CN117956812A - A method for preparing a composite perovskite thick film X-ray detector - Google Patents

Abstract

The present invention relates to the technical field of photoelectric detectors, and provides a method for preparing a composite perovskite thick film X-ray detector, wherein a random copolymer is first used to pretreat an ITO or TFT substrate, and then a perovskite suspension precursor slurry composited with a perovskite/random copolymer is directly prepared into a perovskite polycrystalline thick film by a doctor blade method, and then an Au common electrode is evaporated on the top to prepare a composite perovskite thick film X-ray detector. The advantages of the present invention are that the thick film obtained by the method is not easy to fall off or crack, and has few grain boundary defects, and the obtained perovskite X-ray detector based on an ITO substrate has excellent sensitivity and an extremely low X-ray detection lower limit, and the obtained perovskite X-ray detector based on a TFT substrate has excellent spatial resolution.

Description

A method for preparing a composite perovskite thick film X-ray detector

Technical Field

The present invention relates to the technical field of photoelectric detectors, and in particular to a method for preparing a composite perovskite thick-film X-ray detector.

Background technique

With the rapid development of modern science and technology, the importance of X-ray detection in the fields of industrial detection, security inspection and medical diagnosis is becoming more and more significant. Direct X-ray detectors are based on internal semiconductor absorption layers and can directly convert high-energy radiation into current signals. This simple conversion method enables direct X-ray detectors to have a wider linear response range, faster pulse rise time and high spatial resolution, and have very high working efficiency. Organic-inorganic hybrid perovskites are ideal materials for semiconductor absorption layers of direct X-ray detectors due to their adjustable band gap, high X-ray absorption capacity, long carrier lifetime and excellent charge carrier transport.

To prepare high-performance X-ray detectors based on perovskite materials, it is first necessary to produce a high-quality film or crystal that has sufficient X-ray absorption thickness and excellent photoelectric properties, and is highly compatible with the needs of the back-end electronic readout circuit.

At present, perovskite materials are mainly used in single crystal and polycrystalline devices for X-ray. Among them, the preparation of perovskite single crystals is cumbersome and demanding, and it is difficult to prepare large-area devices, and it is also difficult to integrate with the back-end readout circuit. Polycrystalline films prepared by traditional spin coating, evaporation, scraping and other methods also generally have problems such as insufficient thickness (easy to fall off and crack after the thickness increases) and many grain boundary defects, which seriously affect the performance of detection devices.

Summary of the invention

The technical problem to be solved by the present invention is to provide a method for preparing a composite perovskite thick film X-ray detector. The thick film obtained based on this method is not easy to fall off or crack, and has few grain boundary defects. The corresponding ITO substrate detector has excellent sensitivity and extremely low X-ray detection limit, and the corresponding TFT substrate detector has excellent spatial resolution.

The present invention adopts the following technical solutions to solve the above technical problems:

A method for preparing a composite perovskite thick film X-ray detector comprises the following steps:

(1) dissolving the random copolymer in an organic solvent to obtain a copolymer precursor solution;

(2) applying the copolymer precursor liquid obtained in step (1) on a clean ITO conductive glass or TFT thin film transistor by scraping, followed by annealing to obtain a pretreated ITO or TFT substrate;

(3) dissolving polycrystalline perovskite precursor powder into the copolymer precursor solution of step (1) to obtain a perovskite suspension precursor slurry;

(4) coating the perovskite suspension precursor slurry obtained in step (3) on the ITO or TFT substrate pretreated in step (2) by a doctor blade method, and annealing to form a perovskite absorption layer;

(5) The device obtained in step (4) is placed in a vacuum evaporator to evaporate the top Au common electrode to obtain a perovskite X-ray detector based on an ITO or TFT substrate.

As one of the preferred embodiments of the present invention, in the step (1), a random copolymer having a mass concentration of 5 to 30 mg/mL is weighed and dissolved in an organic solvent, and stirred at room temperature for 5 to 10 minutes to obtain a copolymer precursor solution.

As one of the preferred embodiments of the present invention, in step (1), the random copolymer is one of n-butyl acrylate-co-[N-(hydroxymethyl)-acrylamide]} (PBA-NMA), n-butyl acrylate-co-acrylamide (PBA-MA), and n-butyl acrylate-co-buteneamide (PBA-BM); by selecting a high molecular weight copolymer with polar hydrophilic groups and long-chain hydrophobic groups as an additive, it can play a dual role as an adhesive and a surfactant.

As one of the preferred embodiments of the present invention, in step (1), the organic solvent is one of gamma-butyrolactone (GBL) and dimethoxyethanol (2-Me); by selecting a solvent with high vapor pressure and low coordination, the residual solvent in the perovskite thick film is reduced.

As one of the preferred embodiments of the present invention, in the step (2), when the copolymer precursor liquid is scraped on the ITO and TFT, the thickness between the scraper and the substrate is 10-50 μm.

As one of the preferred embodiments of the present invention, in the step (2), the annealing condition is 100°C.

As one of the preferred embodiments of the present invention, in the step (3), 3-10 M polycrystalline perovskite precursor powder is weighed and dissolved into the copolymer precursor solution, and stirred for 30-60 min to obtain a perovskite suspension precursor slurry.

As one of the preferred embodiments of the present invention, in step (3), the polycrystalline perovskite precursor is one of methylamine lead iodide perovskite (MAPbI ₃ ), formamidine lead iodide perovskite (FAPbI ₃ ), cesium lead bromide perovskite (CsPbBr ₃ ), and trication perovskite (FAMACs).

As one of the preferred embodiments of the present invention, in step (4), when the perovskite suspension precursor slurry is scraped on the corresponding substrate, the distance between the scraper and the substrate is 100-1000 μm; the thickness of the final polycrystalline film is controlled by the distance of the scraper.

As one of the preferred embodiments of the present invention, in step (4), the annealing condition is annealing at 60-100° C. for 30-60 min; a lower annealing temperature helps to reduce the residual tensile stress in the thick film.

As one of the preferred embodiments of the present invention, in step (4), the thickness of the evaporated top Au common electrode is 80-120 nm; while ensuring good ohmic contact between the top electrode and the perovskite, the absorption loss of X-rays by the Au electrode is reduced.

The advantages of the present invention compared to the prior art are:

(1) Thick film is not easy to fall off: random copolymer is used to pre-treat ITO and TFT substrates to form a bidirectional coordination connection between the perovskite absorption layer and the substrate, enhance the adhesion between the perovskite and the substrate, and effectively prevent the perovskite polycrystalline thick film from falling off;

(2) Thick film is not easy to crack: The cross-linking of random copolymers in the polycrystalline thick film can effectively cope with the thermal expansion caused by the annealing process of the thick film, thereby reducing the thermal residual tensile stress, effectively preventing the cracking of the thick film, and improving the mechanical strength and service life of the polycrystalline thick film;

(3) Reduce grain boundary defects, and achieve extremely low dark current and extremely low X-ray detection limit: The perovskite suspension precursor slurry is composed of perovskite and random copolymers. The amphiphilic copolymer effectively reduces the surface tension of the precursor solution, increases the nucleation sites and nucleation rate, and effectively eliminates the pinhole problem caused by slow nucleation and solvent shrinkage in the formation of perovskite thick films, greatly improving the density of the thick film. At the same time, after the formation of the perovskite polycrystalline thick film, the copolymer at the grain boundary can also effectively passivate the perovskite grain boundary defects, effectively reducing the defect density, thereby inhibiting ion migration, so that the final wafer device has extremely low dark current and extremely low X-ray detection limit.

(4) Extremely high detection sensitivity: The dense structure and appropriate thickness of the prepared perovskite thick film ensure the effective absorption of X-rays by the detection device based on the ITO substrate. At the same time, the low defect density in the bulk phase of the polycrystalline thick film also ensures the effective extraction of photogenerated carriers, which ultimately significantly improves the detection sensitivity of the device to X-rays.

(5) Adjustable size and area, good compatibility: Compared with perovskite single crystal and thin film detectors, the polycrystalline thick film device prepared by the present invention is not only convenient, but also has adjustable size and area, and has excellent compatibility with the back-end substrate;

(6) Strong applicability: Due to the increased mechanical stability of the composite polycrystalline thick film, this process can achieve controllable preparation of nanometer to micrometer-level thickness, which can further realize multi-field applications from soft X-ray to hard X-ray large-area detection imaging;

(7) Excellent spatial resolution: Based on the highly compatible preparation process of the present invention, the prepared high-quality polycrystalline thick-film TFT substrate exhibits excellent adaptability after integration. Good interface contact ensures that the photoelectric signal of the perovskite absorption layer can be effectively read by the back-end circuit, ensuring that the imaging system of the X-ray detector has good uniformity and excellent spatial resolution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a physical picture of the perovskite thick film of Example 2;

FIG2 is a diagram showing the bonding state between the bottom of the perovskite thick film and the ITO substrate in Example 2;

FIG3 is a microscopic morphology of the perovskite thick film X-ray detector of Example 2;

FIG4 is a diagram showing the sensitivity test results of the perovskite thick film X-ray detector of Example 2;

FIG5 is a diagram showing the detection limit test results of the perovskite thick film X-ray detector of Example 2;

FIG6 is a physical picture of the perovskite thick film X-ray imager of Example 5;

FIG7 is a diagram showing the actual imaging result of the perovskite thick film X-ray imager of Example 5;

FIG8A is a physical picture of the upper interface of the perovskite thick film prepared in Comparative Example 1;

FIG8B is a physical picture of the lower interface of the perovskite thick film prepared in Comparative Example 1;

FIG9 is a microscopic morphology of the perovskite thick film of Comparative Example 1;

FIG10 is a graph showing the sensitivity test results of the perovskite thick film X-ray detector of Comparative Example 1;

FIG. 11 is a physical picture of the perovskite thick film of Comparative Example 2.

Detailed ways

The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

Example 1

A method for preparing a composite perovskite thick film X-ray detector (based on ITO) in this embodiment includes the following steps:

(1) In a glove box, weigh 5 mg/mL PBA-NMA and dissolve it in the GBL solution. Stir for 5 min at room temperature to obtain a copolymer precursor solution.

(2) The copolymer precursor liquid obtained in step (1) is coated on a clean ITO conductive glass using a scraper to a coating thickness of 10 μm, and then annealed at 100° C. to obtain a pretreated ITO substrate.

(3) Weigh 3M _MAPbI3 perovskite precursor powder and dissolve it in the copolymer precursor solution of step (1), and stir it thoroughly for 30 minutes to obtain a perovskite suspension precursor slurry.

(4) On a slit coater, the distance between the scraper and the ITO substrate was adjusted to 100 μm, and the perovskite suspension precursor slurry was evenly coated on the pretreated ITO by a scraping method, and annealed at 60 °C for 30 min to form a dense perovskite absorption layer.

(5) The device obtained in step (4) is placed in a vacuum evaporator to evaporate an 80 nm thick Au common electrode on the top to obtain a perovskite X-ray detector based on an ITO substrate.

Example 2

A method for preparing a composite perovskite thick film X-ray detector (based on ITO) in this embodiment includes the following steps:

(1) In a glove box, weigh 5 mg/mL PBA-NMA and dissolve it in 2-Me solution. Stir for 10 min at room temperature to obtain a copolymer precursor solution.

(2) The copolymer precursor liquid obtained in step (1) is coated on a clean ITO conductive glass using a scraper to a coating thickness of 10 μm, and then annealed at 100° C. to obtain a pretreated ITO substrate.

(3) Weigh 5 M FAMACs perovskite precursor powder and dissolve it in the copolymer precursor solution of step (1), and stir it thoroughly for 60 minutes to obtain a perovskite suspension precursor slurry.

(4) On a slit coater, the distance between the scraper and the ITO substrate was adjusted to 600 μm, and the perovskite suspension precursor slurry was evenly coated on the pretreated ITO by a scraping method, and annealed at 80 °C for 40 min to form a dense perovskite absorption layer.

(5) The device obtained in step (4) is placed in a vacuum evaporator to evaporate a 100 nm thick Au common electrode on the top to obtain a perovskite X-ray detector based on an ITO substrate.

Example 3

A method for preparing a composite perovskite thick film X-ray detector (based on ITO) in this embodiment includes the following steps:

(1) In a glove box, weigh 20 mg/mL PBA-MA and dissolve it in 2-Me solution. Stir at room temperature for 8 min to obtain a copolymer precursor solution.

(2) The copolymer precursor liquid obtained in step (1) is coated on a clean ITO conductive glass using a scraper to a coating thickness of 20 μm, and then annealed at 100° C. to obtain a pretreated ITO substrate.

(3) Weigh 8 M FAPbI ₃ perovskite precursor powder and dissolve it in the copolymer precursor solution of step (1), and stir it thoroughly for 50 minutes to obtain a perovskite suspension precursor slurry.

(4) On a slit coater, adjust the distance between the scraper and the ITO or TFT substrate to 800 μm, and use a scraping method to evenly coat the perovskite suspension precursor slurry on the pretreated ITO or TFT, and anneal at 80 °C for 50 min to form a dense perovskite absorption layer.

(5) The device obtained in step (4) is placed in a vacuum evaporator to evaporate a 100 nm thick Au common electrode on the top to obtain a perovskite X-ray detector based on an ITO substrate.

Example 4

A method for preparing a composite perovskite thick film X-ray detector (based on ITO) in this embodiment includes the following steps:

(1) In a glove box, weigh 30 mg/mL PBA-BM and dissolve it in the GBL solution. Stir for 10 min at room temperature to obtain a copolymer precursor solution.

(2) The copolymer precursor liquid obtained in step (1) is coated on a clean ITO conductive glass using a scraper to a coating thickness of 50 μm, and then annealed at 100° C. to obtain a pretreated ITO substrate.

(3) Weigh 10 M CsPbBr ₃ perovskite precursor powder and dissolve it in the copolymer precursor solution of step (1), and stir it thoroughly for 60 minutes to obtain a perovskite suspension precursor slurry.

(4) On a slit coater, the distance between the scraper and the ITO substrate was adjusted to 1000 μm, and the perovskite suspension precursor slurry was evenly coated on the pretreated ITO by a scraping method, and annealed at 100 °C for 60 min to form a dense perovskite absorption layer.

(5) The device obtained in step (4) is placed in a vacuum evaporator to evaporate a 120 nm thick Au common electrode on the top to obtain a perovskite X-ray detector based on an ITO substrate.

Example 5

A method for preparing a composite perovskite thick film X-ray detector (based on TFT) in this embodiment includes the following steps:

(1) In a glove box, weigh 5 mg/mL PBA-NMA and dissolve it in 2-Me solution. Stir for 10 min at room temperature to obtain a copolymer precursor solution.

(2) The copolymer precursor liquid obtained in step (1) is coated on a clean TFT thin film transistor using a scraper with a coating thickness of 10 μm, and then annealed at 100° C. to obtain a pretreated TFT substrate.

(3) Weigh 5 M FAMACs perovskite precursor powder and dissolve it in the copolymer precursor solution of step (1), and stir it thoroughly for 60 minutes to obtain a perovskite suspension precursor slurry.

(4) On a slit coater, the distance between the scraper and the TFT substrate was adjusted to 600 μm, and the perovskite suspension precursor slurry was evenly coated on the pretreated TFT by a scraping method, and annealed at 80 °C for 40 min to form a dense perovskite absorption layer.

(5) The device obtained in step (4) is placed in a vacuum evaporator to evaporate a 100 nm thick Au common electrode on the top to obtain a perovskite X-ray detector based on a TFT substrate.

Comparative Example 1

The preparation method of a composite perovskite thick film X-ray detector (based on ITO) in this comparative example is basically the same as that in Example 2, except that in step (3), 5 M FAMACs perovskite precursor powder is weighed and dissolved in 2-Me solvent instead of copolymer precursor solution.

Comparative Example 2

The preparation method of a composite perovskite thick film X-ray detector (based on ITO) in this comparative example is basically the same as that in Example 2, except that no pretreatment step of the ITO substrate is performed, and in step (3), 5 M FAMACs perovskite precursor powder is weighed and dissolved in 2-Me solvent instead of copolymer precursor solution.

Experimental Example 1

This experimental example is used to test the performance of two composite perovskite thick film X-ray detectors of the present invention:

1. Composite perovskite thick film X-ray detector based on ITO:

Taking Example 2 as an example, the perovskite thick film thereof is shown in FIG1 , and the surface is flat and dense, and FIG2 shows that the bottom of the perovskite thick film forms a good adhesion contact with the ITO substrate.

The perovskite X-ray detector of Example 2 was placed in a field emission scanning electron microscope to further observe its microscopic morphology, as shown in FIG3 , indicating that the dense nucleation sites and the accelerated crystallization process promote the formation of dense thick films with fewer grain boundary defects.

The perovskite X-ray detector of Example 2 was placed in a test bench in a shielding box, and a Keithley 6517B electrometer was used to perform relevant photoelectric performance tests. Its sensitivity is shown in FIG4 , which is 3410 μC G _yair ^-1 cm ^-2 , indicating that a high-quality perovskite thick film has excellent photoelectric performance. At the same time, combined with FIG3 , the repair of the pinholes in the thick film and the passivation of the crystal interface make it have a higher resistivity and a lower dark current, which can greatly reduce the detection limit of the detector. FIG5 shows that the detection limit of the prepared X-ray detector reaches 19.4 nGyairS ^-1 .

2. TFT-based composite perovskite thick film X-ray detector (i.e. perovskite thick film X-ray imager):

Taking Example 5 as an example, the appearance of the perovskite thick film X-ray imager prepared based on the TFT substrate is shown in Figure 6. The thickness of the perovskite absorption layer coated on the TFT reaches 600μm, and its sufficient thickness ensures the effective absorption of X-rays. Figure 7 is the actual imaging of the perovskite imager. Based on the excellent performance of the perovskite absorption layer, the components in the tested remote control can be clearly distinguished, indicating that it has excellent spatial resolution.

Experimental Example 2

This experimental example combines comparative examples 1 and 2 to verify the effects of "ITO substrate pretreatment" and "polycrystalline perovskite precursor composite random copolymer" on the perovskite thick film X-ray detector of the present invention:

The upper interface of the perovskite thick film prepared in Comparative Example 1 is shown in Figure 8A, the lower interface is shown in Figure 8B, and the microscopic morphology is shown in Figure 9 (there are grain boundary defects and a large number of pinholes): on the one hand, due to the adhesive effect of the copolymer that is not present in the bulk phase of the single perovskite polycrystalline thick film, after annealing and cooling, the residual shear stress causes cracks on the surface and bottom of the perovskite thick film; on the other hand, due to the large number of grain boundary defects and pinholes, serious signal noise and signal drift are caused, which will greatly affect the detection performance of the detector. The detector sensitivity is shown in Figure 10, and the sensitivity is only 950μC G _yair ^-1 cm ^-2 .

The perovskite thick film prepared in Comparative Example 2 is shown in FIG. 11 . Due to the lack of the bonding and interface effect of the copolymer, the perovskite thick film cracks and completely falls off from the substrate after annealing, making it impossible to perform effective detection.

In summary, the steps of "ITO substrate pretreatment" and "polycrystalline perovskite precursor composite random copolymer" have an important influence on the performance of the perovskite thick film X-ray detector of the present invention. The thick film obtained based on the method of the present invention is not easy to fall off or crack, and has few grain boundary defects. The corresponding detector has excellent sensitivity, extremely low X-ray detection limit, and excellent spatial resolution.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The preparation method of the composite perovskite thick film X-ray detector is characterized by comprising the following steps of:

(1) Dissolving a random copolymer into an organic solvent to obtain a copolymer precursor solution;

(2) Spreading the copolymer precursor liquid obtained in the step (1) on clean ITO conductive glass or TFT thin film transistor, and then annealing to obtain a pretreated ITO or TFT substrate;

(3) Dissolving polycrystalline perovskite precursor powder into the copolymer precursor liquid in the step (1) to obtain perovskite suspension precursor slurry;

(4) Coating the perovskite suspension precursor slurry obtained in the step (3) on the ITO or TFT substrate pretreated in the step (2) by adopting a blade coating method, and annealing to form a perovskite absorption layer;

(5) And (3) placing the device obtained in the step (4) into a vacuum evaporator, evaporating an Au common electrode at the top end, and obtaining the perovskite X-ray detector based on the ITO or TFT substrate.

2. The method for preparing the composite perovskite thick film X-ray detector according to claim 1, wherein in the step (1), the random copolymer with the mass concentration of 5-30 mg/mL is weighed and dissolved in an organic solvent, and the copolymer precursor liquid is obtained by stirring for 5-10 min at normal temperature.

3. The method for preparing a composite perovskite thick film X-ray detector according to claim 1, wherein in the step (1), the random copolymer is one of N-butyl acrylate-co- [ N- (hydroxymethyl) -acrylamide ] }, N-butyl acrylate-co-acrylamide and N-butyl acrylate-co-butenamide.

4. The method for preparing a composite perovskite thick film X-ray detector according to claim 1, wherein in the step (1), the organic solvent is one of gamma butyrolactone and dimethoxy ethanol.

5. The method for preparing a composite perovskite thick film X-ray detector according to claim 1, wherein in the step (2), the thickness of the scraper and the substrate is 10-50 μm when the copolymer precursor liquid is scraped on the ITO and the TFT.

6. The method of manufacturing a composite perovskite thick film X-ray detector as claimed in claim 1, wherein in step (2), the annealing condition is 100 ℃.

7. The method for preparing the composite perovskite thick film X-ray detector according to claim 1, wherein in the step (3), 3-10M of polycrystalline perovskite precursor powder is weighed and dissolved in the copolymer precursor liquid, and the mixture is fully stirred for 30-60 min to obtain perovskite suspension precursor slurry.

8. The method of claim 1, wherein in the step (3), the polycrystalline perovskite precursor is one of methylamine lead-iodine perovskite MAPbI ₃, formamidine lead-iodine perovskite FAPbI ₃, cesium lead-bromine perovskite CsPbBr ₃, and triple-cation perovskite FAMACs.

9. The method for preparing a composite perovskite thick film X-ray detector according to claim 1, wherein in the step (4), when the perovskite suspension precursor slurry is scraped on the corresponding substrate, the distance between the scraper and the substrate is 100-1000 μm.

10. The method for manufacturing a composite perovskite thick film X-ray detector according to claim 1, wherein in the step (4), the annealing condition is that the annealing is performed at 60-100 ℃ for 30-60 min.