A UV photodetector based on non-wide bandgap perovskite and its preparation method

Abstract

The present invention discloses an ultraviolet photodetector based on non-wide bandgap perovskite and a preparation method thereof. The photodetector is based on a mica sheet as a substrate, an ultrathin MAPbBr3 nanosheet is grown on the mica sheet, and a pair of electrodes are arranged on the ultrathin MAPbBr3 nanosheet. The present invention synthesizes the MAPbBr3 nanosheet based on the spatial confinement method and constructs an ultraviolet photodetector whose response peak can be tuned, and at the same time adjusts the thickness of the perovskite nanosheet to achieve ultraviolet photodetection.

Description

Technical Field

[0001] The invention belongs to the technical field of photoelectric detection, and in particular relates to an ultraviolet photoelectric detector and a preparation method thereof. Background Art

[0002] UV photodetectors based on wide bandgap semiconductors (SiC, GaN, Ga2O3, etc.) are widely used in military and civilian fields. However, some inevitable disadvantages, including relatively harsh preparation conditions and high manufacturing costs, hinder their further application. In recent years, with the rapid development of optoelectronic devices, the new concept of narrow bandgap semiconductor UV detectors has attracted the attention of researchers. For example, Xu et al. reported a graphene / ultrathin silicon-based UV photodetector. The prepared device showed a sensitive response to 365nm light, a high photoresponsivity of 0.47A / W, and superior mechanical flexibility (IEEE International Electron Devices Meeting (IEDM), 2017). This interesting study deliberately adjusted the broadband absorption of silicon so that the light absorption was mainly concentrated in the UV range. This strategy provides a new way to achieve UV photodetection using narrow bandgap materials.

[0003] Organic-inorganic hybrid perovskites have good solution processing performance, low cost and excellent optoelectronic properties, including tunable band gap, large absorption coefficient and long carrier diffusion, showing great potential in optoelectronic applications. Among organic-inorganic hybrid perovskites, the most studied materials are MAPbI3, MAPbBr3 and MAPbCl3, which have band gaps of about 1.5eV, 2.2eV and 3.1eV, respectively, and have corresponding absorption edges in the near-infrared, visible and ultraviolet ranges. In order to further expand or adjust the response range, researchers have tried to adjust the electronic band gap by finely controlling the composition of the compounds. So far, impressive progress has been made in the synthesis of excellent visible light absorbing materials for visible light detection using this technology. However, there are few studies on the synthesis of wide-bandgap UV-sensitive hybrid perovskite materials, which are mainly limited to Cl-based hybrid perovskites (e.g., MAPbCl3, MA2MnCl4), and their performance is not satisfactory. Summary of the invention

[0004] In order to avoid the shortcomings of the above-mentioned prior art, the present invention proposes a new type of ultraviolet photodetector based on non-wide bandgap perovskite, synthesizes MAPbBr3 nanosheets based on the spatial confinement method and constructs an ultraviolet photodetector with a tunable response peak. At the same time, by reducing the material thickness, the maximum light response of the photodetector is moved to a lower band.

[0005] In order to achieve the purpose, the present invention adopts the following technical scheme:

[0006] A UV photodetector based on non-wide bandgap perovskite, characterized in that: the photodetector uses a mica sheet as a substrate, an ultrathin MAPbBr3 nanosheet is grown on the mica sheet, and a pair of electrodes is arranged on the ultrathin MAPbBr3 nanosheet; the thickness of the ultrathin MAPbBr3 nanosheet is not more than 100nm.

[0007] Furthermore, the ultra-thin MAPbBr3 nanosheet is obtained by crystallizing and growing a precursor solution of lead bromide PbBr2 and methylamine bromide MABr dissolved in N,N-dimethylformamide DMF between two mica sheets.

[0008] Furthermore, the electrode is a gold electrode.

[0009] The method for preparing the ultraviolet photoelectric detector of the present invention comprises the following steps:

[0010] 1) Use acetone, alcohol, and deionized water to ultrasonically clean the glass reagent bottle, dry it, and then use a plasma cleaner to clean it for 10 to 20 minutes;

[0011] 2) Add MABr and PbBr2 in a molar ratio of 1:1 into a glass reagent bottle, add DMF as a solvent and stir until dissolved, filter, and obtain a perovskite precursor solution with a MAPbBr3 concentration of 0.2-0.25 mol / L;

[0012] 3) Take a mica sheet, peel it from the middle into two pieces, add 5 μL of perovskite precursor solution on one of the mica sheets, and then immediately cover it with another mica sheet; place the mica sheet with the perovskite precursor solution on a 30°C constant temperature heating table and heat it for 18-24 hours, then tear off the upper mica sheet to obtain an ultra-thin MAPbBr3 nanosheet;

[0013] 4) A pair of Au electrodes are deposited on the surface of the ultra-thin MAPbBr3 nanosheet using an electron beam deposition system to obtain an ultraviolet photodetector based on non-wide bandgap perovskite.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] 1. The ultraviolet photodetector of the present invention is realized based on the absorption coefficient of MAPbBr3 related to wavelength. The absorption coefficient of MAPbBr3 decreases with the increase of wavelength, while the penetration depth increases with the increase of wavelength. Therefore, by reducing the thickness of MAPbBr3, the maximum position of its light absorption can appear in the ultraviolet region, and the light absorption in other bands is significantly reduced, so that the device of the present invention exhibits a higher response in the ultraviolet region.

[0016] 2. The ultraviolet photodetector of the present invention is realized by reducing the thickness of MAPbBr3. Compared with the traditional inorganic wide bandgap semiconductor ultraviolet photodetector that uses the band gap to achieve ultraviolet detection, the device of the present invention provides a feasible solution for the application of non-wide bandgap materials in the field of ultraviolet photodetection.

[0017] 3. Compared with the preparation of traditional inorganic wide bandgap semiconductor materials, the preparation method of the ultrathin MAPbBr3 nanosheets proposed in the present invention has a simpler preparation process and lower cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the ultraviolet photodetector of the present invention; the numbers in the figure are: 1 is a mica substrate; 2 is a MAPbBr3 nanosheet; 3 is a gold electrode.

[0019] Figure 2 This is a SEM image of the MAPbBr3 nanosheets prepared in Example 1 of the present invention.

[0020] Figure 3 This is a surface roughness diagram of the MAPbBr3 nanosheets prepared in Example 1 of the present invention.

[0021] Figure 4 (a) and (b) are height diagrams of MAPbBr3 nanosheets prepared in Example 1 and Example 2 of the present invention, respectively.

[0022] Figure 5 These are the photocurrent and dark current characteristics of the ultraviolet photodetector obtained in Example 1 of the present invention.

[0023] Figure 6 These are the light response curves of the ultraviolet photodetector obtained in Example 1 of the present invention and the photodetector prepared in Example 2 under illumination of different wavelengths.

[0024] Figure 7 These are the spectral response curves of the ultraviolet photodetector obtained in Example 1 and the photodetector obtained in Example 2 of the present invention.

[0025] Figure 8 This is a curve showing the change of the responsivity and specific detectivity of the ultraviolet photodetector obtained in Example 1 of the present invention with wavelength.

[0026] Fig. 9 This is a curve showing the change of the responsivity and the ratio of the ultraviolet photodetector obtained in Example 1 of the present invention with the light power when the ultraviolet photodetector is illuminated at 300nm.

[0027] Fig.10This is the height map of MAPbBr3 nanosheets prepared in Example 3.

[0028] Fig.11 (a) and (b) are respectively the light response curve and spectral response curve of the photodetector prepared in Example 3 under illumination of different wavelengths.

[0029] Fig.12 This is a curve showing the change in responsivity and specific detectivity of the photodetector prepared in Example 3 as a function of wavelength.

[0030] Fig.13 This is a curve showing how the responsivity and specific detectivity of the photodetector prepared in Example 3 change with light power when illuminated at 365 nm. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail in combination with the embodiments below. The following content is only an example and explanation of the concept of the present invention. The technicians in the relevant technical field make various modifications or supplements to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

[0032] Example 1

[0033] See also Figure 1 The structure of the photodetector of this embodiment is, from bottom to top, a mica substrate, an ultrathin MAPbBr3 nanosheet, and a pair of parallel and spaced gold electrodes located on the surface of the nanosheet.

[0034] Specifically: The perovskite nanosheets of this embodiment are grown on a mica substrate by a spatial confinement method, wherein the prepared perovskite solution is dripped onto the mica sheet, and then the mica sheet sandwiched with the solution is heated at a constant temperature of 30°C for 18 hours. Finally, MAPbBr3 nanosheets are grown on the surface of the mica sheet, and the thickness is about 42nm.

[0035] The preparation method of the photoelectric detector of this embodiment is as follows:

[0036] 1) Use acetone, alcohol, and deionized water to ultrasonically clean a 5mL glass reagent bottle, dry it, and then clean it with a plasma cleaner for 20 minutes.

[0037] 2) Add 0.0224 g MABr and 0.0734 g PbBr2 in a glass reagent bottle, then add 1 mL of DMF, seal and stir until completely dissolved, and filter with a filter with a diameter of 0.13 μm × 0.13 μm to obtain a perovskite precursor solution with a MAPbBr3 concentration of 0.2 mol / L.

[0038] 3) Take a mica sheet and peel it into two pieces from the middle. Add 5 μL of perovskite precursor solution on one of the mica sheets, and then immediately cover it with another mica sheet. Place the mica sheet with the perovskite precursor solution on a 30°C constant temperature heating table and heat it for 18 hours. Then tear off the upper mica sheet to obtain the ultra-thin MAPbBr3 nanosheet.

[0039] 4) A pair of 50 nm thick Au electrodes were deposited on the surface of ultra-thin MAPbBr3 nanosheets using an electron beam deposition system to obtain a UV photodetector based on non-wide bandgap perovskite.

[0040] Example 2

[0041] The photoelectric detector of this embodiment has the same structure and preparation method as that of Embodiment 1, with the only difference being that: in step 2), 0.0448 g MABr and 0.1468 g PbBr2 are added to obtain a perovskite precursor solution with a MAPbBr3 concentration of 0.4 mol / L; and in step 3), the heating time is 24 h.

[0042] Figure 2 This is a SEM film of the ultrathin MAPbBr3 nanosheet prepared in Example 1. It can be seen that the surface of the nanosheet is smooth, without defects such as holes, and the surface is relatively flat.

[0043] Figure 3 This is a surface roughness diagram of the MAPbBr3 nanosheets prepared in Example 1. It can be seen from the figure that the surface roughness of the nanosheets is very small, less than 1 nm, which indicates that the surface flatness of the nanosheets is very good and the thickness is uniform.

[0044] Figure 4 (a) and (b) are height diagrams of MAPbBr3 nanosheets prepared in Example 1 and Example 2, respectively. It can be seen from the figures that the thickness of the nanosheets is 42.6 nm and 365.5 nm, respectively.

[0045] Figure 5 The ultraviolet photodetector prepared in Example 1 is in dark conditions and the light power is 1.0 mW / cm 2 IV curve under 530nm illumination. The linear relationship in the figure shows that the device is a photoconductive device.

[0046] Figure 6 The ultraviolet photodetector prepared in Example 1 and the photodetector prepared in Example 2 were subjected to a bias voltage of 3 V and a light power of 1.0 mW / cm 2The light response curves under different wavelengths of light (265nm, 300nm, 365nm, 450nm and 530nm). It can be seen from the figure that the responses of the photodetectors prepared based on MAPbBr3 nanosheets of different thicknesses are completely different. The photodetector prepared in Example 1 has a higher sensitivity to ultraviolet light, but a lower sensitivity to visible light. When illuminated at 300nm, the response is the largest. The photodetector prepared in Example 2 responds to visible light more than ultraviolet light, and responds to the largest light at 530nm.

[0047] Figure 7 The spectral response curves of the photodetectors prepared in Example 1 and Example 2 show that the response peak of the device in Example 1 is around 300nm, and the response in the ultraviolet region is higher than that in other bands. This is in sharp contrast to the spectral response of the device in Example 2, where the light response in the ultraviolet region is significantly improved and the light response in other bands is greatly reduced.

[0048] Figure 8 The ultraviolet photodetector prepared in Example 1 was biased at 3V and had an optical power of 1.0 mW / cm 2 The change curves of responsivity and specific detection rate under different wavelengths of light (265nm, 300nm, 365nm, 450nm and 530nm) show that when the light is irradiated at 300nm, the responsivity and specific detection rate are the largest, which are 17.9mA / W and 4.2×10 8 Jones.

[0049] Fig. 9 The curve of the responsivity and specific detection rate of the ultraviolet photodetector prepared in Example 1 as a function of light power, the illumination wavelength is 300nm. It can be seen that as the light power increases, the responsivity and specific detection rate gradually decrease. When the light power is 0.022mW / cm 2 When , the responsivity and specific detectivity are the largest, which are 27.2mA / W and 6.38×10 8 Jones.

[0050] Example 3

[0051] The photodetector of this embodiment has the same structure and preparation method as that of Embodiment 1, with the only difference being that: in step 2), 0.0257 g MABr and 0.0844 g PbBr2 are added to obtain a perovskite precursor solution with a MAPbBr3 concentration of 0.23 mol / L; and in step 3), the heating time is 20 h.

[0052] Fig.10 This is a height diagram of the MAPbBr3 nanosheets prepared in Example 3. It can be seen from the figure that the thickness of the prepared nanosheets is 74.4 nm.

[0053] Fig.11 (a) and (b) are the photodetector prepared in Example 3 at a bias voltage of 3 V and a light power of 1.0 mW / cm 2 The light response curve and spectral response curve under different wavelengths of light (265nm, 300nm, 365nm, 450nm and 530nm). Fig.11 As can be seen in (a), the device has the largest photoresponse under 365nm illumination. Fig.11 (b) shows that the response peak of the device is around 365nm, which is different from the light response of the photodetectors prepared in Examples 1 and 2.

[0054] Fig.12 The photodetector prepared in Example 3 was subjected to a bias voltage of 3 V and a light power of 1.0 mW / cm 2 The change curves of responsivity and specific detection rate under different wavelengths of light (265nm, 300nm, 365nm, 450nm and 530nm) show that when the light is irradiated at 365nm, the responsivity and specific detection rate are the largest, which are 3.2mA / W and 2.01×10 8 Jones.

[0055] Fig.13 The curve of the responsivity and specific detection rate of the photodetector prepared in Example 3 as a function of light power, with an illumination wavelength of 365 nm. It can be seen that as the light power increases, the responsivity and specific detection rate gradually decrease. When the light power is 0.0807 mW / cm 2 When , the responsivity and specific detectivity are the largest, which are 5.8mA / W and 3.6×10 8 Jones.

[0056] The above are only preferred embodiments of the present invention and are 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

1. A non-wide bandgap perovskite-based ultraviolet photodetector, characterized in that: The photodetector uses a mica sheet as a substrate, an ultrathin MAPbBr3 nanosheet is grown on the mica sheet, and a pair of electrodes are arranged on the ultrathin MAPbBr3 nanosheet; the thickness of the ultrathin MAPbBr3 nanosheet is not greater than 100 nm.

2. The non-wide bandgap perovskite-based ultraviolet photodetector according to claim 1, characterized in that: The ultra-thin MAPbBr3 nanosheet is obtained by crystallizing and growing a precursor solution formed by dissolving lead bromide PbBr2 and methylamine bromide MABr in N,N-dimethylformamide DMF between two mica sheets.

3. The non-wide bandgap perovskite-based ultraviolet photodetector according to claim 1, characterized in that: The electrode is a gold electrode.

4. A method for preparing the ultraviolet photodetector according to any one of claims 1 to 3, characterized in that: The steps include: 1) Use acetone, alcohol, and deionized water to ultrasonically clean the glass reagent bottle, dry it, and then use a plasma cleaner to clean it for 10 to 20 minutes; 2) Add MABr and PbBr2 in a molar ratio of 1:1 into a glass reagent bottle, add DMF as a solvent and stir until dissolved, filter, and obtain a perovskite precursor solution with a MAPbBr3 concentration of 0.2-0.25 mol / L; 3) Take a mica sheet, peel it from the middle into two pieces, add 5 μL of perovskite precursor solution on one of the mica sheets, and then immediately cover it with another mica sheet; place the mica sheet with the perovskite precursor solution on a 30°C constant temperature heating table and heat it for 18-24 hours, then tear off the upper mica sheet to obtain an ultra-thin MAPbBr3 nanosheet; 4) A pair of Au electrodes are deposited on the surface of the ultra-thin MAPbBr3 nanosheet using an electron beam deposition system to obtain an ultraviolet photodetector based on non-wide bandgap perovskite.

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