In-situ method and system for testing photoelectric effect of semiconductor film

Abstract

The application relates to the technical field of electrochemical testing, and particularly provides an in-situ testing method and system for photoelectric effect of a semiconductor film, the method comprising the following steps: testing the open circuit potential of a working electrode with a deposited semiconductor film in a solution in a dark state; then adopting a three-electrode system, adjusting an electrochemical workstation to be in a constant potential mode, setting a constant potential parameter as the open circuit potential measured in the dark state; intermittently opening and closing light, the electrochemical workstation outputting zero current when the light is closed, the electrochemical workstation outputting current equal in size and opposite in direction to the photoresponsive current of the semiconductor film when the light is opened; obtaining a current-time curve of the working electrode of the semiconductor film; and evaluating the photoelectric performance of the semiconductor film. The application tests the in-situ photo-induced current of the working electrode with the deposited semiconductor film in the electrolyte, retains the characteristics of the semiconductor film in the real application state, and can be applied to the fields of photocatalysis, solar cell performance testing and the like.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical testing technology, and particularly relates to an in-situ testing method and system for the photoelectric effect of semiconductor films. Background Technology

[0002] During atmospheric corrosion of metallic materials, some corrosion products, such as ZnO, CuO, Cu2O, α-FeOOH, FeO, and Fe2O3, exhibit semiconductor properties. These semiconductor products generate a photovoltaic effect under specific wavelengths of light, where valence band electrons are excited and transition to the conduction band. The resulting photogenerated electrons and holes directly influence the corrosion behavior of the metal substrate. However, current research characterizing the photoelectric response of these corrosion products on the corrosion of the metal substrate requires stripping the corrosion products from the metal substrate and depositing them on fluorine-doped tin oxide (FTO) conductive glass. The FTO photoelectrode is then coupled to the metal electrode via a wire to indirectly test the photoelectrochemical response of the FTO photoelectrode.

[0003] In addition, in the study of photoelectrochemical cathodic protection, the feasibility and magnitude of photocurrent of electrochemical cathodic protection after coupling of the photoelectrode and the metal substrate were investigated by preparing N-type semiconductor materials on the surface of FTO conductive glass. However, this method is not feasible in practical applications because there is no on-site condition to connect an external photoelectrode plate to receive solar radiation and thus provide electrons to the metal substrate. The only feasible method is to directly prepare n-type semiconductor materials on the metal surface for photoelectrochemical cathodic protection. Furthermore, the existing method involves coating the semiconductor material on FTO and then connecting the FTO to the protected steel through wires. This method has two problems of increased resistance: first, the contact resistance between the semiconductor material and FTO is incorporated into the circuit; second, the resistance of the wires between FTO and the protected steel increases the total resistance of the circuit. According to Ohm's law, the measured photocurrent will be smaller than the value measured in situ. In addition, the coating of the semiconductor film on the FTO, the length of the wires, and the welding condition can vary significantly due to different experimental operators' skill levels, resulting in poor experimental reproducibility. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides an in-situ testing method for the photoelectric effect of semiconductor films, comprising the following steps: Step S1: Under dark conditions, test the "open circuit potential-time" curve of the working electrode of the surface-deposited semiconductor film to obtain the stable open circuit potential of the working electrode. Step S2: Set the open circuit potential to the constant potential value of the electrochemical workstation; Step S3: Perform intermittent on / off light tests on the working electrode of the surface-deposited semiconductor film to obtain the "current-time" curve; Step S4: Evaluate the photoelectric effect performance of the semiconductor film based on the current-time curve.

[0005] Based on the above scheme, the method adopts an electrochemical three-electrode system, which includes a working electrode, a counter electrode, and a reference electrode. The working electrode is a metal with a semiconductor film deposited on its surface or an FTO conductive glass with a semiconductor film deposited on its surface. The counter electrode is a platinum electrode, and the reference electrode is a silver or silver chloride reference electrode.

[0006] Specifically, step S3 includes: S31: In the dark, the natural potential of the working electrode is equal to the constant potential of the electrochemical workstation, and the electrochemical workstation does not output current. S32: The working electrode receives light radiation, the semiconductor film generates a photocurrent, and the working electrode potential changes; S33: The electrochemical workstation outputs a compensation current to keep the working electrode at a constant open-circuit potential in the dark state.

[0007] According to an embodiment of the present invention, when the semiconductor film is an N-type semiconductor film, the photogenerated current flows from the conductive substrate to the semiconductor film; when the semiconductor film is a P-type semiconductor film, the photogenerated current flows from the semiconductor film to the conductive substrate.

[0008] Preferably, the N-type semiconductor film is a TiO2 thin film, the P-type semiconductor film is a Cu2O thin film, and the conductive substrate is a metal or FTO conductive glass.

[0009] Specifically, step S4 includes: S41: Identify the current value during illumination in the "current-time" curve in step S3, wherein the current value is the magnitude of the photocurrent; S42: Based on the magnitude of the photocurrent, analyze the photoelectric response performance of the semiconductor film.

[0010] On the other hand, the present invention provides an in-situ testing system for the photoelectric effect of semiconductor films, for implementing the above-mentioned in-situ testing method, including: an electrochemical workstation, a three-electrode system and a light source module; The three-electrode system includes a working electrode, a counter electrode, a reference electrode, and an electrolyte. The working electrode is a metal or FTO conductive glass with a semiconductor film deposited on its surface, and the electrolyte is a 5.2% NaCl solution. The constant potential value of the electrochemical workstation in constant potential mode is configured as the open circuit potential when the working electrode is stable in the dark state. The light source module is used to intermittently switch light on and off on the working electrode.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention combines an electrochemical workstation to keep the working electrode potential constant at the open-circuit potential in the dark state, so that the measured current value is directly equivalent to the magnitude of the photocurrent. This solves the problem that traditional methods can only qualitatively obtain the direction of electron / hole transfer, but cannot accurately characterize the magnitude of the real photocurrent. 2. The in-situ testing of the present invention directly tests the working electrode of the deposited semiconductor film in the electrolyte without removing the sample, thus preserving the characteristics of the semiconductor film under real application conditions. This method can be applied to fields such as photocatalysis and solar cell performance testing. Attached Figure Description

[0012] Figure 1 This is a flowchart illustrating the testing process for the photoelectric effect of the semiconductor film in this invention. Figure 2 This is an electrical schematic diagram of the semiconductor film on the surface of the working electrode used in this invention. Figure 3 The graph shows the changes in photopotential and photocurrent of the conductive glass electrodes with deposited TiO2 and Cu2O, as measured by the testing method of this invention. Figure 4 This is a schematic diagram illustrating the research method of photopotential and photocurrent in traditional photoelectrochemical cathodic protection. Figure 5 A comparison diagram of photopotentials and photocurrents measured by the traditional photoelectrochemical cathodic protection method and the test method of this invention; Figure 6 This is a metal electrode test and comparison diagram of a deposited N-type semiconductor film obtained according to an embodiment of the present invention; Figure 7 This is a comparison diagram of the metal electrode test results of the deposited P-type semiconductor film obtained according to another embodiment of the present invention. Detailed Implementation

[0013] The invention will be further described below with reference to specific embodiments.

[0014] like Figure 1 As shown, the present invention provides an in-situ testing method for the photoelectric effect of semiconductor films. The testing method adopts a traditional electrochemical three-electrode system, which includes a working electrode, a counter electrode, and a reference electrode. The working electrode is a metal with a semiconductor film deposited on its surface or an FTO conductive glass with a semiconductor film deposited on its surface.

[0015] Preferably, in the three-electrode system, the counter electrode is a platinum electrode, the reference electrode is a silver or silver chloride reference electrode, the reference electrode is filled with a saturated KCl solution, and 5.2% NaCl is used as the electrolyte for the working electrode, counter electrode, and reference electrode.

[0016] Those skilled in the art can select the counter electrode, reference electrode, and electrolyte according to actual needs. The counter electrode can be a platinum electrode or a graphite electrode, and the reference electrode can be an Ag / AgCl electrode, a saturated calomel electrode, or a high-purity zinc electrode. The electrolyte is conductive.

[0017] The method includes the following steps: Step S1: Under dark conditions, test the "open circuit potential-time" curve of the working electrode of the surface-deposited semiconductor film to obtain the stable open circuit potential of the working electrode. In this embodiment, the test of the dark-state open-circuit potential in step S1 is as follows: In the dark state, the black probe of the multimeter is connected to the reference electrode, the red probe is connected to the working electrode, the multimeter is set to the voltage range, and the potential difference between the working electrode and the reference electrode is measured.

[0018] Step S2: Set the obtained open circuit potential to the constant potential value in the constant potential mode of the electrochemical workstation; The electrochemical workstation is set to constant potential mode, and its constant potential parameter is set to the open circuit potential in S1, so that the electrochemical workstation controls the potential difference between the working electrode and the reference electrode to be constant at the potential difference in the dark state.

[0019] Step S3: Perform intermittent on / off light tests on the working electrode of the surface-deposited semiconductor film to obtain the "current-time" curve; In step S3 of this embodiment, the intermittent switching test of the working electrode is to evaluate the stability of the photocurrent generated by the semiconductor film. Some semiconductor films have poor stability and no light response after several switching tests. Therefore, this invention obtains the current by intermittent switching tests for subsequent evaluation of its stability.

[0020] Specifically, step S3 includes: S31: In the dark, the natural potential of the working electrode is equal to the constant potential value set by the electrochemical workstation, and the electrochemical workstation has no current output at this time; In this method, the natural electrode is in the dark, the photoelectrode is immersed in a solution, and the black probe of a multimeter is connected to the reference electrode, the red probe is connected to the photoelectrode, and the potential of the photoelectrode relative to the reference electrode is measured.

[0021] S32: When the working electrode of the deposited semiconductor film receives light radiation, the semiconductor film generates a photocurrent, and the working electrode potential will change. S33: In the constant potential mode of the electrochemical workstation, the electrochemical workstation outputs a compensation current to keep the working electrode potential constant at the open circuit potential in the dark state. The compensation current is equal in magnitude and opposite in direction to the photocurrent of the semiconductor film.

[0022] It should be noted that the current measured in step S3 is the current output by the electrochemical workstation under light conditions. Since the output current of the electrochemical workstation cancels out the photocurrent generated by the photoelectrode while keeping the open-circuit potential of the working electrode constant in the dark state, the measured current precisely characterizes the photoresponse current of the photoelectrode.

[0023] Step S4: Evaluate the photoelectric effect performance of the semiconductor film based on the current-time curve.

[0024] Specifically, step S4 includes: S41: Identify the current value during illumination in the "current-time" curve in step S3, wherein the current value is the magnitude of the photocurrent; S42: Based on the magnitude of the photocurrent, analyze the photoelectric response performance of the semiconductor film.

[0025] The above-mentioned method of the present invention achieves the testing of the photocurrent of the working electrode under illumination by setting the constant potential value of the electrochemical workstation to be equal to the open circuit potential value of the working electrode in the dark state. The constant potential value is selected as the stable open circuit potential of the working electrode with a semiconductor film deposited on its surface obtained in the dark state. The measured stable open circuit potential is set as the constant potential value through the "constant potential mode" of the electrochemical workstation.

[0026] The principle of this method is as follows: In the dark, the natural potential of the photoelectrode with the deposited semiconductor film is equal to the constant potential value set by the electrochemical workstation, and there is no potential difference. At this time, the electrochemical workstation has no current output. Under light radiation, the electrode potential of the deposited semiconductor film changes. In order to ensure that the potential of the working electrode remains constant at the open-circuit potential in the dark, the electrochemical workstation will automatically output a current that is equal in magnitude and opposite in direction to the photocurrent generated by the semiconductor film. By intermittently switching the light on and off, a "current-time" curve is obtained.

[0027] Figure 2 To realize the electrical schematic diagram of an in-situ testing method for the photoelectric effect of a semiconductor film, the in-situ testing method of the present invention is implemented through this circuit, according to... Figure 2It can be seen that the working electrode is connected to the first input terminal of the third differential amplifier and the second input terminal of the second differential amplifier respectively. The working electrode is also connected to the second input terminal of the third differential amplifier through Rm. The output terminal of the second differential amplifier is connected to the voltage to ground, and the second input terminal of the second differential amplifier is grounded. The reference electrode is connected to the first input terminal of the second differential amplifier, and the output terminal of the second differential amplifier provides feedback potential difference. The output terminal of the second differential amplifier is connected to the second input terminal of the first differential amplifier. The electrochemical workstation in constant potential mode is connected to the first input terminal of the first differential amplifier, and the output terminal of the first differential amplifier is connected to the counter electrode.

[0028] Example 1 In this embodiment, FTO conductive glass with N-type semiconductor and P-type semiconductor deposited respectively is used as working electrode to perform in-situ testing of the photoelectric effect of N-type semiconductor and P-type semiconductor. The N-type semiconductor is represented by TiO2 semiconductor film, and the P-type semiconductor is represented by Cu2O semiconductor film.

[0029] like Figure 3 As shown, intermittent on / off light tests were performed on FTO conductive glass working electrodes deposited with TiO2 and Cu2O in a three-electrode system to obtain the potential changes of the working electrodes; the photoelectric potential and current changes of the working electrodes were measured using the in-situ testing method of semiconductor film photoelectric effect and electrical principles. Figure 4 As can be seen from a, illumination causes a negative shift in the working electrode potential of TiO2 / FTO. According to... Figure 4 c shows that illumination causes a positive shift in the working electrode potential of Cu2O / FTO, through Figure 4 The potential change diagrams of a and c show the stable open-circuit potentials of the TiO2 / FTO and Cu2O / FTO electrodes in the dark state.

[0030] Furthermore, the stable open-circuit potential in the dark state is set as the constant potential value in the constant-voltage mode of the electrochemical workstation. The change in photoinduced current (photogenerated current) measured using the in-situ testing method of this invention is as follows: Figure 4 As shown in b and d, a positive current was measured at the TiO2 / FTO electrode, while a negative current was measured at the Cu2O / FTO electrode. This indicates that the photocurrent induced by TiO2 flows from FTO to TiO2, while the photocurrent induced by Cu2O flows from Cu2O to FTO. Their magnitudes are 1.5 × 10⁻⁶ and 1.5 × 10⁻⁶, respectively. -5 and 1×10 -6 .

[0031] This embodiment demonstrates that when the semiconductor film is an N-type semiconductor film, the photocurrent flows from the conductive substrate to the semiconductor film; when the semiconductor film is a P-type semiconductor film, the photocurrent flows from the semiconductor film to the conductive substrate. The method of this invention is applicable to the study of the photoelectric effect of semiconductor materials on FTO conductive glass.

[0032] Example 2 In this embodiment, the metal deposited with N-type semiconductor is used as the working electrode to perform in-situ testing of the photoelectric effect of N-type semiconductor. The N-type semiconductor is a TiO2 semiconductor film, and the metal is 316L.

[0033] like Figure 5 As shown, Figure 5 a and b show the changes in photoelectric potential and photoinduced current obtained using the traditional photoelectric cathodic protection test method. This traditional photoelectric cathodic protection research method couples the working electrode of FTO conductive glass with deposited TiO2 with 316L to form TiO2 / FTO-316L. Figure 5 c and d represent the photopotential and current changes of the 316L electrode with deposited TiO2, measured using the in-situ testing method of this invention.

[0034] from Figure 5 As can be seen, the electrode potential measured by the traditional method shifts negatively and a positive photocurrent is obtained through light illumination testing; the electrode potential obtained by the testing method of the present invention also shifts negatively and a positive photocurrent is generated, and the conductive substrate can be metal, proving that the method of the present invention is feasible and can be used for the study of photoelectric effect of metal electrodes deposited with semiconductor materials.

[0035] Example 3 In this embodiment, the metal deposited on the N-type semiconductor is used as the working electrode to perform in-situ testing of the photoelectric effect of the N-type semiconductor. The N-type semiconductor is a TiO2 semiconductor film, and the metal is Cu.

[0036] like Figure 6 As shown, Figure 6 a and b show the changes in photoelectric potential and photoinduced current obtained using the traditional photoelectric cathodic protection test method. This traditional photoelectric cathodic protection research method couples the TiO2-deposited FTO conductive glass working electrode with pure Cu to form TiO2 / FTO-Cu. Figure 6 a indicates a negative shift in electrode potential. Figure 6 b shows the generation of a positive photocurrent.

[0037] Figure 6 c and d show the photopotential and current changes of the TiO2-deposited Cu electrode measured using the in-situ testing method of this invention. The directions of their potential and current changes are consistent with... Figure 6The results shown in a and b are consistent. This further demonstrates that the in-situ testing method of the present invention is applicable to situations where semiconductor materials exist on metal surfaces.

[0038] Furthermore, from Figure 6 It can be seen that there is a difference in the magnitude of the potential drop and current rise obtained by the traditional method and the test method of the present invention. The traditional method can only qualitatively obtain the direction of electron / hole transfer and cannot accurately characterize the magnitude of the actual photocurrent. However, the photocurrent measured by the test method of the present invention is the magnitude of the actual photocurrent.

[0039] Example 4 In this embodiment, the metal deposited on the P-type semiconductor is used as the working electrode to perform in-situ testing of the photoelectric effect of the P-type semiconductor. The P-type semiconductor is a Cu2O semiconductor film, and the metal is Cu.

[0040] Figure 7 a and b represent the changes in photopotential and photoinduced current obtained using the traditional photocathode protection test method. This traditional photocathode protection research method couples the Cu2O-deposited FTO conductive glass working electrode with pure Cu to form Cu2O / FTO-Cu. Figure 7 The electrode potential in a shifts positively. Figure 7 b shows a negative photocurrent.

[0041] Figure 7 c and d represent the photopotential and current changes of a Cu electrode with deposited Cu₂O, measured using the in-situ testing method of this invention. The directions of their potential and current changes are consistent with... Figure 7 The trends in a and b are consistent. This embodiment further demonstrates that the testing method of the present invention is applicable to situations where semiconductor materials exist on metal surfaces.

[0042] Through the above embodiments, the method of the present invention is applicable not only to the study of the photoelectric effect of semiconductor materials on FTO conductive glass, but also to the study of the photoelectric effect of semiconductor materials on metal surfaces.

[0043] The photocurrent measured by the test method and embodiments of the present invention can accurately characterize the magnitude of the photocurrent generated by semiconductor materials deposited on conductive glass or metal, thereby directly evaluating the photoelectric response performance of semiconductor materials.

[0044] Based on the same technical concept, the present invention also provides an in-situ testing system for the photoelectric effect of semiconductor films, for implementing the above-mentioned in-situ testing method for the photoelectric effect of semiconductor films. The system includes: an electrochemical workstation, a three-electrode system, a light source module, and a detection module. The three-electrode system includes a working electrode, a counter electrode, a reference electrode, and an electrolyte. The working electrode is a metal or FTO conductive glass with a semiconductor film deposited on its surface. The semiconductor film can be an N-type semiconductor material or a P-type semiconductor material.

[0045] According to one embodiment of the present invention, the counter electrode is a platinum sheet, the reference electrode is an Ag / AgCl electrode (filled with saturated KCl solution), and the electrolyte is a 5.2% NaCl solution, forming a three-electrode system.

[0046] The constant potential parameters of the electrochemical workstation in constant potential mode are configured as the open circuit potential when the working electrode is stable in the dark. Under illumination, the electrochemical workstation outputs a compensation current that is equal in magnitude and opposite in direction to the photogenerated current. The light source module is used to provide illumination conditions for the working electrode, specifically by intermittently switching the light on and off for the working electrode. The detection module is used to monitor and acquire the potential difference between the working electrode and the reference electrode, as well as the current of the working electrode.

[0047] Based on the current-time curve obtained by the detection module, the photoelectric response performance of the semiconductor film is evaluated by comparing the magnitude of the photocurrent under the same illumination conditions and test time: the larger the photocurrent, the higher the photogenerated carrier separation efficiency of the semiconductor material and the better the photoelectric conversion performance.

[0048] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0049] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. An in-situ testing method for the photoelectric effect of semiconductor films, characterized in that, Includes the following steps: Step S1: Under dark conditions, test the "open circuit potential-time" curve of the working electrode of the surface-deposited semiconductor film to obtain the stable open circuit potential of the working electrode; Step S2: Set the open circuit potential to the constant potential value of the electrochemical workstation; Step S3: Perform intermittent on / off light tests on the working electrode of the surface-deposited semiconductor film to obtain the "current-time" curve; Step S4: Evaluate the photoelectric effect performance of the semiconductor film based on the current-time curve.

2. The in-situ testing method for the photoelectric effect of semiconductor films according to claim 1, characterized in that, The method employs an electrochemical three-electrode system, which includes a working electrode, a counter electrode, and a reference electrode. The working electrode is a metal with a semiconductor film deposited on its surface or an FTO conductive glass with a semiconductor film deposited on its surface. The counter electrode is a platinum electrode, and the reference electrode is a silver / silver chloride reference electrode.

3. The in-situ testing method for the photoelectric effect of semiconductor films according to claim 1, characterized in that, Step S3 includes: S31: In the dark, the natural potential of the working electrode is equal to the constant potential of the electrochemical workstation, and the electrochemical workstation does not output current. S32: The working electrode receives light radiation, the semiconductor film generates a photocurrent, and the working electrode potential changes; S33: The electrochemical workstation outputs a compensation current to keep the working electrode at a constant open-circuit potential in the dark state.

4. The in-situ testing method for the photoelectric effect of semiconductor films according to claim 3, characterized in that, When the semiconductor film is an N-type semiconductor film, the photocurrent flows from the conductive substrate to the semiconductor film; When the semiconductor film is a P-type semiconductor film, the photocurrent flows from the semiconductor film to the conductive substrate.

5. The in-situ testing method for the photoelectric effect of semiconductor films according to claim 4, characterized in that, The N-type semiconductor film is a TiO2 thin film, the P-type semiconductor film is a Cu2O thin film, and the conductive substrate is a metal or FTO conductive glass.

6. The in-situ testing method for the photoelectric effect of semiconductor films according to claim 1, characterized in that, Step S4 includes: S41: Identify the current value during illumination in the "current-time" curve in step S3, wherein the current value is the magnitude of the photocurrent; S42: Based on the magnitude of the photocurrent, analyze the photoelectric response performance of the semiconductor film.

7. A semiconductor film photoelectric effect in-situ testing system for implementing the method according to any one of claims 1-6, characterized in that, include: Electrochemical workstation, three-electrode system and light source module; The three-electrode system includes a working electrode, a counter electrode, a reference electrode, and an electrolyte. The working electrode is a metal or FTO conductive glass with a semiconductor film deposited on its surface, and the electrolyte is a 5.2% NaCl solution. The electrochemical workstation is configured in constant potential mode to the open circuit potential when the working electrode is stable in the dark state. The light source module is used to intermittently switch light on and off on the working electrode.

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