An optoelectronic detector and a method for preparing the same

Abstract

The present invention discloses a photodetector, which includes a glass substrate, a silver nanoparticle coating, an SU-8 negative photoresist layer, a micro-area electrode, and a perovskite thin film layer. The perovskite thin film layer is a methylammonium lead iodide perovskite thin film layer. After photoinduced charges are formed in the perovskite thin film layer, the maximum transport length for separating electrons and holes is less than 5 μm, and the micro-area electrode is in a staggered array structure. The present invention also discloses a preparation method of the photodetector. The present invention introduces silver nanoparticles into the perovskite active layer, and by exciting local surface plasmon resonance, the electric field intensity and the light absorption cross section are increased; the silver nanoparticles are wrapped by an ultrathin SU-8 layer, effectively preventing the recombination of photo-generated carriers at the natural defect sites on the surface of the metal nanoparticles, and the prepared photodetector can effectively improve the detection capabilities in different detection wavelength bands.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic detection, and specifically relates to an optoelectronic detector and a preparation method thereof. Background Art

[0002] Optoelectronic detectors utilize photon effects or photothermal effects to convert light signals that are difficult to identify into electrical signals that are easy to distinguish, and can be widely applied in various fields such as medical imaging, radiation measurement, and industrial automatic control. Broadband optoelectronic detectors currently dominate the mainstream optoelectronic detectors. However, with the continuous expansion of emerging applications, the demand for high-performance electrical detectors for high-performance specific-wavelength spectral light is increasing. Therefore, developing an optimized solution for optoelectronic detection devices that can simultaneously achieve flexible regulation of the spectral detection and identification wavelength and high response efficiency has become an essential link to promote the further development of optoelectronic detectors.

[0003] Organic-inorganic hybrid metal halide perovskite is a direct-bandgap semiconductor with excellent optoelectronic properties such as a large absorption coefficient, high carrier mobility, and low exciton binding energy, and is the best choice for the functional layer material in optoelectronic detectors. Among them, polycrystalline perovskite has advantages such as adjustable bandgap and compatibility with solution methods, showing broad application prospects in the field of optoelectronic detection. However, its low response and low absorption efficiency still seriously hinder the further development of high-performance perovskite optoelectronic detectors.

[0004] To solve this problem, Li et al. utilized the surface plasmon polaritons (SPPs) phenomenon to achieve fast response and high detectivity (1.2×1013 Jones) of the detection device in cesium lead bromide (CsPbBr3) perovskite optoelectronic detectors. However, using the SPPs phenomenon to regulate device performance requires a regular structural distribution (gratings, nanorods, etc.) at the perovskite and metal electrode interface, but the preparation process of specific regular microstructures is complex and costly. Therefore, based on the local surface plasmon resonance (LSPR) phenomenon of metal nanoparticles, optical manipulation can be better performed, and the local optical cross-section can be increased by several orders of magnitude compared to the physical size of the metal particles, ultimately inducing an effective increase in the absorption efficiency of incident light.

[0005] Recently, Ko et al. introduced gold nanoparticles into perovskite devices to achieve optimized light trapping with characteristics of hot electron transfer and high-efficiency light trapping, ultimately achieving high detectivity (1.31×1013 Jones) and high responsivity (5.9×104 A W-1). However, the defect sites on the surface of the metal mixture will capture photo-generated carriers, causing severe charge recombination, resulting in a decrease rather than an increase in the working efficiency of the final device. The perovskite optoelectronic detection devices reported in the above studies only proposed optimization strategies for some defects and could not achieve an overall improvement in the performance of perovskite optoelectronic detection devices. Summary of the Invention

[0006] Object of the Invention: In order to overcome the deficiencies in the prior art, the object of the present invention is to provide a photodetector that can effectively improve the detection ability in different wavelength bands and effectively prevent the recombination of photo-generated carriers at the natural defect sites on the surface of metal nanoparticles. Another object of the present invention is to provide a preparation method for a photodetector with low cost and fast response speed.

[0007] Technical Solution: A photodetector according to the present invention includes a glass substrate, a silver nanoparticle coating, an SU-8 negative photoresist layer, micro-area electrodes, and a perovskite thin film layer. The perovskite thin film layer is a methylammonium lead iodide perovskite thin film layer. After photo-induced charges are formed in the perovskite thin film layer, the maximum transport lengths of separated electrons and holes are less than 5 μm, and the micro-area electrodes are in a staggered array structure.

[0008] Further, the thickness of the SU-8 negative photoresist layer is 20 - 100 nm.

[0009] The preparation method of the above-mentioned photodetector includes the following steps:

[0010] Step 1: Ultrasonically clean the glass substrate successively with acetone, ethanol, and deionized water, dry it to remove surface moisture, and perform ultraviolet cleaning;

[0011] Step 2: Spin-coat silver nanoparticles onto the cleaned glass substrate and bake it to obtain a glass substrate covered with a silver nanoparticle (AgNPs) coating;

[0012] Step 3: Oscillate and dissolve the SU-8 photoresist diluted with cyclopentanone on a heating table, then spin-coat it onto the glass substrate covered with the silver nanoparticle coating, perform pre-baking treatment to remove the residual volatile solvents in the film, cure the substrate by ultraviolet light exposure, and perform post-baking to form an SU-8 negative photoresist layer on the surface of the silver nanoparticle coating;

[0013] Step 4: Evaporate silver film at a constant speed on the surface of the product obtained in Step 3. After evaporation is completed, take it out, spin-coat RZJ-304 positive photoresist, perform pre-baking treatment, cover the pre-prepared mask plate, perform exposure lithography, perform post-baking, then immerse it in a developer to make the micro-area pattern appear, then etch the silver film with a silver etchant, and finally immerse it in an RZJ-304 positive photoresist stripping solution to remove the residual RZJ-304 positive photoresist, and form micro-area electrodes on the surface of the SU-8 negative photoresist layer;

[0014] Step 5: Dissolve PbI2 and MAI with a molar ratio of 1 - 1.5:1 in DMF, stir at 50 - 90 °C to obtain a perovskite solution, spin-coat it on the product obtained in Step 4, and perform thermal annealing at 80 - 120 °C on a heating table for 10 - 30 min to form a methylammonium lead iodide (MAPbI3) thin film layer on the surface of the micro-area electrodes and the SU-8 negative photoresist layer.

[0015] Further, in Step 3, the mass-volume ratio of the SU-8 solution photoresist to cyclopentanone is 100 - 500 mg:1 mL. The spin coating speed is 500 - 3000 rpm, and the spin coating time is 5 - 45 s. The pre-baking temperature is 60 - 100 °C, and the time is 5 - 15 min. The post-baking temperature is 50 - 100 °C, and the post-baking time is 5 - 15 min. By adjusting different parameters, the thickness of the SU-8 photoresist modified film is regulated, and the surface energy of the rigid substrate is adjusted and modified. Finally, the thickness of the SU-8 photoresist film is 20 - 100 nm.

[0016] Further, in Step 4, the vacuum degree of evaporation coating is 2.0×10 -4 ~8×10 -4 Pa, the deposition rate is The thickness of the evaporated silver film is 30 - 120 nm; the spin coating speed is 1000 - 3000 r / min, and the time is 20 - 40 s. The thickness of the RZJ-304 positive photoresist is 0.5 - 5 μm. The pre-baking temperature is 50 - 100 °C, and the time is 1 - 5 min. The exposure and lithography time is 1 - 15 s. The post-baking temperature is 50 - 100 °C, and the time is 1 - 5 min.

[0017] Further, in Step 5, each amount of the spin-coated perovskite solution taken is 20 - 150 μL. The spin coating speed is 1000 - 2000 r / min, and the time is 5 - 20 s; then it rotates at a speed of 2000 - 5000 r / min for 10 - 30 s, and 100 - 150 μL of chlorobenzene is dropped at the 15th - 30th s. Finally, the thickness of the perovskite thin film is 0.5 - 5 μm.

[0018] Preparation principle: By introducing silver nanoparticles into the perovskite active layer, a near-three-dimensional Schottky contact is formed, effectively optimizing the output of photo-generated carriers. Utilizing the local surface plasmon resonance phenomenon generated by AgNPs, the electric field intensity around AgNPs is enhanced, the light absorption cross-section is increased, and the light absorption efficiency of the active layer of the device is enhanced. Using an ultra-thin SU-8 layer for encapsulation can effectively inhibit the capture of photo-generated carriers by the natural defect sites on the surface of AgNPs, greatly optimizing the optoelectronic conversion performance of the device. In addition, by using the non-radiative deactivation process of local surface plasmon polariton resonance to generate hot carriers and transmit them into the perovskite functional layer, the passivation of deep-level defect states in the perovskite material can be effectively achieved, and finally the loss during the transmission of photo-generated carriers can be effectively reduced.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0020] 1. Introduce silver nanoparticles into the perovskite active layer. By exciting local surface plasmon resonance, increase the electric field strength and light absorption cross-section. Use an ultrathin SU-8 layer to wrap the silver nanoparticles, effectively preventing the recombination of photo-generated carriers at the natural defect sites on the surface of metal nanoparticles. The fabricated photodetector can effectively improve the detection capabilities in different detection wavelength bands.

[0021] 2. Adopt the integration of microstructured electrodes, shorten the charge transport path, reduce charge scattering. After forming photo-induced charges in the perovskite layer, the maximum transport lengths of separated electrons and holes can be controlled below 5 μm. Due to the presence of the SU-8 protective layer, the chemical corrosion process will not affect the AgNPs pre-modified on the substrate.

[0022] 3. The perovskite photodetector prepared by the present invention has the advantages of simple structure, low cost, fast response speed, etc. Description of the Drawings

[0023] Figure 1 is the preparation flow chart of the present invention;

[0024] Figure 2 is the micro-region electrode photo of the present invention. Among them, a is the overall view, and b is the partial enlarged view;

[0025] Figure 3 is the scanning electron microscope photo of the MAPbI3 perovskite thin film before and after AgNPs modification of the present invention. Among them, a is before modification, and b is after modification;

[0026] Figure 4 is the XRD diffraction pattern before and after AgNPs modification of the present invention;

[0027] Figure 5 is the ultraviolet-visible light absorption spectrum of the silver nanoparticles of the present invention;

[0028] Figure 6 is the comparison diagram of the steady-state fluorescence spectra (PL) of the photodetector before and after AgNPs modification of the present invention;

[0029] Figure 7 is the comparison diagram of the transient fluorescence spectra (TRPL) of the photodetector before and after AgNPs modification of the present invention;

[0030] Figure 8 is the comparison diagram of the I-V curves of the photodetector before and after AgNPs modification of the present invention under illumination and dark conditions;

[0031] Figure 9 is the periodic photocurrent-time (I-T) curve of the photodetector before and after AgNPs modification of the present invention under 630 nm light irradiation;

[0032] Figure 10 It is a comparison chart of the rise time and fall time of the optoelectronic detection device before and after the modification of AgNPs of the present invention. Among them, a is before the modification, and b is after the modification.

[0033] Figure 11 It is a scanning electron microscope image of the MAPbI3 perovskite thin film after the modification of AgNPs / NOA-63;

[0034] Figure 12 It is the ultraviolet-visible light absorption spectrum of gold nanoparticles. Specific implementation manners

[0035] In the following examples, a traditional white glass substrate is selected as the glass substrate, and the thickness is selected to be 1 mm.

[0036] Example 1

[0037] Such as Figure 1 , a preparation method of an optoelectronic detector, comprising the following steps:

[0038] Step 1, ultrasonically clean the glass substrate in the order of acetone, ethanol, and deionized water, place it in a drying oven at 100 °C for 20 min to remove surface moisture, and then perform ultraviolet cleaning for 15 min with a UV cleaning machine.

[0039] Step 2, spin-coat silver nanoparticles onto the cleaned glass substrate, and place it in a drying oven at 80 °C for 10 min to obtain a glass substrate covered with an AgNPs coating.

[0040] Step 3, dissolve 0.1 g / mL SU-8 photoresist diluted with cyclopentanone by oscillating on a heating table, continuously stir at room temperature for 24 h, and then spin-coat it onto the glass substrate covered with the silver nanoparticle coating. The rotation speed is set to 3000 rpm and the time is 45 s; then put it into a drying oven for pre-baking at 100 °C for 10 min to remove the residual volatile solvents in the film; expose it for 1 min by ultraviolet exposure lithography to cure the substrate, and put it into a drying oven for post-baking at 100 °C for 10 min to form a SU-8 negative photoresist layer with a thickness of 60 nm on the surface of the silver nanoparticle coating.

[0041] Step 4, in an organic metal evaporation instrument, deposit a silver film with a thickness of 75 nm at a constant speed on the surface of the product obtained in Step 3, and the deposition rate is The vacuum degree in the furnace during operation is 5.0×10 -4Pa; After the evaporation coating is completed, take it out, spin-coat a positive photoresist RZJ-304 with a thickness of 3 μm, set the rotation speed to 3000 r / min, the time to 30 s, then put it into a drying oven for pre-baking at 100 °C for 5 min, cover the pre-prepared mask plate, perform exposure and lithography through a lithography machine for 7 s, then put it into a drying oven for post-baking at 100 °C for 3 min, immerse it in the developer for 1 min to make the micro-region pattern appear; then etch the silver thin film with a silver etchant for 3 s to completely react the silver thin film outside the microelectrode region; finally, immerse it in the RZJ-304 positive photoresist stripper for 15 s to remove the residual RZJ-304 positive photoresist, and form a micro-region electrode on the surface of the SU-8 negative photoresist layer.

[0042] Step five, use the product obtained in step four as a substrate to carry out the subsequent perovskite spin-coating process to form a methylammonium lead iodide perovskite thin film layer on the surface of the micro-region electrode and the SU-8 negative photoresist layer. Prepare to dissolve PbI2 and MAI with a molar ratio of 1:1 in 1 mL of DMF, heat at 60 °C, and stir at a rotation speed of 1000 rpm for 24 h to obtain a perovskite solution. The amount of the perovskite solution taken for each spin-coating is 80 μL, the spin-coating rotation speed is 1000 r / min, the time is 15 s, then rotate at a speed of 5000 r / min for 25 s, and add 150 μL of chlorobenzene (CB) at the 21st second. Then perform thermal annealing at 100 °C on a heating table for 10 min, and finally form a MAPbI3 perovskite thin film with a thickness of 3 μm on the electrode layer.

[0043] As Figure 2 , for the micro-region electrode (silver electrode) prepared in this embodiment, its array structure is evenly and completely distributed, and the structure period is 5 μm.

[0044] Comparative Example 1

[0045] The remaining steps of this embodiment are the same as those of Example 1, and the only difference is that the preparation of the silver nanoparticle coating is omitted.

[0046] As Figure 3 , after AgNPs / SU-8 is modified on the glass substrate, the perovskite crystal size at the silver nanoparticle-modified part is significantly increased, and the pinholes are also significantly reduced. This optimization is mainly due to the appropriate surface energy of the SU-8 photoresist and the nucleation sites provided by the hump-shaped AgNPs.

[0047] As Figure 4, the diffraction peaks at 14.1° (110), 28.4° (220), and 31.8° (310) are the characteristic peaks of the perovskite phase, respectively reflecting the formation of pure perovskite crystals in the sample obtained in Example 1. The modification of Ag nanoparticles enhanced the diffraction peak intensity of the perovskite crystal plane, indicating that the orientation of perovskite at specific crystallization points was improved. Meanwhile, the diffraction peaks of the AgNPs / SU-8-based perovskite obtained in Example 1 were much stronger than those of the perovskite prepared directly on the glass substrate, indicating the crystallization optimization of perovskite, which was consistent with the scanning electron microscope images.

[0048] As Figure 5 , the simulated absorption peak was not much different from the actually measured absorption peak, showing a slight red shift (from 630 nm to 634 nm) and full width at half maximum, which might be due to the size difference of AgNPs. And there was a weak absorption peak near 550 nm, and this slight enhancement might be caused by interstitial surface plasmons.

[0049] As Figures 6 - 7 , the encapsulation of the ultrathin SU-8 photoresist in Example 1 effectively prevented the quenching of the PL spectrum, indicating that the electron transfer between AgNPs and perovskite was hindered. The weakening of radiative recombination might provide a larger photocurrent. In addition, the enhancement of LSPR excitation ionization and charge separation could also cause a slight PL quenching phenomenon. Meanwhile, the PL lifetime (161.11 ns) of the AgNPs-doped perovskite film was shorter than that of the perovskite film without AgNPs doping (284.04 ns). The corresponding enhancement of PL lifetime quenching was consistent with the observation results of the steady-state PL spectrum, indicating that the charge diffusion in the LSPR-assisted perovskite device was improved and the exciton separation was enhanced.

[0050] As Figure 8 , the dark currents of the photodetectors before and after AgNPs modification were almost the same, but under the irradiation of a 630 nm laser, the addition of AgNPs significantly increased the photocurrent intensity.

[0051] As Figure 9 , in the dark, the plasma perovskite photodetector device obtained in Example 1 showed a small dark current. But when the illumination was turned on, at a wavelength of 630 nm, the photocurrent quickly reached the level of hundreds of μA, and when the illumination was turned off, the current decreased sharply to the initial value, and its reproducible photocurrent switching characteristics could be clearly seen.

[0052] As Figure 10 , the response (rise) and recovery (decay) time values ( Figure 10 b) of the photodetector device modified with AgNPs in Example 1 were 222 ms and 210 ms, respectively, and for the perovskite photodetector device on a normal glass substrate, the rise and fall time values ( Figure 10a) They are 277 and 248 ms respectively. Compared with the perovskite photodetector of Comparative Example 1, the perovskite photodetector modified with AgNPs shows improved and faster response time, indicating that the perovskite photodetector modified with silver nanoparticles can be used as a good optical switch for detecting visible light signals.

[0053] Example 2

[0054] A method for preparing a photodetector, comprising the following steps:

[0055] Step 1, ultrasonically clean the glass substrate in the order of acetone, ethanol, and deionized water successively, place it in a drying oven at 100 °C for 20 min to remove surface moisture, and then perform ultraviolet cleaning for 15 min with a UV cleaning machine.

[0056] Step 2, spin-coat silver nanoparticles onto the cleaned glass substrate, and place it in a drying oven at 80 °C for 10 min to obtain a glass substrate covered with an AgNPs coating.

[0057] Step 3, dissolve 0.5 g / mL SU-8 photoresist diluted with cyclopentanone by oscillating on a heating table, continuously stir at room temperature for 24 h, and then spin-coat it onto the glass substrate covered with the silver nanoparticle coating, with the rotation speed set at 500 rpm and the time at 40 s; then place it in a drying oven for pre-baking at 60 °C for 5 min to remove the residual volatile solvents in the film; expose it for 1 min by ultraviolet exposure lithography to cure the substrate, place it in a drying oven for post-baking at 50 °C for 5 min to form a 20-nm-thick SU-8 negative photoresist layer on the surface of the silver nanoparticle coating.

[0058] Step 4, in an organic metal evaporation instrument, deposit a 30-nm-thick silver film on the surface of the product obtained in Step 3 at a constant speed, and the deposition rate is The vacuum degree in the furnace during operation is 2.0×10 -4 Pa; after the evaporation is completed, take it out, spin-coat a 0.5-μm-thick RZJ-304 positive photoresist, with the rotation speed set at 1000 r / min and the time at 20 s, then place it in a drying oven for pre-baking at 50 °C for 1 min, cover the pre-prepared mask plate, perform exposure lithography with a lithography machine for 1 s, then place it in a drying oven for post-baking at 50 °C for 1 min, immerse it in the developer for 1 min to make the micro-region pattern appear; then etch the silver film with silver etchant for 3 s to completely react the silver film outside the micro-electrode region; finally, immerse it in the RZJ-304 positive photoresist stripper for 15 s to remove the residual RZJ-304 positive photoresist, and form micro-region electrodes on the surface of the SU-8 negative photoresist layer.

[0059] Step 5: Use the product obtained in Step 4 as the substrate and perform the subsequent perovskite spin-coating process to form a methylammonium lead iodide perovskite thin film layer on the surface of the microelectrode and the SU-8 negative photoresist layer. Prepare a solution by dissolving PbI2 and MAI with a molar ratio of 1.5:1 in 1 mL of DMF, heating it at 50 °C, and stirring it at a speed of 1000 rpm for 24 h to obtain a perovskite solution. The amount of the perovskite solution taken for each spin-coating is 20 μL, the spin-coating speed is 2000 r / min, the time is 5 s, then spin at 2000 r / min for 10 s, and add 100 μL of chlorobenzene (CB) at the 15th second. Then perform thermal annealing on a hot plate at 80 °C for 30 min, and finally form a MAPbI3 perovskite thin film with a thickness of 0.5 μm on the electrode layer.

[0060] Example 3

[0061] A method for preparing a photodetector, comprising the following steps:

[0062] Step 1: Ultrasonically clean the glass substrate in the order of acetone, ethanol, and deionized water, place it in a drying oven at 100 °C for 20 min to remove surface moisture, and then perform ultraviolet cleaning with a UV cleaning machine for 15 min.

[0063] Step 2: Spin-coat silver nanoparticles onto the cleaned glass substrate, place it in a drying oven at 80 °C for 10 min to obtain a glass substrate covered with an AgNPs coating.

[0064] Step 3: Oscillate and dissolve 0.3 g / mL of SU-8 photoresist diluted with cyclopentanone on a hot plate, continuously stir it at room temperature for 24 h, and then spin-coat it onto the glass substrate covered with the silver nanoparticle coating. The rotation speed is set to 1000 rpm and the time is 30 s; then place it in a drying oven for pre-baking at 80 °C for 15 min to remove the residual volatile solvents in the film; expose it by ultraviolet exposure lithography for 1 min to cure the substrate, and place it in a drying oven for post-baking at 60 °C for 15 min to form an SU-8 negative photoresist layer with a thickness of 100 nm on the surface of the silver nanoparticle coating.

[0065] Step 4: In an organic metal evaporation instrument, deposit a silver thin film with a thickness of 50 nm at a constant speed on the surface of the product obtained in Step 3, and the deposition rate is The vacuum degree in the furnace during operation is 8×10 -4Pa; After the evaporation coating is completed, take it out, spin-coat a 5-μm-thick RZJ-304 positive photoresist, set the rotation speed to 2000 r / min, the time to 40 s, then put it into a drying oven for pre-baking at 75 °C for 3 min, cover the pre-prepared mask plate, perform exposure lithography through a lithography machine for 15 s, then put it into a drying oven for post-baking at 60 °C for 5 min, immerse it in the developer for 1 min to make the micro-region pattern appear; then etch the silver thin film with a silver etchant for 3 s to completely react the silver thin film outside the microelectrode region; finally, immerse it in the RZJ-304 positive photoresist stripper for 15 s to remove the residual RZJ-304 positive photoresist, and form a micro-region electrode on the surface of the SU-8 negative photoresist layer.

[0066] Step five, use the product obtained in step four as a substrate to perform the subsequent perovskite spin-coating process to form a methylammonium lead iodide perovskite thin film layer on the surface of the micro-region electrode and the SU-8 negative photoresist layer. Dissolve PbI2 and MAI with a molar ratio of 1.2:1 in 1 mL of DMF, heat at 90 °C, and stir at a rotation speed of 1000 rpm for 24 h to obtain a perovskite solution. The amount of the perovskite solution taken for each spin-coating is 150 μL, the spin-coating rotation speed is 1500 r / min, the time is 20 s, then rotate at 3000 r / min for 30 s, and add 120 μL of chlorobenzene (CB) at the 30th second. Then perform thermal annealing at 110 °C on a heating table for 20 min, and finally form a 5-μm-thick MAPbI3 perovskite thin film on the electrode layer.

[0067] Example 4

[0068] A preparation method of a photodetector includes the following steps:

[0069] Step one, ultrasonically clean the glass substrate in the order of acetone, ethanol, and deionized water, place it in a drying oven at 100 °C for 20 min to remove surface moisture, and then perform ultraviolet cleaning with a UV cleaning machine for 15 min.

[0070] Step two, spin-coat silver nanoparticles onto the cleaned glass substrate, place it in a drying oven at 80 °C for 10 min to obtain a glass substrate covered with an AgNPs coating.

[0071] Step three, dissolve 0.2 g / mL of SU-8 photoresist diluted with cyclopentanone by oscillating on a heating table, continuously stir at room temperature for 24 h, and then spin-coat it onto the glass substrate covered with the silver nanoparticle coating, set the rotation speed to 2000 rpm, and the time to 5 s; then put it into a drying oven for pre-baking at 70 °C for 8 min to remove the residual volatile solvent in the thin film; expose and cure the substrate by ultraviolet exposure lithography for 1 min, put it into a drying oven for post-baking at 70 °C for 8 min, and form a 40-nm-thick SU-8 negative photoresist layer on the surface of the silver nanoparticle coating.

[0072] Step 4: In an organic metal evaporation coater, a silver thin film with a thickness of 120 nm is evaporated at a constant speed on the surface of the product obtained in Step 3, and the deposition rate is When working, the vacuum degree in the furnace is 4.0×10 -4 Pa; After the evaporation is completed, take it out, spin-coat a positive photoresist RZJ-304 with a thickness of 1 μm, set the rotation speed to 1500 r / min, the time to 25 s, then put it into a drying oven for pre-baking at 60 °C for 2 min, cover the pre-prepared mask plate, expose and lithograph through a lithography machine for 5 s, then put it into a drying oven for post-baking at 80 °C for 2 min, immerse it in the developer for 1 min to make the micro-area pattern appear; then etch the silver thin film with silver etchant for 3 s to completely react the silver thin film outside the microelectrode area; finally immerse it in the RZJ-304 positive photoresist stripper for 15 s to remove the residual RZJ-304 positive photoresist, and form a micro-area electrode on the surface of the SU-8 negative photoresist layer.

[0073] Step 5: Use the product obtained in Step 4 as a substrate to perform the subsequent perovskite spin-coating process to form a methylammonium lead iodide perovskite thin film layer on the surface of the micro-area electrode and the SU-8 negative photoresist layer. Dissolve PbI2 and MAI with a molar ratio of 1.4:1 in 1 mL of DMF, heat at 70 °C, and stir at a rotation speed of 1000 rpm for 24 h to obtain a perovskite solution. The amount of perovskite solution taken for each spin-coating is 120 μL, the spin-coating rotation speed is 1200 r / min, the time is 8 s, then rotate at 4000 r / min for 15 s, and add 130 μL of chlorobenzene (CB) at the 18th s. Then perform thermal annealing at 120 °C on a heating table for 15 min, and finally form a MAPbI3 perovskite thin film with a thickness of 2 μm on the electrode layer.

[0074] Example 5

[0075] A method for preparing a photodetector, comprising the following steps:

[0076] Step 1: Ultrasonically clean the glass substrate in the order of acetone, ethanol, and deionized water, place it in a drying oven at 100 °C for drying for 20 min to remove surface moisture, and then perform ultraviolet cleaning with a UV cleaning machine for 15 min.

[0077] Step 2: Spin-coat silver nanoparticles onto the cleaned glass substrate, place it in a drying oven at 80 °C for drying for 10 min to obtain a glass substrate covered with an AgNPs coating.

[0078] Step 3: Oscillate and dissolve 0.4 g / mL SU-8 photoresist diluted with cyclopentanone on a heating table, continuously stir at room temperature for 24 h, then spin-coat it onto the glass substrate covered with silver nanoparticles coating, with the rotation speed set at 1800 rpm and the time at 20 s; then place it in a drying oven for pre-baking at 90 °C for 12 min to remove the residual volatile solvents in the film; expose it for 1 min by ultraviolet exposure lithography to cure the substrate, place it in a drying oven for post-baking at 90 °C for 12 min to form an SU-8 negative photoresist layer with a thickness of 80 nm on the surface of the silver nanoparticles coating.

[0079] Step 4: In an organic metal evaporation instrument, deposit a silver thin film with a thickness of 100 nm at a constant speed on the surface of the product obtained in Step 3, and the deposition rate is The vacuum degree in the furnace during operation is 6.0×10 -4 Pa; after the evaporation is completed, take it out, spin-coat a positive photoresist RZJ-304 with a thickness of 4 μm, with the rotation speed set at 2500 r / min and the time at 35 s, then place it in a drying oven for pre-baking at 90 °C for 4 min, cover the pre-prepared mask plate, expose it by a lithography machine for 10 s, then place it in a drying oven for post-baking at 90 °C for 4 min, immerse it in the developer for 1 min to make the micro-area pattern appear; then etch the silver thin film with silver etchant for 3 s to completely react the silver thin film outside the microelectrode area; finally, immerse it in the RZJ-304 positive photoresist stripping solution for 15 s to remove the residual RZJ-304 positive photoresist and form a micro-area electrode on the surface of the SU-8 negative photoresist layer.

[0080] Step 5: Use the product obtained in Step 4 as the substrate to perform the subsequent perovskite spin-coating process to form a methylammonium lead iodide perovskite thin film layer on the surface of the micro-area electrode and the SU-8 negative photoresist layer. Dissolve PbI2 and MAI with a molar ratio of 1.1:1 in 1 mL of DMF, heat at 80 °C, and stir at a rotation speed of 1000 rpm for 24 h to obtain a perovskite solution. The amount of perovskite solution taken for each spin-coating is 20 - 150 μL, the spin-coating rotation speed is 1800 r / min, the time is 12 s, then spin at 3500 r / min for 20 s, and add 110 μL of chlorobenzene (CB) at the 25th s. Then perform thermal annealing at 90 °C on a heating table for 25 min to finally form a MAPbI3 perovskite thin film with a thickness of 1 μm on the electrode layer.

[0081] Comparative Example 2

[0082] The remaining steps of this example are the same as those of Example 1, except that the SU-8 solution photoresist is replaced with NOA-63 photoresist.

[0083] As Figure 11, due to the mismatch between the surface energy of the NOA-63 photoresist and the perovskite crystallization, the perovskite crystallization tends to form a more fragmented amorphous morphology, and compared with the glass substrate and the SU-8 modified substrate, the formed holes are more obvious. Therefore, using the SU-8 photoresist modification is more conducive to the subsequent formation of perovskite.

[0084] Comparative Example 3

[0085] The remaining steps of this example are the same as those of Example 1, except that: the silver nanoparticle coating is replaced with an Au nanoparticle coating with the same structural size.

[0086] As Figure 12 shown, due to the change in the size of the metal nanoparticles, the peak value of the absorption enhancement peak shown undergoes an obvious red shift, and the absorption enhancement wavelength is about 590 nm. In order to achieve the absorption enhancement matching the perovskite material, it is necessary to further increase the size of the Au nanoparticles, and the corresponding consumable cost will increase significantly. Therefore, through comprehensive comparative analysis, coating the substrate with the Ag nanoparticle layer shows an obvious cost advantage, and with a relatively small nanoparticle size, ensuring a relatively small roughness of the overall surface, which is also more conducive to the crystallization and formation of the subsequent perovskite layer.

Claims

1. A photodetector, characterized in that: It includes a glass substrate, a silver nanoparticle coating, an SU-8 negative photoresist layer, microzone electrodes, and a perovskite thin film layer. The perovskite thin film layer is a methylammonium lead iodide perovskite thin film layer. After photogenerated charges are formed in the perovskite thin film layer, the maximum transport length for separating electrons and holes is less than 5 μm. The microzone electrodes are in a staggered array structure.

2. The photodetector according to claim 1, wherein: The thickness of the SU-8 negative photoresist layer is 20 - 100 nm, and the thickness of the perovskite thin film layer is 0.5 - 5 μm.

3. The manufacturing method of a photodetector according to claim 1, characterized in that, It includes the following steps: Step 1, ultrasonically clean the glass substrate successively with acetone, ethanol, and deionized water, dry it, and perform ultraviolet cleaning; Step 2, spin-coat silver nanoparticles onto the cleaned glass substrate and dry them to obtain a glass substrate covered with a silver nanoparticle coating; Step 3, dissolve the SU-8 photoresist diluted with cyclopentanone by oscillation on a heating platform, then spin-coat it onto the glass substrate covered with the silver nanoparticle coating, perform pre-baking treatment, expose it to ultraviolet light to cure the substrate, and perform post-baking to form an SU-8 negative photoresist layer on the surface of the silver nanoparticle coating; Step 4, evaporate silver film at a constant speed on the surface of the product obtained in Step 3, take it out after evaporation, spin-coat RZJ-304 positive photoresist, perform pre-baking treatment, cover the pre-prepared mask plate, perform exposure lithography, perform post-baking and then immerse it in a developer to make the microzone pattern appear, then etch the silver film with a silver etchant, and finally immerse it in an RZJ-304 positive photoresist stripping solution to form microzone electrodes on the surface of the SU-8 negative photoresist layer; Step 5, dissolve PbI2 and MAI with a molar ratio of 1 - 1.5:1 in DMF, stir at 50 - 90 °C to obtain a perovskite solution, spin-coat it on the product obtained in Step 4, and perform thermal annealing at 80 - 120 °C on a heating platform for 10 - 30 min to form a methylammonium lead iodide perovskite thin film layer on the surface of the microzone electrodes and the SU-8 negative photoresist layer.

4. The manufacturing method of a photodetector according to claim 3, wherein: In Step 3, the mass-volume ratio of the SU-8 solution photoresist to cyclopentanone is 100 - 500 mg:1 mL.

5. The manufacturing method of a photodetector according to claim 3, characterized in that: In Step 3, the spin-coating speed is 500 - 3000 rpm, and the spin-coating time is 5 - 45 s.

6. The manufacturing method of a photodetector according to claim 3, characterized in that: In Step 3, the pre-baking temperature is 60 - 100 °C, and the time is 5 - 15 min.

7. The manufacturing method of a photodetector according to claim 3, characterized in that: In Step 3, the post-baking temperature is 50 - 100 °C, and the post-baking time is 5 - 15 min.

8. The manufacturing method of a photodetector according to claim 3, characterized in that: In the fourth step, the vacuum degree of evaporation coating is 2.0×10 -4 ~8×10 -4 Pa, the deposition rate is The spin coating speed is 1000 - 3000 r / min, and the time is 20 - 40 s.

9. The manufacturing method of a photodetector according to claim 3, characterized in that: In Step 4, the pre-baking temperature is 50 - 100 °C, the time is 1 - 5 min, the exposure lithography time is 1 - 15 s, the post-baking temperature is 50 - 100 °C, and the time is 1 - 5 min.

10. The manufacturing method of a photodetector according to claim 3, characterized in that: In Step 5, each time 20 - 150 μL of the perovskite solution is taken for spin-coating, the spin-coating speed is 1000 - 2000 r / min, and the time is 5 - 20 s; then spin at 2000 - 5000 r / min for 10 - 30 s, and add 100 - 150 μL of chlorobenzene at the 15 - 30 s.

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