Silicon nanowire array double heterojunction self-driven photodetector and preparation method

Abstract

The present invention discloses a self-driven double-heterojunction photodetector based on a silicon nanowire array and its preparation method. From top to bottom, the structure consists of a PEDOT:PSS top electrode (treated with ethylene glycol), a PbSe quantum dot film layer, a ZnO bulk material film layer, a silicon nanowire array layer, and a silicon bottom electrode. The ethylene glycol-treated PEDOT:PSS significantly enhances its conductivity, making it a transparent electrode for the device and reducing incident light loss. The PbSe / ZnO and ZnO / Si-NWA double heterojunctions broaden the device's spectral response range and accelerate the separation of photogenerated excitons. The silicon nanowire array structure reduces incident light reflection. Furthermore, the introduction of the ZnO film significantly reduces dark current compared to the previous simple Si-NW / PbSe structure. This structure can effectively improve the detection performance of silicon-based photodetectors.

Description

Technical Field

[0001] The present invention relates to a double heterojunction self-driven photodetector based on a silicon nanowire array, and specifically to a method of preparing a silicon nanowire array on a silicon wafer, and then preparing a self-driven infrared photodetector based on a Si-NW / ZnO / PbSe double heterojunction, belonging to the field of photodetectors. Background Art

[0002] Photodetectors have been continuously studied and developed due to their wide applications in environmental monitoring, bioimaging, optical communications, and other fields. Infrared detectors are a particularly important research direction. From the realization of the first practical PbS infrared detector during World War II to the present day, infrared photoelectric detection technology has been undergoing continuous progress. For example, Chinese patents CN110311007B and CN 102110736 B both disclose a near-infrared detector based on lead sulfide quantum dots. With the increasing demand for infrared information detection and intelligent perception, reducing the size of photodetectors, reducing the preparation cost, reducing the power consumption of detectors, and increasing the sensing band range of detectors are all issues that need to be addressed urgently.

[0003] After the PbS infrared detector, infrared detection materials with better performance, such as PbTe, PbSe, and InSb, have also been developed and put into use. PbSe and PbS are both chalcogenides of Pb and have the same cubic crystal structure. However, PbSe has a larger exciton Bohr radius, which increases the probability of electron coupling. Its small band gap can provide a multi-exciton generation effect. Compared with PbS detectors operating in the near-infrared band, the light response range of PbSe can reach the mid-wave infrared. In addition, the advantages of colloidal quantum dot materials such as simple synthesis and low preparation cost give it great application prospects in the field of infrared detection. Chinese patent CN114623933A provides a method for the preparation of an uncooled lead selenide near-infrared photodetector that can perform detection work in an uncooled environment. However, its inherent disadvantages include poor air stability, a large dielectric constant, and a large thermal expansion coefficient, which to a certain extent limit its application in the field of photoelectric detection. Chinese patent CN114231286A provides a method for preparing ionic liquid-modified quantum dots, which improves the stability of quantum dots in air, makes the resulting film more continuous and uniform, and significantly improves the photoelectric performance of the device.

[0004] To improve device performance, reducing incident light loss is also crucial. As one of the important nanophotoelectric materials, silicon nanowires not only have the original advantages of silicon bulk materials, but also exhibit properties different from bulk materials due to their reduced size, such as better photoluminescence performance, lower thermal conductivity, and so on. Silicon nanowire arrays are composed of many one-dimensional silicon nanowires arranged vertically. This unique structure has excellent anti-reflection properties, greatly improving its utilization rate and sensitivity to incident light, giving it a unique advantage in high-sensitivity photodetectors. Therefore, using silicon nanowire arrays as photodetector substrates can effectively reduce incident light loss and improve device performance. In addition, silicon nanowires also have good application prospects in flexible devices.

[0005] On the other hand, the large specific surface area of ​​silicon nanowires leads to more surface defects, which is not conducive to improving the photoelectric conversion efficiency. Therefore, people have also conducted in-depth research on the surface passivation of silicon materials. Currently, the commonly used surface passivation films include TiO2, SiO2, Al2O3 and α-SiN x :H thin films, etc. Among them, SiO2 can be directly oxidized on the silicon surface through high temperature, and is not affected by the initial surface condition. However, high temperature will cause more surface defects and introduce unwanted impurities, and a single layer of SiO2 is difficult to play an anti-reflection role for incident light. Al2O3 film has the advantages of low surface state density, thermal expansion coefficient close to that of silicon, and relatively low preparation temperature. However, the ALD deposition method used in its preparation has too low a rate and is not suitable for industrial production.

[0006] Combining silicon nanowires with suitable semiconductor materials, leveraging the advantages of both to create high-performance photodetectors, is crucial and necessary, and has become a key research direction. Silicon nanowire arrays can enhance the device's utilization of incident light, forming a "core / shell" heterojunction with semiconductor materials that reduces the distance photogenerated carriers must travel to escape. Furthermore, PbSe quantum dot films can broaden the spectral response range of silicon-based devices. Reducing surface defects in silicon nanowires and improving the surface morphology of quantum dot films can enhance device detection performance. Summary of the Invention

[0007] In response to the above-mentioned deficiencies in the prior art, one purpose of the present invention is to prepare a self-driven infrared photodetector based on a double heterojunction of a silicon nanowire array. The device has a significant spectral response in the ultraviolet to infrared bands, can realize self-driving function, and can improve the absorption rate and utilization rate of incident light.

[0008] A double heterojunction self-driven infrared photodetector based on a silicon nanowire array, the photodetector comprising a PEDOT:PSS transparent electrode, a PbSe quantum dot thin film layer, a ZnO thin film layer, a silicon nanowire array, and a planar silicon substrate electrode;

[0009] A silicon nanowire array consisting of multiple silicon nanowires is arranged vertically on a planar single-crystalline silicon substrate, that is, the lower end of the silicon nanowire is directly generated on the upper surface of the planar single-crystalline silicon substrate through metal-assisted etching; the outer surface of each silicon nanowire is covered with a ZnO thin film layer; the outer surface of the ZnO thin film layer is covered with a PbSe quantum dot thin film layer; then, a PEDOT:PSS transparent electrode layer is prepared on the PbSe quantum dot thin film layer.

[0010] Furthermore, before preparing the PEDOT:PSS transparent electrode on the PbSe quantum dot film layer, a metal nanoparticle film layer is first coated in the gaps between the silicon nanowires.

[0011] Preferably, the height of the silicon nanowires is 2 μm to 10 μm, the diameter of the silicon nanowires is 30 nm to 100 nm, and the gap between the silicon nanowires is 200 nm to 300 nm.

[0012] A method for preparing a double heterojunction self-driven infrared photodetector based on a silicon nanowire array comprises the following steps:

[0013] (1) Silicon nanowire arrays were prepared on N-type single crystal thin silicon wafers using metal-assisted chemical etching;

[0014] (2) ZnO thin film is prepared by spraying and coated on the surface of silicon nanowires to form a heterojunction Si-NW / ZnO;

[0015] (3) PbSe quantum dot film was prepared by spin coating and coated on the surface of ZnO film, thereby forming a double heterojunction Si-NW / ZnO / PbSe with the existing radial heterojunction Si-NW / ZnO;

[0016] (4) PEDOT:PSS was spin-coated on top of the silicon nanowire array covered with PbSe quantum dot film to prepare a transparent electrode, thereby obtaining a double heterojunction-based photodetector Si / Si-NW / ZnO / PbSe / PEDOT:PSS.

[0017] Preferably, 100 μL of ZnO precursor solution is sprayed to coat the silicon nanowires, and after high-temperature annealing, a Si-NW array with a surface covered with a ZnO nanoparticle film is obtained.

[0018] Preferably, the method for preparing PbSe quantum dot thin film by spin coating includes:

[0019] A 10 mg / mL PbSe quantum dot solution was prepared using n-octane as the solvent. After filtering through a 0.44 μm filter, the PbSe quantum dot solution was spin-coated on a ZnO film. The film was then immersed in a 10 mg / mL TBAB / MeOH solution for ligand replacement and annealed at 70°C for 15 minutes. The above spin-coating, immersion, and annealing steps were repeated four times to obtain a PbSe quantum dot film of a certain thickness.

[0020] Preferably, the PbSe colloidal quantum dot solution is synthesized by a hot injection method, specifically as follows:

[0021] Prepare Se precursor solution and Pb precursor solution separately:

[0022] 1.28 g of Se powder was dissolved in 12.8 mL of trioctylphosphine (TOP) and ultrasonically cleaned to dissolve it to obtain a Se precursor solution.

[0023] Place 1.784 g of PbO powder in a three-necked flask, add 5.4 mL of oleic acid OA and 32.5 mL of octadecene, and stir to dissolve;

[0024] First evacuate the three-necked flask and then fill it with nitrogen. After the three-necked flask is filled with nitrogen, heat it to 180℃;

[0025] After the temperature of the Pb precursor solution stabilized, the Se precursor solution was injected. After reacting for 4 minutes, 10 mL of n-hexane was injected to terminate the chemical reaction.

[0026] The cooled crude solution was centrifuged three times at 6800 rpm for 10 min, 5 min, and 5 min, respectively. The centrifuge solution was a mixture of acetone and isopropanol in a volume ratio of V = 1:1.

[0027] After centrifugation, the precipitate was collected and dispersed in n-octane at a concentration of 10 mg / mL.

[0028] Preferably, the method for preparing a PEDOT:PSS transparent electrode is as follows: PEDOT:PSS and IPA are uniformly mixed at a volume ratio of V = 20:1, filtered using a 0.44 μm filter, and then 80 μL of the solution is spin-coated at 2000 rpm for 30 seconds, and the spin-coating step is repeated twice; annealed at 80°C for 15 minutes, and then 80 μL of the above solution is spin-coated at 2000 rpm for 30 seconds, followed by immersion in ethylene glycol, treatment at 110°C for 15 minutes, and finally annealed at 80°C for 15 minutes to obtain a PEDOT:PSS transparent electrode. The present invention has the following beneficial effects:

[0029] The present invention introduces a ZnO bulk material thin film layer between the Si-NW array and the PbSe quantum dot film. ZnO forms a double heterojunction Si-NW / ZnO / PbSe with Si-NW and PbSe respectively. On the one hand, ZnO broadens the response of the device in the ultraviolet band, and PbSe broadens the response of the device in the infrared band. Finally, the device has a significant spectral response from the ultraviolet to the infrared band (365nm to 1550nm), and the photogenerated carriers can be quickly separated. On the other hand, as a common electron transport layer material, the introduction of ZnO makes the conduction band curvature smoother, which facilitates the transmission of photogenerated electrons, while blocking some photogenerated holes, effectively reducing the dark current passing through the device. Therefore, no external bias is required to detect the incident weak infrared light signal (12.1μW / cm 2 980nm incident light) has a larger "bright / dark" current ratio, thus realizing the self-driving function.

[0030] Using highly conductive PEDOT:PSS as a raw material, the transparent electrode, prepared by spin coating and treating with ethylene glycol, can reduce the loss of incident light. Therefore, the introduction of the ZnO interlayer and the transparent PEDOT:PSS electrode both contribute to the improved device performance. In addition, the Si-NW array can effectively improve the device's absorption and utilization of incident light.

[0031] The preparation method of the present invention has low preparation cost and simple preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the device structure of the Si-NW / ZnO / PbSe double heterojunction self-driven infrared photodetector based on the silicon nanowire array prepared in Example 1 of the present invention;

[0033] Figure 2 1 is the UV-visible absorption spectrum of the samples of Si-NW array, ZnO, PbSe and Si-NW / ZnO / PbSe composite structure prepared in Example 1 of the present invention;

[0034] Figure 3 is a transmission electron microscope (TEM) photograph of PbSe prepared in Example 1 of the present invention;

[0035] Figure 4 is the X-ray diffraction (XRD) pattern of PbSe prepared in Example 1 of the present invention;

[0036] Figure 5 is a scanning electron microscope (SEM) image of Si-NW / ZnO prepared in Example 1 of the present invention;

[0037] Figure 6is a scanning electron microscope (SEM) image of Si-NW / ZnO / PbSe prepared in Example 1 of the present invention;

[0038] Figure 7 is an X-ray energy dispersive spectrometry (XPS) spectrum of the Zn element in the Si-NW / ZnO / PbSe prepared in Example 1 of the present invention;

[0039] Figure 8 is an X-ray energy dispersive spectrometry (XPS) spectrum of the O element in the Si-NW / ZnO / PbSe prepared in Example 1 of the present invention;

[0040] Figure 9 is an X-ray energy dispersive spectrometry (XPS) spectrum of the Pb element in the Si-NW / ZnO / PbSe prepared in Example 1 of the present invention;

[0041] Figure 10 is an X-ray energy dispersive spectrometry (XPS) spectrum of Se element in Si-NW / ZnO / PbSe prepared in Example 1 of the present invention;

[0042] Figure 11 The Si-NW / ZnO / PbSe / PEDOT:PSS self-driven photodetector prepared in Example 1 of the present invention is 5.9μW / cm 2 IV curve under 365nm light irradiation;

[0043] Figure 12 The Si-NW / ZnO / PbSe / PEDOT:PSS self-driven photodetector prepared in Example 1 of the present invention is 10.2μW / cm 2 IV curve under 630nm light irradiation;

[0044] Figure 13 The Si-NW / ZnO / PbSe / PEDOT:PSS self-driven photodetector prepared in Example 1 of the present invention is 12.1μW / cm 2 IV curve under 980nm light irradiation;

[0045] Figure 14 It is a graph of the Si-NW / ZnO / PbSe / PEDOT:PSS self-driven photodetector prepared in Example 1 of the present invention under irradiation with 365nm to 1550nm light of different power densities;

[0046] Figure 15 Schematic diagram of the device band structure of the Si-NW / ZnO / PbSe / PEDOT:PSS self-driven photodetector prepared in Example 1 of the present invention under a bias voltage of 0V;

[0047] Figure 16 1 is the IV curve of the Si-NW / ZnO / PbSe / PEDOT:PSS self-driven photodetector prepared in Example 1 of the present invention under irradiation with 980nm light of different power densities;

[0048] Figure 17 The Si-NW / ZnO / PbSe / PEDOT:PSS self-driven photodetector prepared in Example 1 of the present invention and the Si-NW / PbSe simple structure photodetector have a power consumption of 12.1μW / cm 2 Comparison of It curves under 980nm light irradiation;

[0049] Figure 18 The Si-NW / ZnO / PbSe / PEDOT:PSS self-driven photodetector prepared in Example 1 of the present invention and the Si-NW / PbSe simple structure photodetector have a power consumption of 12.1μW / cm 2 Comparison of responsivity and specific detectivity under 980nm light irradiation;

[0050] Figure 19 The Si-NW / ZnO / PbSe / PEDOT:PSS self-driven photodetector prepared in Example 1 of the present invention is 12.1μW / cm 2 Response rise time diagram under 980nm light irradiation;

[0051] Figure 20 The Si-NW / ZnO / PbSe / PEDOT:PSS self-driven photodetector prepared in Example 1 of the present invention is 12.1μW / cm 2 Response fall time diagram under 980nm light irradiation. DETAILED DESCRIPTION

[0052] The present invention will be described below based on embodiments with reference to the accompanying drawings. However, the present invention is not limited to the embodiments, and the various numerical values ​​and materials in each embodiment are merely illustrative. The description will be made in the following order.

[0053] The present invention provides a self-powered infrared photodetector based on a double heterojunction (Si-NW / ZnO / PbSe) of a silicon nanowire array. The method involves first fabricating a silicon nanowire (Si-NW) array on a single-crystal silicon wafer using a metal-assisted etching (MACE) method. A double heterojunction Si-NW / ZnO / PbSe layer is then fabricated on the silicon nanowire array (Si-NWA), along with a self-powered infrared photodetector Si / Si-NW / ZnO / PbSe / PEDOT:PSS based on this heterojunction. The photodetector's structure includes a PEDOT:PSS top electrode (treated with ethylene glycol), a PbSe quantum dot thin film layer, a ZnO thin film layer, a silicon nanowire array, and a planar, highly doped silicon bottom electrode.

[0054] A silicon nanowire array (Si-NWA) consisting of multiple silicon nanowires (Si-NWs) is vertically arranged on a planar silicon substrate electrode. The lower ends of the Si-NWs are directly connected to the planar silicon substrate. This is because the Si-NWA is directly produced on a silicon single wafer using metal-assisted etching. After being fabricated into a photodetector, the outer surface of each Si-NW is coated with a ZnO thin film, which is then coated with a PbSe quantum dot thin film. A PEDOT:PSS top electrode is then placed on the PbSe quantum dot thin film.

[0055] Typically, before preparing a PEDOT:PSS transparent electrode on the PbSe quantum dot film layer, some metal nanoparticles can be coated into the gaps of the silicon nanowires. The detection performance of the device can be further enhanced through the plasmon enhancement effect of the metal particles.

[0056] The operating principle of a self-powered infrared photodetector based on a silicon nanowire array (Si-NW) / ZnO / PbSe) double heterojunction can be summarized as follows: when the incident photon energy matches the material band gap, the photon is absorbed and generates photogenerated electron-hole pairs. Subsequently, the built-in electric field at the heterojunction interface separates the photogenerated electron-hole pairs and is then collected by their respective electrodes. Therefore, to achieve high-performance photodetectors, it is necessary to first enhance the device's utilization of incident light. Therefore, the unique anti-reflection properties of the Si-NW array are exploited to enhance incident light absorption, and PEDOT:PSS is used as a transparent electrode to reduce absorption and reflection losses. Secondly, energy level matching at the material interface facilitates the rapid dissociation of photogenerated electron-hole pairs. The introduction of the ZnO film further aligns the conduction band bending between the Si-NW and PbSe. Finally, the device's dark current, which is caused by various factors, should be minimized. Experimental results show that the introduction of the ZnO film effectively reduces the device's dark current.

[0057] like Figure 2As shown, the UV-visible absorption spectra of three structures: Si-NW array, Si-NW / ZnO and Si-NW / ZnO / PbSe, prove that the composite structure Si-NW / ZnO / PbSe indeed combines the incident light absorption wavelength range of Si-NW array, ZnO and PbSe, and absorbs the ultraviolet-infrared band range, thereby improving the response range of the device.

[0058] The present invention confirms the crystallinity and purity of PbSe by TEM and XRD patterns. Figure 3 As shown in the figure, the size and distribution of PbSe quantum dots are uniform, with a particle size of ~2.91nm. Figure 4 As shown, the obtained PbSe nanocrystals were compared with the standard cards, and the characteristic peaks were obvious and consistent.

[0059] The present invention proves that ZnO and PbSe are uniformly coated on Si-NW through SEM images and EDS spectra. Figure 5 As shown in Figure 2, ZnO is coated on the surface of Si-NW, and the diameter of the entire nanowire becomes larger than that of Si-NW without ZnO. Figure 6 As shown in Figure 1, PbSe is evenly coated on the Si-NW / ZnO surface, the quantum dots are evenly distributed, and there are obvious edge lines between the quantum dots. Figure 7-10 As shown, Zn, O, Pb and Se elements are evenly distributed on the surface of the Si-NW array, and the side proves the uniform distribution of ZnO and PbSe films.

[0060] The present invention is characterized and obtained Figure 11-Figure 15 The data results from Figure 11-13 It can be seen from the figure that the response range of the Si-NW / ZnO / PbSe double heterojunction device can be from 365nm to 1550nm, and it can also be detected under weak incident light intensity (~10μW / cm 2 ) and at 0V bias, the devices have obvious "bright / dark" current ratios. Figure 14 3 is the It curve observed under the illumination of the above-mentioned 365nm~1550nm light source. It can be seen that the device has the largest "bright / dark" current ratio under the incident light of 980nm. Figure 15The energy band diagram of the device under 0V bias describes the migration mechanism of photogenerated carriers in response to incident light. The highest occupied molecular orbital (HOMO) energies of the Si-NW, ZnO, and PbSe are -5.17eV, -7.72eV, and -5.77eV, respectively, while their lowest unoccupied molecular orbital (LUMO) energies are -4.05eV, -4.35eV, and -4.83eV, respectively. The Fermi levels of the closely contacted heterojunction are identical, and the conduction band continuously bends, facilitating the migration of photogenerated electrons toward the Si-NW side. Some photogenerated holes are blocked by the ZnO layer, but due to the thinness of the ZnO film, some can still migrate from the Si-NW side to the PbSe side under the action of the built-in electric field. Consequently, the photogenerated excitons are rapidly separated by the built-in electric field and transferred to the two electrodes. Upon completion of the circuit, a photogenerated current can be observed.

[0061] The present invention is obtained by characterization Figure 16-Figure 18 , Figure 16 Figure 3 shows the IV characteristic curve of the device under 980nm incident light of different power densities. It can be seen that due to the photovoltaic effect, the IV curve shifts after illumination, and the greater the light intensity, the greater the shift, which proves that the intensity of the photovoltaic electric field is greater. Figure 17 For Si-NW / PbSe and Si-NW / ZnO / PbSe at 12.1μW / cm 2 The comparison of the "on / off" current under 980nm incident light shows that the introduction of ZnO film significantly reduces the dark current of the device by two orders of magnitude, while the photocurrent does not change significantly. Figure 18 The comparison of the responsivity and specific detection rate of Si-NW / PbSe and Si-NW / ZnO / PbSe heterojunction structures under 980nm incident light of different power densities is shown in the figure. 2 Under weak light irradiation, the device's responsiveness and specific detection rate are greatly improved after the introduction of ZnO thin film.

[0062] In the present invention, Figure 19-20 As shown, we also measured 12.1μW / cm 2 The device response time is calculated from the It curve under 980nm incident light. It can be seen that the rise time of the device is 66.41ms and the fall time is 67.37ms.

[0063] The advantages of the present invention are that the introduction of the double heterojunction Si-NW / ZnO / PbSe, on the one hand, broadens the light response range of the original single heterojunction device; on the other hand, it also provides a stronger built-in electric field, allowing the device to operate without an external bias, and the introduction of the ZnO film significantly reduces the dark current of the device.

[0064] In order to evaluate the performance of self-driven photodetectors, the “bright / dark” current ratio (K), photoresponsivity (R) and specific detectivity (D) are usually used. * ) and other parameters to characterize the performance of the photodetector.

[0065] The ratio of the photocurrent generated by the device under illumination to the dark current generated by the device in the dark state is called the "On / Off" current ratio (also known as the "bright / dark" current ratio). Its calculation formula is:

[0066]

[0067] Among them I ill is the current of the device under light conditions, I dark is the dark current generated by the device in the absence of light, and the difference between the two is the photocurrent I ph . Generally speaking, the larger the "on / off" current ratio, the better the performance of the device. Increasing the "on / off" current ratio of the device can be done from two aspects: First, to increase the photocurrent: Common methods include changing the structure of the device, such as changing the structure of the photodetector from a diode to a field-effect transistor, and regulating the charge separation and transmission by adjusting the gate voltage, thereby increasing the internal gain and achieving the purpose of increasing the photocurrent; increasing the device's absorption rate of incident light, such as replacing the planar silicon base with a silicon nanowire array, which can enhance the absorption of incident light and thus increase the photocurrent. The second is to reduce the dark current: Common methods include optimizing the device structure, material doping, improving the surface morphology, and adding a charge blocking layer.

[0068] In the present invention, at 12.1 μW / cm 2 Under 980nm incident light, without external bias, K = 1.361×10 3 K increases with the increase of lighting intensity, such as Figure 16 shown.

[0069] The ratio of the photocurrent generated by a photodetector under illumination to the incident light power is defined as the responsivity (R). It directly reflects the photoelectric conversion capability of the photodetector and is an important measure of the spectral and frequency characteristics of the photoelectric conversion. Its calculation formula is:

[0070]

[0071] Among them I ph is the photocurrent of the device, P in is the incident light power per unit area (i.e., light intensity), and A is the effective illumination area on the device.

[0072] In the present invention, at 12.1 μW / cm2 When the device is exposed to 980nm incident light and has no external bias, it achieves a responsivity of 252.536mA / W. Figure 18 As shown in Figure 2, the responsivity decreases with the increase of illumination power intensity.

[0073] The signal-to-noise ratio obtained by the device under unit power radiation is called "Specific detectivity" (D * ), also known as the "normalized detectivity." It is a crucial performance parameter of a photodetector and an important measure of its sensitivity and detection capability. Its general formula is Equation (1.3). If the photodetector is dominated by scattering noise, it can be expressed as Equation (1.4):

[0074]

[0075] Where Δf is the electrical frequency width, i n is the noise current, e is the elementary charge; R is the responsivity, A is the effective illumination area of ​​the device, I d Obviously, for a photodetector, the lower its dark current is, the higher its detection sensitivity to weak incident light signals is.

[0076] In the present invention, under 0V bias and 12.1μW / cm 2 Under the 980nm incident light, the self-driven photodetector achieved high D * =5.82×10 12 Jones. Apparently, D * Strongly dependent on R and dark current. To obtain high D * , the dark current should be reduced, R should be as high as possible, and the highest R value can be obtained under a certain lighting intensity. 2 , 24.6μW / cm 2 and 634 μW / cm 2 ) incident light, the device's D * The change curve is as follows Figure 18 shown.

[0077] The UV-visible spectrum of Example 1 of the present invention represents the mutual influence of the three materials Si-NW, ZnO and PbSe alone and in the composite structure, which broadens the light absorption region of the device (365nm~1550nm). Figure 17The advantages of introducing ZnO thin films in reducing device dark current are shown. Therefore, in the preparation of photodetectors, the introduction of suitable materials can effectively reduce dark current and enhance the transport of photogenerated carriers. This is due to the combined effects of factors such as high carrier mobility, matching of the HOMO and LUMO energy levels, and a broadening of the active layer's absorption spectrum.

[0078] The preparation method provided by the present invention is as follows:

[0079] First, the silicon wafer was ultrasonically cleaned with deionized water, isopropyl alcohol, and ethanol for 15 minutes each. The Si-NW array was prepared by a two-step metal (Ag) assisted chemical etching method.

[0080] Then, a ZnO precursor solution Zn(AC)2 / (96% MOE and 4% MEA mixed solution) is sprayed to uniformly cover the silicon nanowires, and after high-temperature annealing, a Si-NW array with a surface uniformly covered with a ZnO bulk material film is obtained.

[0081] A PbSe quantum dot solution with a concentration of 10 mg / mL was prepared using n-octane as the solvent. After filtering through a 0.44 μm filter head, 50 μL of the solution was spin-coated on Si-NW / ZnO at speeds of 600 rpm (for a total of 6 s) and 2000 rpm (for a total of 30 s). The solution was then immersed in a 10 mg / mL TBAB / MeOH solution for ligand replacement and annealed at 70°C for 15 min. This step was repeated four times to obtain a PbSe quantum dot film.

[0082] PEDOT:PSS and IPA were uniformly mixed at a volume ratio of V = 20:1 and filtered using a 0.44μm filter. 80μL of the solution was then spin-coated at 2000rpm for 30s. This step was repeated twice, followed by annealing at 80°C for 15min. Another 80μL of the solution was spin-coated at 2000rpm for 30s. The electrode was then immersed in ethylene glycol and treated at 110°C for 15min. Finally, the electrode was annealed at 80°C for 15min to obtain a PEDOT:PSS transparent electrode. The entire device was finally fabricated. The schematic diagram of the fabricated photodetector is shown below. Figure 1 shown.

[0083] The present invention synthesizes a high-quality PbSe quantum dot solution using a hot injection method. Se and Pb precursor solutions are prepared separately: 1.28g of Se powder is dissolved in 12.8mL of trioctylphosphine (TOP) and thoroughly dissolved using ultrasonic cleaning to obtain the Se precursor solution. 1.784g of PbO powder is placed in a three-necked flask, followed by 5.4mL of oleic acid (OA) and 32.5mL of octadecene (ODE) and thorough stirring to dissolve. The flask is then evacuated and filled with nitrogen. Once the three-necked flask is filled with nitrogen, the temperature is rapidly raised to 180°C. After the temperature of the Pb precursor solution stabilizes, the Se precursor solution is rapidly injected. After a 4-minute reaction, 10mL of n-hexane is quickly injected to terminate the reaction. The cooled crude solution is centrifuged three times at 6800 rpm for 10 minutes, 5 minutes, and 5 minutes, respectively. The centrifuged solution is a mixture of acetone and isopropanol in a 1:1 volume ratio. After centrifugation, the precipitate was collected and dispersed in n-octane at a concentration of 10 mg / mL.

[0084] The above are only specific embodiments of the present invention, but are not limited thereto. Any simple changes, equivalent substitutions or modifications based on the present invention that solve basically the same technical problems or achieve basically the same technical effects are within the scope of protection of the present invention.

Claims

1. A double heterojunction self-driven infrared photodetector based on silicon nanowire array, characterized in that: The photodetector includes a PEDOT:PSS transparent electrode, a PbSe quantum dot thin film layer, a ZnO thin film layer, a silicon nanowire array, and a planar silicon substrate electrode; A silicon nanowire array consisting of multiple silicon nanowires is arranged vertically on a planar single-crystalline silicon substrate, that is, the lower ends of the silicon nanowires are directly generated on the upper surface of the planar single-crystalline silicon substrate through metal-assisted etching; the outer surface of each silicon nanowire is covered with a ZnO thin film layer; the outer surface of the ZnO thin film layer is covered with a PbSe quantum dot thin film layer; then, a layer of PEDOT:PSS transparent electrode is prepared on the PbSe quantum dot thin film layer.

2. The double heterojunction self-driven infrared photodetector based on silicon nanowire array according to claim 1, characterized in that: Before preparing the PEDOT:PSS transparent electrode on the PbSe quantum dot film layer, a metal nanoparticle film layer is first coated in the gaps between the silicon nanowires.

3. The double heterojunction self-driven infrared photodetector based on silicon nanowire array according to claim 1, characterized in that: The height of the silicon nanowires is 2 μm to 10 μm, the diameter of the silicon nanowires is 30 nm to 100 nm, and the gap between the silicon nanowires is 200 nm to 300 nm.

4. A method for preparing a double heterojunction self-driven infrared photodetector based on a silicon nanowire array according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Silicon nanowire arrays were prepared on N-type single crystal thin silicon wafers using metal-assisted chemical etching; (2) ZnO thin film is prepared by spraying and coated on the surface of silicon nanowires to form a heterojunction Si-NW / ZnO; (3) PbSe quantum dot film was prepared by spin coating and coated on the surface of ZnO film, thereby forming a double heterojunction Si-NW / ZnO / PbSe with the existing radial heterojunction Si-NW / ZnO; (4) PEDOT:PSS was spin-coated on top of the silicon nanowire array covered with PbSe quantum dot film to prepare a transparent electrode, thereby obtaining a double heterojunction-based photodetector Si / Si-NW / ZnO / PbSe / PEDOT:PSS.

5. The preparation method according to claim 4, characterized in that: 100 μL of ZnO precursor solution was sprayed to coat the silicon nanowires, and after high-temperature annealing, a Si-NW array with a surface covered with a ZnO nanoparticle film was obtained.

6. The preparation method according to claim 4, characterized in that: The method for preparing a PbSe quantum dot film by spin coating includes: A 10 mg / mL PbSe quantum dot solution was prepared using n-octane as the solvent. After filtering through a 0.44 μm filter, the PbSe quantum dot solution was spin-coated on a ZnO film. The film was then immersed in a 10 mg / mL TBAB / MeOH solution for ligand replacement and annealed at 70°C for 15 minutes. The above spin-coating, immersion, and annealing steps were repeated four times to obtain a PbSe quantum dot film of a certain thickness.

7. The preparation method according to claim 6, characterized in that: The PbSe colloidal quantum dot solution was synthesized by hot injection method, specifically: Prepare Se precursor solution and Pb precursor solution separately: 1.28 g of Se powder was dissolved in 12.8 mL of trioctylphosphine (TOP) and ultrasonically cleaned to dissolve it to obtain a Se precursor solution. Place 1.784 g of PbO powder in a three-necked flask, add 5.4 mL of oleic acid OA and 32.5 mL of octadecene, and stir to dissolve; First evacuate the three-necked flask and then fill it with nitrogen. After the three-necked flask is filled with nitrogen, heat it to 180℃; After the temperature of the Pb precursor solution stabilized, the Se precursor solution was injected. After reacting for 4 minutes, 10 mL of n-hexane was injected to terminate the reaction. The cooled crude solution was centrifuged three times at 6800 rpm for 10 min, 5 min, and 5 min, respectively. The centrifuge solution was a mixture of acetone and isopropanol in a volume ratio of V = 1:

1. After centrifugation, the precipitate was collected and dispersed in n-octane at a concentration of 10 mg / mL.

8. The preparation method according to claim 4, characterized in that The method for preparing a PEDOT:PSS transparent electrode is as follows: PEDOT:PSS and IPA are uniformly mixed at a volume ratio of V=20:1, filtered using a 0.44μm filter head, and then 80μL of the solution is spin-coated at a speed of 2000rpm for 30s, and the spin-coating step is repeated twice; annealed at 80°C for 15min, and then 80μL of the above solution is spin-coated at a speed of 2000rpm for 30s, then immersed in ethylene glycol, treated at 110°C for 15min, and finally annealed at 80°C for 15min to obtain a PEDOT:PSS transparent electrode.

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