Perovskite wafer x-ray detector with surface passivation to inhibit ion migration and method of making

Abstract

The application discloses a perovskite wafer X-ray detector with surface passivation and ion migration inhibition and a preparation method thereof. Ethylenediamine dihydroiodide is doped into methylamine lead iodine, and a wafer is prepared by a vacuum hot pressing method, so that an X-ray detector device based on ethylenediamine dihydroiodate passivated wafer surface / grain boundary defects with a structure of Au / wafer / Au is obtained. The introduced ethylenediamine dihydroiodate provides additional I ions, which can fill the vacancies of halides in the methylamine lead iodine, so that ion migration in the grain boundary is inhibited, and the perovskite grain boundary is passivated. The prepared X-ray detector has increased ion migration activation energy, the current remains stable under a high bias voltage, and a high sensitivity of 10016.11 mu C Gy air ‑1 cm ‑2 is achieved under a bias voltage of 10 V, which is 26 times the optimal sensitivity of a commercial amorphous selenium detector.

Description

Technical Field

[0001] The present invention belongs to the technical field of X-ray detector devices and relates to a perovskite wafer X-ray detector with surface passivation for suppressing ion migration and a preparation method thereof. Background Art

[0002] X-rays are widely used in fields such as crystallography, medical diagnosis, and space exploration, and the precise detection of high-performance X-ray detectors is of great significance. In recent years, organic-inorganic hybrid halide perovskites have been considered as highly efficient X-ray detector materials. They have the advantages of strong radiation blocking ability, large mobility lifetime (μτ) product, adjustable band gap, strong radiation resistance, and low cost. They have shown great application potential in the preparation of low-cost, large-area, high-performance X-ray detectors. However, perovskites usually have serious ion migration problems, which not only cause baseline drift and affect signal acquisition, but also lead to low imaging resolution, reduced detection sensitivity, accelerated decomposition of perovskites, and seriously damage the stability of the device. In addition, under high external bias, the current drift is more serious, which greatly limits their application in X-ray detectors.

[0003] To address the above issues, two main methods are currently used to inhibit ion migration in perovskites: (1) reducing the defect concentration of large-sized grains through surface passivation or ion doping; and (2) reducing the dimensionality of the perovskite structure to limit charge transport and ion migration within the quantum well plane. In addition, thick perovskite films are essential for ideal X-ray detection because they can withstand the penetration of high-intensity X-rays and can completely absorb X-rays. Currently, it is extremely difficult to prepare large-area, millimeter-thick, high-quality perovskite films for imaging applications. In traditional solution processes, the inevitable evaporation of solvents will leave a large number of pinholes in the thick film, seriously hindering charge transport and reducing imaging resolution. In order to reduce the porosity of the grains, researchers used cold isostatic pressing (Nat. Commun. 2019, 10, 1989) and hot pressing (ACS Appl. Mater. Interfaces. 2020, 12, 16592-16600; J. Mater. Chem. A. 2021, 9, 25603-25610) to prepare highly dense wafers and produce highly sensitive X-ray detectors, fully demonstrating the advantages of the sheet pressing method in preparing large-area and large-size perovskite films. However, due to the serious ion migration problem under high voltage, it will cause baseline drift, affecting the stability of the device, which is very common in MAPbI3 devices.

[0004] In summary, there is an urgent need to research and develop some effective solutions to solve the ion migration problem, which is of great significance for the development of large-size, high-quality perovskite X-ray detectors with excellent optoelectronic performance. Summary of the Invention

[0005] The present invention aims to provide a perovskite wafer X-ray detector with surface passivation to suppress ion migration and a method for preparing the same. This method uses ethylenediamine dihydroiodide (EDDI) as a surface passivator, which not only fills surface iodide vacancies but also exhibits a strong binding effect. This X-ray detector, which suppresses ion migration through surface passivation, exhibits superior performance.

[0006] The technical solutions for achieving the purpose of the present invention are as follows:

[0007] A method for preparing a perovskite wafer X-ray detector with surface passivation to inhibit ion migration comprises the following steps:

[0008] Step 1: methylamine lead iodine powder and EDDI powder are blended and ground. The ground MAPbI3@EDDI composite powder is loaded into a hot pressing device and hot pressed at a pressure of 25 MPa, a holding time of 10 to 15 minutes, and a temperature of 150 to 155°C to obtain a large-sized MAPbI3@EDDI composite wafer;

[0009] Step 2: Deposit a layer of gold film on the upper and lower surfaces of the MAPbI3@EDDI composite wafer to obtain an X-ray detector.

[0010] In the present invention, MAPbI3 powder can be prepared using conventional methods. In a specific embodiment of the present invention, the preparation method of MAPbI3 powder is as follows: methylamine iodine and lead iodide are first mixed in a molar ratio of 1:2, and heated to 60-70°C with stirring to obtain a MAPbI3 precursor solution. Chloroform is then added to the precursor solution, and the mixture is rapidly stirred for 30 seconds to obtain methylamine lead iodine microcrystals. Finally, the microcrystals are centrifuged at 8000 rpm for 2 minutes, dried, and ground for 10-20 minutes to obtain MAPbI3 powder.

[0011] In the present invention, ethylenediamine dihydroiodide (EDDI) powder can be prepared using conventional methods or purchased directly. In a specific embodiment of the present invention, the EDDI powder is prepared as follows: an ethylenediamine solution and a hydroiodic acid solution are stirred and mixed in an ice bath at a molar ratio of 1:1. The ethylenediamine solution and the hydroiodic acid solution are then subjected to rotary evaporation. The rotary evaporation is stopped when a white powdery solid appears. The EDDI powder is then rinsed repeatedly with anhydrous ether 6-7 times to remove impurities, thereby obtaining the EDDI powder. Preferably, the rotary evaporation speed is 33 rpm and the temperature is 65°C.

[0012] Furthermore, in step 1, the doping amount of EDDI is 0.5% to 2%, more preferably 1% to 1.5%.

[0013] Furthermore, in step 2, the size of the MAPbI3@EDDI composite wafer is 20 mm, and the thickness of the gold film is 80 nm.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] (1) The raw materials of the method of the present invention are easily available, the cost is low, and the preparation method is simple.

[0016] (2) The present invention introduces cheap and non-toxic EDDI as a passivating agent. Due to the uncoordinated effect between Pb and I atoms, the chance of electron capture increases. The presence of EDDI can compensate for the I by connecting the amine group to the crystal through electrons. - loss in the crystal and uses the excess I to fill the surface I - vacancies, suppressing most of the I - Vacancies are formed, thereby suppressing most vacancies and reducing ion migration channels, thereby suppressing ion migration in the device. The X-ray detector prepared by the present invention has increased ion migration activation energy, and the current remains stable under high bias voltage, achieving 10016.11μC Gy at a bias voltage of 10V. air - 1 cm -2 The high sensitivity is 26 times that of the best commercial amorphous selenium detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the principle of surface passivation to inhibit ion migration.

[0018] Figure 2 This is an analysis diagram of the current-voltage (IV) characteristics of the reference samples prepared at different holding times and hot pressing temperatures in Comparative Examples 1-4.

[0019] Figure 3 This is the current-voltage (IV) characteristic analysis diagram of the sample modified with 1% EDDI prepared in Comparative Example 5.

[0020] Figure 4 Graphs showing the current-voltage (IV) characteristics of the reference sample prepared in Comparative Example 1 and the modified samples with different EDDI doping ratios prepared in Examples 1-4.

[0021] Figure 5 Surface and cross-sectional SEM images of the reference sample prepared in Comparative Example 1 and the 1% EDDI modified sample prepared in Example 2.

[0022] Figure 6The time-resolved PL decay curves of the reference sample prepared in Comparative Example 1 and the 1% EDDI modified sample prepared in Example 2 were obtained, and the carrier lifetimes before and after EDDI modification were calculated to be 1.46 ns and 6.01 ns, respectively, by double exponential fitting.

[0023] Figure 7 The PL spectra of the reference sample prepared in Comparative Example 1 and the 1% EDDI modified sample prepared in Example 2.

[0024] Figure 8 The ion transport activation energy (E a ) fitting curve of the reference sample prepared in Comparative Example 1 before 1% EDDI modification. a The E

[0025] Figure 9 The ion transport activation energy (E a ) fitting curve of the 1% EDDI modified sample prepared in Example 2 before 1% EDDI modification. a The E

[0026] Figure 10 The X-ray response current curves of the 1% EDDI modified sample prepared in Example 2 at different dose rates under 1 V, 2 V, 5 V and 10 V bias voltages.

[0027] Figure 11 The relationship curve between electric field function and sensitivity of the 1% EDDI modified sample prepared in Example 2.

[0028] Figure 12 The device working stability comparison chart of the reference sample prepared in Comparative Example 1 and the 1% EDDI modified sample prepared in Example 2 under 1 V bias voltage. The stability test was carried out in ambient air without packaging.

[0029] Figure 13 The device working stability comparison chart of the 1% EDDI modified sample prepared in Example 2 under 5 V and 10 V bias voltages. DETAILED DESCRIPTION

[0030] The present application will be further illustrated below in conjunction with the accompanying drawings and specific examples, which should be understood as merely illustrating the present application and not limiting the scope of the present application. After reading the present application, those skilled in the art can make various modifications to the present application, which fall within the scope defined by the appended claims.

[0031] Comparative Example 1

[0032] Preparation of MAPbI3 powder: 0.8g of methylamine iodine and 2.3g of lead iodide are added to a 20mL glass vial. A rotor is then added, and 5mL of γ-butyrolactone is pipetted into the vial. Stirring is carried out at 60°C for 3h to obtain a clear, transparent yellow MAPbI3 solution. MAPbI3 microcrystals are then precipitated using an antisolvent method: 1mL of MAPbI3 solution is rapidly stirred for 30s, followed by the addition of 15mL of chloroform. The solution will turn black instantly, indicating precipitation of MAPbI3. After stirring for 30s, the solution is transferred to a 50mL centrifuge tube and centrifuged at 8000 rpm for 2min. The supernatant is discarded, and the precipitate is retained. Another 15mL of chloroform is then added to the precipitate and centrifuged once more to obtain relatively pure methylamine lead iodine. After repeating this step 5 times, the obtained MAPbI3 is placed in a vacuum drying oven and dried for 12 hours to obtain a MAPbI3 block solid. After grinding for 10 minutes, a black powder of uniform size is obtained.

[0033] Preparation method for a MAPbI3 chip X-ray detector: The prepared MAPbI3 powder is sieved and collected. 0.5g of powder is weighed and placed into a homemade hot-pressing mold. Before hot-pressing, the hot-pressing gasket is cleaned to prevent surface contamination. After confirmation, the hot-pressing mold containing the MAPbI3 powder is placed into a hot press. The pressure is set to 25MPa, the holding time is set to 60min, and the hot-pressing temperature is set to 120°C. After the program settings are complete, the hot-pressing switch is activated for hot-pressing. After approximately 6 hours, when the temperature inside the cavity cools to room temperature, the mold is removed and demolded to obtain the MAPbI3 chip. Gold electrodes are then deposited using thermal evaporation. Using a vacuum coating apparatus, metal Au is evaporated onto the upper and lower surfaces of the MAPbI3 chip (approximately 80nm thick), resulting in a complete X-ray detector device.

[0034] Comparative Example 2

[0035] This comparative example is basically the same as comparative example 1, except that the hot pressing temperature is 140°C.

[0036] Comparative Example 3

[0037] This comparative example is basically the same as comparative example 1, the only difference being that the holding time is 10 min.

[0038] Comparative Example 4

[0039] This comparative example is basically the same as comparative example 1, except that the holding time is 10 min and the hot pressing temperature is 140°C.

[0040] Comparative Example 5

[0041] The preparation method of MAPbI3 powder is the same as that of Comparative Example 1.

[0042] The preparation method of the MAPbI3@1%PEAI composite chip X-ray detector is as follows: 0.5g MAPbI3 and 0.005g phenylethylamine iodine (PEAI) are blended and ground for 10 minutes to obtain MAPbI3@1%PEAI composite powder; the ground MAPbI3@1%PEAI composite powder is loaded into a hot pressing device, and hot pressed at a pressure of 25MPa, a holding time of 10min and a temperature of 150°C to obtain a micron-thick and large-sized MAPbI3@1%PEAI composite chip.

[0043] The current-voltage (IV) characteristics of the detectors prepared in Comparative Examples 1-4 and Comparative Example 5 were measured (see Figure 2 and Figure 3 ) tests were performed to characterize the device's dark current and on-off ratio. The test results showed that the on-off ratio was low and the dark current was high under four different thermal stress conditions, indicating device performance variation. Furthermore, the on-off ratio of the MAPbI3 composite wafer X-ray detector, doped with PEAI, was low, resulting in poor device responsiveness.

[0044] Example 1

[0045] Preparation of EDDI powder: Add 1.1946g of ethylenediamine solution and 27.1210g of hydroiodic acid solution to a reaction vessel. Then, slowly drip 10mL of anhydrous ethanol into the vessel. Place a rotor, seal the container with a dust-free cloth, and stir in an ice bath (0°C) for 6 hours. After stirring, remove the rotor, set the rotary evaporator speed to 33 rpm, and the water bath to 65°C. Secure the flask to the evaporator interface, close the vent valve, turn on the circulating water vacuum pump, adjust the position between the water bath and the flask, and begin rotary evaporation. After waiting for 30 minutes, a white powdery solid will appear in the flask. If no noticeable solvent evaporation continues for about 3 minutes, stop rotary evaporation to obtain a slightly yellowish EDDI powder. The powder at this point contains a lot of impurities and needs to be repeatedly rinsed with anhydrous ether 6-7 times until no visible yellow impurities remain in the flask. This will result in a high-purity white ethylenediamine hydroiodide powder.

[0046] Preparation method of MAPbI3 powder: 0.8 g of methylamine iodine and 2.3 g of lead iodide were added into a 20 mL glass bottle, a rotor was added, 5 mL of γ-butyrolactone was removed by a pipette gun into the glass bottle, and stirring was performed at 60°C for 3 h to obtain a clear and transparent MAPbI3 yellow solution. Next, MAPbI3 microcrystals were precipitated by using an anti-solvent method: 1 mL of the MAPbI3 solution was first measured, 15 mL of chloroform was added after rapid stirring for 30 s, and it was observed that the solution turned black instantaneously, indicating that MAPbI3 had been precipitated. After stirring for 30 s, the solution was removed into a 50 mL centrifuge tube and centrifuged at a speed of 8000 rpm for 2 min. The supernatant was discarded, and the precipitate was retained. 15 mL of chloroform was added into the precipitate and centrifuged once. Thus, relatively pure methylamine lead iodine was obtained. After repeating this step 5 times, the obtained MAPbI3 was placed in a vacuum drying oven and dried for 12 h to obtain a MAPbI3 block solid. After grinding for 10 min, a uniform size black powder of MAPbI3 was obtained.

[0047] Preparation method of MAPbI3@0.5% EDDI composite wafer X-ray detector: 0.5 g of MAPbI3 and 0.0025 g of EDDI were blended and ground for 10 min to obtain MAPbI3@0.5% EDDI composite powder. The ground MAPbI3@0.5% EDDI composite powder was loaded into a hot pressing device, and hot pressing was performed at a pressure of 25 MPa, a pressure holding time of 10 min, and a temperature of 150°C to obtain a micrometer-thickness and large-size MAPbI3@0.5% EDDI composite wafer.

[0048] Example 2

[0049] This example is basically the same as Example 1, the only difference being that the doping amount of EDDI is 1%, and the mass of EDDI is 0.005 g. The prepared device is a MAPbI3@1% EDDI composite wafer X-ray detector.

[0050] Example 3

[0051] This example is basically the same as Example 1, the only difference being that the doping amount of EDDI is 1.5%, and the mass of EDDI is 0.0075 g. The prepared device is a MAPbI3@1.5% EDDI composite wafer X-ray detector.

[0052] Example 4

[0053] This example is basically the same as Example 1, the only difference being that the doping amount of EDDI is 2%, and the mass of EDDI is 0.01 g. The prepared device is a MAPbI3@2% EDDI composite wafer X-ray detector.

[0054] The surface morphology SEM of the detector prepared under the above conditions is shown in FIG. 1. Figure 5 ) to determine the passivation effect of EDDI on the surface of MAPbI3 wafers. The test results show that after EDDI passivation, the surface morphology of the wafer is denser and the grains are larger ( Figure 5 c and Figure 5 d).

[0055] The detectors prepared under the above conditions were tested for fluorescence spectrum, carrier lifetime and migration activation energy. The test results show that after EDDI passivation, the fluorescence intensity and carrier lifetime of the perovskite wafer (see Figure 6 、 Figure 7 、 Figure 8 and Figure 9 ) increase, and the ion migration activation energy increases, indicating that the ion migration in the chip is significantly inhibited.

[0056] The sensitivity and stability of the detector prepared under the above conditions were tested. The test results showed that after EDDI passivation, the detector achieved a Gyair sensitivity of 10016.11μC at a bias voltage of 10V. -1 cm -2 High sensitivity ( Figure 10 and Figure 11 ), which is 26 times the best sensitivity of commercial amorphous selenium detectors. In addition, the prepared X-ray detector can work for a long time (300min) at a high bias voltage (20V) ( Figure 12 and Figure 13 ), the baseline remains flat.

[0057] The above embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for preparing a perovskite wafer X-ray detector with surface passivation to inhibit ion migration, characterized in that: The steps include: Step 1: methylamine lead iodine powder and EDDI powder are blended and ground. The ground MAPbI3@EDDI composite powder is loaded into a hot pressing device and hot pressed at a pressure of 25 MPa, a holding time of 10 to 15 minutes, and a temperature of 150 to 155°C to obtain a large-sized MAPbI3@EDDI composite wafer; Step 2: Deposit a layer of gold film on the upper and lower surfaces of the MAPbI3@EDDI composite wafer to obtain an X-ray detector.

2. The preparation method according to claim 1, characterized in that The preparation method of MAPbI3 powder is as follows: according to the molar ratio of methylamine iodine and lead iodide of 1:2, methylamine iodine, lead iodide and γ-butyrolactone are first mixed and stirred and heated to 60-70°C to obtain a MAPbI3 precursor solution, and then chloroform is added to the precursor solution. After rapid stirring for 30 seconds, methylamine lead iodine microcrystals are obtained. Finally, the microcrystals are centrifuged at 8000 rpm for 2 minutes, dried, and ground for 10-20 minutes to obtain MAPbI3 powder.

3. The preparation method according to claim 1, characterized in that The preparation method of EDDI powder is as follows: according to the molar ratio of ethylenediamine and hydroiodic acid being 1:1, ethylenediamine solution and hydroiodic acid solution are first stirred and mixed in an ice bath to obtain an ethylenediamine dihydroiodide precursor solution, and then the ethylenediamine dihydroiodide precursor solution is rotary evaporated. When a white powdery solid appears, the rotary evaporation is stopped, and the solution is repeatedly rinsed with anhydrous ether 6-7 times to remove impurities to obtain ethylenediamine dihydroiodide powder.

4. The preparation method according to claim 3, characterized in that The rotation speed during rotary evaporation was 33 rpm and the temperature was 65°C.

5. The preparation method according to claim 1, characterized in that In step 1, the doping amount of EDDI is 0.5% to 2%.

6. The preparation method according to claim 1, characterized in that In step 1, the doping amount of EDDI is 1% to 1.5%.

7. The preparation method according to claim 1, characterized in that In step 2, the size of the MAPbI3@EDDI composite wafer is 20 mm, and the thickness of the gold film is 80 nm.

8. An X-ray detector manufactured according to the manufacturing method according to any one of claims 1 to 7.

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