Flexible polarization sensitive photoelectric detector and application thereof

Abstract

The invention relates to a flexible polarization sensitive photoelectric detector and application thereof. The flexible polarization sensitive photoelectric detector comprises a flexible substrate, a P-type two-dimensional material layer, a two-dimensional metal trihalogen phosphorus compound layer, a first electrode in contact with the P-type two-dimensional material layer and a second electrode in contact with the two-dimensional metal trihalogen phosphorus compound layer, wherein the P-type two-dimensional material layer and the two-dimensional metal trihalogen phosphorus compound layer are located on the flexible substrate; the P-type two-dimensional material layer and the two-dimensional metal trihalogen phosphorus compound layer are partially overlapped to form an anisotropic Van der Waals heterojunction; the flexible polarization sensitive photoelectric detector has a photovoltaic effect and polarization sensitive detection capability, imaging application of the device on a flexible substrate becomes possible, the device has remarkable rectification behavior and wide spectral response, the spectral response range is 405 nm-1310 nm, the potential application range of the heterojunction device in the flexible and polarization photoelectron field is widened, and the photoelectric detector has wide application prospects. Meanwhile, the preparation process is simple, the technology is mature, equipment is easy to obtain, cost is low, and commercialized popularization is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric detection technology, and in particular to a flexible polarization-sensitive photoelectric detector and applications thereof. Background Art

[0002] Two-dimensional layer materials have attracted great attention due to their unique electrical and optical properties and compatibility with silicon technology, owing to their weak van der Waals (vdW) interactions and mechanical flexibility. The lack of surface covalent bonds and lattice matching allow various two-dimensional materials to be assembled on any substrate, providing a promising platform for wearable and portable optoelectronic applications, including flexible photodetectors, transistors, solar cells, and light-emitting diodes.

[0003] In various optoelectronic applications, polarization photodetectors have the advantage of extracting clearer and more information about the imaged object, and therefore play a vital role in both military and civilian fields. Conventional polarization-sensitive detectors require the integration of pre-polarizers and lenses, which increases the size, cost, and complexity of the imaging system. Therefore, the development of polarizer-free polarization devices is essential to meet the requirements of miniaturization, compactness, excellent performance, and high integration. Summary of the invention

[0004] The primary purpose of the present invention is to provide a flexible polarization-sensitive photodetector and its application, which comprises a P-type two-dimensional material layer and a typical two-dimensional metal trihalide phosphorus compound (MPTs) layer on a flexible substrate to form an anisotropic van der Waals heterojunction. The heterostructure exhibits significant photovoltaic effect and polarization-sensitive detection capability, making imaging applications and polarized light detection of the device on a flexible substrate possible.

[0005] The present invention adopts at least the following technical solutions:

[0006] On the one hand, the present invention provides a flexible polarization-sensitive photodetector, comprising a flexible substrate, a P-type two-dimensional material layer and a two-dimensional metal trihalide phosphorus compound layer located on the flexible substrate, a first electrode in contact with the P-type two-dimensional material layer and a second electrode in contact with the two-dimensional metal trihalide phosphorus compound layer, wherein the P-type two-dimensional material layer and the two-dimensional metal trihalide phosphorus compound layer partially overlap to form an anisotropic van der Waals heterojunction; the flexible polarization-sensitive photodetector has a photovoltaic effect.

[0007] Furthermore, the P-type two-dimensional material layer is one of MoTe2, WSe2, MoS2, and WS2.

[0008] Furthermore, the two-dimensional metal trihalogen phosphorus compound layer is NiPS3 or NiPSe3.

[0009] Furthermore, the wavelength response range of the photodetector is 405nm to 1310nm, and the rectification ratio is not less than 2.5×10 3 .

[0010] Furthermore, the flexible substrate is a PET substrate.

[0011] Furthermore, the thickness of the P-type two-dimensional material layer is 1 nm to 100 nm.

[0012] Furthermore, the thickness of the two-dimensional metal trihalogen phosphorus compound layer is 1 nm to 50 nm.

[0013] Furthermore, at 635 nm and zero bias, the photodetector has a response rate of no less than 440 mA / W and a response speed of no less than 1×10 11 Jones.

[0014] Furthermore, at a wavelength of 635 nm, a polarization ratio of the photodetector is not less than 11.

[0015] In one aspect, the present invention provides an imaging system, which comprises the above-mentioned flexible polarization-sensitive photodetector.

[0016] Furthermore, the flexible polarization-sensitive photodetector acts as an individual sensing pixel.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] The present invention uses a P-type two-dimensional material layer with mechanical flexibility and a bondless surface and a two-dimensional metal trihalogen phosphorus compound layer to build a van der Waals (vdW) heterostructure with type II band arrangement and high quality. The heterostructure exhibits significant photovoltaic effect and polarization-sensitive light detection capability, making the imaging application of the device on a flexible substrate possible. The device has significant rectification behavior, and the rectification ratio is not less than 2.5×10 3 , with a wide spectral response range of 405nm to 1310nm. Due to the in-plane optical anisotropy of the two-dimensional metal trihalogen phosphorus compound, the photodetector also exhibits significant polarization-dependent photocurrent. In one embodiment, its maximum polarization ratio (PR) value is ~11.2. The van der Waals heterostructure provided by the present invention broadens the potential application scope in the field of flexible and polarized optoelectronics. At the same time, the preparation process is simple, the technology is mature, the equipment is easily available, and the cost is low, which is very conducive to commercial promotion.

[0019] In one embodiment of the present invention, the NiPS3 / MoTe2 heterostructure device exhibits significant photovoltaic effect and polarization-sensitive light detection performance. At 635nm and photovoltaic mode (zero bias), the device achieves a high R of 500mA / W and an on / off ratio of 2.7×103 , the specific D* is 1.5×10 11 Jones, which can be attributed to the low noise level and effective separation of carriers on the interface; at the same time, it shows excellent performance in polarization-sensitive light detection, with a high PR value of 11.2. It can be widely used in important fields such as optical communications and medical imaging.

[0020] The heterojunction of the present invention is integrated onto a flexible substrate, achieving clear single-pixel photocurrent imaging with high-resolution contrast, and providing a new platform for flexible and polarized optoelectronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of a flexible polarization-sensitive photodetector according to an embodiment of the present invention.

[0022] Figure 2 FIG. 1 is an optical microscope image of a flexible polarization-sensitive photodetector according to an embodiment of the present invention.

[0023] Figure 3 The performance diagram of the flexible polarization-sensitive photodetector according to an embodiment of the present invention is shown in FIG. (a) at V SD =0; (b) shows the response rate and photocurrent with different light powers; (c) shows the rise and decay time of the device when excited by a laser with a wavelength of 635nm; (d) shows the stability results of the detector.

[0024] Figure 4 The performance diagram of the flexible polarization-sensitive photodetector according to an embodiment of the present invention is shown in FIG. (a) shows the angle-resolved photocurrent of the detector under polarized light with a polarization angle ranging from 0 to 330° under light with a wavelength of 635 nm; (b) shows the angle-resolved photocurrent of the detector under V SD = 0V 635nm linearly polarized laser irradiation polarization-sensitive photocurrent as a function of polarization angle in polar coordinates.

[0025] Figure 5 Performance diagram of a flexible polarization-sensitive photodetector according to an embodiment of the present invention, (a) is an optical device diagram of the detector based on a PET flexible substrate; (b) is an optical microscope diagram of the detector; (c) is a schematic diagram of an imaging system according to an embodiment of the present invention; (d) is an imaging result of the detector in a "two-dimensional" mode under light with a wavelength of 405 nm. DETAILED DESCRIPTION

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention. The experimental methods described in the following embodiments are all conventional methods unless otherwise specified; the reagents and materials, unless otherwise specified, can be obtained from public commercial channels.

[0027] Spatially relative terms such as "below," "beneath," "below," "above," "upper," etc. are used in this specification to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures.

[0028] In addition, the use of terms such as "first", "second", etc. to describe various elements, layers, regions, sections, etc. is not intended to be limiting. The use of "having", "containing", "including", "comprising", etc. is open-ended, indicating the presence of the stated elements or features, but does not exclude additional elements or features. Unless the context clearly states otherwise.

[0029] An embodiment of the present invention provides a flexible polarization-sensitive photodetector, which includes a flexible substrate, a P-type two-dimensional material layer, a two-dimensional metal trihalogen phosphorus compound layer, a first electrode and a second electrode. The flexible substrate is, for example, a PET flexible substrate, or other flexible substrates.

[0030] The P-type two-dimensional material layer and the two-dimensional metal trihalide phosphorus compound layer are partially overlapped and arranged on a flexible substrate, the first electrode is located on the P-type two-dimensional material layer, and the second electrode is located on the two-dimensional metal trihalide phosphorus compound layer. The first electrode is a source electrode and the second electrode is a drain electrode. The P-type two-dimensional material layer is, for example, one of MoTe2, WSe2, MoS2, and WS2, and its thickness is 1nm to 100nm; the two-dimensional metal trihalide phosphorus compound layer is, for example, NiPS3 or NiPSe3, and its thickness is 1nm to 50nm. The two-dimensional metal trihalide phosphorus compound has an in-plane anisotropic atomic structure, and the P-type two-dimensional material layer and the two-dimensional metal trihalide phosphorus compound layer partially overlap to form a type II band arrangement and a high-quality anisotropic van der Waals heterojunction. The P-type two-dimensional material layer and the two-dimensional metal trihalide phosphorus compound layer are compatible with any substrate due to their mechanical flexibility and bondless surface. The heterostructure device exhibits obvious photovoltaic effect and polarization-sensitive light detection performance without the need for a polarizer.

[0031] like Figure 1As shown, in a preferred embodiment, the P-type two-dimensional material layer is MoTe2, and the two-dimensional metal trihalogen phosphorus compound layer is a typical MPTs material NiPS3. MoTe2 and NiPS3 form a heterojunction, realizing a flexible broadband polarization photodetector. Figure 2 is an optical microscope (OM) image of a representative NiPS3 and MoTe2 heterojunction device.

[0032] An embodiment of the present invention provides a method for preparing the flexible polarization-sensitive photodetector, which comprises the following steps:

[0033] First, a 300nm SiO2 / Si substrate is selected. Since the SiO2 / Si substrate is purple, the two-dimensional material is mechanically peeled onto the substrate, making it easier to find a suitable target area for heterojunction construction. In the subsequent steps, the selected target two-dimensional material is transferred to the flexible substrate by dry method. The selected SiO2 / Si substrate is placed in ethanol, acetone, and isopropanol in turn for 1-30 minutes each; then the substrate is placed in ozone ultraviolet or oxygen plasma for cleaning for 2-5 minutes, with an oxygen flow rate of 30-60sccm and a plasma power of 80-110W.

[0034] Next, a PET flexible substrate of a certain size was selected and cleaned with plasma to make the OH on the surface of the substrate - In one embodiment, the size of the PET substrate is 1 cm×1 cm, and the plasma cleaning time is 90 seconds.

[0035] Next, multilayer MoTe2 and NiPS3 material layers were obtained on the SiO2 / Si substrate by mechanical exfoliation.

[0036] Subsequently, the MoTe2 and NiPS3 material layers were transferred to the PET substrate using a dry transfer process.

[0037] Specifically, a PVA solvent is coated on a PDMS film, and then heated at 50-80°C for 6-10 minutes to obtain a solid PVA / PDMS film, which is then stacked on the above-mentioned multi-layer MoTe2 material layer, and then heated at 70-90°C for 6-10 minutes, and peeled off from the SiO2 / Si substrate to obtain a PDMS / PVA / MoTe2 film. The PDMS / PVA / MoTe2 film is then stacked on a PET substrate, and then the PET substrate is immersed in deionized water to remove PVA, thereby obtaining a PET / MoTe2 laminate.

[0038] A PVA solvent is coated on the PDMS film, and then heated at 50-80°C for 6-10 minutes to obtain a solid PVA / PDMS film, which is then stacked on the above-mentioned NiPS3 material layer, and then heated at 70-90°C for 6-10 minutes, and peeled off from the SiO2 / Si substrate to obtain a PDMS / PVA / NiPS3 film. The PDMS / PVA / NiPS3 film is then stacked on the above-mentioned PET / MoTe2 laminate, and then the PET substrate is immersed in deionized water to remove PVA, thereby obtaining a PET / MoTe2 / NiPS3 laminate.

[0039] Finally, laser direct writing and evaporation processes were used to prepare Cr / Au electrodes on the MoTe2 layer and NiPS3 layer, respectively. The thickness of the Cr layer was 10nm and the thickness of the Au layer was 50nm. Then, acetone was used to remove the excess gold; finally, a stable and efficient flexible polarization-sensitive photodetector was obtained.

[0040] The performance of the MoTe2 / NiPS3 photodetector obtained above was tested, such as Figure 3 As shown, the photocurrent value is extracted as a function of the optical power density and plotted in Figure (a). The power law equation I ph ~P α Fitting curve, where P is the laser power density and α is the fitting index. It is worth noting that at wavelengths of 405nm and 635nm, the exponent α is 0.89 and 0.83, respectively, indicating a special conversion efficiency from incident photons to captured electrons. As a key parameter of the photodetector, the responsivity (R) is defined as: Among them I ph is the photocurrent, A is the effective illumination area, and P is the incident light power density. As shown in Figure (a), R decreases with increasing light power due to the gradual saturation of the light sensing state within the heterostructure. Specifically, under weak light conditions, R can reach 440mA / W at 635nm, and the corresponding external quantum efficiency (EQE) is close to 98%, as shown in Figure (b). Detectivity (D*) is another key parameter that describes the sensitivity of the detector in Jones units and is defined as D*=RA 1 / 2 / (2qI dark ) 1 / 2 , where q is the electron charge, I dark is the dark current. The D* of this photodetector at 635nm is calculated to be 1.5×10 11Jones. (c) shows the dynamic photoresponse under zero bias, showing fast speed, with a rise time of 18ms and a decay time of 36ms, which meets the standards for video imaging applications. The stability test results are shown in (d). After 1000 cycles of laser switching, the photocurrent and switching characteristics of the detector remain unchanged, indicating that the NiPS3 / MoTe2 heterojunction photodetector has good stability and repeatability.

[0041] like Figure 4 As shown, angle-resolved polarized Raman spectroscopy (ARPRS) was used to elucidate the crystal orientation and vibrational symmetry of the chemical bonds of NiPS3. The polarization angle is characterized by the angle between the incident light and the x-axis of the NiPS3 sample coordinate system. (a) The figure shows the NiPS3 / MoTe2 heterojunction at V under 635nm linearly polarized light. SD = 0V polarization angle-dependent photocurrent. The amplitude of the photocurrent fluctuates periodically as a function of the polarization angle, with a maximum of 4.08nA at 90 degrees and a minimum of 0.36nA at 0 degrees. These recorded values ​​are used to construct the angle-dependent photocurrent in polar coordinates as shown in (b), revealing a robust polarization-sensitive response with a 180-degree periodic feature, which is consistent with the periodicity observed in the Raman spectrum. These data can be accurately fitted with the following equation:

[0042]

[0043] In the above formula, θ is the angle of linear polarization laser, a min and a max are the minimum and maximum fitting parameters, The device shows a significant polarization ratio (PR), which is defined as the ratio of the maximum and minimum photocurrents, reaching 11.2 and 7.1 at wavelengths of 635 nm and 405 nm, respectively.

[0044] like Figure 5As shown, (a) and (b) show the optical microscope images of the NiPS3 / MoTe2 heterojunction detector on the PET flexible substrate obtained in the above embodiment. Since there is no overhanging boundary, the NiPS3 / MoTe2 heterostructure is compatible with the PET substrate. Using a single pixel scanning imaging system, we explored the device on the flexible substrate by visible light imaging. (c) shows a schematic diagram of an imaging system, in which the device acts as a single sensing pixel, and there is a hollow "2D" mask between the photodetector and the single-mode laser. It automatically moves along the XY direction at a distance of 2μm per step. When the system is illuminated with a beam, the laser beam emitted by the laser passes through the mask to the surface of the detector, and the lock-in amplifier collects the real-time photocurrent signal of the detector and generates a position-dependent photocurrent mapping image. Under the irradiation of a 405nm laser beam, we obtained a "2D" mode image with high-resolution contrast, as shown in (d). This result shows that the NiPS3 / MoTe2 device on a flexible substrate (PET) has important application potential in flexible devices.

[0045] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A flexible polarization-sensitive photodetector, characterized in that: It includes a flexible substrate, a P-type two-dimensional material layer and a two-dimensional metal trihalide phosphorus compound layer located on the flexible substrate, a first electrode in contact with the P-type two-dimensional material layer and a second electrode in contact with the two-dimensional metal trihalide phosphorus compound layer, wherein the P-type two-dimensional material layer and the two-dimensional metal trihalide phosphorus compound layer partially overlap to form an anisotropic van der Waals heterojunction; the flexible polarization-sensitive photodetector has a photovoltaic effect.

2. The flexible polarization-sensitive photodetector according to claim 1, characterized in that: The P-type two-dimensional material layer is one of MoTe2, WSe2, MoS2, and WS2.

3. The flexible polarization-sensitive photodetector according to claim 2, characterized in that: The two-dimensional metal trihalogen phosphorus compound layer is NiPS3 or NiPSe3.

4. The flexible polarization-sensitive photodetector according to claim 3, characterized in that: The wavelength response range of the photodetector is 405nm~1310nm, and its rectification ratio is not less than 2.5×10 3 .

5. The flexible polarization-sensitive photodetector according to any one of claims 1 to 4, characterized in that: The flexible substrate is a PET substrate.

6. The flexible polarization-sensitive photodetector according to claim 5, characterized in that: The thickness of the P-type two-dimensional material layer is 1 nm to 100 nm.

7. The flexible polarization-sensitive photodetector according to claim 5, characterized in that: The thickness of the two-dimensional metal trihalogen phosphorus compound layer is 1 nm to 50 nm.

8. The flexible polarization-sensitive photodetector according to claim 6 or 7, characterized in that: At 635nm and zero bias, the photodetector has a responsivity of no less than 440mA / W, a response speed of less than 20ms, and a specific detection rate of no less than 1×10 11 Jones.

9. The flexible polarization-sensitive photodetector according to claim 8, characterized in that: At a wavelength of 635 nm, the polarization ratio of the photodetector is no less than 11.

10. An imaging system, characterized in that: The flexible polarization-sensitive photodetector comprises the flexible polarization-sensitive photodetector according to any one of claims 1 to 9.

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