Perovskite photodetector based on controllable growth of PbSe / CsPbBr3 heterojunction and preparation method

Abstract

The present invention discloses a novel nanostructured carbon nanotube based on PbSe / CsPbBr 3 A perovskite photodetector with controllable heterojunction growth and a preparation method thereof, which relates to the field of photoelectric detection technology. The detector comprises: a substrate, a PbSe thin film layer grown on the substrate, and a CsPbBr epitaxially grown on the PbSe thin film layer. 3 Thin film layer; the PbSe and the CsPbBr 3 Formation of PbSe / CsPbBr 3 Heterojunction. The preparation method includes: depositing a PbSe thin film on the surface of a substrate to form a PbSe thin film layer; using CsBr and PbBr as raw materials, growing on the surface of the substrate with the PbSe thin film by chemical vapor deposition to form a CsPbBr 3 The invention has the beneficial effect of preparing high-quality, excellent single crystal and smooth surface CsPbBr 3 Thin film, heterojunction can effectively reduce non-radiative recombination of carriers and suppress dark current.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectric detection, and in particular relates to a perovskite photoelectric detector based on controllable growth of a PbSe / CsPbBr3 heterojunction and a preparation method thereof. Background Art

[0002] Lead halide materials have been widely used in solar cells, lasers, photodetectors and light-emitting diodes due to their special perovskite crystal structure, due to their excellent properties such as light-matter interaction, high mobility, long carrier diffusion length and excellent photoelectric conversion efficiency. However, the high density of grain boundaries in polycrystalline films can lead to higher trap states, which are associated with non-radiative recombination and affect the charge carrier lifetime, resulting in a decrease in device performance. Compared with polycrystalline films, lead halide single crystal films have lower trap density, which can improve device performance.

[0003] However, the growth of large-area single-crystalline thin films of metal halides remains very challenging, especially for all-inorganic metal halides, which have more competitive optoelectronic properties and better stability than organic-inorganic hybrid structures. Recently, strategies such as introducing ultrasonic pulses or inversion crystallization from solution plus spatial confinement during antisolvent diffusion growth have been proposed, but these methods are limited to hybrid crystals such as MAPbX3. Inorganic solution growth is generally more challenging due to the lower solubility of inorganic crystals and the more complex phase diagram of Cs-Pb-X. For example, there are three phases, CsPbBr3, CsPb2Br5, and Cs4PbBr6. The crystallization of a specific phase requires careful control of the stoichiometry in the precursor solution, which changes during the crystal growth process. Therefore, it is very necessary to develop an effective method to grow large-area inorganic halide crystals.

[0004] Chemical vapor deposition growth is a powerful technology that has achieved great success in the growth of single-crystalline thin films of traditional semiconductors. It not only effectively controls morphology and reduces defects, but also enables monolithic integration of single-crystalline semiconductors with multifunctional epitaxial substrates to manufacture advanced devices. Over the past few decades, chemical vapor deposition technology has promoted the development of semiconductor heterostructure devices, but little progress has been made in halide materials.

[0005] The crystal structure of strontium titanate has always been a universal substrate for the epitaxial growth of a variety of oxides with different properties. However, despite its same structural type and name, it is rarely used as a substrate for the growth of metal halides, especially in the case of heteroepitaxial growth of two metal halides and their actual application. Summary of the invention

[0006] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a perovskite photodetector based on controllable growth of a PbSe / CsPbBr3 heterojunction and a preparation method thereof.

[0007] The technical solution of the present invention is as follows:

[0008] The first aspect of the present invention provides a perovskite photodetector based on a controllable growth of a PbSe / CsPbBr3 heterojunction, the detector comprising: a substrate, a PbSe thin film layer grown on the substrate, and a CsPbBr3 thin film layer epitaxially grown on the PbSe thin film layer;

[0009] The PbSe and the CsPbBr3 form a PbSe / CsPbBr3 heterojunction.

[0010] Optionally, the substrate is strontium titanate whose growth crystal plane is (100) plane.

[0011] Optionally, the detector also includes gold electrodes respectively arranged on the PbSe thin film layer and the CsPbBr3 thin film layer, the gold electrodes have a thickness of 70nm~90nm, a width of 0.5mm~1.5mm, a length of 2mm~4mm, and an electrode spacing of 1.5mm~2.5mm.

[0012] Optionally, the thickness of the PbSe thin film layer is 90 nm to 100 nm.

[0013] Optionally, the thickness of the CsPbBr3 thin film layer is 2 μm to 16 μm.

[0014] The second aspect of the present invention provides a method for preparing a perovskite photodetector based on a controllable growth of a PbSe / CsPbBr3 heterojunction, comprising the following steps:

[0015] Depositing a PbSe thin film on the surface of the substrate to form a PbSe thin film layer;

[0016] Using CsBr and PbBr as raw materials, a chemical vapor deposition method is used to grow a CsPbBr3 thin film layer on the surface of the substrate on which the PbSe thin film layer is formed;

[0017] Electrodes are prepared on the PbSe thin film layer and the CsPbBr3 thin film layer respectively.

[0018] Optionally, the step of forming a CsPbBr3 thin film layer comprises:

[0019] The raw materials CsBr and PbBr and the substrate for forming the PbSe thin film layer are arranged along the flow direction of the carrier gas from upstream to downstream, and vacuum is drawn, and the temperature is first increased, then kept, and finally cooled to form a CsPbBr3 thin film layer.

[0020] Optionally, the heating temperature of the raw materials CsBr and PbBr is 550°C to 600°C, the heating rate is ≤10°C / min, and the time for heating from room temperature to the heating temperature of CsBr and PbBr is 50min to 60min;

[0021] The heating temperature of the substrate for forming the PbSe thin film layer is 300°C to 400°C;

[0022] The insulation time is 2min~8min.

[0023] Optionally, the vacuum is evacuated to a vacuum degree of 2Pa-4Pa, and the carrier gas flow rate is controlled to be 50sccm-70sccm;

[0024] The PbBr and CsBr are mixed in a mass ratio of 4-6:5-7.

[0025] Optionally, the step of depositing a PbSe thin film on the substrate surface comprises:

[0026] Along the flow direction of the carrier gas from upstream to downstream, using PbSe as the evaporation source material and selenium powder as the supplementary source, a substrate is set, vacuumed, first heated, then kept warm, and finally cooled to obtain a substrate with a PbSe film.

[0027] Optionally, the mass ratio of PbSe to selenium powder is 1:1.5-1:2.5, and the vacuum is evacuated to a vacuum degree of 1×10 - 3 Pa~5×10 -3 Pa, control the carrier gas flow rate to 25sccm~35sccm;

[0028] The heating temperature of the selenium powder is 250°C to 350°C, the heating temperature of the PbSe is 700°C to 750°C, and the heating temperature of the substrate is 400°C to 500°C;

[0029] The time for heating from room temperature to the heating temperature of PbSe is 70 min to 80 min;

[0030] The vapor formed by the PbSe and the selenium powder reacts on the surface of the substrate for 4 to 6 minutes.

[0031] The present invention has at least one of the following beneficial effects:

[0032] The present invention grows a PbSe thin layer on the surface of the substrate, and then grows a CsPbBr3 thin film again by a chemical vapor deposition method on the strontium titanate substrate with the PbSe thin layer, and the single-crystal CsPbBr3 thin film with adjustable thickness can be obtained by adjusting the growth time; PbSe and CsPbBr3 can form a PbSe / CsPbBr3 heterojunction, and in addition, gold electrodes are thermally evaporated on the two end films to obtain a PbSe / CsPbBr3 heterojunction device. The present invention makes it easier to obtain a high-quality, excellent single crystal, and flat surface CsPbBr3 thin film, and the heterojunction can effectively reduce the non-radiative recombination of carriers and suppress dark current.

[0033] The controllably grown perovskite film provided by the present invention has a flat surface and extremely high crystallinity, can be stably stored at room temperature, and has an obvious spectral response to visible light; and by adjusting the growth time, the growth kinetics of CsPbBr3 are obtained to better modulate the film thickness; at the same time, the grown high single crystal CsPbBr3 has the characteristics of high mobility, long carrier diffusion length and excellent photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the chemical vapor growth process of the PbSe / CsPbBr3 heterojunction thin film in Inventive Example 1;

[0035] Figure 2 The scanning electron microscope surface morphology of PbSe / CsPbBr3 heterojunctions of different thicknesses obtained by regulating the growth time in Example 1 of the present invention;

[0036] Figure 3 The scanning electron microscope cross-sectional images of PbSe / CsPbBr3 heterojunctions of different thicknesses obtained by controlling the growth time in Example 1 of the present invention;

[0037] Figure 4 The x-ray diffraction patterns of PbSe / CsPbBr3 heterojunctions of different thicknesses are obtained by regulating the growth time in Example 1 of the present invention;

[0038] Figure 5 The transmission characteristic curve spectrum and current noise spectrum of the PbSe / CsPbBr3 heterojunction photodetector in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] An embodiment of the present invention provides a perovskite photodetector based on a controllable growth of a PbSe / CsPbBr3 heterojunction, the detector comprising: a substrate, a PbSe thin film layer grown on the substrate, and a CsPbBr3 thin film layer epitaxially grown on the lead selenide thin film layer;

[0041] The PbSe and the CsPbBr3 form a PbSe / CsPbBr3 heterojunction.

[0042] In some embodiments, the PbSe / CsPbBr3 heterojunction composition mainly includes: strontium titanate with a (100) crystal plane as a substrate, a lead selenide (PbSe) thin film layer grown on the strontium titanate, a perovskite thin film layer epitaxially grown on the PbSe, and a heterojunction device formed by thermally evaporated gold electrodes on the thin film layers at both ends.

[0043] In some embodiments, the substrate is strontium titanate whose growth crystal plane is (100).

[0044] In some embodiments, the thickness of the PbSe thin film layer is 90 nm to 100 nm.

[0045] In some embodiments, the thickness of the CsPbBr3 thin film layer is 2 μm to 16 μm.

[0046] Another embodiment of the present invention provides a method for preparing a perovskite photodetector based on a controllable growth of a PbSe / CsPbBr3 heterojunction, comprising the following steps:

[0047] Depositing a PbSe film on the surface of the substrate to obtain a substrate with the PbSe film;

[0048] Using CsBr and PbBr as raw materials, a chemical vapor deposition method is used to grow on the surface of the substrate with the PbSe film to obtain a PbSe / CsPbBr3 heterojunction.

[0049] In some embodiments, the present invention provides a perovskite photodetector based on controllable growth of a PbSe / CsPbBr3 heterojunction and a preparation method, comprising the following steps:

[0050] An ultra-thin PbSe film is grown on a strontium titanate substrate with a (100) crystal plane using a high vacuum chemical vapor deposition technique to obtain a strontium titanate substrate with a PbSe film.

[0051] A CsPbBr3 single crystal film layer is grown on the surface of the strontium titanate substrate with the grown PbSe film, and the thickness of the CsPbBr3 single crystal film layer is controlled by controlling the reaction time using chemical vapor deposition, so that the CsPbBr3 single crystal film is obtained on the surface of the strontium titanate substrate with a (100) crystal plane.

[0052] The electrodes were deposited on the two films using thermal evaporation equipment.

[0053] In some embodiments, growing perovskite structure films of different thicknesses comprises the following steps:

[0054] The mixed powder of CsBr and PbBr is used as raw material to grow on the surface of a strontium titanate substrate with a PbSe film by chemical vapor deposition; the chemical vapor deposition includes a heating stage, a deposition stage and a cooling stage; the flow rate of the carrier gas during the chemical vapor deposition process is preferably 60sccm.

[0055] In some embodiments, the chemical vapor deposition includes the following steps: along the flow direction of the carrier gas from upstream to downstream, a CsPbBr3 evaporation source and a strontium titanate substrate with a PbSe film are sequentially arranged; the CsPbBr3 evaporation source is a mixed powder of CsBr and PbBr, the heating temperature of the CsPbBr3 evaporation source is 570°C, and the heating temperature of the strontium titanate substrate with a PbSe film is 300°C~400°C; the heating rate of the mixed powder in the heating stage is ≤10°C / min.

[0056] In some embodiments, the holding time of the deposition stage is 2 min to 8 min; and the deposition thickness of the PbSe single crystal film layer is 2 μm to 16 μm.

[0057] In some embodiments, the raw material powder used to grow the cesium lead bromide (CsPbBr3) thin film is preferably a mixed powder of lead bromide (PbBr) and cesium bromide (CsBr) powders in a mass ratio of 5:6.

[0058] In some embodiments, the thickness of the PbSe film grown on the surface of strontium titanate is preferably 100 nm, and its thickness determines the lower limit thickness of the entire subsequently grown film.

[0059] In some embodiments, by controlling the chemical vapor deposition growth time to 2 min to 8 min, a perovskite structure film with a thickness of 2 μm to 16 μm can be obtained.

[0060] In some embodiments, the crystal quality of the grown PbSe / CsPbBr3 heterojunction thin film measured by an X-ray diffractometer increases as the growth time increases.

[0061] In some embodiments, the PbSe / CsPbBr3 heterojunction device exhibits a 0V bias voltage of less than 3.2×10 -12 A / Hz dark current noise.

[0062] In some embodiments, the heterojunction has a high degree of lattice orientation and good thickness controllability and further reduces dark current noise. The characterization methods used include X-ray diffraction spectra, scanning electron microscope cross-sectional images and various electrical test source tables.

[0063] The present invention is further described in detail below with specific examples, but the present invention is not limited to the following specific examples.

[0064] Example 1

[0065] This embodiment provides a perovskite photodetector based on controllable growth of a PbSe / CsPbBr3 heterojunction and a preparation method, which specifically comprises the following steps:

[0066] Schematic diagram of the chemical vapor growth process for preparing PbSe / CsPbBr3 heterojunction thin films Figure 1 As shown, including:

[0067] (1) Growth of PbSe thin film. Along the flow direction of the carrier gas from upstream to downstream, 0.2 g of PbSe (99.99%) was placed in the center of a horizontal tube furnace with a diameter of 12 inches as an evaporation source material, and 0.4 g of selenium powder was placed in the front of the furnace as a supplementary source; the purchased (100)-face strontium titanate substrate was placed at the end of the furnace, 10 cm away from the outlet. After the tube furnace was sealed, a mechanical pump and a molecular pump were used to evacuate the vacuum to a vacuum degree of 1×10 -3 Pa, and the carrier gas flow rate was controlled to be 30sccm. The heating temperature of the selenium powder supplement source was 300℃, the heating temperature of the PbSe powder was set to 750℃, and the temperature of the strontium titanate substrate was set to 450℃; the time for the tubular furnace to heat up from room temperature to the heating temperature of the PbSe powder (750℃) was 75min, and the steam formed by the reaction source and the selenium powder supplement source was transported to the surface of the strontium titanate substrate by the carrier gas for 5min of reaction, and then the heating power of the tubular furnace was cut off, and the furnace body was naturally cooled to room temperature to obtain an ultra-thin PbSe film.

[0068] (2) Growth of CsPbBr3 thin film. On the basis of the strontium titanate substrate on which PbSe has been grown, 0.25g of PbBr (99.999%) and 0.3g of CsBr (99.999%) were placed as evaporation source materials in the center of a horizontal tube furnace with a diameter of 12 inches along the flow direction of the carrier gas from upstream to downstream; the strontium titanate substrate on which PbSe has been grown was placed at the end of the furnace, 3cm away from the outlet. After the tube furnace was sealed, it was evacuated to a vacuum degree of 3Pa using a mechanical pump, and the carrier gas flow rate was controlled to 60sccm. The heating temperature of the evaporation source material was set to 570°C, and the temperature of the strontium titanate substrate on which PbSe was grown was set to 400°C; the time for the tubular furnace to heat up from room temperature to the heating temperature of the evaporation source material (570°C) was 57 minutes, and the vapor formed by the reaction source was transported by the carrier gas to the surface of the strontium titanate substrate on which PbSe was grown to react for 2 minutes, 4 minutes, 6 minutes and 8 minutes respectively, then the heating power of the tubular furnace was cut off, and the furnace body was naturally cooled to room temperature to obtain a PbSe / CsPbBr3 heterojunction.

[0069] (3) Electrodes were prepared on the surface of the PbSe / CsPbBr3 heterojunction. The specific preparation method was as follows: a strip mask shape was designed according to the area of ​​the prepared PbSe / CsPbBr3 heterojunction, the mask was covered on the PbSe / CsPbBr3 heterojunction, and two gold electrodes (thickness 80 nm, width 1 mm, length 3 mm, electrode spacing 2 mm) were evaporated using an evaporation coating device.

[0070] This method can produce inch-scale heterojunction devices.

[0071] The thickness control results of the PbSe / CsPbBr3 heterojunction photodetector prepared in this example are shown in Figure 2 As shown in the figure, the heterojunction devices of different thicknesses obtained by chemical vapor deposition need to ensure that the electrode on CsPbBr3 cannot directly contact PbSe, which requires the density of the film to be guaranteed. It can be seen from the figure that the film begins to connect to form a dense film at 4 minutes of growth, and it is completely covered with a dense film at 6 minutes. At this time, it can be ensured that the heterojunction photodetector can achieve the function of reducing dark current.

[0072] Figure 3 This is the experimental result of regulating the thickness of the PbSe / CsPbBr3 heterojunction by different deposition times in this embodiment. It can be observed from the figure that when the thickness is 5.3~7.4 microns, the heterojunction film shows an extremely flat cross-section, and the film cannot be formed if the time is too short.

[0073] Figure 4The x-ray diffraction patterns of PbSe / CsPbBr3 heterojunctions of different thicknesses are obtained by controlling the growth time in Example 1 of the present invention, wherein STO / PbSe is strontium titanate grown with PbSe. From the peak position and relative intensity, it can be judged that the crystal quality of CsPbBr3 increases with the extension of the growth time.

[0074] Figure 5 The transmission characteristic curve spectrum and noise current spectrum of the PbSe / CsPbBr3 heterojunction photoelectric device grown in the embodiment of the present invention. From the noise spectrum, it can be seen that the heterojunction photoelectric device has extremely low background current noise, which is beneficial to improving the sensitivity of the photodetector.

[0075] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A perovskite photodetector based on controllable growth of PbSe / CsPbBr3 heterojunction, characterized in that: The detector comprises: a substrate, a PbSe thin film layer grown on the substrate, and a CsPbBr3 thin film layer epitaxially grown on the PbSe thin film layer; The PbSe and the CsPbBr3 form a PbSe / CsPbBr3 heterojunction; The thickness of the PbSe thin film layer is 90 nm to 100 nm; The thickness of the CsPbBr3 thin film layer is 2 μm to 16 μm; The preparation method comprises: Depositing a PbSe thin film on the surface of the substrate to form a PbSe thin film layer; Using CsBr and PbBr as raw materials, a chemical vapor deposition method is used to grow a CsPbBr3 thin film layer on the surface of the substrate on which the PbSe thin film layer is formed; Electrodes are prepared on the PbSe thin film layer and the CsPbBr3 thin film layer respectively; The step of depositing a PbSe film on the substrate surface specifically includes: Along the flow direction of the carrier gas from upstream to downstream, using PbSe as an evaporation source material and selenium powder as a supplementary source, setting a substrate, evacuating, first heating, then keeping the temperature, and finally cooling, to obtain a substrate with a PbSe film; The mass ratio of PbSe to selenium powder is 1:1.5-1:2.5, and the vacuum is evacuated to a vacuum degree of 1×10 -3 Pa~5×10 - 3 Pa, control the carrier gas flow rate to 25sccm~35sccm; The heating temperature of the selenium powder is 250° C. to 350° C., the heating temperature of the PbSe is 700° C. to 750° C., and the heating temperature of the substrate is 400° C. to 500° C.; The time for heating from room temperature to the heating temperature of PbSe is 70 min to 80 min; The time for the vapor formed by the PbSe and the selenium powder to react on the surface of the substrate is 4 min to 6 min; The step of forming the CsPbBr3 thin film layer comprises: Arranging the raw materials CsBr and PbBr and the substrate for forming the PbSe thin film layer along the flow direction of the carrier gas from upstream to downstream, evacuating, first heating, then keeping the temperature, and finally cooling to form the CsPbBr3 thin film layer; The heating temperature of the CsBr and PbBr is 550°C to 600°C, the heating rate is ≤10°C / min, and the time for heating from room temperature to the heating temperature of the CsBr and PbBr is 50min to 60min; The heating temperature of the substrate for forming the PbSe thin film layer is 300°C to 400°C; The insulation time is 2min~8min; The vacuum is evacuated to a vacuum degree of 2Pa-4Pa, and the carrier gas flow rate is controlled to be 50sccm-70sccm.

2. A perovskite photodetector based on controllable growth of PbSe / CsPbBr3 heterojunction according to claim 1, characterized in that: The substrate is strontium titanate whose growth crystal plane is (100); The detector also includes gold electrodes respectively arranged on the PbSe thin film layer and the CsPbBr3 thin film layer, the thickness of the gold electrodes is 70nm~90nm, the width is 0.5mm~1.5mm, the length is 2mm~4mm, and the electrode spacing is 1.5mm~2.5mm.

3. A perovskite photodetector based on controllable growth of PbSe / CsPbBr3 heterojunction according to claim 1, characterized in that: The PbBr and CsBr are mixed in a mass ratio of 4-6:5-7.

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