A narrow-band photodetector based on bromine lead cesium / methylamine lead bromide single crystal heterojunction and a preparation method thereof

Abstract

The application discloses a narrow-band photodetector based on a bromine lead cesium / methylamine lead bromide single crystal heterojunction and a preparation method thereof, and realizes light detection through a heterojunction formed by a CsPbBr3 single crystal and a MAPbBr3 single crystal. The photodetector has the advantages of narrow detection waveband range and high selectivity.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic materials and devices, specifically relating to a narrowband photodetector based on a cesium bromide / methylamine lead bromide single-crystal heterojunction and its fabrication method. Background Technology

[0002] The primary function of photodetectors is to convert light signals, which are difficult to quantify, into quantifiable and precisely measurable electrical signals. They play a crucial role in industry and scientific research, such as imaging, optical communication, sensors, and environmental monitoring. The key technology of photodetectors lies in finding a semiconductor material with excellent light response performance. This semiconductor material, acting as a photosensitive layer, absorbs photon energy and generates electron-hole pairs (charge carriers). These separated electrons and holes are transported to the electrodes under the influence of a built-in electric field or an applied bias voltage, thus generating a current. Currently, commercially available detectors primarily use inorganic semiconductor materials, such as gallium nitride, silicon, and indium gallium arsenide. These detectors have advantages such as mature fabrication processes and well-defined working principles, but their fabrication processes are complex, manufacturing costs are high, and they require very high driving voltages. These drawbacks limit their application prospects and scope. In recent decades, low-cost, easy-to-process, and low-consumption photoelectric materials, such as organic materials, nanomaterials, and nanocomposite materials, have shown great application potential in the field of flexible large-area detectors. However, since around 2016, perovskite materials have become a rising star in optoelectronics, becoming a hot research topic in optics and optoelectronics, from zero-dimensional quantum dots to one-dimensional nanowires, and then to two-dimensional thin films and three-dimensional perovskite single crystals. Perovskite single crystals have attracted widespread attention in the field of optoelectronics due to their significant optical and optoelectronic properties, including tunable direct bandgap, high carrier mobility, long electron-hole diffusion length, large absorption coefficient, and ease of integration with various semiconductor materials. The general formula for perovskite is: ABX3[A=CH3NH3] + (methylammonium, MA) + ),CH(NH2)2 + (formamidinium,FA + ), or Cs+; B=Pb 2+ Sn 2+ ,or Ge 2+ [;X = I-,Br-,Cl- or mixtures thereof], and other similar crystal structures, such as the well-known CaTiO3. These unique properties make perovskite materials promising candidates for various optoelectronic devices, such as photovoltaics, photoluminescent devices, and photodetectors.

[0003] Highly selective narrowband photodetectors have significant applications in biomedical sensing, machine vision, and image processing. Traditionally, broadband spectra are filtered or dispersed using optical filters or spectrometers, then detected by broadband photodetectors to identify wavelengths. However, this approach is costly and results in large systems. Summary of the Invention

[0004] This invention proposes a high-performance narrowband photodetector based on an all-inorganic perovskite lead bromide cesium single crystal / organic-inorganic hybrid perovskite methylamine lead bromide single crystal heterojunction and its fabrication method, aiming to achieve highly selective detection in a specific wavelength band.

[0005] To achieve its objectives, the present invention employs the following technical solution:

[0006] A narrowband photodetector based on a cesium bromide / methylamine lead bromide single-crystal heterojunction is characterized in that: the narrowband photodetector achieves light detection through a heterojunction composed of CsPbBr3 single crystal and MAPbBr3 single crystal.

[0007] The fabrication method of the narrowband photodetector described in this invention is as follows: First, a CsPbBr3 single crystal is prepared by solvent evaporation. Then, a MAPbBr3 single crystal is epitaxially grown on the upper surface and around the CsPbBr3 single crystal using a temperature inversion method to form a CsPbBr3 / MAPbBr3 single crystal heterojunction. Finally, the upper and lower electrodes are fabricated using carbon paste, thus obtaining the narrowband photodetector. Specifically, the method includes the following steps:

[0008] Step 1: Preparation of CsPbBr3 single crystals

[0009] PbBr2 and CsBr were added to DMSO in a molar ratio of 1:1 and stirred until completely dissolved. The mixture was then placed in an open container and placed on a hot table at 35-40℃ to wait for single crystal precipitation, thus obtaining CsPbBr3 single crystal.

[0010] Step 2: Preparation of CsPbBr3 single crystal / MAPbBr3 single crystal heterojunction

[0011] PbBr2 and MABr powders were dissolved in DMF and stirred thoroughly to obtain a 0.7-1M MAPbBr3 solution. The CsPbBr3 single crystal obtained in step 1 was placed at the bottom of the MAPbBr3 solution, with its lower surface in close contact with the bottom of the container. Then it was placed on a hot table at 90-95℃ and waited for the MAPbBr3 single crystal to gradually precipitate on the upper surface and around the CsPbBr3 single crystal to obtain a CsPbBr3 / MAPbBr3 single crystal heterojunction.

[0012] Step 3: Fabrication of photodetector

[0013] Carbon electrodes were fabricated using carbon paste on the lower surface of a CsPbBr3 single crystal without MAPbBr3 growth and on a MAPbBr3 single crystal grown on the upper surface of a CsPbBr3 single crystal, and then thoroughly dried to obtain a narrowband photodetector.

[0014] The beneficial effects of this invention are reflected in:

[0015] This invention provides a narrowband photodetector based on a cesium bromide / methylamine lead bromide single-crystal heterojunction, which can achieve wavelength discrimination without any additional optical components. The detector's spectral response peak is at 550 nm (the high detectivity wavelength range is 530 nm-570 nm), and its responsivity to 550 nm laser illumination reaches 0.15 A / W under a -3V bias voltage. The detector's specific detectivity is as high as ~1 × 10⁻⁶. 12 Jones, dark current as low as 2×10 -9 A. Light-to-shine ratio ~10 3 The response time is 260 μs. This fast response and highly selective narrowband detection can be attributed to the high mobility, long carrier diffusion length, absence of grain boundaries, and anisotropic conductivity of the perovskite single crystal, which facilitate narrowband charge collection. Attached Figure Description

[0016] Figure 1 The images show the XRD patterns of CsPbBr3 single crystal and MAPbBr3 single crystal in the CsPbBr3 / MAPbBr3 single crystal heterojunction prepared in Example 1, with the upper image showing the CsPbBr3 single crystal and the lower image showing the MAPbBr3 single crystal.

[0017] Figure 2 The image shows an optical microscope image of the CsPbBr3 / MAPbBr3 single-crystal heterojunction prepared in Example 1. It can be clearly observed that methylamine lead bromide single crystals are epitaxially grown around the cesium bromine single crystal.

[0018] Figure 3 The current-voltage characteristic curves of the sensor prepared in Example 1 under dark conditions and laser irradiation at different wavelengths of 350nm, 550nm, 600nm, and 650nm are shown.

[0019] Figure 4 This is the normalized curve of the voltage change over time measured by the sensor prepared in this embodiment under 550nm laser irradiation and a 20Hz sine wave.

[0020] Figure 5 In accordance with Figure 4 The rise and fall times of the curve are calculated.

[0021] Figure 6The sensor prepared in Example 1 operates at 10 μW / cm 2 The optical power and detectivity at different wavelengths under a bias voltage of -3V. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0023] Example 1

[0024] Step 1: Preparation of CsPbBr3 single crystals

[0025] Add PbBr2 and CsBr to DMSO in a molar ratio of 1:1 (DMSO was chosen as the solvent because CsPbBr3 has a higher solubility in DMSO than in DMF at room temperature). Stir on a magnetic stirrer until the powder is completely dissolved (approximately 1 hour). Filter the solution through a 0.22 μm diameter filter. Add 1 μL of hydroiodic acid (AR, ≥47.0%, containing ≤1.5% H3PO2 stabilizer, which can promote better and faster single crystal growth) to the filtered solution and continue stirring for 30 minutes. Place the stirred pale yellow solution in an open container and place it on a 40°C hot plate. Observe the precipitation of CsPbBr3 single crystals. After about 12 hours, single crystals can be observed precipitating at the bottom of the container. When they reach a suitable size, remove them and wash off the residual solvent on the surface with DMF solution. After the DMF on the surface has completely evaporated, dry the single crystals and store them for later use.

[0026] Step 2: Preparation of CsPbBr3 single crystal / MAPbBr3 single crystal heterojunction

[0027] PbBr2 and MABr powders were dissolved in DMF at a molar ratio of 1:1 (DMF was chosen as the solvent because of its good evaporation rate in air and the good solubility of MAPbBr3). The solution was stirred thoroughly on a magnetic stirrer to form a 1M MAPbBr3 solution. A pre-prepared CsPbBr3 single crystal of suitable size was placed at the bottom of the MAPbBr3 solution, with its lower surface in close contact with the bottom of the container (to limit the growth of MAPbBr3). The solution containing the CsPbBr3 single crystal was placed on a hot stage at approximately 90°C. MAPbBr3 single crystals precipitated around and on the surface of the CsPbBr3 single crystal. The size of the epitaxially grown methylamine lead bromide was controlled by adjusting the growth time. Once the desired size was reached, the solution was removed. Because the lower surface of the CsPbBr3 / MAPbBr3 single-crystal heterojunction is in close contact with the bottom of the container during synthesis, the MAPbBr3 single crystal can only grow around the perimeter and upper surface of the CsPbBr3 single crystal. A small amount of MAPbBr3 single crystal grown on the lower surface is washed away with DMF solution. Characterization observation and performance testing clearly show that the CsPbBr3 single crystal and the MAPbBr3 single crystal constitute a heterojunction.

[0028] Step 3: Fabrication of photodetector

[0029] Carbon electrodes were fabricated using carbon paste on the lower surface of a CsPbBr3 single crystal without MAPbBr3 growth and on a MAPbBr3 single crystal grown on the upper surface of a CsPbBr3 single crystal, and then dried in a vacuum drying oven at 90°C for 90 minutes to obtain a narrowband photodetector.

[0030] Figure 1 The images show the XRD patterns of the core CsPbBr3 single crystal and the epitaxially grown MAPbBr3 single crystal in the CsPbBr3 / MAPbBr3 single crystal heterojunction prepared in this embodiment. The upper image shows the CsPbBr3 single crystal, and the lower image shows the MAPbBr3 single crystal. It can be seen that the grown single crystals have excellent crystallinity. The epitaxially grown MAPbBr3 single crystal continues to grow along the crystal orientation of the inner CsPbBr3 single crystal, forming a heterojunction.

[0031] Figure 2 The image shows an optical microscope image of the CsPbBr3 / MAPbBr3 single-crystal heterojunction prepared in this embodiment. It can be clearly observed that MAPbBr3 single crystals are epitaxially grown around the CsPbBr3 single crystal.

[0032] Figure 3The current-voltage characteristic curves of the sensor prepared in this embodiment under dark conditions and laser irradiation at different wavelengths of 350nm, 550nm, 600nm, and 650nm show that the device has excellent rectification characteristics and is basically non-conductive under negative bias. This is because a CsPbBr3 / MAPbBr3 single-crystal heterojunction is formed.

[0033] Figure 4 This is the normalized curve of the voltage change over time measured by the sensor prepared in this embodiment under 550nm laser irradiation and a 20Hz sine wave. Figure 5 Based on the rise and fall times calculated from this curve, it can be seen that the rise time is 260μs and the fall time is 610μs, indicating that the detector has an extremely fast response speed.

[0034] Figure 6 The sensor prepared for this embodiment operates at 10 μW / cm². 2 The optical power and detectivity at different wavelengths under a bias voltage of -3V. Combined with... Figure 4 It can be seen that the detector has excellent photoelectric properties in the wavelength range of 538-570nm, and the highest detectivity in this narrow band is as high as ~1×10⁻⁶. 12 Jones is highly selective.

[0035] The above are merely exemplary 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 within the protection scope of the present invention.

Claims

1. A narrowband photodetector based on a lead-bromine-cesium / methylamine-lead bromide single-crystal heterojunction, characterized in that: The narrowband photodetector achieves light detection through a heterojunction composed of CsPbBr3 single crystal and MAPbBr3 single crystal; the spectral response peak of the narrowband photodetector is at 550nm, and the detection wavelength range is 530nm-570nm. The fabrication method of the narrowband photodetector is as follows: First, CsPbBr3 single crystals are prepared by solvent evaporation. Then, MAPbBr3 single crystals are epitaxially grown on the upper surface and around the CsPbBr3 single crystals by temperature inversion to form a CsPbBr3 / MAPbBr3 single crystal heterojunction. Finally, the upper and lower electrodes are fabricated using carbon paste to obtain the narrowband photodetector. The specific steps include the following: Step 1: Preparation of CsPbBr3 single crystals PbBr2 and CsBr were added to DMSO in a molar ratio of 1:1 and stirred until completely dissolved. The mixture was then placed in an open container and placed on a hot table at about 35-40°C to wait for single crystal precipitation, thus obtaining CsPbBr3 single crystal. Step 2: Preparation of CsPbBr3 single crystal / MAPbBr3 single crystal heterojunction PbBr2 and MABr powders were dissolved in DMF and stirred thoroughly to obtain a 0.7-1M MAPbBr3 solution. The CsPbBr3 single crystal obtained in step 1 was placed at the bottom of the MAPbBr3 solution, with its lower surface in close contact with the bottom of the container. Then it was placed on a hot table at 90-95℃ and waited for the MAPbBr3 single crystal to gradually precipitate on the upper surface and around the CsPbBr3 single crystal to obtain a CsPbBr3 / MAPbBr3 single crystal heterojunction. Step 3: Fabrication of photodetector Carbon electrodes were fabricated using carbon paste on the lower surface of a CsPbBr3 single crystal without MAPbBr3 growth and on a MAPbBr3 single crystal grown on the upper surface of a CsPbBr3 single crystal, and then thoroughly dried to obtain a narrowband photodetector.

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