A bias voltage-regulated MoS2 / PbS heterojunction optoelectronic device

Abstract

The present invention belongs to the technical field of optoelectronic devices, and discloses a bias-regulated MoS2 / PbS heterojunction optoelectronic device. Taking FTO glass as the conductive substrate, a MoS2 thin film and a PbS thin film are successively grown on the surface of the FTO glass, and the PbS thin film forms a three-dimensional skeleton coating structure on MoS2. Two Ag electrodes are deposited on the PbS thin film and the FTO glass. The optoelectronic device of the present invention integrally realizes two performances of neuromorphic optoelectronic synapses and broadband optoelectronic detection: the synaptic characteristics of the device come from the modulation of interface defects, realizing advanced synaptic functions such as light-regulated short-term and long-term memory conversion (STM / LTM) and repeated learning and forgetting; while the excellent detection performance of the device comes from the rapid separation of carriers at the heterojunction interface. The preparation process of the optoelectronic device of the present invention is simple, and large-area thin films can be applied to industrial production, expanding the development in the fields of simulating human visual nerve memory and detecting in the ultraviolet to short-wave infrared band.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic devices, and particularly relates to a bias-regulated MoS2 / PbS heterojunction optoelectronic device. Background Art

[0002] In the context of the rapid development of artificial intelligence (AI), the development of optoelectronic devices towards intelligent systems capable of integrated sensing, memory, and computing has become imperative. Modern advanced technologies, including intelligent medical devices, robotics, space, etc., not only require multi-spectral optical signal acquisition in the ultraviolet (UV) to near-infrared (NIR) wavelength range, but also require an adaptive information processing ability similar to that of biological sensory neurons. Computers are very similar to the human brain. Humans use the visual system to perceive and identify external light, and then quickly transmit it to the brain through synapses for rapid processing. Therefore, artificial synapses fabricated by mimicking biological synapses can integrate computing and memory functions, thus breaking through the von Neumann bottleneck existing in traditional computers.

[0003] MoS2 in transition metal dichalcogenides (TMDCs) has become a popular choice for optoelectronic devices due to its atomically scaled thickness-tunable bandgap (1.2 - 1.8 eV) and special optical interactions. However, the bandgap limitation of MoS2 itself results in insufficient response to near-infrared (NIR, 800 - 2000 nm) light. Therefore, it is possible to combine it with materials with high response to the near-infrared band, such as Si, PbS, etc., through heterojunction engineering to expand the device into fields such as night vision and lidar. However, the complex preparation process of the heterojunction, the limited contact area and limited light absorption of traditional planar heterojunctions have led to most reported devices having low light response and slow speed in the detection field, poor retention characteristics and high power consumption in the synaptic field, and single functions achieved. Due to the contradiction in the light response speed, traditional synaptic devices and detection devices cannot be integrated, so it is urgent to achieve simple preparation and functional integration of optical devices. Summary of the Invention

[0004] Based on the above deficiencies of the existing technology, the present invention provides a bias-regulated MoS2 / PbS heterojunction optoelectronic device, explores the basic artificial synaptic functions and excellent detection performances achieved under different biases, provides a simple and efficient way to improve the performance of optoelectronic devices, and solves the problem that the optoelectronic synaptic and detection functions cannot be integrated on a single device.

[0005] To achieve the purpose, the present invention adopts the following technical solutions:

[0006] A bias-regulated MoS2 / PbS heterojunction optoelectronic device, characterized in that it is a vertical structure two-terminal device, with an FTO glass as the conductive substrate, on the surface of the FTO glass, a MoS2 thin film with a nanoflower spherical morphology is grown by a hydrothermal method, and a PbS thin film is grown on the MoS2 thin film by a water bath method, and the PbS thin film forms a three-dimensional skeleton coating structure on the MoS2; a first Ag electrode is arranged on the PbS thin film, and a second Ag electrode is arranged on the area of the FTO glass where the MoS2 thin film and the PbS thin film are not grown.

[0007] The MoS2 / PbS heterojunction optoelectronic device of the present invention integrates two performances of neuromorphic optoelectronic synapses and broadband optoelectronic detection. The synaptic characteristics of the device come from the modulation of interface defects, realizing advanced synaptic functions such as light-regulated short-term and long-term memory conversion (STM / LTM) and repeated learning and forgetting. The excellent detection performance of the device comes from the rapid separation of carriers at the heterojunction interface. Specifically, by adjusting the magnitude of the bias voltage applied to the two Ag electrodes and irradiating light in the ultraviolet to short-wave infrared band (wavelength range 405 - 1650 nm), the two optoelectronic characteristics of the MoS2 / PbS heterojunction optoelectronic device are regulated: at a bias voltage of 0 V, the MoS2 / PbS heterojunction optoelectronic device realizes broadband optoelectronic detection; as the bias voltage increases, the optoelectronic synaptic performance of the MoS2 / PbS heterojunction optoelectronic device gradually increases.

[0008] The present invention further discloses a preparation method of the bias-regulated MoS2 / PbS heterojunction optoelectronic device, comprising the following steps:

[0009] Step 1: Ultrasonically clean the FTO glass successively with acetone, ethanol and deionized water to remove impurities on the surface, and then dry it with nitrogen.

[0010] Step 2: Add 0.09 g of sodium molybdate and 0.18 g of thiourea to 60 mL of deionized water and stir evenly, then transfer it to a reaction kettle, and add the cleaned FTO glass to the reaction kettle, and react at 200 °C for 20 - 24 h; after the reaction is completed, take out the sample, wash it alternately with deionized water and absolute ethanol, and then dry it in an oven at 40 - 60 °C for 1 - 2 h to obtain a MoS2 thin film with a nanoflower spherical morphology.

[0011] Step 3: Add 9.475 g of lead acetate into 100 mL of deionized water and stir until completely dissolved to obtain a lead acetate solution; dissolve 14.7 g of trisodium citrate, 5.71 g of thiourea, and 7.84 g of potassium hydroxide in 50 mL of deionized water respectively to obtain a trisodium citrate solution, a thiourea solution, and a potassium hydroxide solution; vertically suspend the FTO glass with the grown MoS2 film in the lead acetate solution, then sequentially add the trisodium citrate solution, the thiourea solution, and the potassium hydroxide solution and stir evenly in sequence, and then place it in a water bath at 40 °C and let it stand for reaction for 10 - 20 min; after the reaction is completed, take out the sample and wash it alternately with deionized water and absolute ethanol, and then put it in an oven at 40 - 60 °C and dry it for 1 - 2 h to obtain a PbS film;

[0012] Step 4: Scrape off the MoS2 film and the PbS film on a partial area of the FTO glass surface to expose the FTO conductive layer; then deposit a first Ag electrode on the PbS film and deposit a second Ag electrode on the area of the FTO glass where the MoS2 film and the PbS film are not grown, thus completing the preparation of the MoS2 / PbS heterojunction optoelectronic device.

[0013] The beneficial effects of the present invention are reflected in:

[0014] 1. In the structure of the MoS2 / PbS heterojunction optoelectronic device of the present invention, the PbS film and the MoS2 film form a high-quality van der Waals heterojunction. And the special nanoflower spherical morphology of MoS2 provides a rich active interface, greatly increasing the contact area, enabling the PbS film to form a three-dimensional skeleton coating structure on it during growth. This structure enhances the absorption of incident light through multi-path scattering and increases the photo-response ability of photoelectric detection. At a bias voltage of 0 V, due to the built-in electric field formed by the heterojunction, carriers can be quickly separated, improving the photo-response speed. After increasing the bias voltage to 0.4 V, the large contact area has more defects, and the potential barrier at the heterojunction interface becomes higher with the increase of the bias voltage, generating a stronger persistent photoconductivity effect (PPC effect), thereby improving the synaptic performance of the device. Therefore, the MoS2 / PbS heterojunction optoelectronic device of the present invention realizes the integration of photoelectric detection and artificial synaptic performance.

[0015] 2. The MoS2 / PbS heterojunction optoelectronic device of the present invention is prepared by a fully liquid-phase low temperature process, and the process flow is simple, greatly saving the preparation cost.

[0016] 3. The optoelectronic properties were tested using a Keithley 4200 instrument. The MoS2 / PbS heterojunction optoelectronic device of the present invention achieved advanced synaptic functions such as short-term plasticity, long-term plasticity, the transition from short-term memory to long-term memory, and repeated learning and forgetting by applying optical pulses of different frequencies at a bias voltage of 0.4 V. Moreover, the paired-pulse facilitation index (PPF index) was as high as 171.6%. At a bias voltage of 0 V, by applying light in the range of 405 - 1650 nm, optoelectronic detection from ultraviolet to short-wave infrared was achieved, and the maximum responsivity (0.013 A·W -1 ), specific detectivity (7.6×10 10 Jones), and an ultra-high response speed (rise / decay time of 360 / 351 µs) were obtained at 980 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 FIG. is a schematic structural diagram of the MoS2 / PbS heterojunction optoelectronic device provided by the present invention.

[0018] Figure 2 In (a) and (b) of FIG., they are respectively the surface scanning electron microscope (SEM) image and the SEM cross-sectional image of the MoS2 thin film with a nanoflower spherical morphology prepared in step 2 of Example 1.

[0019] Figure 3 FIG. is the SEM surface image of the MoS2 / PbS heterojunction optoelectronic device prepared in Example 1.

[0020] Figure 4 FIG. is the cross-sectional image of the MoS2 / PbS heterojunction prepared in Example 1 ( Figure 4 in (a) of FIG.) and the energy spectrum diagram of the corresponding elements, where (b) corresponds to the Pb element, (c) corresponds to the S element, and (d) corresponds to the Mo element.

[0021] Figure 5 FIG. is the X-ray diffraction (XRD) pattern of the MoS2 / PbS heterojunction prepared in Example 1.

[0022] Figure 6 FIG. is the absorption spectrum of the MoS2 / PbS heterojunction ( Figure 6 in (a) of FIG.) and the MoS2 thin film prepared in Example 1 ( Figure 6 in (b) of FIG.).

[0023] Figure 7 FIG. is the photocurrent response diagram of the MoS2 / PbS heterojunction optoelectronic device in Example 1 under different bias voltages (0 V, 0.01 V, 0.1 V, 0.2 V, 0.4 V), where the wavelength of the irradiated light is 980 nm and the power is 42.7 mW·cm -2 .

[0024] Figure 8 Double-pulse current diagram ((a) in Figure 8 ) and double-pulse facilitation (PPF) functional diagram ((b) in Figure 8 ) of the MoS2 / PbS heterojunction optoelectronic device in Example 1 under 980 nm pulsed light (bias voltage of 0.4 V).

[0025] Figure 9 Optical response current diagrams of the MoS2 / PbS heterojunction optoelectronic device in Example 1 at different frequencies ((a) in Figure 9 ) and different irradiation durations ((b) in Figure 9 ), with the wavelength of the irradiation light being 980 nm and the power being 42.7 mW·cm -2 .

[0026] Figure 10 Optical response current diagram of the MoS2 / PbS heterojunction optoelectronic device in Example 1 under irradiation of 980 nm pulsed light (bias voltage of 0.4 V) for simulating repeated learning and forgetting functions.

[0027] Figure 11 In ((a) in ), the circuit diagrams of the "AND" and "OR" gates of the MoS2 / PbS heterojunction optoelectronic device in Example 1 are shown. In ((b) in ), the spike pulse current diagrams under irradiation of 980 nm and 650 nm light at different optical powers (31.5 mW·cm -2 , 42.7 mW·cm -2 ) are shown. In ((c) in ), the logical truth tables of the "AND" and "OR" gates are shown. In ((d) in ), the relationship between the "AND" and "OR" gates regarding spike pulse current is shown.

[0028] Figure 12 Voltage-current diagram of the MoS2 / PbS heterojunction optoelectronic device in Example 1 under irradiation of 405 - 1650 nm light with a power of 42.7 mW·cm -2 .

[0029] Figure 13 Optical response current diagram of the MoS2 / PbS heterojunction optoelectronic device in Example 1 under irradiation of 405 - 1650 nm light with a power of 42.7 mW·cm -2 .

[0030] Figure 14 1 kHz frequency diagram of the MoS2 / PbS heterojunction optoelectronic device in Example 1 under irradiation of 980 nm light with a power of 42.7 mW·cm -2 (0 V).

[0031] Figure 15Photoresponse current diagram of the MoS2 / PbS heterojunction optoelectronic device in Example 2 under 405 - 1650 nm light irradiation with 42.7 mW·cm -2 The light response current diagram of the MoS2 / PbS heterojunction optoelectronic device under 405 - 1650 nm light irradiation with 42.7 mW·cm Detailed implementation mode

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The drawings are used to describe the features and performance of the embodiments in detail. However, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0033] Example 1

[0034] As Figure 1 shown, this embodiment provides a bias - regulated MoS2 / PbS heterojunction optoelectronic device, which is a vertical - structure two - terminal device. Using FTO glass as the conductive substrate, a MoS2 thin film with a nanoflower spherical morphology is grown on the surface of the FTO glass by hydrothermal method, and a PbS thin film is grown on the MoS2 thin film by water - bath method, and the PbS thin film forms a three - dimensional skeleton coating structure on MoS2; a first Ag electrode is arranged on the PbS thin film, and a second Ag electrode is arranged in the area of the FTO glass where the MoS2 thin film and the PbS thin film are not grown.

[0035] This embodiment prepares the bias - regulated MoS2 / PbS heterojunction optoelectronic device according to the following steps:

[0036] Step 1: Ultrasonically clean the FTO glass with acetone, ethanol and deionized water in sequence for 20 min to remove surface impurities, and then dry it with nitrogen (purity above 99.5%) for standby.

[0037] Step 2: Add 0.09 g of sodium molybdate (purity AR 99.0%) and 0.18 g of thiourea (purity AR 99.0%) to 60 mL of deionized water and stir evenly, then transfer it to a 100 - mL Teflon - lined reaction kettle, and add the cleaned FTO glass to the reaction kettle, and react at 200 °C for 21 h; after the reaction, take out the sample, wash it alternately with deionized water and absolute ethanol to remove possible residual reactants, and then dry it in an oven at 60 °C for 2 h to obtain a MoS2 thin film with a nanoflower spherical morphology.

[0038] Step 3: Add 9.475 g of lead acetate (purity: AR 99.5%) into 100 mL of deionized water, and stir until completely dissolved to obtain a lead acetate solution; dissolve 14.7 g of trisodium citrate (purity: AR 99.0%), 5.71 g of thiourea (purity: AR 99.0%) and 7.84 g of potassium hydroxide (purity: AR 90.0%) in 50 mL of deionized water respectively to obtain a trisodium citrate solution, a thiourea solution and a potassium hydroxide solution; vertically suspend the FTO glass with the grown MoS2 film in the lead acetate solution, then sequentially add the trisodium citrate solution, the thiourea solution and the potassium hydroxide solution and stir evenly in sequence, and then place it in a water bath at 40 °C and let it stand for reaction for 20 min; after the reaction is completed, take out the sample and wash it alternately with deionized water and absolute ethanol, and then put it into an oven at 60 °C and dry it for 2 h to obtain a PbS film and form a MoS2 / PbS heterojunction.

[0039] Step 4: Scrape off the MoS2 film and the PbS film in some areas on the surface of the FTO glass to expose the FTO conductive layer; then deposit a first Ag electrode on the PbS film, and deposit a second Ag electrode on the area of the FTO glass where the MoS2 film and the PbS film are not grown, thus completing the preparation of the MoS2 / PbS heterojunction optoelectronic device.

[0040] The MoS2 / PbS heterojunction optoelectronic device prepared in the above embodiment was subjected to XRD testing using Cu target Kα rays, morphological testing using a JSM-7001F model scanning electron microscope, and optical performance testing using a Keithley 4200 test system. The specific results are analyzed as follows in combination with the attached drawings:

[0041] Figure 2 In (a) and (b), they are respectively the SEM surface map and the SEM cross-sectional map of the MoS2 film prepared in Step 2 of this embodiment. It can be seen that the special nanoflower spherical morphology of MoS2 provides a rich active interface, greatly increasing the contact area.

[0042] Figure 3 and Figure 4 In (a) of this embodiment, they are respectively the SEM surface map and the SEM cross-sectional map of the MoS2 / PbS heterojunction prepared in Step 3. It can be seen that the obtained MoS2 / PbS heterojunction has a unique semi-surrounding skeleton-coated hierarchical heterointerfacial structure. This structure enhances the absorption of incident light through multi-path scattering, increases the light response ability of photoelectric detection, and at the same time the large contact area increases the defects at the interface and enhances the photoelectric synaptic performance. Figure 4Figures (b - d) are energy spectrum diagrams corresponding to the cross-section of the MoS2 / PbS heterojunction. Among them, (b) corresponds to the Pb element, (c) corresponds to the S element, and (d) corresponds to the Mo element. It can be seen from the figure that a heterojunction with good contact is fabricated.

[0043] Figure 5 This is the X-ray diffraction (XRD) pattern of the MoS2 / PbS heterojunction prepared in step 3 of this example. It can be seen that except for some peaks from the FTO glass substrate, most peaks match well with the standard diffraction card of lead sulfide (5 - 0592). Specifically, peaks such as (111), (200), (220), (311), and (400) are clearly visible, indicating the successful preparation of the PbS thin film. The absence of MoS2-related peaks is attributed to the growth of PbS in a wrapping manner on the surface, resulting in the diffraction peak intensity of MoS2 being very weak compared to PbS.

[0044] Figure 6 Figures (a) and (b) in this are the absorption spectra of the MoS2 / PbS heterojunction and the MoS2 thin film of this example, respectively. It can be seen that compared with the limited absorption range of the MoS2 thin film in the ultraviolet and visible light, the absorption of the MoS2 / PbS heterojunction extends to the short-wave infrared range, enhancing the light response ability to short-wave infrared light.

[0045] Figure 7 This is the photocurrent response diagram of the MoS2 / PbS heterojunction optoelectronic device of this example under different bias voltages (0 V, 0.01 V, 0.1 V, 0.2 V, 0.4 V). The wavelength of the light used for irradiation is 980 nm and the power is 42.7 mW·cm -2 . From Figure 7 it can be seen that the device shows a fast photocurrent response speed at a bias voltage of 0 V because the photo-generated carriers are quickly separated by the built-in electric field; however, as the bias voltage increases, the trend of the current decay after turning off the light slows down with the increase of the voltage. Because after increasing the bias voltage, the potential barrier at the heterojunction interface increases and the defects at the heterojunction interface increase, restricting the recombination of carriers, and the photocurrent of the device gradually stabilizes in the PPC state. Therefore, the device of this example can change the optoelectronic performance by regulating the magnitude of the bias voltage, realizing the integration of photodetection and photoelectric synapse on a single device.

[0046] Figure 8 Figures (a) and (b) in this are the double-pulse current diagram and the double-pulse facilitation (PPF) function diagram of the MoS2 / PbS heterojunction optoelectronic device of this example under a 980 nm pulsed light (bias voltage is 0.4 V). Figure 8 Figure (a) shows that under the condition of a bias voltage of 0.4 V, two light powers of 42.7 mW·cm are applied to the PbS / MoS2 heterojunction device -2, a pulse with a light illumination time of 150 ms successfully simulated the characteristics of paired-pulse facilitation (PPF), indicating that the device can simulate the short-term plasticity of synapses. As Figure 8 shown in (b), due to the relaxation phenomenon of carriers, the PPF index decays with the increase in the interval time between two pulsed lights. When the interval time is 0.1 s, the maximum paired-pulse facilitation PPF index reaches 171.6%.

[0047] Figure 9 Figures (a) and (b) in it are the photocurrent response diagrams of the MoS2 / PbS heterojunction optoelectronic device of this embodiment under different frequencies (0.1 Hz, 0.5 Hz, 1 Hz, 2 Hz, 4 Hz) and different irradiation durations (1 s, 5 s, 15 s, 30 s). The wavelength of the light used for irradiation is 980 nm and the power is 42.7 mW·cm -2 . It can be seen that by increasing the frequency of light pulses (0.1 Hz - 4 Hz) or prolonging the irradiation duration (1 s, 5 s, 15 s, 30 s), the magnitude of the photocurrent increases, and the trend of current decay after turning off the light slows down, realizing the transformation from short-term plasticity to long-term synaptic plasticity. The phenomenon that the connection strength of biological synapses can be enhanced by repeated external stimuli indicates that the device in this embodiment can simulate the short-term and long-term memory conversion function of biological visual nerve synapses.

[0048] Figure 10 This is the photocurrent response diagram of the MoS2 / PbS heterojunction optoelectronic device of this embodiment under the irradiation of 980 nm pulsed light (bias voltage is 0.4 V), simulating the repeated learning and forgetting functions. The figure shows three cycles of the learning-forgetting process in synaptic plasticity by continuously turning on and off the light. After continuously exciting 43 consecutive pulses of 980 nm light, the conductance response of the device gradually increases from 204 µA to 214 µA, and then decays to 206.8 µA after a period of time when the light pulse stimulation ends, indicating that the learned information will be partially forgotten over time. However, when using the second stimulation process to relearn, the current only needs 26 pulses to recover to the original learning level (214 µA), which is much lower than the number required in the first learning stage. It can also be observed that in the second stage, the synaptic weight drop after the second stimulation event is significantly lower than that after the first stimulation event. In addition, the third learning only requires 16 pulses, and due to the slower decay in the third time, it finally remains at a higher 208.3 µA. This interesting phenomenon is similar to the relearning process in the human brain.

[0049] Figure 11 Figure (a) in it is the circuit diagram of the MoS2 / PbS heterojunction optoelectronic device of this embodiment applied to "AND" and "OR" gates, and (b) is under different light powers (31.5 mW·cm-2 ), and the peak pulse current diagrams under 980 nm and 650 nm light irradiation at 42.7 mW·cm -2 ). (c) is the logical truth table of "AND" and "OR" gates, and (d) is the relationship diagram between "AND" and "OR" gates regarding the peak pulse current. The present invention further explores the potential ability of the MoS2 / PbS heterojunction optoelectronic device in this embodiment to perform logical operations by applying light pulses of different wavelengths, and realizes the "AND" and "OR" logic functions using 980 nm and 650 nm light pulses. Taking these two light pulses with the same intensity and duration as two inputs, as Figure 11 shown in (a). The turning on and off of light symbolize the logical states of the input signals, where "1" represents the light being on and "0" represents the light being off. As Figure 11 shown in (b), according to the current characteristics under 980 nm and 650 nm light irradiation with different light intensities (31.5 mW·cm -2 and 42.7 mW·cm -2 ), a threshold current of 207 µA is established to distinguish "0" and "1". When the light response current value generated by the device is higher than 207 µA, "1" will be output. On the contrary, when the current is lower than 207 µA, the output is "0". The corresponding truth table is as Figure 11 shown in (c), including two light inputs and two output values. As Figure 11 shown in (d), it shows the input (light pulse signal) and output (light response current) characteristics of the "AND" and "OR" logic functions, where the yellow dashed line represents the critical threshold separating different output states. In the "AND" logic operation, when the intensity of the light input is 31.5 mW·cm -2 and the duration is 150 ms, the current will exceed the critical value only when both inputs (650 nm light pulse as input 1 and 980 nm light pulse as input 2) are applied simultaneously. Different from this, when using a stronger light pulse of 42.7 mW·cm -2 to irradiate the device separately or simultaneously, it will generate a current higher than the threshold (207 µA), thus realizing the light-controlled logic function of the "OR" gate. More significantly, this innovative method of manipulating optical "OR" and "AND" gates is expected to be extended in the future by fabricating a large number of integrated devices to facilitate advanced information processing tasks.

[0050] Figure 12 This is the voltage-current diagram of the MoS2 / PbS heterojunction optoelectronic device in this embodiment under 42.7 mW·cm -2 of 405 - 1650 nm light irradiation. The device generates an obvious photocurrent under light irradiation and exhibits obvious rectifying behavior, indicating the formation of a well-contact heterojunction.

[0051] Figure 13 The photocurrent response diagram of the MoS2 / PbS heterojunction optoelectronic device in this embodiment under 405 - 1650 nm light irradiation with a power of 42.7 mW·cm -2 is shown. The results confirm the excellent detection ability of the device in this embodiment within an ultra-wide working wavelength range. The strongest photocurrent response is at 980 nm, and the maximum responsivity (0.013 A·W -1 ), specific detectivity (7.6×10 10 Jones) are achieved at 980 nm, and it extends to the SWIR region (1650 nm), broadening the application of the device in the field of infrared detection.

[0052] Figure 14 The frequency diagram at 1 kHz of the MoS2 / PbS heterojunction optoelectronic device in this embodiment under 980 nm light (0 V) irradiation with a power of 42.7 mW·cm -2 is shown. The device can operate stably within a wide frequency range with a 3 dB bandwidth of 1 kHz. The measured rise time (τ r ) and fall time (τ f ) are 360 µs and 351 µs respectively, with fast response ability, suitable for fast communication applications.

[0053] Embodiment 2

[0054] By adjusting the thickness of the PbS thin film, the optoelectronic properties of the MoS2 / PbS heterojunction optoelectronic device can be further adjusted. Specifically, the water bath reaction time during the preparation of the PbS thin film in step 3 of Embodiment 1 is reduced to 10 min to make the PbS thin film thinner. The photocurrent response diagram of the obtained device under 405 - 1650 nm light irradiation with a power of 42.7 mW·cm -2 is as shown in Figure 15 . It can be seen that compared with Embodiment 1, the photocurrent magnitude of the device under light irradiation at each wavelength has been significantly improved.

[0055] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A bias-controlled MoS2 / PbS heterojunction optoelectronic device, characterized in that: The invention is a vertical structure two-terminal device, which uses FTO glass as a conductive substrate, and a MoS2 film with a nano-flower ball morphology is grown on the surface of the FTO glass by a hydrothermal method, and a PbS film is grown on the MoS2 film by a water bath method, and the PbS film forms a three-dimensional skeleton coating structure for the MoS2; a first Ag electrode is arranged on the PbS film, and a second Ag electrode is arranged in the area of ​​the FTO glass where the MoS2 film and the PbS film are not grown; the photoelectric characteristics of the MoS2 / PbS heterojunction photoelectric device are regulated by adjusting the bias voltage applied to the two Ag electrodes and irradiating light in the ultraviolet to short-wave infrared band: under a bias voltage of 0V, the MoS2 / PbS heterojunction photoelectric device realizes broadband photoelectric detection; As the bias voltage increases, the photoelectric synaptic performance of the MoS2 / PbS heterojunction photoelectric device gradually increases.

2. The bias-controlled MoS2 / PbS heterojunction optoelectronic device according to claim 1, characterized in that: The wavelength of the light in the ultraviolet to short-wave infrared band ranges from 405 to 1650 nm.

3. A method for preparing a bias-controlled MoS2 / PbS heterojunction optoelectronic device according to claim 1 or 2, characterized in that: The following steps are involved: Step 1: ultrasonically clean the FTO glass with acetone, ethanol and deionized water in sequence to remove impurities on the surface, and then blow dry with nitrogen; Step 2: Add 0.09 g sodium molybdate and 0.18 g thiourea to 60 mL deionized water and stir evenly, then transfer to a reactor, add the cleaned FTO glass to the reactor, and react at 200 °C for 20-24 h; after the reaction, take out the sample, wash it alternately with deionized water and anhydrous ethanol, and then dry it in an oven at 40-60 °C for 1-2 h to obtain a MoS2 film with a nanoflower morphology; Step 3, add 9.475 g of lead acetate to 100 mL of deionized water and stir until completely dissolved to obtain a lead acetate solution; dissolve 14.7 g of trisodium citrate, 5.71 g of thiourea and 7.84 g of potassium hydroxide in 50 mL of deionized water respectively to obtain a trisodium citrate solution, a thiourea solution and a potassium hydroxide solution; vertically suspend the FTO glass with the MoS2 film grown in the lead acetate solution, then add the trisodium citrate solution, the thiourea solution and the potassium hydroxide solution in turn and stir evenly, then place in a 40°C water bath to react for 10 to 20 min; after the reaction is completed, take out the sample and wash it alternately with deionized water and anhydrous ethanol, then place it in an oven at 40 to 60°C and dry it for 1 to 2 h to obtain a PbS film; Step 4: Scrape off the MoS2 film and PbS film on part of the surface of the FTO glass to expose the FTO conductive layer; then deposit a first Ag electrode on the PbS film, and deposit a second Ag electrode on the area of ​​the FTO glass where the MoS2 film and PbS film are not grown, thereby completing the preparation of the MoS2 / PbS heterojunction photoelectric device.

4. An application of the bias-regulated MoS2 / PbS heterojunction optoelectronic device according to claim 1 or 2 in light-responsive artificial synapses or photoelectric detection in the ultraviolet to short-wave infrared range.

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