An optoelectronic absorption conversion layer, a self-powered optoelectronic detector, and a preparation method thereof

Abstract

The present invention provides a photoabsorptive conversion layer, a self-powered photodetector and a preparation method thereof, belonging to the field of photodetection. The photoabsorptive conversion layer provided by the present invention comprises three layers of Bi x FeO3 film layers, where 1 ≤ x < 1.1 in each Bi x FeO3 film layer, and the values of x in each Bi x FeO3 film layer are different. The open-circuit voltage of the self-powered photodetector prepared from the photoabsorptive conversion layer provided by the present invention is 0.46 - 0.66 V and the short-circuit current is 1.13 - 1.6×10 ‑4 A / cm 2 under the illumination condition of 500 nm. The zero-bias I-t curve under the illumination condition of 500 nm shows that the self-powered photodetector has a stable optical response phenomenon; by adjusting the values of x in each Bi x FeO3 film layer, a photoabsorptive conversion layer with different longitudinal distributions of defect concentrations is designed, and further the regulation of the photocurrent density and the photogenerated voltage of the self-powered photodetector is realized.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic detection, and particularly to a photoabsorption conversion layer, a self-powered photodetector and a preparation method thereof. Background Art

[0002] Optoelectronic detectors have broad application prospects in fields such as communication, environmental monitoring, missile detection, and astronomical research. Optoelectronic detectors can be divided into optoelectronic detectors with an externally applied bias voltage and self-powered optoelectronic detectors. Optoelectronic detectors with an externally applied bias voltage need to apply an external bias voltage to the device as the driving force for the separation of photo-generated electrons and holes to obtain excellent detection performance. However, the addition of an external power supply is not conducive to the miniaturization and integration of optoelectronic detection devices. Therefore, the research and development of self-powered optoelectronic detectors have gradually become the mainstream.

[0003] The main working mode of a self-powered optoelectronic detector is to separate photo-generated electrons and holes through the built-in electric field inside the device, so as to generate a significant photocurrent under the condition of no externally applied bias voltage. Ferroelectric material thin films use the internal polarization electric field as the built-in electric field to drive the separation and transport of photo-generated carriers, and can realize optoelectronic detection, and can be used as the photoabsorption conversion layer in self-powered optoelectronic detectors. However, the depolarization field inside a single-component ferroelectric material is too high, resulting in the unstable existence of the internal polarization electric field in the ferroelectric material thin film, which is not conducive to the improvement of optoelectronic performance and stability. It is necessary to regularly maintain the stability of the internal polarization electric field by means of external electric field polarization. This polarization step makes the application process of the device more cumbersome; when a thin film formed by compounding different ferroelectric materials is used as the photoabsorption conversion layer in a self-powered optoelectronic detector, due to the diffusion between different ferroelectric materials, the detection performance of the optoelectronic detector is unstable. Summary of the Invention

[0004] The purpose of the present invention is to provide a photoabsorption conversion layer, a self-powered photodetector and a preparation method thereof. The photoabsorption conversion layer provided by the present invention has high detection stability and light responsivity when used in a self-powered photodetector.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a photoabsorption conversion layer, including three Bi x FeO3 film layers, where 1≤x<1.1 in each Bi x FeO3 film layer, and the x values in each Bi x FeO3 film layer are different.

[0007] Preferably, the thicknesses of each Bi x FeO3 film layer are the same, all being 75~100nm.

[0008] The present invention also provides a self-powered photoelectric detector, comprising a substrate, a bottom electrode, the photoelectric absorption conversion layer described in the above technical solution, and a top electrode which are arranged in sequence.

[0009] Preferably, the bottom electrode and the top electrode are both made of gold.

[0010] Preferably, the thickness of the bottom electrode and the top electrode is independently 30-50 nm.

[0011] The present invention also provides a method for preparing the self-powered photodetector described in the above technical solution, comprising the following steps:

[0012] (1) sputtering a bottom electrode on a substrate to obtain a first composite;

[0013] (2) preparing Bi on the bottom electrode surface of the first composite obtained in step (1) layer by layer x FeO3 film layer, the second composite is obtained; each layer of Bi x The preparation of FeO3 film includes spin coating Bi x FeO3 gel and annealing treatment;

[0014] (3) sputtering a top electrode on the surface of the photoelectric absorption conversion layer of the second composite obtained in step (2) to obtain a self-powered photodetector.

[0015] Preferably, the temperature of each annealing treatment in step (2) is 600° C., and the time of each annealing treatment is 3 minutes.

[0016] Preferably, a thermal decomposition treatment is performed before each annealing treatment.

[0017] Preferably, the temperature of each thermal decomposition treatment is 320-380° C., and the time of each thermal decomposition treatment is 3-5 min.

[0018] Preferably, in step (1) and step (3), the sputtering power is independently 6-10 W, the sputtering time is independently 280-320 s, and the rotation speed of the turntable during sputtering is independently 14-16 r / min.

[0019] The present invention provides a photoelectric absorption conversion layer, comprising three layers of Bi x FeO3 film, each layer of Bi x In the FeO3 film, 1≤x<1.1, and each layer of Bi x The x value in the FeO3 film is different. x FeO3 film is used as photoelectric absorption conversion layer, Bi x FeO3 has room temperature multiferroicity and high remanent polarization strength (about 100µC / cm 2)(and Curie temperature (about 830 °C), a relatively low bandgap (<2.8 eV). At the same time, as the chemical composition of the optoelectronic absorption conversion layer is single, it can make the detection performance of the self-powered photodetector prepared from this optoelectronic absorption conversion layer stable and the response time short; by adjusting the x value of each layer of the optoelectronic absorption conversion layer, the longitudinal distribution of the internal defect concentration of the optoelectronic absorption conversion layer is realized. Different distributions of the longitudinal defect concentration in the optoelectronic absorption conversion layer can affect the longitudinal polarization electric field inside the thin film, thereby realizing the regulation of the detection performance of the photodetector. The results of the examples show that the open-circuit voltage of the self-powered photodetector prepared from the optoelectronic absorption conversion layer provided by the present invention is 0.46 - 0.66 V and the short-circuit current is 1.13 - 1.6×10 -4 A / cm 2 , and the zero-bias I-t curve under 500 nm light illumination shows that the self-powered photodetector has a stable light response phenomenon.

[0020] In addition, the optoelectronic absorption conversion layer provided by the present invention can design optoelectronic absorption conversion layers with different longitudinal distributions of defect concentrations by adjusting the x value in each layer of Bi x FeO3 film layer, thereby realizing the regulation of the photocurrent and photovoltage of the self-powered photodetector. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of the self-powered photodetector in the embodiment of the present invention;

[0022] Figure 2 is a photovoltaic curve graph of the self-powered photodetector in Examples 1 - 3 of the present invention under dark and 500 nm light illumination;

[0023] Figure 3 is a zero-bias I-t curve graph of the self-powered photodetector in Examples 1 - 3 of the present invention under 500 nm light illumination;

[0024] Figure 4 is a photovoltaic curve graph of the self-powered photodetector in Comparative Example 1 of the present invention under 500 nm light illumination;

[0025] Figure 5 is a photovoltaic curve graph of the self-powered photodetector in Comparative Example 2 of the present invention under 500 nm light illumination;

[0026] Figure 6 is a photovoltaic curve graph of the self-powered photodetector in Comparative Example 3 of the present invention under 500 nm light illumination and 365 nm ultraviolet light illumination. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present invention provides an optoelectronic absorption conversion layer, including 3 layers of Bi xFeO3 film layer, each layer of Bi x In the BiFeO3 film layer, 1 ≤ x < 1.1, and each layer of Bi x The values of x in the BiFeO3 film layer are different.

[0028] In the present invention, the Bi x The number of layers of the BiFeO3 film layer is 3. In the present invention, each layer of Bi x In the BiFeO3 film layer, 1 ≤ x < 1.1, preferably 1 ≤ x < 1.07; each layer of Bi x The values of x in the BiFeO3 film layer are different. In the embodiments of the present invention, the Bi x The value of x in the FeO3 film layer can be 1, 1.03, and 1.07. The present invention limits the number of layers of the Bi x FeO3 film layer, the value range of x in each layer of Bi x FeO3 film layer to the above range and limits that the values of x in each layer of Bi x FeO3 film layer are different, which can ensure the existence of a longitudinal defect concentration difference inside the photoabsorption conversion layer, and further improve the photodetection performance of the self-powered photodetector.

[0029] In the present invention, the thickness of each layer of the photoabsorption conversion layer is preferably the same, all being 75 - 100 nm, more preferably all being 75 - 90 nm, and further preferably all being 75 - 80 nm. Limiting the thickness of each layer of the photoabsorption conversion layer to the above range in the present invention can make the overall photoabsorption conversion layer have an appropriate thickness and is beneficial to the regulation of defects in the photoabsorption conversion layer.

[0030] The present invention uses a multi-layer Bi x FeO3 film layer as the photoabsorption conversion layer. Bi x FeO3 has room-temperature multiferroicity, a relatively high remanent polarization intensity (about 100 µC / cm 2 ), and a Curie temperature (about 830 °C), a relatively low bandgap (<2.8 eV). At the same time, as the chemical composition of the photoabsorption conversion layer is single, it can make the self-powered photodetector prepared from this photoabsorption conversion layer have stable detection performance and short response time; by adjusting the value of x of each layer of the photoabsorption conversion layer, the longitudinal distribution of defect concentration inside the photoabsorption conversion layer is realized. Different distributions of longitudinal defect concentration in the photoabsorption conversion layer can change the state of the polarization electric field inside the thin film, and thus realize the regulation of the detection performance of the photodetector.

[0031] The present invention also provides a self-powered photodetector, including a substrate, a bottom electrode, the photoabsorption conversion layer described in the above technical solution, and a top electrode arranged in sequence.

[0032] The self-powered photodetector provided by the present invention includes a substrate. As an embodiment of the present invention, the substrate can be a Si / SiO2 substrate.

[0033] The self-powered photodetector provided by the present invention further includes a bottom electrode disposed on the surface of the substrate.

[0034] As an embodiment of the present invention, when the substrate is a Si / SiO2 substrate, the bottom electrode is disposed on the SiO2 surface of the substrate.

[0035] In the present invention, the material of the bottom electrode is preferably gold; the thickness of the bottom electrode is preferably 30-50 nm, more preferably 40-50 nm, and further preferably 50 nm. Limiting the material and thickness of the bottom electrode within the above ranges in the present invention can keep the bottom electrode layer having good electrical conductivity and light transmittance.

[0036] The self-powered photodetector provided by the present invention further includes a photoabsorption conversion layer disposed on the surface of the bottom electrode. The photoabsorption conversion layer is the photoabsorption conversion layer described in the above technical solution.

[0037] The self-powered photodetector provided by the present invention further includes a top electrode disposed on the surface of the photoabsorption conversion layer.

[0038] In the present invention, the material of the top electrode is preferably gold; the thickness of the top electrode is preferably 30-50 nm, more preferably 40-50 nm, and further preferably 50 nm. Limiting the material and thickness of the top electrode within the above ranges in the present invention can keep the top electrode layer having good electrical conductivity and light transmittance.

[0039] In the present invention, the top electrode does not completely cover the photoabsorption conversion layer. In the present invention, the top electrode not completely covering the photoabsorption conversion layer can promote the utilization of light by the photoabsorption conversion layer and ensure that the self-powered photodetector has good photodetection performance.

[0040] As an embodiment of the present invention, the top electrode can be a circular dot electrode with a diameter of 200 μm.

[0041] The present invention also provides a preparation method of the self-powered photodetector described in the above technical solution, including the following steps:

[0042] (1) Sputtering a bottom electrode on the substrate to obtain a first composite;

[0043] (2) Layer by layer preparing a Bi x FeO3 film layer on the surface of the bottom electrode of the first composite obtained in the step (1) to obtain a second composite; The preparation of each layer of Bi x FeO3 film layer includes spin-coating Bi xFeO3 gel and annealing treatment;

[0044] (3) Sputter a top electrode on the surface of the photoabsorption conversion layer of the second composite obtained in the step (2) to obtain a self-powered photodetector.

[0045] In the present invention, a bottom electrode is sputtered on a substrate to obtain a first composite.

[0046] In the present invention, the substrate is preferably pretreated before use; the pretreatment is preferably ultrasonic cleaning; the cleaning liquids used for the ultrasonic cleaning are preferably dilute hydrochloric acid, acetone, deionized water, and absolute ethanol in sequence. The present invention has no special requirements for the concentration of the dilute hydrochloric acid, and the dilute hydrochloric acid concentration commonly used by those skilled in the art in ultrasonic cleaning can be adopted. The present invention has no special limitations on the frequency and time of the ultrasonic cleaning, and the ultrasonic cleaning frequency and time commonly used by those skilled in the art can be adopted.

[0047] As an embodiment of the present invention, when the cleaning liquid used for the ultrasonic cleaning is dilute hydrochloric acid, the time of the ultrasonic cleaning can be 2 min; when the cleaning liquid used for the ultrasonic cleaning is acetone, deionized water, or absolute ethanol, the time of the ultrasonic cleaning can be 8 min.

[0048] After the ultrasonic cleaning, the present invention preferably wipes and dries the substrate after the ultrasonic cleaning to obtain a pretreated substrate.

[0049] In the present invention, the wiping is preferably performed with lens cleaning paper.

[0050] As an embodiment of the present invention, the drying can be carried out above a flat furnace; the temperature of the drying can be 150 °C; the time of the drying can be 5 min.

[0051] After the drying is completed, the present invention preferably air-cools the dried substrate to room temperature.

[0052] In the present invention, the sputtering of the bottom electrode is preferably carried out in a magnetron sputtering instrument; the power of the sputtering is preferably 6 - 10 W, more preferably 8 W; the time of the sputtering is preferably 280 - 320 s, more preferably 300 s; the rotation speed of the turntable during the sputtering is preferably 14 - 16 r / min, more preferably 15 r / min. The present invention sets the sputtering parameters of the bottom electrode within the above ranges to ensure uniform sputtering of the bottom electrode and the top electrode, improve the quality of the bottom electrode layer and the top electrode layer, and further improve the photoelectric detection performance of the self-powered photodetector.

[0053] After obtaining the first composite, the present invention prepares a Bi x FeO3 film layer on the surface of the bottom electrode of the first composite to obtain a second composite.

[0054] In the present invention, each layer of Bi x The preparation of the FeO3 film layer includes spin-coating Bi x FeO3 gel and annealing treatment in sequence.

[0055] The present invention does not particularly limit the preparation method of the Bi x FeO3 gel. The Bi x FeO3 gel can be prepared by using the sol-gel method commonly used by those skilled in the art.

[0056] The present invention does not particularly limit the operation of the spin-coating. The operation well-known to those skilled in the art can be adopted, and the thickness of each layer of spin-coated Bi x FeO3 gel after annealing treatment is 75 - 100 nm.

[0057] The present invention preferably performs a thermal decomposition treatment before each annealing treatment.

[0058] As an embodiment of the present invention, the temperature of each thermal decomposition treatment can be 320 - 380 °C, or can also be 350 °C; the time of each thermal decomposition treatment can be 3 - 5 min, or can also be 4 min. The present invention limits the temperature and time of each thermal decomposition treatment within the above ranges to remove the organic solvents inside the film formed by spin-coating the Bi x FeO3 gel.

[0059] In the present invention, the temperature of each annealing treatment is preferably 580 - 620 °C, more preferably 600 °C; the time of each annealing treatment is preferably 2 - 4 min, more preferably 3 min. The present invention sets the temperature and time of each annealing within the above ranges to crystallize the Bi x FeO3 gel and obtain a crystalline Bi x FeO3 film layer (photoelectric absorption conversion layer).

[0060] After the heat preservation of each annealing treatment is completed, the present invention preferably air-cools the composite body after the heat preservation of the annealing treatment to room temperature.

[0061] After obtaining the second composite body, the present invention sputters a top electrode on the upper surface of the second composite body to obtain a self-powered photodetector.

[0062] In the present invention, the parameter setting range and preferred value of sputtering the top electrode are the same as those of sputtering the bottom electrode, and will not be elaborated here.

[0063] As an embodiment of the present invention, before sputtering, a mask plate with an aperture of 200 μm can be covered on the optoelectronic absorption conversion layer, and then sputtering is carried out to obtain a dot-shaped electrode with a diameter of 200 μm.

[0064] In a specific embodiment of the present invention, the structural schematic diagram of the self-powered photodetector is as Figure 1 shown:

[0065] As can be seen from Figure 1 it, the self-powered photodetector includes a Si / SiO2 substrate, a bottom electrode, a first layer of optoelectronic absorption conversion layer, a second layer of optoelectronic absorption conversion layer, a third layer of optoelectronic absorption conversion layer, and a top electrode, which are arranged in sequence.

[0066] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0067] Example 1

[0068] An optoelectronic absorption conversion layer is composed of three Bi x FeO3 film layers, specifically, a BiFeO3 film layer, a Bi 1.03 FeO3 film layer, and a Bi 1.07 FeO3 film layer arranged in sequence. The thickness of each Bi x FeO3 film layer is 75 nm.

[0069] Example 2

[0070] An optoelectronic absorption conversion layer is composed of three Bi x FeO3 film layers, specifically, a Bi 1.07 FeO3 film layer, a Bi 1.03 FeO3 film layer, and a BiFeO3 film layer arranged in sequence. The thickness of each Bi x FeO3 film layer is 75 nm.

[0071] Example 3

[0072] An optoelectronic absorption conversion layer is composed of three Bi x FeO3 film layers, specifically, a Bi 1.03 FeO3 film layer, a BiFeO3 film layer, and a Bi 1.07 FeO3 film layer arranged in sequence. The thickness of each Bi x FeO3 film layer is 75 nm.

[0073] Comparative Example 1

[0074] An optoelectronic absorption conversion layer is a BiFeO3 film layer with a thickness of 225 nm.

[0075] Comparative Example 2

[0076] An optoelectronic absorption conversion layer is Bi 1.1 FeO3 film layer with a thickness of 225 nm.

[0077] Comparative Example 3

[0078] An optoelectronic absorption conversion layer is composed of a BiFeO3 film layer and a BaTiO3 film layer arranged in sequence. The thickness of the BiFeO3 film layer is 190 nm, and the thickness of the BaTiO3 film layer is 35 nm.

[0079] Application Example 1

[0080] A self-powered photodetector is composed of a Si / SiO2 substrate, a bottom electrode, the optoelectronic absorption conversion layer in Example 1, and a top electrode arranged in sequence; the BiFeO3 film layer of the optoelectronic absorption conversion layer in Example 1 is in contact with the bottom electrode; the materials of the bottom electrode and the top electrode are both gold; the thickness of the bottom electrode is 50 nm; the top electrode is a circular dot electrode with a diameter of 200 μm and a thickness of 50 nm;

[0081] The preparation method of the self-powered photodetector is as follows:

[0082] (1) The Si / SiO2 substrate is first ultrasonically cleaned in dilute hydrochloric acid for 2 min, and then ultrasonically cleaned in acetone, deionized water, and absolute ethanol for 8 min each in sequence. After taking it out, it is wiped clean with lens paper, and finally placed on a flat furnace and dried at 150 °C for 5 min and then air-cooled to room temperature to obtain a pretreated substrate. The pretreated substrate is fixed on a turntable, and a bottom electrode is sputtered on a magnetron sputtering instrument at a sputtering power of 8 W for 300 s to obtain a first composite body; the rotation speed of the turntable during the sputtering is 15 r / min;

[0083] (2) Three layers of Bi x FeO3 gels are spin-coated layer by layer on the surface of the bottom electrode of the first composite body obtained in step (1). The first layer is spin-coated with BiFeO3 gel, the second layer is spin-coated with Bi 1.03 FeO3 gel, and the third layer is spin-coated with Bi 1.07 FeO3 gel. After each spin-coating, it is first thermally decomposed at 350 °C for 5 min and then annealed at 600 °C for 3 min to obtain a second composite body;

[0084] (3) Fix the second composite obtained in step (2) on a turntable, cover a mask plate with an aperture of 200 μm on the surface of the photo - electric absorption conversion layer of the second composite in a magnetron sputtering instrument, and sputter for 300 s with a sputtering power of 8 W to prepare a top electrode, obtaining a self - powered photodetector; the rotation speed of the turntable during sputtering is 15 r / min.

[0085] Application Example 2

[0086] The difference between Application Example 2 and Application Example 1 is only that the photo - electric absorption conversion layer in Example 2 is adopted. The BiFeO3 film layer of the photo - electric absorption conversion layer in Example 2 contacts the bottom electrode. In the preparation method, in step (2), three layers of BiFeO3 gel with corresponding components are spin - coated, and the rest is the same as Application Example 1. 1.07 FeO3 film layer contacts the bottom electrode. In the preparation method, in step (2), three layers of Bi x FeO3 gel with corresponding components are spin - coated, and the rest is the same as Application Example 1.

[0087] Application Example 3

[0088] The difference between Application Example 3 and Application Example 1 is only that the photo - electric absorption conversion layer in Example 3 is adopted. The BiFeO3 film layer of the photo - electric absorption conversion layer in Example 3 contacts the bottom electrode. In the preparation method, in step (2), three layers of Bi 1.03 FeO3 gel with corresponding components are spin - coated, and the rest is the same as Application Example 1. x FeO3 gel with corresponding components are spin - coated, and the rest is the same as Application Example 1.

[0089] Comparative Application Example 1

[0090] The difference between Comparative Application Example 1 and Application Example 1 is only that the photo - electric absorption conversion layer in Comparative Example 1 is adopted. In the preparation method, in step (2), one layer of BiFeO3 gel with corresponding composition and thickness is spin - coated, and the rest is the same as Application Example 1.

[0091] Comparative Application Example 2

[0092] The difference between Comparative Application Example 2 and Application Example 1 is only that the photo - electric absorption conversion layer in Comparative Example 2 is adopted. In the preparation method, in step (2), one layer of Bi 1.1 FeO3 gel with corresponding composition and thickness is spin - coated, and the rest is the same as Application Example 1.

[0093] Comparative Application Example 3

[0094] The difference between Comparative Application Example 3 and Application Example 1 is only that the photo - electric absorption conversion layer in Comparative Example 3 is adopted. The BiFeO3 film layer of the photo - electric absorption conversion layer in Comparative Example 3 contacts the bottom electrode. In the preparation method, in step (2), two layers of gel with corresponding composition and thickness are spin - coated, the annealing treatment temperature of the BaTiO3 film layer is 650 °C, and the rest is the same as Application Example 1.

[0095] The electrical properties of the self-powered photodetectors in Application Examples 1 to 3 and Comparative Application Examples 1 to 3 were tested using a semiconductor device analyzer. The light source was provided by a single-wavelength LED lamp with wavelengths of 500 nm and 365 nm.

[0096] The photovoltaic curves of the self-powered photodetectors in Application Example 1, Application Example 2, and Application Example 3 under dark and 500-nm light illumination are as Figure 2 shown. As can be seen from Figure 2 , the abscissa and ordinate are voltage and current density, respectively. The open-circuit voltage and short-circuit current of the self-powered photodetector in Application Example 1 are 0.46 V and 1.18×10 -4 A / cm 2 , respectively. The open-circuit voltage and short-circuit current of the self-powered photodetector in Application Example 2 are 0.66 V and 1.6×10 -4 A / cm 2 , respectively. The open-circuit voltage and short-circuit current of the self-powered photodetector in Application Example 3 are 0.6 V and 1.13×10 -4 A / cm 2 , respectively. Application Examples 1 to 3 all exhibit a certain intensity of photocurrent density under the condition of zero voltage, indicating that there is a stable built-in electric field for separating photo-generated carriers inside the two devices. However, the photovoltaic effects of Application Examples 1 to 3 are different, indicating that by adjusting the composition of each layer in the photoabsorption conversion layer, the distribution of internal defects in the device can be controlled, which helps to regulate the detection performance of the self-powered photodetector.

[0097] The zero-bias I-t curves of the self-powered photodetectors in Application Example 1, Application Example 2, and Application Example 3 under 500-nm light illumination are as Figure 3 shown. As can be seen from Figure 3 , the abscissa and ordinate are time and current density, respectively, and the switching interval time is 10 s. The self-powered photodetectors in Application Examples 1 to 3 all have a stable light response phenomenon, but the photocurrent density (detection performance) is different, indicating that by controlling the distribution of internal defects in the device, the light response behavior of the device can be regulated, and thus the detection performance of the self-powered photodetector can be regulated.

[0098] The photovoltaic curve of the self-powered photodetector in Comparative Application Example 1 under 500-nm light illumination is as Figure 4 shown. As can be seen from Figure 4 , the abscissa and ordinate are voltage and current density, respectively. The open-circuit voltage and short-circuit current of the self-powered photodetector in Comparative Application Example 1 are 0.35 V and 2.9×10 -5 A / cm 2, since the optoelectronic absorption conversion layer is made of BiFeO3 gel during preparation, a large number of defects are present inside the thin film due to the volatilization of Bi elements during the annealing process of the optoelectronic absorption conversion layer, resulting in excessive defects, which become carrier recombination centers, leading to a decrease in photocurrent and being unfavorable for the improvement of optoelectronic detection performance.

[0099] The photovoltaic curve of the self-powered photodetector in Application Example 2 under 500 nm light illumination is as Figure 5 shown. As can be seen from Figure 5 , the abscissa and ordinate are voltage and current density respectively. The open-circuit voltage and short-circuit current of the self-powered photodetector in Application Example 2 are 0.4 V and 6.8×10 -5 A / cm 2 , respectively. Since the optoelectronic absorption conversion layer is made of Bi 1.1 FeO3 gel during preparation, the Bi element is in excess by 10%, resulting in excessive defects inside the thin film, which is unfavorable for the increase of the current value (improvement of optoelectronic detection performance); and the composition is single (all Bi 1.1 FeO3), which is unfavorable for the regulation of the built-in electric field of the thin film and the performance of the detection device.

[0100] The photovoltaic curves of the self-powered photodetector in Application Example 3 under 500 nm light illumination and 365 nm ultraviolet light illumination are as Figure 6 shown. As can be seen from Figure 6 , the abscissa and ordinate are voltage and current density respectively. The open-circuit voltage and short-circuit current of the self-powered photodetector in Application Example 3 under 500 nm light illumination are 0.35 V and 4.9×10 -6 A / cm 2 , respectively, and the open-circuit voltage and short-circuit current under 365 nm ultraviolet light illumination are 0.63 V and 3.35×10 -5 A / cm 2 , respectively. The response light wavelength of the self-powered photodetector is in the ultraviolet light band and has a weak response in the visible light band.

[0101] The open-circuit voltage of the self-powered photodetector prepared with the optoelectronic absorption conversion layer provided by the present invention is 0.46 - 0.66 V and the short-circuit current is 1.13 - 1.6×10 -4 A / cm 2 under 500 nm light illumination. The zero-bias I-t curve under 500 nm light illumination shows that the self-powered photodetector has a stable light response phenomenon. In addition, the optoelectronic absorption conversion layer provided by the present invention can design an optoelectronic absorption conversion layer with different longitudinal distributions of defect concentrations by adjusting the value of x in each Bi x FeO3 film layer, and further realize the regulation of the photocurrent and photovoltage performance of the self-powered photodetector.

[0102] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A photoabsorptive conversion layer, characterized in that, Composed of three layers of Bi x FeO3 film layers, where for each layer of Bi x FeO3 film layer, 1 ≤ x < 1.1, and the values of x in each layer of Bi x FeO3 film layer are different; Each layer of Bi x The thickness of the FeO3 film layer is the same, all being 75 - 100 nm.

2. A self-powered photodetector, comprising a substrate, a bottom electrode, the photoabsorption conversion layer described in claim 1, and a top electrode, which are sequentially arranged.

3. The self-powered photodetector according to claim 2, wherein, The materials of the bottom electrode and the top electrode are both gold.

4. The self-powered photodetector according to claim 2 or 3, characterized in that, The thicknesses of the bottom electrode and the top electrode are independently 30 - 50 nm.

5. The method for preparing the self-powered photodetector according to any one of claims 2 - 4, comprising the following steps: (1) Sputtering a bottom electrode on the substrate to obtain a first composite; (2) Prepare a BiFeO3 film layer layer by layer on the surface of the bottom electrode of the first composite obtained in the step (1) to obtain a second composite; the preparation of each BiFeO3 film layer includes spin-coating BiFeO3 gel and annealing treatment carried out in sequence; x FeO3 film layer to obtain a second composite; each layer of Bi x The preparation of the FeO3 film layer includes spin-coating Bi x FeO3 gel and annealing treatment in sequence; (3) Sputtering a top electrode on the surface of the photoabsorption conversion layer of the second composite obtained in step (2) to obtain a self-powered photodetector.

6. The preparation method according to claim 5, characterized in that, In step (2), the temperature of each annealing treatment is 600 °C, and the time of each annealing treatment is 3 min.

7. The preparation method according to claim 5 or 6, characterized in that, Thermal decomposition treatment is carried out before each annealing treatment.

8. The preparation method according to claim 7, characterized in that, The temperature of each thermal decomposition treatment is 320 - 380 °C, and the time of each thermal decomposition treatment is 3 - 5 min.

9. The preparation method according to claim 6, wherein In steps (1) and (3), the sputtering power is independently 6 - 10 W, the sputtering time is independently 280 - 320 s, and the rotation speed of the turntable during sputtering is independently 14 - 16 r / min.

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