A device based on porous carbon-doped electrodes and its fabrication method

Abstract

This invention relates to a device based on a porous carbon-doped electrode and its fabrication method, belonging to the field of optical communication technology. The device provided by this invention sequentially comprises a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a porous carbon-doped electrode; the porous carbon-doped electrode is a porous carbon electrode doped with a conductive metal, at least one of Ag, Cu, Al, and Au. The device fabricated using the specific method of this invention can solve the problems of small bandwidth and slow PD response speed of existing perovskite devices. Simultaneously, the device, with its high transmission speed and wide transmission bandwidth, can achieve stable and complete signal transmission at higher frequencies in the field of optical communication, and has high application value.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to a device based on a porous carbon-doped electrode and its fabrication method. Background Technology

[0002] Photodetectors are essential components in optical communication, imaging, medicine, and military fields, capable of sensing light signals and converting them into electrical signals. Commercial photodetectors typically use common semiconductor materials such as crystalline silicon (Si) and gallium arsenide (GaAs) as the active layer. These devices often require complex fabrication processes such as epitaxy and chemical vapor deposition. The high-temperature processes not only increase energy consumption and production costs but also limit the application scenarios of photodetectors. Therefore, the development of novel photosensitive materials is urgently needed.

[0003] Organic-inorganic hybrid perovskites have attracted much attention in the photovoltaic field due to their excellent photoelectric properties, including high absorption coefficient, high carrier mobility, and long carrier diffusion length. Compared with traditional semiconductor devices, devices based on organic-inorganic hybrid perovskites can be fabricated at lower temperatures and are widely used as active layers in solar cells, photodetectors, LEDs, and other devices. However, the A-site organic cations in hybrid perovskites are prone to decomposition in warm and humid environments, greatly reducing the stability of perovskite films and limiting their application scenarios. Using inorganic cesium ions to replace organic cations is an effective solution. Among them, cesium lead bromide (CsPbBr3) based on all-inorganic perovskites has comparable excellent photoelectric performance to hybrid perovskites, higher carrier mobility, and better stability in water, heat, and oxygen.

[0004] Traditional underwater wireless optical communication systems typically use the blue-green band, with most UWOC systems using blue LEDs as the light source. In this system, the transmission efficiency, response speed, detectivity, and stability of the underwater transmitter determine the signal transmission distance, bandwidth, rate, and quality. Cesium lead bromine (CsPbBr3), with a bandgap of 2.4 eV, has a highly suitable response window for blue-green light in water, and also boasts advantages such as short emission lifetime, high detectivity, and excellent hydrothermal stability. However, cesium lead bromine-based photodetectors struggle to meet the high transmission speeds and wide bandwidths required in communication applications. Currently reported related PDs have response speeds in the microsecond range and bandwidths typically less than 1 MHz.

[0005] Therefore, developing a cesium lead-bromine-based photodetector with faster response speed and wider response bandwidth is crucial for the development of fields such as underwater wireless optical communication. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a device based on a porous carbon-doped electrode and its fabrication method. The device provided by this invention can achieve f 3dB With significantly expanded bandwidth and greatly improved response speed, it has high application value in the field of optical communication.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a device based on a porous carbon-doped electrode, comprising, in sequence, a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer and a porous carbon-doped electrode.

[0009] The porous carbon-doped electrode is a porous carbon electrode doped with a conductive metal, wherein the conductive metal is at least one of Ag, Cu, Al, and Au.

[0010] The optoelectronic device of this invention employs a porous carbon electrode doped with conductive metal, which significantly increases the conductivity of the top electrode, accelerates the extraction of charge carriers by the electrode, and significantly speeds up the migration rate of holes inside the device. Simultaneously, due to the numerous pores within the porous carbon material's internal structure, a hole transport layer is provided between the perovskite layer and the porous carbon-doped electrode to effectively control and prevent excessive conductive metal ions from penetrating into the perovskite layer, thus blocking excessive conductive metal ions from penetrating into the perovskite layer.

[0011] By using a specific high-conductivity conductive metal as defined in this invention to dope the porous carbon electrode of the device, the response speed of the device can be improved from the microsecond level to the nanosecond level. This effectively solves the key problem of long response time for perovskite-based optoelectronic devices; simultaneously, the device's f... 3dB With the bandwidth extended to 3MHz, the signal transmission speed is significantly improved, enabling stable and complete signal transmission at higher frequencies in the field of optical communication.

[0012] Without conductive metal doping, devices using pure porous carbon electrodes can only achieve microsecond-level response speeds. The fall time is an order of magnitude slower than the doped devices of this invention, and the response bandwidth is significantly narrower. If the aforementioned high-conductivity metal is directly used as the top electrode of the device, the response speed is also in the microsecond range, which cannot significantly improve the response speed and response bandwidth. At the same time, due to the direct contact between the conductive metal material and the perovskite, the device has a large leakage current, which can cause the device to break down directly at higher voltages.

[0013] This invention utilizes porous carbon materials doped with highly conductive metals to obtain devices with faster response speeds and higher response bandwidths based on highly conductive porous carbon-doped electrodes. This concept can be applied to photodetectors and extended to other optoelectronic and electronic devices. The technical solution of this invention effectively overcomes the shortcomings of conventional porous carbon electrodes in all-inorganic perovskite vertical structure photodetectors. In communication fields such as underwater wireless optical communication, it can transmit signals quickly, completely, and stably, adapting to the complex marine environment and possessing broad application prospects.

[0014] Preferably, the thickness of the porous carbon-doped electrode is ≥5 μm.

[0015] Ensuring the thickness of the porous carbon electrode is 5 μm or more can prevent excessive copper ions in the porous carbon doped electrode from passing through the perovskite layer it contacts, thus preventing large leakage current.

[0016] Preferably, the conductive substrate includes at least one of ITO substrate and FTO substrate, and the electron transport layer comprises SnO2, TiO2, and PC. 61 The hole transport layer comprises at least one of P3HT, PTAA, and Ploy-TPD, and the perovskite layer comprises CsPbBr3.

[0017] It should be noted that the selection schemes of the conductive substrate, electron transport layer, hole transport layer and perovskite layer described in this invention are not limited to the specific ones mentioned above. Those skilled in the art can use other commonly used conductive substrate types and electron transport layer, hole transport layer and perovskite layer components according to actual needs, as long as it does not affect the structure and performance of the device.

[0018] More preferably, the electron transport layer comprises SnO2, and the hole transport layer comprises P3HT; the mass ratio of SnO2, CsPbBr3, and P3HT is SnO2:CsPbBr3:P3HT = (0.004-0.006):(48-49):(1.2-1.4).

[0019] Secondly, the present invention provides a method for fabricating the above-mentioned device based on porous carbon-doped electrodes, comprising the following steps:

[0020] (1) A SnO2 solution was spin-coated on the surface of a conductive substrate at a speed of 3900-4100 rpm for 28-32 s, followed by a single annealing process to obtain an electron transport layer.

[0021] (2) The precursor solution is spin-coated on the surface of the electron transport layer at a speed of 1900-2100 rpm for 85-95 s, then chlorobenzene is added and spin-coated for 25-35 s, followed by secondary annealing to obtain an intermediate CsPbBr3 film; the precursor solution includes 1.5 M PbBr2 and 0.4 M CsBr.

[0022] (3) Solution B is spin-coated onto the surface of the intermediate CsPbBr3 film at a speed of 2900-3100 rpm for 9-11 s, followed by three annealing processes to obtain a perovskite layer; the solution B comprises 0.6 M CsBr.

[0023] (4) P3HT solution was spin-coated on the surface of the perovskite layer at a speed of 4900-5100 rpm for 55-65 s, and annealed four times to obtain a hole transport layer.

[0024] (5) Porous carbon is deposited on the surface of the hole transport layer, and then conductive metal is doped by thermal evaporation to obtain a porous carbon-doped electrode, thus completing the fabrication of the device based on the porous carbon-doped electrode.

[0025] The device based on porous carbon-doped electrodes provided by this invention is fabricated using the above-mentioned method. The stable structure of the device is mainly controlled by a relatively precise spin-coating method. At the same time, by reducing the concentration of the precursor solution, the thickness of the perovskite layer is reduced, the carrier transport distance is shortened, and the response speed of the device is accelerated by shortening the transit time. By controlling the coating of a thin P3HT layer on the perovskite layer, it can act as a hole transport layer while blocking direct contact between the perovskite film and the electrode, preventing leakage current, and further accelerating carrier transport and shortening the response time of the device.

[0026] Preferably, the conductive substrate is a conductive substrate whose surface has been cleaned, dried, and treated with ultraviolet ozone.

[0027] Preferably, the temperature of the first annealing is 170-190℃ and the time is 8-12 min; the temperature of the second annealing is 85-95℃ and the time is 8-12 min; the temperature of the third annealing is 240-260℃ and the time is 4-6 min; and the temperature of the fourth annealing is 95-105℃ and the time is 1-3 min.

[0028] Preferably, the SnO2 concentration in the SnO2 solution is 5%wt, and the P3HT concentration in the P3HT solution is 20mg / mL.

[0029] Preferably, the solvent of the precursor solution is DMSO, and the solvent of solution B is a mixed solvent of isopropanol and water in a volume ratio of 7:3.

[0030] Preferably, the volume ratio of the precursor solution to the solution B is (5-7):(9-11).

[0031] This invention employs a two-step method based on CsBr intercalated nanostructure intermediates to fabricate perovskite layers. During the preparation process, the concentration of PbBr2 in the precursor solution is slightly excessive to ensure precise control of the amount of CsPbBr3 in the perovskite layer.

[0032] Preferably, in step (5), the deposition step is: coating the porous carbon material onto the hole transport layer by screen printing, and annealing at 95-105℃ for 4-6 minutes.

[0033] Preferably, the mesh count of the screen printing is 350-450 mesh.

[0034] Preferably, the thermal evaporation step is as follows: using a single-chamber high-vacuum resistance coating device, 1-1.2g of conductive metal is thermally evaporated, and the vacuum degree of the thermal evaporation is (4×10⁻⁶). -4 )-(6×10 -4 Pa, time is 0.8-1.2h.

[0035] Because the carbon electrode has a porous structure, under the equipment conditions and the amount of conductive metal used, a small number of metal ions can easily penetrate the carbon electrode and contact the perovskite below; the infiltration of a few ions passivates the interface layer of the perovskite layer / electrode layer, which can significantly reduce the defect density of the interface layer.

[0036] This invention does not impose any special limitation on the temperature of thermal evaporation, but it should be noted that the thermal evaporation temperature used by the device is mainly determined by the evaporation temperature of the conductive metal under the given conditions. For example, when the conductive metal is copper, the thermal evaporation temperature used needs to be above 1100°C.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1. High-conductivity metal doping of porous carbon electrodes via thermal evaporation increases the device's ability to extract carriers accumulated within the transport layer from the top electrode. Simultaneously, it fills vacancies in the porous carbon electrode, reducing the interface defect concentration between the perovskite layer and the electrode layer, thereby shortening the device's response time to the nanosecond level. 3dB Bandwidth extended to the MHz level;

[0039] 2. By reducing the concentration of the precursor solution, the thickness of the perovskite layer is reduced, the carrier transport distance is shortened, and the device response speed is accelerated by shortening the transit time;

[0040] 3. By coating a very thin layer of P3HT on the perovskite layer, it can act as a hole transport layer while blocking direct contact between the perovskite film and the electrode, thus preventing leakage current. As a hole transport layer, P3HT can further accelerate carrier transport and shorten the response time of the device.

[0041] In summary, this invention provides a device based on porous carbon-doped electrodes with faster response speed and higher response bandwidth, which has great application prospects in fields such as underwater wireless optical communication. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the process of doping a conductive metal onto a porous carbon electrode by thermal evaporation in Embodiment 1 of the present invention.

[0043] Figure 2 This is a SEM cross-sectional view of the device based on porous carbon-doped electrodes in Embodiment 1 of the present invention;

[0044] Figure 3 The figures show the test results of the device response speed in the examples and comparative examples;

[0045] Figure 4 The graph shows the comparison of the response bandwidth of the devices in Example 1 and Comparative Example 1. Detailed Implementation

[0046] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available reagents and materials.

[0047] Example 1

[0048] This invention provides an embodiment of a device based on a porous carbon-doped electrode. The device in this embodiment includes, in sequence, a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a porous carbon-doped electrode. The conductive substrate is an ITO substrate, the electron transport layer is composed of SnO2, the perovskite layer is composed of CsPbBr3, the hole transport layer is composed of P3HT, and the porous carbon-doped electrode is a porous carbon electrode doped with Cu.

[0049] The device fabrication method based on porous carbon-doped electrodes described in this embodiment is as follows:

[0050] S1. The ITO conductive substrate was ultrasonically cleaned sequentially with deionized water, acetone, and anhydrous ethanol for 20 min each; the cleaned ITO conductive substrate was dried with nitrogen and treated with ultraviolet ozone for 40 min.

[0051] S2. Deionized water and 12% wt SnO2 hydrophilic colloidal dispersion were mixed at a volume ratio of 1.4:1 to obtain a 5% wt SnO2 solution; 100 μL of SnO2 solution was spin-coated onto the above-treated substrate at a speed of 4000 rpm for 30 s, and then annealed in air at a temperature of 180 °C for 10 minutes.

[0052] S3. Mix 1.5 mmol of PbBr2 powder and 0.4 mmol of CsBr powder, dissolve in 1 mL of DMSO to prepare the first-step precursor solution; then spin-coat 60 μL of the clarified precursor solution at 2000 rpm for 120 seconds, and add 130 μL of chlorobenzene in the last 30 seconds, and then anneal at 90 °C for 10 min to obtain a smooth mirror-like intermediate CsPbBr3 film;

[0053] S4. Dissolve 0.6 mmol of CsBr powder in 1 mL of a mixture with a volume ratio of IPA:H2O of 7:3 to obtain solution B; spin-coat the intermediate CsPbBr3 film on a smooth mirror surface in air at 3000 rpm for 20 seconds, and then drop 100 μL of solution B onto the intermediate CsPbBr3 film in the last 10 seconds; then anneal at 250 °C for 5 min to obtain a pure phase CsPbBr3 perovskite layer.

[0054] S5. Dissolve 20 mg of P3HT fiber in 1 mL of chlorobenzene, filter to obtain a P3HT solution, then uniformly drop 65 μL of P3HT solution onto the perovskite layer, spin coat at 5000 rpm for 60 s, and then anneal at 100 °C for 2 min to obtain the hole transport layer.

[0055] S6. By screen printing with a mesh size of 400, conductive porous carbon paste is deposited on the hole transport layer to a thickness of 5μm, and then annealed at 100℃ for 5 minutes to obtain a porous carbon electrode.

[0056] S7. Using a single-chamber high-vacuum resistance coating apparatus, place the material obtained in step S6 into the chamber, prepare 1.15g of metallic Cu, and set the apparatus vacuum level to 5×10⁻⁶. -4 At a temperature of 1200℃ and a time of 1 hour, copper was doped into the porous carbon electrode of the device through thermal evaporation and penetration (see schematic diagram of the doping process). Figure 1 The device based on the porous carbon-doped electrode was obtained, and its SEM cross-sectional structure is shown below. Figure 2 .

[0057] Depend on Figure 2 As can be seen, through thermal evaporation, conductive copper metal was successfully doped into the porous carbon electrode structure, resulting in a device based on a porous carbon-doped electrode.

[0058] Comparative Example 1

[0059] The only difference between the device fabrication method of Comparative Example 1 and Example 1 is that the top electrode is a pure porous carbon electrode, and its fabrication method is the same as that of Example 1, but the thermal evaporation doping step in step S7 is not performed.

[0060] Comparative Example 2

[0061] The only difference between the device fabrication method of Comparative Example 2 and Example 1 is that the top electrode is a pure copper electrode, and its fabrication method is the same as that of Example 1, but the porous carbon deposition step in step S6 is not performed.

[0062] Example of effect 1

[0063] To investigate the response speed and response bandwidth of the device based on porous carbon-doped electrodes of this invention, the following tests were conducted:

[0064] The frequency response and response speed of a continuous semiconductor laser (485nm) were measured by triggering it with square wave function generators of different frequencies.

[0065] Test results are as follows Figure 3 , Figure 4 ,in Figure 3 -(a) to (c) show the response time results of the devices in Example 1, Comparative Examples 1 and 2, respectively. Figure 4 This is a comparison chart of the response bandwidth of the devices in Example 1 and Comparative Example 1. Figure 3 , 4 It can be known that:

[0066] Figure 3 In (a), the device based on porous carbon-doped electrodes provided by the present invention has a response speed that is almost an order of magnitude faster than the device in the comparative example, moving from the microsecond level to the nanosecond level, with a rise time of 233 ns and a fall time of 511 ns, respectively, which solves the key problem of long response time of CsPbBr3-based photodetectors.

[0067] Figure 3 -(b) shows the response speed of the pure porous carbon electrode device without conductive metal doping in Comparative Example 1. Its structure is ITO / SnO2 / CsPbBr3 / P3HT / Carbon. The response speed of this device is in the microsecond range, with a rise time of 348 ns and a fall time of 5.15 μs. Its fall time is an order of magnitude slower than the device based on porous carbon doped electrode of this invention.

[0068] Figure 3-(c) shows the response speed of the device when the conductive metal copper is directly used as the top electrode in Comparative Example 2. The response speed is in the microsecond range, with a rise time of 435 ns and a fall time of 2.6 μs, which are still in the microsecond range. At the same time, due to the direct contact between the highly conductive metal and the perovskite, the device has a large leakage current, which leads to the device breaking down directly at higher voltages.

[0069] from Figure 4 As can be seen in Comparative Example 1, the pure porous carbon electrode device without conductive metal doping, f 3dB The bandwidth is approximately 500 kHz, while the device based on porous carbon-doped electrodes in Embodiment 1 of this invention... 3dB The bandwidth is significantly extended to 3MHz; meanwhile, the response bandwidth in Comparative Example 2, which uses conductive copper as the device electrode, is also significantly reduced.

[0070] In summary, this invention provides a device based on porous carbon-doped electrodes with significantly faster response speed and wider response bandwidth, which can simultaneously meet the high transmission speed and wide transmission bandwidth required in the field of communication, and has high application prospects in underwater wireless optical communication and other fields.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A device based on a porous carbon-doped electrode, characterized in that, It consists of, in sequence, a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a porous carbon-doped electrode; The porous carbon-doped electrode is a porous carbon electrode doped with a conductive metal, wherein the conductive metal is at least one of Ag, Cu, Al, and Au. The fabrication method of the device based on porous carbon-doped electrodes includes the following steps: (1) A SnO2 solution was spin-coated on the surface of a conductive substrate at a speed of 3900-4100 rpm for 28-32 s, followed by a single annealing process to obtain an electron transport layer. (2) The precursor solution is spin-coated on the surface of the electron transport layer at a speed of 1900-2100 rpm for 85-95 s, then chlorobenzene is added and spin-coated for 25-35 s, followed by secondary annealing to obtain an intermediate CsPbBr3 film; the precursor solution includes 1.5 M PbBr2 and 0.4 M CsBr. (3) Solution B is spin-coated onto the surface of the intermediate CsPbBr3 film at a speed of 2900-3100 rpm for 9-11 s, followed by three annealing processes to obtain a perovskite layer; the solution B comprises 0.6MCsBr. (4) P3HT solution is spin-coated on the surface of the perovskite layer at a speed of 4900-5100 rpm for 55-65 s, and annealed four times to obtain a hole transport layer. (5) Porous carbon is deposited on the surface of the hole transport layer, and then conductive metal is doped by thermal evaporation to obtain a porous carbon-doped electrode, thus completing the fabrication of the device based on the porous carbon-doped electrode.

2. The device based on a porous carbon-doped electrode as described in claim 1, characterized in that, The thickness of the porous carbon-doped electrode is ≥5 μm.

3. The device based on a porous carbon-doped electrode as described in claim 1, characterized in that, The conductive substrate includes at least one of ITO substrate and FTO substrate, and the electron transport layer comprises SnO2, TiO2, and PC. 61 The hole transport layer comprises at least one of P3HT, PTAA, and Ploy-TPD, and the perovskite layer comprises CsPbBr3.

4. The device based on a porous carbon-doped electrode as described in claim 3, characterized in that, The electron transport layer comprises SnO2, and the hole transport layer comprises P3HT; the mass ratio of SnO2, CsPbBr3, and P3HT is SnO2:CsPbBr3:P3HT = (0.004-0.006):(48-49):(1.2-1.4).

5. The device based on a porous carbon-doped electrode as described in claim 1, characterized in that, The first annealing temperature is 170-190℃ and the time is 8-12 min; the second annealing temperature is 85-95℃ and the time is 8-12 min; the third annealing temperature is 240-260℃ and the time is 4-6 min; the fourth annealing temperature is 95-105℃ and the time is 1-3 min.

6. The device based on a porous carbon-doped electrode as described in claim 1, characterized in that, The volume ratio of the precursor solution to solution B is (5-7):(9-11).

7. The device based on a porous carbon-doped electrode as described in claim 1, characterized in that, In step (5), the deposition step is as follows: the porous carbon material is screen-printed onto the hole transport layer and annealed at 95-105℃ for 4-6 minutes.

8. The device based on a porous carbon-doped electrode as described in claim 7, characterized in that, The mesh count for the screen printing is 350-450.

9. The device based on a porous carbon-doped electrode as described in claim 1, characterized in that, The thermal evaporation step is as follows: using a single-chamber high-vacuum resistance coating equipment, 1-1.2g of conductive metal is thermally evaporated, and the vacuum degree of the thermal evaporation is (4×10⁻⁶). -4 )-(6×10 -4 Pa, time is 0.8-1.2h.

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