Flexible ZnO / CsPbBr3 QD photoelectric detector for monitoring illumination intensity accepted by plant

Abstract

The invention provides a flexible ZnO / CsPbBr3QD photoelectric detector for monitoring the illumination intensity accepted by a plant, and belongs to the technical field of plant illumination intensity monitoring. According to the flexible ZnO / CsPbBr3QD photoelectric detector, an indium tin oxide electrode material is processed on a flexible PET substrate through laser etching, a flexible ITO / PET substrate is formed, ZnO nano columns grow on the flexible ITO / PET substrate, and then CsPbBr3QD dispersion liquid is attached to the ZnO nano columns in a spin coating mode to complete preparation. The flexible photoelectric detector serves as a flexible device to be attached to a plant leaf, the light intensity and the light current change rule are determined according to the change of the light current of the photoelectric detector along with time, and the light intensity received by a plant is continuously monitored. As a flexible device, the flexible photoelectric detector has good flexibility, mechanical durability and stability, better portability and low manufacturing cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of plant light intensity monitoring, and in particular relates to a flexible ZnO / CsPbBr3 QD photoelectric detector for monitoring the light intensity received by plants. Background Art

[0002] Perovskite materials are gaining more and more attention in optoelectronic devices due to their advantages such as large absorption coefficient, high carrier mobility, and long exciton diffusion length. Photodetectors based on low-dimensional inorganic perovskite materials have good environmental stability in the air and can realize high-sensitivity and fast-response photodetectors; however, as flexible electronic devices become a research hotspot, higher requirements are placed on the low cost, softness, robustness, and excellent and unique optical properties that flexible photodetectors should have, which also reveals the defects in the performance of flexible photodetectors. The main problems faced by flexible photodetectors are: first, high cost and cumbersome preparation process; second, insufficient development of materials for preparing flexible devices; third, they cannot meet the small size and stability requirements of flexible devices; fourth, the application of flexible devices is limited. Therefore, it is necessary to continue to make new breakthroughs in flexible photodetection technology and broaden the various applications of flexible photodetectors.

[0003] In 2020, Wang H, Zhang P, Zang Z. High performance CsPbBr3 quantum dots photodetectors by using zinc oxide nanorods arrays as an electron-transport layer [J]. Applied physics letters, 2020, 116 (16). It was disclosed that a 20 nm thick ZnO seed layer was deposited on the washed indium tin oxide (ITO) by pulsed laser deposition, quantum dots (QD) were slowly spin-coated on the ZnO nanorods (ZnO NRs), and then an organic layer was spin-coated and Ag was evaporated. The finally prepared ZnO NRs / CsPbBr3 quantum dot photodetector has good response parameters and has broad application prospects in the future. In 2019, Zheng J, Luo C, Shabbir B, et al. Flexible photodetectors based on reticulated SWNT / perovskite quantum dotheterostructures with ultrahigh durability [J]. Nanoscale, 2019, 11 (16): 8020-8026. A high-performance flexible photodetector was prepared, which was composed of a mesh SWNT (single-walled carbon nanotube) film covered with a CsPbI3 perovskite colloidal quantum dot film. The flexible device has repeated bending and stretching properties, as well as good stability, indicating its applicability as a large-area wearable flexible photodetector. At present, there is no report on the preparation of perovskite flexible photodetectors for monitoring the light intensity received by plants. Summary of the invention

[0004] In view of the problems of the prior art, the present invention prepares a flexible ZnO / CsPbBr3 QD photodetector with good flexibility and stability, and uses it as a flexible device to test the light intensity received by plants. The flexible device is attached to the leaves of plants, and the plants are irradiated with LED plant lights of different colors. The change of the photocurrent of the flexible photodetector over time is used to represent the light intensity received by the plants. The flexible device can be used to continuously monitor the light intensity received by plants under different environmental light intensities.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a flexible ZnO / CsPbBr3QD photodetector for monitoring the light intensity received by plants. The flexible ZnO / CsPbBr3QD photodetector is prepared by laser etching an indium tin oxide (ITO) electrode material on a flexible PET substrate to form a flexible ITO / PET substrate, growing ZnO nanorods (ZnO NRs) on the flexible ITO / PET substrate, and then spin coating a CsPbBr3 QD dispersion on the ZnO nanorods to complete the preparation; the flexible ZnO / CsPbBr3QD photodetector is attached to plant leaves as a flexible device, and the color and height of the LED plant lamp are adjusted to change the light intensity, and the law of light intensity and photocurrent change is determined in combination with the change of the photocurrent of the flexible ZnO / CsPbBr3QD photodetector over time, so as to continuously monitor the light intensity received by the plants under different environmental light intensities.

[0007] Furthermore, the electrode channel length L=2 mm and the width W=0.05 mm of the indium tin oxide electrode material processed by laser etching; the thickness of the flexible ITO / PET substrate is 0.125 mm.

[0008] Furthermore, the CsPbBr3 QD dispersion is prepared by uniformly dispersing CsPbBr3 QD in n-hexane.

[0009] Furthermore, the ZnO nanocolumns are synthesized by a hydrothermal method, and the average length of the ZnO nanocolumns is 2 μm.

[0010] Preferably, the ZnO nanorods are synthesized by a hydrothermal method and grown on a flexible ITO / PET substrate, comprising the following steps:

[0011] Zinc acetate was dissolved in methanol, ultrasonically dissolved for 5 minutes, and stirred at 60°C for 30 minutes. At the same time, NaOH solution was prepared in the methanol solution, ultrasonicated for 30 minutes, and NaOH was used as a reducing agent. After heating at 60°C for 5 minutes, the NaOH solution was added dropwise to the zinc acetate solution, and stirred at 60°C for 2 hours with a magnetic stirrer to obtain a ZnO nanocolumn seed solution. The ZnO nanocolumn seed solution was spin-coated on a clean flexible ITO / PET substrate, and the flexible ITO / PET substrate was heated at 14 Sinter in a tubular furnace at 0°C for 30 min; dissolve equimolar Zn(NO3)2·6H2O and hexamethylenetetramine (HMTA) in deionized water, ultrasonicate for 5 min, place the sintered flexible ITO / PET substrate in an oil bath cup, then pour in the dissolved Zn(NO3)2·6H2O and hexamethylenetetramine (HMTA) solution, stir with a magnetic stirrer at 95°C for 6 h, and finally put into an oven for drying to obtain ZnO nanocolumns grown on the flexible ITO / PET substrate.

[0012] Furthermore, the CsPbBr3 QD dispersion is synthesized by hot injection method.

[0013] Preferably, the CsPbBr3 QD dispersion is synthesized by hot injection method, comprising the following steps: first, CsCO3, octadecene and oleic acid are placed in a three-necked flask, nitrogen is used as a protective gas, an oil bath is placed at 120°C, magnetic stirring is performed for 1 hour, the temperature is raised to 150°C, and the reaction is stirred for 3 hours to form a cesium oleate solution; secondly, PbBr2 and octadecene are placed in a three-necked flask and mixed to obtain a crude solution, nitrogen is used as a protective gas, and the solution is dried at 120°C for 0.5 hours, and then oleic acid and oleylamine are quickly injected into the crude solution to obtain a PbBr2 mixed solution, and then the cesium oleate solution preheated at 150°C is quickly injected into the PbBr2 mixed solution, and the three-necked flask is immediately cooled in an ice-water bath after reacting for 5 seconds to ensure that the CsPbBr3 obtained by the reaction The crude QD solution was crystallized; finally, tert-butanol was added to centrifuge the crude CsPbBr3QD solution twice, with the speed and time being 12000r, 4min and 8000r, 4min respectively, and the supernatant was discarded. After purification, n-hexane was added to the centrifuge tube to make the CsPbBr3 QD evenly dispersed in the n-hexane solvent to obtain a CsPbBr3 QD dispersion.

[0014] Furthermore, a method for preparing a flexible ZnO / CsPbBr3 QD photodetector is provided, wherein the CsPbBr3 QD dispersion synthesized by the hot injection method is spin-coated on the ZnO nanorods synthesized by the hydrothermal method at 3000r, 20s, 3 times, and then placed on a heating platform at 80°C for 1min-2min.

[0015] Furthermore, the flexible ZnO / CsPbBr3QD photodetector is used to monitor the light intensity received by plants, and the monitoring method comprises the following steps:

[0016] (1) Build a shade shed, place the plant seedlings in the shade shed, build a plant fill light bracket, and place a plant LED lamp on the plant fill light bracket. The plant fill light bracket is used to adjust the height between the plant lamp and the plant;

[0017] (2) Select a resistor R with the same resistance value as the flexible ZnO / CsPbBr3QD photodetector, and solder the resistor R to the circuit board. The circuit board, the flexible ZnO / CsPbBr3QD photodetector, and the data acquisition card are connected in parallel to the power supply to form a circuit loop; the resistance value of the flexible ZnO / CsPbBr3 QD photodetector is equal to that of the resistor R on the circuit board, ensuring that the voltage across the resistor R is the same as the voltage across the flexible ZnO / CsPbBr3 QD photodetector;

[0018] (3) Connect the data acquisition card to the computer. The data acquisition system software is Smacq USB-5000SeriesDAQ;

[0019] (4) Using 80 μm thick double-sided transparent tape, the flexible ZnO / CsPbBr3 QD photodetector was pasted on the leaves of the plant seedlings;

[0020] (5) Turn on the switch of the plant LED light, use the plant fill light bracket to adjust the height of the plant LED light to change the light intensity, obtain the light power density value of the flexible ZnO / CsPbBr3QD photodetector irradiated on the leaves of the plant seedlings through the optical power meter, and record the data;

[0021] (6) The voltage changes over time under different light intensities were collected by Smacq USB-5000Series DAQ system software, and the current value was calculated using Ohm's law according to the voltage and the resistance value of resistor R, and then the change law of the photocurrent-time characteristic curve monitored by the flexible ZnO / CsPbBr3 QD photodetector was recorded;

[0022] (7) Change the color of the plant LED light and adjust the different light power densities. According to the regular and significant changes in the photocurrent, perform data processing and graphing, record the changes in light intensity and photocurrent in the monitoring experiment, and then determine the most suitable light intensity for the plant seedlings under different light conditions during their growth.

[0023] Furthermore, the plant seedlings in step (1) are tomato seedlings, and the plant fill light bracket is a single-row bracket.

[0024] Furthermore, the color light of the LED lamp in step (7) includes white light, purple light or blue light.

[0025] Advantages and effects of the present invention:

[0026] Compared with the ZnO / CsPbBr3 QD photodetector in the prior art, the present invention prepares a flexible ZnO / CsPbBr3 QD photodetector with ITO / PET as the substrate, and the preparation process is very simple. It can not only maintain excellent light detection capability and specific light detection range, but also has good flexibility, mechanical durability and stability as a flexible device, better portability and low manufacturing cost compared with rigid devices.

[0027] A flexible ZnO / CsPbBr3 QD photodetector prepared by the present invention is used to monitor the light intensity received by plants. The photodetector can be used as a flexible device to be attached to plant leaves. Under different light intensities, the change in the photocurrent of the flexible photodetector reflects the light intensity received by the plant. According to the change law of light intensity and photocurrent, the light intensity received by the plant under different environmental light intensities is continuously monitored. When used to monitor the light intensity of plant leaves, the photodetector can fit well with the plant leaves, and will hardly have any impact on the plants during the test, so it will not be affected by any other interference factors on the experimental results.

[0028] The flexible ZnO / CsPbBr3 QD photoelectric detector of the present invention continuously monitors the changes in the light intensity received by the plants during the growth process, so as to determine the most suitable light intensity for the plant seedlings during the growth process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a scanning electron microscope (SEM) image of the ZnO nanorods in Example 1;

[0030] Figure 2 This is a transmission electron microscope (TEM) image of CsPbBr3 QDs attached to ZnO nanorods in Example 1;

[0031] Figure 3 This is a scanning electron microscopy (SEM) image of CsPbBr3 QDs attached to ZnO nanorods in Example 1;

[0032] Figure 4 Comparative spectra of the flexible ZnO / CsPbBr3QD photodetector in Example 1 and the existing CsPbBr3QD, wherein Figure (a) is an absorption spectrum, and Figure (b) is a photoluminescence spectrum (PL) diagram;

[0033] Figure 5 This is a schematic diagram of the preparation process of a flexible ZnO / CsPbBr3QD photodetector in Example 1;

[0034] Figure 6 This is a physical picture of a flexible ZnO / CsPbBr3QD photodetector in Example 1 at bending radii of 30°, 60° and 90°;

[0035] Figure 7 The circuit design diagram and the physical connection diagram of the method for using a flexible ZnO / CsPbBr3 QD photoelectric detector to monitor the light intensity received by plants in Example 1, wherein Figure (a) is the circuit design diagram, Figure (b) is the physical connection diagram, and Figure (c) is the physical connection diagram of the flexible ZnO / CsPbBr3 QD photoelectric detector attached to the plant leaf;

[0036] Figure 8 The IT curves of the photocurrent variation over time after the number of bending cycles is changed at different bending radii for a flexible ZnO / CsPbBr3QD photodetector in Example 1, wherein Figure (a) is a 30° bending radius, Figure (b) is a 60° bending radius, and Figure (c) is a 90° bending radius;

[0037] Fig. 9 This is an IT curve diagram of the photocurrent variation over time of a flexible ZnO / CsPbBr3QD photodetector in Application Example 1 after changing the light power under different color lights, where Figure (a) is white light, Figure (b) is blue light, and Figure (c) is purple light. DETAILED DESCRIPTION

[0038] The present invention is described in detail below with reference to the embodiments.

[0039] Example 1

[0040] A flexible ZnO / CsPbBr3 QD photodetector is used to monitor the light intensity received by plants. The flexible ZnO / CsPbBr3QD photodetector is prepared by laser etching indium tin oxide (ITO) electrode material on a flexible PET substrate to form a flexible ITO / PET substrate, growing ZnO nanocolumns on the flexible ITO / PET substrate, and spin coating a CsPbBr3 QD dispersion on the ZnO nanocolumns. The flexible ZnO / CsPbBr3 QD photodetector is attached to plant leaves as a flexible device, and the color and height of the LED plant lamp are adjusted to change the light intensity. The light intensity and the law of photocurrent change are determined by combining the change of the photocurrent of the flexible ZnO / CsPbBr3QD photodetector over time, thereby continuously monitoring the light intensity received by plants under different environmental light intensities.

[0041] ZnO nanorods were synthesized by hydrothermal method and grown on flexible ITO / PET substrates, including the following steps:

[0042] Laser etching ITO electrode material on a flexible PET substrate, the electrode channel length L = 2 mm, width W = 0.05 mm, to obtain a flexible ITO / PET substrate, the substrate thickness of which is 0.125 mm;

[0043] 43.87 mg ZnAc was dissolved in 20 mL methanol, ultrasonically dissolved for 5 min, and stirred on a hot plate at 60 ° C for 30 min with a magnetic stirrer; at the same time, 72 mg NaOH solution was prepared in 20 mL methanol solution, ultrasonicated for 30 min; NaOH was used as a reducing agent and heated at 60 ° C for 5 min; then, the NaOH solution was added dropwise to the ZnAc solution, and stirred at 60 ° C for 2 h with a magnetic stirrer to prepare a ZnO nanocolumn seed solution; 20 μL of the ZnO nanocolumn seed solution was taken with a pipette, 3000 r, 20 s, and spin-coated twice on a clean flexible ITO / PET substrate to make ZnO nanocolumns. Grow on a flexible ITO / PET substrate, then place the flexible ITO / PET substrate in a tubular furnace at 140°C for 30 minutes; add 535.482 mg of Zn(NO3)2·6H2O and 252.342 mg of HMTA into 60 mL of deionized water to dissolve, and ultrasonicate for about 5 minutes; put the ITO / PET flexible substrate on which the ZnO nanocolumns are grown after sintering in the tubular furnace into an oil bath cup, then pour in the dissolved Zn(NO3)2·6H2O and HMTA solution, magnetically stir at 95°C for 6 hours, and finally put into an oven for drying to obtain a ZnO nanocolumn array grown on a flexible ITO / PET substrate;

[0044] like Figure 1 The figure shows the SEM image of ZnO nanocolumns synthesized by the hydrothermal method in this embodiment. It can be seen that the average length of the ZnO nanocolumns is about 2 μm.

[0045] The CsPbBr3 QD dispersion was synthesized by hot injection method, which includes the following steps:

[0046] First, 0.814g CsCO3, 35mL octadecene, and 0.5mL oleic acid were placed in a 250mL three-necked flask, and nitrogen was used as a protective gas. The mixture was placed in an oil bath at 120°C, magnetically stirred for 1h, heated to 150°C, and stirred for 3h to obtain a cesium oleate solution. At the same time, 0.138g PbBr2 and 10mL octadecene were placed in a 250mL three-necked flask and mixed to obtain a crude solution. The mixture was dried at 120°C for 0.5h using nitrogen as a protective gas. Then, 1mL oleic acid and 1mL oleylamine were quickly injected into the crude solution to obtain a PbBr2 mixed solution. The prepared cesium oleate solution was then preheated at 150°C, and 0.8mL cesium oleate solution was quickly injected into the PbBr2 mixed solution. After reacting for 5s, the three-necked flask was immediately cooled in an ice-water bath to ensure that the crude CsPbBr3 QD solution obtained by the reaction was crystallized. Finally, tert-butanol was added to CsPbBr3 The crude QD solution was centrifuged twice at a speed of 12000 r, 4 min and 8000 r, 4 min, respectively. The supernatant was discarded, and 6 mL of n-hexane was added to the centrifuge tube after purification to make the CsPbBr3 QDs evenly dispersed in the n-hexane solvent to obtain a CsPbBr3 QD dispersion.

[0047] A method for preparing a flexible ZnO / CsPbBr3 QD photodetector, such as Figure 5 As shown, in the present embodiment, a preparation process of a flexible ZnO / CsPbBr3 QD photoelectric detector is performed, in which an ITO electrode material is laser-etched on a flexible PET substrate to obtain a flexible ITO / PET substrate, and a ZnO nanocolumn is grown on the flexible ITO / PET substrate; the ZnO nanocolumn grown on the flexible ITO / PET substrate is subjected to spin coating three times with a CsPbBr3 QD dispersion prepared at 3000r and 20s, and the mixture is placed on a heating platform at 80°C for 1min-2min to obtain a flexible ZnO / CsPbBr3 QD photoelectric detector;

[0048] like Figure 2 , Figure 3 As shown in the figure, they are TEM and SEM images of CsPbBr3 QD attached to ZnO nanopillars in this embodiment, respectively. It can be seen that the present invention attaches CsPbBr3 QD to ZnO nanopillars grown on flexible ITO / PET substrates, and successfully prepares flexible ZnO / CsPbBr3 QD photodetectors;

[0049] like Figure 4 (a) Figure 4 (b) shows the absorption spectrum and PL emission spectrum of the ZnO / CsPbBr3 QD photoelectric detector in this embodiment compared with the CsPbBr3 QD in the prior art, respectively. It can be seen that the ZnO / CsPbBr3 QD photoelectric detector test sample of the present invention is basically consistent with the spectrum of CsPbBr3 QD, wherein the absorption spectrum wavelength is about 510nm, and the emission spectrum wavelength is about 525nm, which fully demonstrates that the present invention successfully prepared CsPbBr3 QD.

[0050] A method for monitoring the light intensity received by plants using a flexible ZnO / CsPbBr3 QD photodetector comprises the following steps:

[0051] (1) Build a 60 cm × 50 cm × 45 cm shade shed, place one or two plant seedlings in the shade shed, build a single-row bracket for plant fill lights, and place a plant LED light. The single-row bracket can adjust the height between the plant light and the plant;

[0052] (2) Testing the resistance of the flexible ZnO / CsPbBr3 QD photodetector in this embodiment, selecting a resistor R with the same resistance value as the flexible ZnO / CsPbBr3 QD photodetector, and soldering the resistor R to a circuit board. The circuit board, the flexible ZnO / CsPbBr3 QD photodetector, and the data acquisition card are connected in parallel to a power supply to form a circuit loop; the resistance value of the flexible ZnO / CsPbBr3 QD photodetector is equal to that of the resistor R on the circuit board, ensuring that the voltage across the resistor R is the same as the voltage across the flexible ZnO / CsPbBr3 QD photodetector;

[0053] (3) Connect the data acquisition card to the computer. The data acquisition system software is Smacq USB-5000SeriesDAQ;

[0054] (4) Using 80 μm thick double-sided transparent tape, the flexible ZnO / CsPbBr3 QD photodetector was pasted on the leaves of the plant seedlings;

[0055] (5) Turn on the switch of the plant LED lamp, use the plant fill light single-row bracket to adjust the height of the plant LED lamp to change the light intensity, obtain the light power density value of the flexible ZnO / CsPbBr3QD photodetector irradiated on the leaves of the plant seedlings in step (4) through the optical power meter, and record the data;

[0056] (6) The voltage changes over time under different light intensities were collected by Smacq USB-5000Series DAQ system software, and the current value was calculated using Ohm's law according to the voltage and the resistance value of resistor R, and then the change law of the photocurrent-time characteristic curve monitored by the flexible ZnO / CsPbBr3 QD photodetector was recorded;

[0057] (7) Change the color of the plant LED light (white light, purple light or blue light) and adjust different light power densities to find regular and significant changes in the photocurrent. Then perform data processing and plot to record the experimental law of light intensity and photocurrent changes.

[0058] Under environmental conditions with different light intensities, during the growth process of plants, the photocurrent changes of flexible photodetectors can be used to monitor the light intensity received by the plants, so as to ensure that the plants receive the most suitable light intensity under different light conditions during their growth process;

[0059] according to Figure 7 The circuit design diagram in (a) connects the components involved in step (2) to obtain Figure 7 (b) shows the physical connection diagram, Figure 7 (c) is the actual connection diagram of the flexible ZnO / CsPbBr3QD photodetector attached to the leaves of plant seedlings.

[0060] Performance Analysis

[0061] like Figure 6 As shown, the bending radii of the flexible ZnO / CsPbBr3 QD photodetector in this embodiment are 30°, 60°, and 90°, indicating that the flexible ZnO / CsPbBr3 QD photodetector prepared by the present invention has good flexibility;

[0062] A flexible ZnO / CsPbBr3 QD photodetector is subjected to 1V bias, 405nm wavelength laser irradiation, and 0, 100, 200, 300, and 400 bending cycles at bending radii of 30°, 60°, and 90°, respectively. The IT curves of the photocurrent of the flexible ZnO / CsPbBr3 QD photodetector over time are studied, as shown in FIG. Figure 8 As shown, it can be seen that after multiple bending cycles, the photocurrent does not change significantly, which further shows that the flexible ZnO / CsPbBr3 QD photodetector of the present invention has good flexibility, mechanical durability and stability.

[0063] Application Example 1

[0064] According to the monitoring method of using a flexible ZnO / CsPbBr3 QD photodetector to monitor the light intensity received by plants in Example 1, tomato seedlings were irradiated with white light, blue light, and purple light LED plant lights, respectively, and the light power density was changed to study the change of the photocurrent of the flexible ZnO / CsPbBr3 QD photodetector over time, such as Fig. 9 As shown, the photocurrent shows regular and significant changes, and the experimental law of light intensity and photocurrent changes is recorded; according to the most suitable light intensity value for tomato seedlings (or other seedlings) in the literature, the light intensity of the LED lamp is adjusted, and the photocurrent changes of the flexible ZnO / CsPbBr3QD photodetector are observed to continuously monitor whether the plant seedlings are in the most suitable light intensity.

[0065] Application Example 2

[0066] According to the monitoring method of using a flexible ZnO / CsPbBr3QD photoelectric detector to monitor the light intensity received by plants in Example 1, LED plant lights of different wavelengths are used for irradiation, the light power density is changed, the plants are grouped for irradiation experiments, and the growth of each group of plant seedlings is observed to determine the most suitable color light and light intensity for the plant seedlings during their growth process.

Claims

1. A flexible ZnO / CsPbBr3QD photodetector for monitoring the light intensity received by plants, characterized in that: The flexible ZnO / CsPbBr3QD photodetector is prepared by laser etching indium tin oxide (ITO) electrode material on a flexible PET substrate to form a flexible ITO / PET substrate, growing ZnO nanocolumns on the flexible ITO / PET substrate, and then spin coating a CsPbBr3QD dispersion on the ZnO nanocolumns. The flexible ZnO / CsPbBr3 QD photodetector is attached to plant leaves as a flexible device, and the color and height of the LED plant light are adjusted to change the light intensity. The light intensity and photocurrent change law are determined by combining the change of the photocurrent of the flexible ZnO / CsPbBr3 QD photodetector over time, thereby continuously monitoring the light intensity received by the plant under different environmental light intensities.

2. A flexible ZnO / CsPbBr3QD photodetector as claimed in claim 1 for monitoring the light intensity received by plants, characterized in that: The electrode channel length L=2 mm and the width W=0.05 mm of the laser-etched indium tin oxide electrode material; the thickness of the flexible ITO / PET substrate is 0.125 mm.

3. A flexible ZnO / CsPbBr3QD photodetector as claimed in claim 1 for monitoring the light intensity received by plants, characterized in that: The CsPbBr3 QD dispersion is prepared by uniformly dispersing CsPbBr3 QD in n-hexane.

4. A flexible ZnO / CsPbBr3QD photodetector as claimed in claim 1 for monitoring the light intensity received by plants, characterized in that: The ZnO nanocolumns are synthesized by a hydrothermal method, and the average length of the ZnO nanocolumns is 2 μm.

5. A flexible ZnO / CsPbBr3QD photodetector as claimed in claim 4 for monitoring the light intensity received by plants, characterized in that: The following steps are involved: Zinc acetate was dissolved in methanol, ultrasonically dissolved for 5 minutes, and stirred at 60°C for 30 minutes. At the same time, NaOH solution was prepared in the methanol solution, ultrasonically dissolved for 30 minutes, and NaOH was used as a reducing agent. After heating at 60°C for 5 minutes, the NaOH solution was dropped into the zinc acetate solution and stirred at 60°C for 2 hours with a magnetic stirrer to obtain a ZnO nanocolumn seed solution; the ZnO nanocolumn seed solution was spin-coated on a clean flexible ITO / PET substrate, and the flexible ITO / PET substrate was sintered in a tube furnace at 140°C for 30 minutes; equimolar Zn(NO3)2·6H2O and hexamethylenetetramine were dissolved in deionized water, ultrasonically dissolved for 5 minutes, the sintered flexible ITO / PET substrate was placed in an oil bath cup, and then the dissolved Zn(NO3)2·6H2O and hexamethylenetetramine solution was poured in, stirred at 95°C for 6 hours with a magnetic stirrer, and finally placed in an oven for drying to obtain ZnO nanocolumns grown on the flexible ITO / PET substrate.

6. A flexible ZnO / CsPbBr3QD photodetector as claimed in claim 1 for monitoring the light intensity received by plants, characterized in that: The CsPbBr3 QD dispersion is synthesized by hot injection method, comprising the following steps: First, CsCO3, octadecene and oleic acid were placed in a three-necked flask, nitrogen was used as a protective gas, an oil bath was set at 120°C, magnetic stirring was performed for 1 hour, the temperature was raised to 150°C, and the reaction was stirred for 3 hours to form a cesium oleate solution; secondly, PbBr2 and octadecene were placed in a three-necked flask and mixed to obtain a crude solution, nitrogen was used as a protective gas, and the solution was dried at 120°C for 0.5 hours, and then oleic acid and oleylamine were quickly injected into the crude solution to obtain a PbBr2 mixed solution, and then the cesium oleate solution preheated at 150°C was quickly injected into the PbBr2 mixed solution. After reacting for 5 seconds, the three-necked flask was immediately cooled in an ice water bath to ensure that the CsPbBr3 QD crude solution obtained by the reaction was crystallized; finally, tert-butanol was added to centrifuge the CsPbBr3QD crude solution twice, with a rotation speed and time of 12000r, 4min and 8000r, 4min, respectively, and the supernatant was discarded. After purification, n-hexane was added to the centrifuge tube to make CsPbBr3 QDs were uniformly dispersed in n-hexane solvent to obtain CsPbBr3QD dispersion.

7. A flexible ZnO / CsPbBr3QD photodetector as claimed in any one of claims 1 to 6 for monitoring the light intensity received by plants, characterized in that: The CsPbBr3QD dispersion synthesized by the hot injection method was spin-coated onto the ZnO nanorods synthesized by the hydrothermal method at 3000r for 20s for 3 times, and then placed on a heating platform at 80°C for 1 min-2 min.

8. A flexible ZnO / CsPbBr3QD photodetector as claimed in claim 1 for monitoring the light intensity received by plants, characterized in that: The monitoring method includes the following steps: (1) Build a shade shed, place the plant seedlings in the shade shed, build a plant fill light bracket, and place a plant LED lamp on the plant fill light bracket. The plant fill light bracket is used to adjust the height between the plant lamp and the plant; (2) selecting a resistor R with the same resistance value as the flexible ZnO / CsPbBr3QD photodetector, welding the resistor R to the circuit board, and connecting the circuit board, the flexible ZnO / CsPbBr3QD photodetector, and the data acquisition card in parallel to the power supply to form a circuit loop; (3) Connect the data acquisition card to the computer. The data acquisition system software is Smacq USB-5000Series DAQ. (4) Using 80 μm thick double-sided transparent tape, the flexible ZnO / CsPbBr3 QD photodetector was pasted on the leaves of the plant seedlings; (5) Turn on the switch of the plant LED light, use the plant fill light bracket to adjust the height of the plant LED light to change the light intensity, obtain the light power density value of the flexible ZnO / CsPbBr3QD photodetector irradiated on the leaves of the plant seedlings through the optical power meter, and record the data; (6) The voltage changes over time under different light intensities were collected by Smacq USB-5000Series DAQ system software, and the current value was calculated using Ohm's law according to the voltage and the resistance value of the resistor R, and then the change law of the photocurrent-time characteristic curve monitored by the flexible ZnO / CsPbBr3QD photodetector was recorded; (7) Change the color of the plant LED light and adjust the different light power densities. According to the regular and significant changes in the photocurrent, perform data processing and graphing, record the changes in light intensity and photocurrent in the monitoring experiment, and then determine the most suitable light intensity for the plant seedlings under different light conditions during their growth.

9. A flexible ZnO / CsPbBr3QD photodetector as claimed in claim 8 for monitoring the light intensity received by plants, characterized in that: The plant seedlings described in step (1) are tomato seedlings, and the plant fill light bracket is a single-row bracket.

10. A flexible ZnO / CsPbBr3QD photodetector as claimed in claim 9 for monitoring the light intensity received by plants, characterized in that: The color light of the LED lamp in step (7) includes white light, purple light or blue light.

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