Photoelectric device based on self-assembled monomolecular layer modified perovskite and preparation method and application thereof

Abstract

The invention provides a photoelectric device based on self-assembled monomolecular layer modified perovskite and a preparation method and application thereof, and the photoelectric device comprises a perovskite layer which is deposited on a self-assembled monomolecular layer; wherein the self-assembled monomolecular layer comprises one or two of a phosphoric acid self-assembled monomolecular layer based on a carbazole structure and a phosphonic acid self-assembled monomolecular layer based on the carbazole structure. By introducing the self-assembly monomolecular layer, the synergistic effect of interface regulation and crystallization optimization is realized in the photoelectric device structure, and the crystallization quality and interface uniformity of the perovskite thin film are remarkably improved, so that the carrier recombination rate is effectively reduced in the photoelectric conversion process, dark current is remarkably inhibited, and the photoelectric conversion efficiency is improved. Key performance indexes such as photocurrent response and specific detection rate of the device are improved, and the device is suitable for high-performance photoelectron application scenes such as photoelectric detection and weak signal identification and has excellent sensitivity and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoelectric detection, in particular to a perovskite modified by a self-assembled monolayer, a photoelectric device, a preparation method and an application thereof. BACKGROUND

[0002] With the continuous progress of wearable electronic devices and flexible optoelectronic technology, flexible photoelectric detectors are gradually becoming key devices in the fields of health monitoring, intelligent medical treatment, human-computer interaction and other frontier application fields due to their strong bendability, fast response speed and high photoelectric conversion efficiency. Perovskite materials have become the core material for constructing high-performance flexible photoelectric detectors due to their excellent adjustable optical absorption performance, high carrier mobility and low-cost, low-temperature preparation process.

[0003] However, although perovskite materials have excellent photoelectric performance and provide a solid foundation for the functional realization of flexible devices, they still face many technical challenges in specific device structures. In particular, in the flexible application scenario, polycrystalline perovskite thin films often have problems such as grain boundary defects, poor film uniformity, and are easy to form carrier recombination centers, which significantly inhibit the photoelectric conversion efficiency of the device. At the same time, there are energy level mismatching and defect state accumulation phenomena at the interface between the perovskite and the carrier transport layer, which further reduces the response capability and specific detectivity of the device. In addition, under the condition of repeated mechanical bending or stress impact, the perovskite film structure is easily damaged, leading to degradation of device performance, making it difficult to meet the requirements of long-term stability and reliability of flexible electronic devices.

[0004] Although current technologies attempt to improve the overall performance of flexible photoelectric devices by introducing nanostructure regulation, constructing single-crystal perovskite thin films and adding functional interface layers, for example, “NIR-OPD with double electron injection and blocking structure” has shown certain application potential in enhancing near-infrared detection sensitivity, but these technical paths still face many limitations in practical applications. On the one hand, the material system used is usually limited, making it difficult to balance device performance and flexibility; on the other hand, related structure design often has problems such as poor universality, difficulty in device integration and complex preparation process, which is difficult to meet the comprehensive needs of flexible photoelectric devices in terms of high performance, low cost and large-scale manufacturing.

[0005] Therefore, the present application is proposed. SUMMARY

[0006] The technical problem to be solved by the present application is to overcome the performance degradation of perovskite photoelectric devices caused by poor thin film crystallinity, many interface defects, insufficient mechanical stability and poor flexibility compatibility in the prior art, thereby providing a perovskite modified by a self-assembled monolayer, a photoelectric device, a preparation method and an application thereof.

[0007] According to the embodiments of the present application, in a first aspect, a perovskite-based optoelectronic device is provided, which comprises a perovskite (CsFAMA) layer deposited on a self-assembled monolayer (SAM).

[0008] The self-assembled monolayer comprises one or both of a phosphoric acid-based self-assembled monolayer based on a carbazole structure and a phosphonic acid-based self-assembled monolayer based on a carbazole structure.

[0009] The present application introduces a phosphoric acid-based or phosphonic acid-based self-assembled monolayer (SAM) based on a carbazole structure between the perovskite layer and the underlying substrate, achieving a synergistic enhancement of interface regulation and crystallization optimization in the device structure. The SAM layer effectively improves the crystalline quality and surface uniformity of the perovskite thin film, reduces the grain boundary defect density, and at the same time, enhances the energy level matching between the perovskite and the adjacent functional layer, thereby suppressing carrier recombination in the photoelectric conversion process, significantly reducing the dark current of the device and enhancing the photoelectric response capability. In addition, the introduction of SAM also significantly improves the mechanical stability of the device under multiple bending conditions, providing strong support for its application in wearable electronics, flexible sensing and other high-sensitivity and high-stability application scenarios, and showing good interface engineering regulation effect and application prospect.

[0010] In some optional embodiments, the self-assembled monolayer comprises one or both of a [4-(7H-dibenzo carbazole-7-yl)butyl]phosphonic acid (4PADCB) layer and a [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) layer.

[0011] The 4PADCB and MeO-2PACz can form a dense and ordered functionalized monolayer film on the surface of the transparent conductive layer due to their excellent molecular structure and polar functional groups.

[0012] In some optional embodiments, the optoelectronic device comprises, from bottom to top, a transparent conductive substrate layer, a self-assembled monolayer, a perovskite layer, an electron transport layer, a buffer layer, and a top electrode.

[0013] The transparent conductive substrate provides good light transmittance and conductive support for the device. The self-assembled monolayer (SAM) as a key interface regulation unit effectively guides the directional growth of perovskite crystals, improves the film density and crystalline quality, and reduces the interface defect state density, thereby significantly suppressing the dark current and improving the extraction efficiency of photo-generated carriers. The subsequently deposited electron transport layer and buffer layer promote the rapid migration of carriers and block reverse injection through energy level gradient design, while enhancing the interface stability. The top electrode constructed finally ensures that the device has good carrier collection performance and electrical contact characteristics.

[0014] In some alternative embodiments, the optoelectronic device comprises, from bottom to top, a transparent conductive substrate layer, a dielectric layer, a self-assembled monolayer, a perovskite layer, and a source-drain electrode.

[0015] The transparent conductive substrate has good electro-optical properties and can be used as a device gate; the dielectric layer, such as Al2O3, provides a high-quality insulating interface, ensuring good gate control performance and low leakage of the device. The self-assembled monolayer (SAM) forms an ordered molecular interface structure between the dielectric layer and the perovskite layer, which can effectively regulate the nucleation and crystallization behavior of the perovskite, reduce the surface energy level mismatch and carrier recombination, and improve the migration efficiency of the channel carriers. The perovskite layer serves as the core photosensitive channel material, providing high light absorption and high mobility characteristics; the source-drain electrode realizes high spatial resolution and excellent carrier injection capability through precise patterning (such as interdigital structure).

[0016] In some alternative embodiments, the buffer layer comprises a C60 electron auxiliary transport layer and a 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) hole blocking layer deposited on the C60 electron auxiliary transport layer.

[0017] The C60 material has excellent electron migration ability, can efficiently transport and selectively extract electrons generated by the perovskite layer, and helps to suppress electron-hole recombination; the BCP as a hole blocking layer can effectively prevent holes from being injected from the anode to the electron transport layer region, further reducing the dark current and improving the photoelectric conversion efficiency of the device.

[0018] In some alternative embodiments, the transparent conductive substrate layer is an indium tin oxide (ITO) layer or an indium tin oxide (ITO) layer deposited on a flexible substrate.

[0019] The flexible substrate can be a polyethylene terephthalate (PET) material, which has good mechanical flexibility, optical transparency, and thermal stability, and is suitable for the preparation and integration of bendable electronic devices. By depositing an ITO layer on a PET flexible substrate, not only the good conductivity and light transmittance of ITO are retained, but also the device as a whole has good bending ability and flexibility compatibility, meeting the multiple deformation use requirements in wearable devices, flexible displays, and biosensing scenarios.

[0020] According to an embodiment of the present application, a second aspect provides a preparation method of the optoelectronic device as described in any of the above embodiments, comprising:

[0021] S1, spin-coating a self-assembled monolayer solution on the surface of the substrate, annealing to form a self-assembled monolayer (SAM);

[0022] The self-assembled monomolecular solution comprises one or both of a phosphoric acid-based organic solution based on a carbazole structure and a phosphonic acid-based organic solution based on a carbazole structure.

[0023] S2, spin-coating a perovskite precursor solution on the surface of the self-assembled monolayer, annealing, and forming a perovskite layer;

[0024] S3, constructing a device functional structure on the surface of the perovskite layer, and packaging.

[0025] The present application introduces a functional self-assembled monolayer (SAM) between the substrate and the perovskite layer, which not only optimizes the crystallization process of the perovskite thin film, but also effectively improves the interface energy level matching and carrier transport characteristics, thereby significantly improving the photoelectric response performance and environmental stability of the device.

[0026] After spin-coating and annealing at an appropriate temperature and for an appropriate time, the ordered arrangement and dense adsorption of the self-assembled monolayer are promoted, and the complete growth of perovskite grains and defect passivation are promoted, thereby further improving the density and crystallinity of the thin film, reducing the grain boundary traps, and enhancing the overall electrical and mechanical stability of the device.

[0027] In some optional embodiments, in the step S1, the spin-coating speed is 2500-3500 rpm, and the spin-coating time is 25-40 s.

[0028] In some optional embodiments, in the step S1, the annealing temperature is 90-105℃, and the annealing time is 8-15 min.

[0029] In some optional embodiments, in the step S2, an anti-solvent is added during the process of spin-coating the perovskite precursor solution.

[0030] In some optional embodiments, in the step S2, the annealing temperature is 100-120℃, and the annealing time is 8-25 min.

[0031] Preferably, in the step S2, the spin-coating speed is 5000-6500 rpm, the spin-coating time is 25-40 s, and the anti-solvent ethyl acetate is added at about 24-28 s.

[0032] In some optional embodiments, the step S3 includes depositing an electron transport layer on the surface of the perovskite layer, and sequentially evaporating a buffer layer and a top electrode.

[0033] In some optional embodiments, the step S3 includes evaporating a source-drain electrode on the surface of the perovskite layer.

[0034] According to the embodiments of the present application, a third aspect provides a human health monitoring system, comprising:

[0035] LED light source for emitting near-infrared light signal to human target area;

[0036] The photoelectric device according to any one of the above embodiments, for receiving light signal transmitted through human target area and converting it into electrical signal;

[0037] Signal processing unit for processing electrical signal output by the photoelectric device.

[0038] The human health monitoring system provided by the present application integrates high-sensitivity perovskite photoelectric device, near-infrared LED light source and signal processing unit, which can accurately capture and convert weak light signal transmitted through human tissue into electrical signal. Based on the good tissue penetration ability of near-infrared light, combined with the advantages of the photoelectric device described in the present application in specific detectivity, dark current control and flexible adaptability, the system can realize non-invasive, high-precision and real-time physiological signal monitoring, such as pulse wave (PPG) and heart rate parameter extraction. The system has compact structure and fast response, and is suitable for wearable health devices, especially in continuous monitoring scenarios such as smart bracelets and health patches, showing excellent practicability and expansibility, and providing reliable support for the development of flexible health electronics.

[0039] According to the embodiments of the present application, the fourth aspect provides an application of the photoelectric device according to any one of the above embodiments in health monitoring and analysis of human body.

[0040] The technical scheme of the present application has the following advantages:

[0041] The present application introduces a self-assembled monolayer based on carbazole structure phosphoric acid or phosphonic acid between perovskite layer and its underlying substrate, realizing the synergistic effect of interface regulation and crystallization optimization in photoelectric device structure, significantly improving the crystalline quality and interface uniformity of perovskite thin film, thereby effectively reducing the carrier recombination rate in the process of photoelectric conversion, significantly suppressing the dark current, and improving the key performance indicators such as photoelectric current response and specific detectivity of the device. In high-performance optoelectronic application scenarios such as photoelectric detection and weak signal recognition, it has higher sensitivity and stability. In addition, the photoelectric device exhibits excellent mechanical flexibility and environmental adaptability in flexible electronic devices, providing an effective solution for the practical application of high-sensitivity, low-power-consumption and wearable photoelectric detection devices.

[0042] The preparation method of the application effectively regulates the nucleation behavior and crystallization process of the perovskite layer by spin-coating a self-assembled monolayer solution containing a carbazole structure on the surface of a substrate and forming a high-quality self-assembled monolayer through annealing, thereby significantly improving the compactness and uniformity of the perovskite film. Subsequently, by spin-coating a perovskite precursor solution on the functionalized interface and annealing, the film structure and interface bonding quality are further optimized, thereby reducing defect states and carrier recombination from the source, which is conducive to improving the photoelectric response performance and stability of the device.

[0043] The photoelectric device of the application has significant application advantages and technical effects in near-infrared biological signal detection. The LED light source irradiates the target area of the human body to achieve non-invasive and deep light signal transmission. The photoelectric device of the application has excellent light responsivity, high specific detectivity and low dark current characteristics, and can sensitively capture weak light signals that penetrate the target area of the human body and quickly convert them into electrical signals. In combination with the signal processing unit for amplifying and analyzing the electrical signals, non-invasive, high-precision and real-time physiological signal monitoring such as pulse wave (PPG) and heart rate parameter extraction can be achieved.

[0044] Additional aspects and advantages of the embodiments of the application will be described and shown in part in the following description, or will be explained by the implementation of the embodiments of the application. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings described below are some embodiments of the application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0046] Figure 1 is a schematic diagram of the hierarchical structure of the photodiode of the application;

[0047] Figure 2 is a schematic diagram of the hierarchical structure of the field effect transistor of the application;

[0048] Figure 3 is a schematic diagram of the assembly structure of the human health monitoring system of the application;

[0049] Figure 4 is a PPG signal waveform diagram collected by the human health monitoring system of the application;

[0050] Figure 5 is a current-voltage (I-V) curve diagram corresponding to the photoelectric device of Example 1 and Comparative Example 1 of the application;

[0051] Figure 6is a specific plot of specific detectivity of the photoelectric device of Example 1 and Comparative Example 1 of the present application;

[0052] Figure 7 is a specific plot of the results of the bending cycle test of the photoelectric device of Example 1 and Comparative Example 1 of the present application.

[0053] Reference signs:

[0054] 11-Ag electrode; 12-BCP layer; 13-C60 layer; 14-PCBM layer; 15-first CsFAMA layer; 16-first SAM layer; 17-first ITO layer; 18-PET layer; 21-source-drain electrode; 22-second CsFAMA layer; 23-second SAM layer; 24-Al2O3 dielectric layer; 25-second ITO layer; 31-LED light source; 32-amplifier; 33-oscilloscope; 34-photoelectric device. DETAILED DESCRIPTION

[0055] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0056] The specific experimental steps or conditions not mentioned in the following examples and comparative examples can be performed according to the conventional experimental steps described in the literature in the art or the operation or conditions. The reagents or instruments not mentioned by the manufacturer are all conventional reagent products that can be obtained by purchase.

[0057] Example 1

[0058] The present embodiment provides a photoelectric diode structure for a photoelectric detector, as shown in Figure 1 The structure is sequentially from bottom to top: PET layer 18, first ITO layer 17, first SAM layer 16, first CsFAMA layer 15, PCBM layer 14, C60 layer 13, BCP layer 12, Ag electrode 11.

[0059] The preparation steps include:

[0060] S100, cleaning of the transparent conductive substrate layer

[0061] The transparent conductive substrate layer is sequentially ultrasonically cleaned with ethanol, acetone and deionized water for 15 minutes each time, then dried with nitrogen, and then treated with ultraviolet ozone for 15 minutes; the transparent conductive substrate layer is formed by a flexible substrate PET layer 18 and a first ITO layer 17 deposited on the PET layer 18, and the overall thickness of the transparent conductive substrate layer can be flexibly adjusted according to the design requirements of the device, and the thickness used in the present embodiment is 175 μm;

[0062] S101, depositing a self-assembled monolayer (SAM)

[0063] [4-(7H-dibenzo[carbazol-7-yl)butyl]phosphonic acid (4PADCB) is dissolved in anhydrous ethanol to form a self-assembled monolayer solution with a concentration of 0.5 mg / mL;

[0064] The self-assembled monolayer solution is spin-coated on the surface of the substrate, i.e., the first ITO layer 17, and annealed to form a self-assembled monolayer, i.e., the first SAM layer 16; the spin-coating speed is 3000 rpm, the spin-coating time is 30 s, the thickness is 1-5 nm, the annealing temperature is 100°C, and the annealing time is 10 min;

[0065] S200, preparing a perovskite (CsFAMA) precursor solution

[0066] N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) are mixed in a volume ratio of 4:1 to obtain a mixed solvent;

[0067] Methylammonium bromide (MABr), lead bromide (PbBr2), lead iodide (PbI2), formamidinium iodide (FAI), and cesium iodide (CsI) powders are dissolved in the mixed solvent to obtain a perovskite (CsFAMA) precursor solution; the molar ratio of MABr, PbBr2, PbI2, FAI, and CsI is 0.2:0.2:1.2:1.15:0.07, and the concentration of Pb 2 + is 1.75 mol / L.

[0068] S201, preparing a perovskite layer

[0069] The perovskite precursor solution is spin-coated on the first SAM layer 16 and annealed to form a first CsFAMA layer 15; the spin-coating speed is 6000 rpm, the spin-coating time is 30 s, and the thickness of the first CsFAMA layer 15 is 500 nm; the anti-solvent ethyl acetate is added dropwise at about 27 s; the annealing temperature is 105°C, and the annealing time is 25 min;

[0070] S300, preparing an electron transport layer

[0071] Phenyl-C61-butyric acid methyl ester (PCBM) is dissolved in chlorobenzene to obtain a PCBM solution with a concentration of 20 mg / mL; the PCBM solution is deposited on the surface of the first CsFAMA layer 15 by spin-coating to form a PCBM layer 14; the spin-coating speed is 3000 rpm, the spin-coating time is 30 s, and the thickness of the PCBM layer 14 is 50 nm.

[0072] S301, preparing a buffer layer and an electrode

[0073] A C60 layer 13 with a thickness of 30 nm is formed by evaporation on the PCBM layer 14;

[0074] A 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline BCP layer 12 with a thickness of 7 nm is formed by evaporation on the C60 layer 13;

[0075] An Ag electrode 11 with a thickness of 80 nm is formed by evaporation on the BCP layer 12 as the top electrode of the device;

[0076] The above evaporation processes are all completed under high vacuum conditions with a vacuum degree lower than 1×10 - Pa.

[0077] S302, encapsulation processing, the effective photoelectric detection area of the obtained photodiode structure is 6 mm 2 .

[0078] Embodiment 2

[0079] This embodiment provides a field effect transistor (FET) structure, as shown in the figure, the structure is sequentially from bottom to top: a second ITO layer 25, an Al2O3 dielectric layer 24, a second SAM layer 23, a second CsFAMA layer 22, and a source-drain electrode 21. Figure 2

[0080] S100, cleaning of the transparent conductive substrate layer

[0081] The transparent conductive substrate layer is an indium tin oxide (ITO) material, denoted as the second ITO layer 25, and the thickness of the second ITO layer 25 can be selected, such as 100-200 nm, and the thickness of the second ITO layer 25 in this embodiment is 150 nm.

[0082] The conductive layer is pre-patterned to form a bottom gate structure required by the device; the second ITO layer 25 is sequentially subjected to ultrasonic cleaning in ethanol, acetone and deionized water for 15 minutes each time, then dried with nitrogen, and treated under ultraviolet ozone conditions for 15 minutes;

[0083] S101, dielectric layer deposition

[0084] An Al2O3 dielectric layer 24 with a thickness of 50 nm is deposited on the second ITO layer 25 by atomic layer deposition (ALD);

[0085] S102, self-assembled monolayer (SAM) deposition

[0086] [4-(7H-dibenzo[7H]carbazol-7-yl)butyl]phosphonic acid (4PADCB) is dissolved in anhydrous ethanol to form a self-assembled monolayer solution with a concentration of 0.5 mg / mL; ​

[0087] The self-assembled monomolecular solution is spin-coated on the Al2O3 dielectric layer 24 and annealed to form the second SAM layer 23; wherein the spin-coating speed is 3000 rpm, the spin-coating time is 30 s, the thickness of the second SAM layer 23 is 1-5 nm, the annealing temperature is 100°C, and the annealing time is 10 min;

[0088] S200, preparing a perovskite (CsFAMA) precursor solution

[0089] N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) are mixed in a volume ratio of 4:1 to obtain a mixed solvent;

[0090] Methylamine bromide (MABr), lead bromide (PbBr2), lead iodide (PbI2), formamidinium hydroiodide (FAI), and cesium iodide (CsI) powder are dissolved in the mixed solvent, i.e. the precursor solution is obtained; wherein the molar ratio of MABr, PbBr2, PbI2, FAI, and CsI is 0.2:0.2:1.2:1.15:0.07, and the concentration of Pb2+ in the precursor solution can be adjusted, such as 1.0-1.8 mol / L, and 1.5 mol / L is selected in this embodiment. 2

[0091] S201, preparing a perovskite layer

[0092] The perovskite precursor solution is spin-coated on the second SAM layer 23 and annealed to form the second CsFAMA layer 22; the thickness of the second CsFAMA layer 22 can be selected, such as 300-700 nm, and in this embodiment, the spin-coating speed is 6000 rpm, the spin-coating time is 30 s, and the thickness of the second CsFAMA layer 22 is 400 nm;

[0093] The anti-solvent ethyl acetate is added at about 27 s; in addition, the annealing temperature is 105°C, and the annealing time is 25 min;

[0094] S300, preparing an electron transport layer

[0095] A chromium (Cr) layer with a thickness of 3 nm and a gold (Au) layer with a thickness of 30 nm are sequentially deposited on the surface of the second CsFAMA layer 22 by thermal evaporation to form an interdigital source-drain electrode 21. The electrode pattern is formed by direct evaporation using a metal mask, and the finally constructed source-drain electrode 21 has a channel length of 5 μm and a channel width of 15 mm.

[0096] Example 3

[0097] The embodiment provides a preparation method of a photodiode structure for a photodetector, comprising the following steps:

[0098] S100, cleaning a transparent conductive substrate layer​

[0099] The transparent conductive substrate layer was ultrasonically cleaned with ethanol, acetone and deionized water in turn, each for 15 minutes, and then dried with nitrogen, and then treated with ultraviolet ozone for 15 minutes;

[0100] S101, self-assembled monolayer (SAM) deposition

[0101] Dissolve [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl] phosphonic acid (MeO-2PACz) in anhydrous ethanol to form a self-assembled monolayer solution with a concentration of 0.5 mg / mL;

[0102] Spin-coat the self-assembled monolayer solution on the surface of the substrate and anneal to form a self-assembled monolayer; the spin-coating speed is 2500 rpm, the spin-coating time is 25 s, the annealing temperature is 90°C, and the annealing time is 8 min;

[0103] S200, preparation of perovskite (CsFAMA) precursor solution

[0104] Mix N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of 4:1 to obtain a mixed solvent;

[0105] Dissolve methylammonium bromide (MABr), lead bromide (PbBr2), lead iodide (PbI2), formamidinium hydroiodide (FAI), and cesium iodide (CsI) powder in the mixed solvent to obtain a perovskite (CsFAMA) precursor solution; wherein the molar ratio of MABr, PbBr2, PbI2, FAI, and CsI is 0.2:0.2:1.2:1.15:0.07.

[0106] S201, preparation of perovskite layer

[0107] Spin-coat the perovskite precursor solution on the SAM layer and anneal to form a CsFAMA layer; wherein the spin-coating speed is 5000 rpm, the spin-coating time is 25 s, and the anti-solvent ethyl acetate is added at about 24 s; the annealing temperature is 100°C, and the annealing time is 8 min;

[0108] S300, preparation of electron transport layer

[0109] Dissolve phenyl-C61-butyric acid methyl ester (PCBM) in chlorobenzene to obtain a PCBM solution with a concentration of 20 mg / mL; deposit the PCBM solution on the surface of the CsFAMA layer using a spin-coating method to form a PCBM layer; wherein the spin-coating speed is 3000 rpm, and the spin-coating time is 30 seconds.

[0110] S301, preparation of buffer layer and electrode

[0111] A C60 layer with a thickness of 30 nm is formed by evaporation on the PCBM layer;

[0112] A BCP layer with a thickness of 7 nm is formed by evaporation on the C60 layer;

[0113] An Ag electrode with a thickness of 80 nm is formed by evaporation on the BCP layer as a top electrode of the device;

[0114] The above evaporation processes are all completed under high vacuum conditions with a vacuum degree less than 1x10 - Pa.

[0115] S302, packaging processing, to obtain a photodiode.

[0116] Embodiment 4

[0117] The embodiment provides a preparation method of a photodiode structure for a photodetector, including the following steps:

[0118] S100, cleaning of a transparent conductive substrate layer

[0119] The transparent conductive substrate layer is sequentially subjected to ultrasonic cleaning with ethanol, acetone and deionized water, each for 15 minutes, and then dried with nitrogen, and then subjected to ultraviolet ozone treatment for 15 minutes;

[0120] S101, deposition of a self-assembled monolayer (SAM)

[0121] [4-(7H-dibenzocarbazole-7-yl)butyl] phosphonic acid (4PADCB) is dissolved in anhydrous ethanol to form a self-assembled monolayer solution with a concentration of 0.5 mg / mL;

[0122] The self-assembled monolayer solution is spin-coated on the surface of the substrate and annealed to form a self-assembled monolayer; the spin-coating speed is 3500 rpm, the spin-coating time is 40 s, the annealing temperature is 105 DEG C, and the annealing time is 15 min;

[0123] S200, preparation of a perovskite (CsFAMA) precursor solution

[0124] N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) are mixed in a volume ratio of 4:1 to obtain a mixed solvent;

[0125] Methyl amine bromide (MABr), lead bromide (PbBr2), lead iodide (PbI2), formamidinium hydroiodide (FAI) and cesium iodide (CsI) powders are dissolved in the mixed solvent to obtain a perovskite (CsFAMA) precursor solution; wherein the molar ratio of MABr, PbBr2, PbI2, FAI and CsI is 0.2:0.2:1.2:1.15:0.07.

[0126] S201, Preparation of perovskite layer

[0127] A perovskite precursor solution was spin-coated onto the SAM layer and annealed to form a CsFAMA layer. The spin-coating speed was 6500 rpm and the spin-coating time was 40 s. Ethyl acetate was added dropwise when the spin-coating time was about 28 s. The annealing temperature was 120 °C and the annealing time was 15 min.

[0128] S300, Fabrication of electron transport layer

[0129] Methyl phenyl-C61-butyrate (PCBM) was dissolved in chlorobenzene to obtain a PCBM solution with a concentration of 20 mg / mL. The PCBM solution was then deposited onto the surface of a CsFAMA layer using a spin-coating method to form a PCBM layer. The spin-coating speed was 3000 rpm and the spin-coating time was 30 seconds.

[0130] S301, Preparation of buffer layer and electrode

[0131] A C60 layer with a thickness of 30 nm was deposited on the PCBM layer by vapor deposition;

[0132] A BCP layer with a thickness of 7 nm was deposited on the C60 layer by vapor deposition;

[0133] An 80 nm thick Ag electrode is deposited on the BCP layer to serve as the top electrode of the device.

[0134] The above vapor deposition processes are all performed under vacuum conditions below 1×10⁻⁶. - Completed under high vacuum conditions of Pa.

[0135] S302, Packaging process, resulting in a photodiode.

[0136] Example 5

[0137] like Figure 3 As shown, this embodiment provides a human health monitoring system, including: an LED light source 31, an optoelectronic device 34, and a signal processing unit. The LED light source 31 emits near-infrared light signals to illuminate a target area of ​​the human body (such as a finger). Because near-infrared light has good tissue penetration capabilities, its intensity periodically decreases with changes in blood flow within the tissue, providing a basis for subsequent optical signal detection.

[0138] The optoelectronic device 34 is positioned below the target area (e.g., on the other side of a finger) to receive residual light signals after penetrating the tissue. The perovskite-based optoelectronic device 34, such as a photodiode, converts the received light signal into an electrical signal corresponding to changes in light intensity; the signal processing unit can then visualize the electrical signal as a voltage-time image.

[0139] Preferably, the health monitoring system of the present application further comprises an amplifier 32 and an oscilloscope 33, the amplifier 32 is electrically connected with the optoelectronic device 34 for amplifying the electrical signal output by the optoelectronic device 34, improving the signal amplitude and signal-to-noise ratio, and facilitating subsequent analysis. The oscilloscope 33 is connected with the amplifier 32 for real-time acquisition and display of the amplified electrical signal waveform; wherein, the oscilloscope 33 is internally integrated with a signal processing unit for converting the electrical signal into a voltage-time image, and extracting PPG feature information based on the waveform period change, and then calculating and outputting the parameter results reflecting the heart rate of the human body.

[0140] Further, the perovskite photodiode described in Example 1 of the present application is used as the optoelectronic device 34, an LED light source with a wavelength of 700 nm is selected to irradiate the finger target area, and the PPG signal waveform of the human body obtained by the system is as shown in Figure 4 From the figure, the periodic electrical signal change corresponding to the pulse activity of the human body can be clearly observed, verifying the effective acquisition and conversion capability of the system for the pulse signal, and indicating that the system can stably realize real-time monitoring of the heart rate of the human body.

[0141] The optoelectronic device provided by the present application has a good flexible structure and excellent photoelectric performance, and is suitable for the field of human health monitoring and analysis, especially for real-time monitoring of various physiological signals such as heart rate, blood oxygen, skin temperature, etc. Preferably, the optoelectronic device can be integrated into various wearable electronic devices, such as smart bracelets, health patches, electronic skins, etc., forming a lightweight and flexible health perception system; at the same time, the device can also be used in flexible display and sensing systems as a photosensitive component or multifunctional sensor, and is widely used in environmental monitoring, human-computer interaction, intelligent terminals and other flexible electronic scenes.

[0142] Comparative Example 1

[0143] The difference between the present comparative example and Example 1 is only that no SAM layer is deposited, but a traditional PEDOT:PSS is used as a hole transport layer;

[0144] The specific process is as follows:

[0145] PEDOT:PSS solution is prepared and spin-coated on the ITO layer, annealed, the spin-coating speed is 3000 rpm, the spin-coating time is 30 s; the annealing temperature is 100℃, and the annealing time is 10 min.

[0146] Experimental Example 1

[0147] The performance of the photodiodes prepared in Example 1 and Comparative Example 1 is tested in the present experimental example, which specifically includes:

[0148] (1) Photocurrent, dark current

[0149] To further verify the photoelectric response performance of the photoelectric device, a solar simulator (model: SS-F5-3A, Enlitech) was used to test the device under AM 1.5 standard light conditions (light intensity of 100 mW / cm 2 ). The current response curve of the device under different voltages was recorded by a source table (model: Keithley 2612B). The dark current and photocurrent performance of the devices prepared by Example 1 and Comparative Example 1 were tested, respectively, and the test results are shown in Figure 5 .

[0150] As can be seen from Figure 5 , the dark current density of the device of Comparative Example 1 is as high as 1.51 x 10 - A / cm 2 , while the dark current density of the device of Example 1 is significantly reduced, only 1.92 x 10 - A / cm 2 , which is nearly an order of magnitude lower, indicating that the introduction of the self-assembled monolayer in this embodiment effectively suppresses the interface defects and carrier recombination, and improves the dark state stability and noise control ability of the device.

[0151] Under light conditions, the device of Example 1 exhibits higher light response performance, with a photocurrent density significantly higher than that of the device of Comparative Example 1. This performance improvement is mainly due to the more regular surface morphology and higher crystalline quality of the perovskite film in Example 1, as well as the more optimal interface energy level arrangement achieved under the regulation of the self-assembled monolayer, thereby improving the separation efficiency and collection efficiency of the photo-generated carriers.

[0152] The present application significantly improves the crystalline quality and interface energy level matching of the perovskite film by introducing a self-assembled monolayer (SAM) instead of a traditional PEDOT:PSS hole transport layer in the structure of a perovskite photoelectric device, effectively reduces interface defects and carrier recombination, thereby significantly suppressing dark current, improving photocurrent response, and enhancing the stability of the device in a flexible state. Compared to the PEDOT:PSS layer, which is easily hygroscopic, strongly acidic, and easily degradable, the SAM layer has superior interface regulation ability, chemical stability, and processing simplicity, and exhibits higher performance potential and application value for flexible electronic devices.

[0153] (2) Specific detectivity performance

[0154] To verify the detection sensitivity of the photoelectric device, the specific detectivity performance of the photoelectric devices prepared by Example 1 and Comparative Example 1 was compared and tested, and the test results are shown in Figure 6 . Figure 6It can be seen that, by introducing the self-assembled monolayer (SAM), the embodiment 1 effectively regulates the crystallization behavior of the perovskite film, significantly improves the compactness and uniformity of the film, and further improves the interface quality and carrier transport efficiency. Benefiting from the above optimization, the maximum specific detectivity of the device corresponding to the embodiment 1 is better than that of the comparative example 1.

[0155] The specific detectivity is one of the key parameters for measuring the performance of a photodetector. The higher the value, the stronger the photodetector is in low light intensity environment, which can effectively identify weak light signals, reflecting the high sensitivity and low noise characteristics of the device. By introducing the self-assembled monolayer (SAM) to accurately regulate the interface, the crystalline quality of the perovskite layer and the interface energy level matching are significantly improved, thereby effectively suppressing the dark current and enhancing the light response signal, achieving a higher specific detectivity.

[0156] (3) Mechanical bending stability test

[0157] To verify the structural stability and performance retention ability of the photodetector in the flexible condition, the mechanical bending stability test was performed on the devices of the embodiment 1 and the comparative example 1. During the test, the standard bending test fixture was used to repeatedly bend the device sample, and the cumulative cycle number was 1000 times. As shown in Figure 7 , the photodetector prepared in the embodiment 1 still maintains more than 80% of the initial value after 1000 bending cycles, showing good mechanical stability; in contrast, the response degree of the photodetector of the comparative example 1 decreases to about 50% of the initial value, and the performance decays obviously.

[0158] It can be seen that the self-assembled monolayer (SAM) introduced in the present application not only optimizes the crystalline quality and interface structure of the perovskite film, but also significantly improves the mechanical strain adaptability of the device on the flexible substrate, thereby enhancing the bending resistance and long-term operation stability of the overall device, which has important significance for the practical application of wearable health monitoring devices and flexible electronic devices.

[0159] Obviously, the above embodiments are only examples for clearly illustrating, but not limiting the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A photovoltaic device based on self-assembled monolayer modified perovskite, characterized in that: comprising a perovskite layer, the perovskite layer is deposited on a self-assembled monolayer; wherein the self-assembled monolayer comprises one or both of a phosphoric acid-based self-assembled monolayer based on a carbazole structure and a phosphonic acid-based self-assembled monolayer based on a carbazole structure. The self-assembled monolayer comprises one or both of a [4-(7H-dibenzo carbazole-7-yl) butyl] phosphonic acid layer and a [2-(3, 6-dimethoxy-9H-carbazole-9-yl) ethyl] phosphonic acid layer. The photovoltaic device comprises, from bottom to top, a transparent conductive substrate layer, a self-assembled monolayer, a perovskite layer, an electron transport layer, a buffer layer, and a top electrode.

2. The perovskite-modified optoelectronic device based on self-assembled monolayers according to claim 1, wherein: Alternatively, the photovoltaic device comprises, from bottom to top, a transparent conductive substrate layer, a dielectric layer, a self-assembled monolayer, a perovskite layer, and a source-drain electrode.

3. The self-assembled monolayer-modified perovskite-based optoelectronic device according to claim 1 or 2, wherein: The buffer layer comprises a C60 electron auxiliary transport layer and a 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline hole blocking layer deposited on the C60 electron auxiliary transport layer. And / or, the dielectric layer comprises an aluminum oxide dielectric layer.

4. The perovskite-modified optoelectronic device based on self-assembled monolayers according to claim 3, wherein: And / or, the transparent conductive substrate layer is an indium tin oxide layer or an indium tin oxide layer deposited on a flexible substrate. Comprising: S1, spin coating a self-assembled monolayer solution on the surface of a substrate, annealing to form a self-assembled monolayer; 5. A method of fabricating an optoelectronic device as claimed in any one of claims 1 to 4, characterized in that: wherein the self-assembled monolayer solution comprises one or both of a phosphoric acid-based organic solution based on a carbazole structure and a phosphonic acid-based organic solution based on a carbazole structure; S2, spin coating a perovskite precursor solution on the surface of the self-assembled monolayer, annealing to form a perovskite layer; S3, constructing a device functional structure on the surface of the perovskite layer, packaging, and obtaining. 6.The method of claim 5, characterized in that: in the step S1, the spin coating speed is 2500-3500 rpm, and the spin coating time is 25-40 s; And / or, in the step S1, the annealing temperature is 90-105℃, and the annealing time is 8-15 min. 7.The method of claim 5 or 6, characterized in that: in the step S2, an anti-solvent is added during the process of spin coating the perovskite precursor solution; Preferably, in the step S2, the spin coating speed is 5000-6500 rpm, and the spin coating time is 25-40 s, and the anti-solvent is added at about 24-28 s. In the step S3, an electron transport layer is deposited on the surface of the perovskite layer, and a buffer layer and a top electrode are sequentially evaporated. Alternatively, in the step S3, a source-drain electrode is evaporated on the surface of the perovskite layer.

8. A method of fabricating an optoelectronic device according to any one of claims 5-7, wherein: Comprising: an LED light source for emitting near-infrared light signals to a human target area; 9. A human health monitoring system characterized by: the photovoltaic device of any one of claims 1-4 for receiving light signals transmitted through the human target area and converting them into electrical signals; a signal processing unit for processing the electrical signals output by the photovoltaic device. 10.Use of the photovoltaic device of any one of claims 1-4 in health monitoring and analysis of the human body; Preferably, the photovoltaic device is used in wearable electronic devices, flexible displays, or sensing systems. ​ ​

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