoelectron spectroscopy (XPS) analysis of the Pb 4f core level revealed a negative shift of 0.30 eV in the binding energy of the PVK@HOF composite film compared to the original PVK. This shift can be attributed to the carboxyl groups and uncoordinated Pb on the perovskite surface. 2+ Coordination interactions between ions effectively passivate electron-trapped states.

[0047] Performance testing The light absorption performance, current response performance, cycle stability, current response on the flexible substrate, and Weber's law verification of the PVK@HOF device obtained in Example 1 were tested.

[0048] like Figure 9 As shown, the responses of PVK devices, HOF devices, and PVK@HOF devices to pulsed light of different wavelengths were compared. Figure a shows the photocurrent curve of the PVK device, Figure b shows the photocurrent curve of the HOF device, and Figure c shows the photocurrent curve of the PVK@HOF device. The pulsed light frequency used in the tests was 1 Hz, and the optical power density was 1.2 mW·cm². -2 The original HOF film showed no response to light beyond 520 nm. The original PVK film lacked photocurrent attenuation characteristics, failing to meet the requirements of adaptive imaging. The introduction of HOF successfully altered the photocurrent response characteristics of perovskite, enabling its application in biomimetic adaptive imaging.

[0049] like Figure 10As shown, the PVK@HOF device exhibits a three-stage current response. The first stage: a stable dark current exists in the dark. The second stage: upon application of light, the current rapidly reaches its peak and then gradually decays, simulating the light adaptation process of the human eye. The third stage: when the light is removed, the current decays below the dark current and gradually recovers, simulating the dark adaptation process of the human eye.

[0050] like Figure 11 As shown, PVK@HOF exhibits good cycling stability. Figure a shows the photocurrent curves of a single PVK@HOF device from the 1st to the 60th cycle. Figure b shows the photocurrent curves of 50 PVK@HOF devices. The applied pulsed light wavelength was 365 nm, the frequency was 1 Hz, and the optical power density was 1.2 mW·cm⁻¹. -2 .

[0051] like Figure 12 As shown, this invention tested the photoresponsivity of the PVK@HOF device as a function of light intensity. The photoresponsivity was calculated using the formula R=ΔI / PS, where ΔI is the increase in current after illumination, P is the incident light power density, and S is the electrode area. The tested light intensity ranged from 0.01 μW·cm². -2 Change to 14000 μW·cm -2 The photoresponsivity of PVK@HOF decreases with increasing light intensity, which is consistent with the characteristics of the human eye, exhibiting high sensitivity in low light and low sensitivity in strong light.

[0052] like Figure 13 The figure shows the photocurrent response of the PVK@HOF device to different flash stimuli under different background light intensities. The testing method involved applying a fixed background illumination to the device in a dark environment, with background light power densities of 0.8, 1, 2, 4, and 6 mW·cm⁻¹. -2 After approximately 20 seconds of background illumination, six flash stimuli were simultaneously applied, with light power densities of 0.06, 0.2, 0.5, 1.2, 2, and 3 mW·cm⁻¹. -2 The interval between each flash was 25 seconds. The test results showed that the stronger the background light intensity, the lower the device's response to the flash, while the minimum resolvable threshold increased. This indicates that when exposed to strong light, the device ignores weak flash changes, which is consistent with Weber's Law.

[0053] like Figure 14 As shown, PVK@HOF exhibits a photocurrent response on a flexible ITO substrate that is similar to that on a rigid FTO substrate. The testing method involved bending PVK@HOF devices fabricated on flexible ITO substrates to curvature radii of 1 and 2 cm, followed by photoresponse testing. The testing method is the same as... Figure 13 The selected background light power density is 6 mW·cm².-2 The flash power densities were 0.5, 1.2, 2, and 3 mW·cm⁻¹. -2 .

[0054] The embodiments described above are merely preferred embodiments for fully illustrating the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A retina-like adaptive visual device based on a perovskite and hydrogen-bonded organic framework heterostructure, characterized in that, It includes a conductive substrate layer, an electrode layer, and a functional thin film layer disposed between the conductive substrate layer and the electrode layer; the functional thin film layer includes PVK@HOF. The PVK@HOF includes PVK and HOF; The PVK is (FA) 0.85 Cs 0.15 Pb(Br) 0.05 I 0.95 3. The HOF is self-assembled from H4TBAPY monomers via hydrogen bonding; through the carboxyl groups in the H4TBAPY monomers and the uncoordinated Pb in PVK 2+ The combination induces tensile strain in the PVK lattice, forming a PVK@HOF functional thin film layer with adaptive function.

2. The retina-like adaptive vision device based on a perovskite and hydrogen-bonded organic framework heterostructure as described in claim 1, characterized in that, The electrode layer has a thickness of 100-200 nm, and the functional thin film layer has a thickness of 300-500 nm.

3. A method for fabricating a retina-like adaptive visual device based on a perovskite and hydrogen-bonded organic framework heterostructure as described in claim 1 or 2, characterized in that, Includes the following steps: An FTO substrate with a fluorine-doped tin oxide conductive layer deposited on its surface is provided; Formamidin iodide, lead iodide and cesium bromide were dissolved in a mixed solvent and stirred to obtain a PVK precursor solution; 1,3,6,8-tetra(4-carboxyphenyl)pyrene was dispersed in a mixed solvent and ultrasonically dispersed to obtain an H4TBAPY solution; The PVK precursor solution and H4TBAPY solution were mixed and then ultrasonically dispersed to obtain a uniform PVK@HOF precursor mixture. In an inert atmosphere, a mixture of PVK@HOF precursors is drop-coated onto the surface of the FTO substrate, and a functional thin film layer is prepared by spin coating and annealing. An electrode layer is prepared on the surface of the functional thin film layer by magnetron sputtering to obtain the retina-like adaptive vision device.

4. The preparation method according to claim 3, characterized in that, The molar ratio of formamidinium iodide, lead iodide, and cesium bromide is 6:7:

1.

5. The preparation method according to claim 3, characterized in that, The mixed solvent is a mixture of N,N-dimethylformamide and dimethyl sulfoxide, wherein the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is (4:1) to (5:1).

6. The preparation method according to claim 3, characterized in that, The concentration of the H4TBAPY solution is 15-20 mg / mL; the volume ratio of the PVK precursor solution to the H4TBAPY solution is (2:1) to (1:1).

7. The preparation method according to claim 3, characterized in that, Spin coating consists of three stages, as shown below: First stage: Spin coat at 1000~1500 rpm for 10 s~15 s to spread the solution evenly; Second stage: spin coating at 4000~5000 rpm for 30~50 s to control the thickness of the film formed by spin coating; 5~10 s before the end of this step, chlorobenzene is dropped onto the film surface to back-extract perovskite crystals; Third stage: Spin coat at 1000~1500 rpm for 10~15 s to remove excess chlorobenzene; Annealing process: Heat to 100~120℃ and anneal for 15~30 minutes.

8. The preparation method according to claim 3, characterized in that, The electrode layer was deposited using magnetron sputtering technology, with specific parameters: vacuum level of (4~5)×10⁻⁶. -2 Deposition was performed at Pa and a current of 30–40 mA for 100–150 s, followed by deposition at a current of 30–40 mA for 150–200 s.

9. The preparation method according to claim 3, characterized in that, The metal in the electrode layer includes platinum, gold, graphite, FTO, or ITO.

10. The application of the adaptive vision device based on the heterostructure of perovskite and hydrogen-bonded organic framework according to claim 1 or 2 in biomimetic vision sensing, high dynamic range imaging, photosynaptic neural networks, and intelligent sensing systems.

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