A method for enhancing raman signal of perovskite substrate
By subjecting the perovskite thin film to heating annealing and oxygen plasma treatment, the problem of internal defects in the perovskite thin film affecting charge transfer was solved, the Raman signal was enhanced, the operation process was simplified, and the signal enhancement effect was improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NANTONG UNIV
- Filing Date
- 2024-01-10
- Publication Date
- 2026-05-19
AI Technical Summary
Surface and internal defects in perovskite thin films affect charge transfer, resulting in poor Raman signal enhancement.
By subjecting ITO conductive glass with spin-coated perovskite thin film to heating annealing and oxygen plasma treatment, the internal interstitial iodine is partially oxidized, filling deep energy level defects and promoting charge transfer.
It improves the Raman signal enhancement effect on perovskite substrates, requires no additional precious metal materials, is simple to operate, and achieves oxidation effect by controlling reaction time and power.
Smart Images
Figure CN117923806B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of surface-enhanced Raman spectroscopy (SERS) technology and relates to a method for enhancing Raman signals on perovskite substrates. Background Technology
[0002] Organic-inorganic hybrid perovskites have attracted widespread attention due to their superior light absorption coefficient, long carrier diffusion length, and tunable bandgap. Recently, studies have revealed that perovskite films also exhibit Raman enhancement, primarily through chemical reinforcement. This Raman enhancement mainly stems from charge transfer. However, perovskite materials suffer from numerous defects, including surface defects and deep-level defects, which severely impact charge transfer within the perovskite and at its interfaces. To address this, researchers have proposed various strategies to improve film growth and reduce surface defects, thereby enhancing charge transfer and improving surface Raman enhancement. Passivation and other techniques can effectively increase grain size and improve morphology, thus promoting charge transfer. Summary of the Invention
[0003] To address the shortcomings of existing technologies, this invention provides a method for enhancing Raman signals on perovskite substrates by partially oxidizing the perovskite to eliminate energy level defects caused by interstitial iodine, thereby enhancing the Raman signal.
[0004] The technical solution provided by this invention is as follows:
[0005] A method for enhancing the Raman signal on a perovskite substrate specifically involves: heating and annealing an ITO conductive glass coated with a perovskite film to crystallize it into a film, followed by oxygen plasma treatment, wherein the oxygen plasma treatment has a power of 20W and a duration of 20s-60s.
[0006] Furthermore, the method for preparing the ITO conductive glass spin-coated with a perovskite thin film is as follows:
[0007] S1. The ITO conductive glass is ultrasonically cleaned with acetone and anhydrous ethanol in sequence, and then dried with nitrogen for later use.
[0008] S2. After treating the ITO conductive glass obtained in step S1 with ultraviolet ozone, spin-coating a perovskite precursor solution is performed to obtain the ITO conductive glass with a perovskite film spin-coated.
[0009] Furthermore, the ultrasonic cleaning of the ITO conductive glass using acetone and anhydrous ethanol in sequence is specifically as follows: ultrasonic cleaning is performed alternately with acetone and anhydrous ethanol, twice each time for 30 minutes each time, followed by drying with nitrogen gas, and then placed in a drying oven for later use.
[0010] Furthermore, the ultraviolet ozone treatment time is 25 minutes.
[0011] Furthermore, the spin-coating perovskite precursor solution is specifically described as follows: ITO conductive glass treated with ultraviolet ozone is placed in a nitrogen glove box, and 50 μL of perovskite precursor solution is spin-coated using a spin coater at a low speed of 1500 rpm for 20 s and a high speed of 4000 rpm for 40 s. During the last 20 s of the spin-coating process, 120 μL of chlorobenzene solution is rapidly added dropwise.
[0012] Furthermore, the specific formulation of the perovskite precursor solution is as follows: Methylamine lead iodide (MAI) and lead iodide (PbI2) are added in a molar ratio of 1:1 to a mixed solution of dimethyl sulfoxide and butyrolactone (volume ratio of dimethyl sulfoxide to butyrolactone is 3:7). The mixture is stirred and heated to prepare the perovskite precursor solution. The stirring time is at least 12 hours, and the heating temperature is 60℃. The final solution should be yellow and transparent, with no turbidity or sediment, indicating normal operation.
[0013] Furthermore, the heating annealing specifically involves: placing the ITO conductive glass coated with the perovskite precursor solution on a heating stage, annealing at 110°C for 15 minutes to allow the perovskite to crystallize into a film, and then cooling at room temperature for 30 minutes after annealing.
[0014] Furthermore, the oxygen plasma treatment specifically involves placing the spin-coated perovskite film in a SAOD-5D plasma generator for oxygen plasma treatment, setting the power to 20W and the time to within 60 seconds.
[0015] Furthermore, the oxygen flow rate was set to 0.2 mL / min, and the time was set to 20 s.
[0016] Compared with the prior art, the present invention has the following technical effects:
[0017] 1) ITO conductive glass with spin-coated perovskite precursor solution is heated and annealed to crystallize into a film, and then subjected to oxygen plasma treatment to partially oxidize the perovskite film, filling the deep energy level defects inside the perovskite, suppressing nonradiative recombination, prolonging the existence time of charge, promoting charge transfer at the interface, and improving the surface Raman enhancement of perovskite-based probe molecules without the need for additional precious metal materials.
[0018] 2) The experimental process is simple to operate. With simple oxygen plasma treatment, the corresponding oxidation effect can be achieved by controlling the reaction time and power. The interstitial iodine will preferentially react with oxygen. Attached Figure Description
[0019] Figure 1 Scanning electron microscope images of the perovskite thin film obtained in Example 1 of the present invention: (a) oxygen-free plasma treatment; (b) oxygen-enriched plasma treatment for 20 s;
[0020] Figure 2 The surface elemental analysis spectrum of the perovskite thin film I 3d obtained in Example 1 of this invention is shown.
[0021] Figure 3 The image shows the ultraviolet-visible absorption spectrum of the perovskite thin film obtained in Example 1 of this invention.
[0022] Figure 4 Here are schematic diagrams of the Raman signals of the perovskite thin film obtained in Example 1 of this invention under different probe molecules: (a) CuPc; (b) R6G;
[0023] Figure 5 (a) is a schematic diagram of the time-dependent Raman signal of oxygen plasma treatment of perovskite in this invention; Figure 5 (b) is a schematic diagram showing the content of pentavalent iodine on the perovskite surface in this invention;
[0024] Figure 6 This is a schematic diagram of Raman signals obtained at 15 randomly selected points on a perovskite substrate treated with oxygen plasma, using CuPc as a probe. Detailed Implementation
[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the scope of protection of the present invention. The embodiments described in this invention are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0026] Example 1
[0027] This invention provides a method for enhancing the Raman spectroscopy of perovskites, the specific steps of which are as follows:
[0028] Step 1: Cleaning ITO conductive glass: Perform ultrasonic cleaning with acetone and anhydrous ethanol alternately, twice each time, for 30 minutes each time, dry with nitrogen, and place in a drying oven for later use.
[0029] Step 2: Treat the ITO conductive glass treated in Step 1 with ultraviolet ozone for 25 minutes to change the hydrophilicity of the ITO conductive glass surface.
[0030] Step 3: Prepare the perovskite precursor solution. Mix 700 μl of butyrolactone and 300 μl of dimethyl sulfoxide to obtain a mixed solution. Add 162.4 mg of methylamine lead iodide (MAI) and 470.9 mg of lead iodide (PbI2) to the mixed solution to obtain the perovskite precursor solution. The final solution should be yellow and transparent, with no turbidity or sedimentation, which is normal.
[0031] Step 4: Spin-coating perovskite precursor solution: Place the ITO conductive glass obtained in Step 3 in a nitrogen glove box. Under nitrogen atmosphere, spin-coat 50 μL of perovskite precursor solution using a spin coater at a low speed of 1500 rpm for 20 s and a high speed of 4000 rpm for 40 s. During the last 20 s of the spin-coating process, rapidly add 120 μL of chlorobenzene solution.
[0032] Step 5, Annealing: Place the spin-coated ITO conductive glass on a heating stage, anneal at 110℃ for 15 minutes to allow the perovskite to crystallize into a film. After annealing, cool at room temperature for 30 minutes.
[0033] Step 6, Partial Oxidation Treatment: Place the spin-coated perovskite film in a SAOD-5D plasma generator for oxygen plasma treatment. Set the power to 20W, the oxygen flow rate to 0.2mL / min, and the time to 0s, 20s, 40s, and 60s.
[0034] Test Example 1
[0035] Surface morphology observation: The perovskite film treated with oxygen plasma for 20 seconds was observed under a scanning electron microscope (SEM) to check for morphological changes and determine the presence of any damage marks. The results are as follows: Figure 1 As shown, the crystal structure is obvious before and after treatment, the grain boundaries are clear and undamaged, and the grain size does not change significantly. It can be concluded that the crystal lattice was not destroyed, so the iodine in the crystal lattice was not oxidized, and the morphology of the perovskite did not change significantly before and after treatment.
[0036] Test Example 2
[0037] Observation of changes in elemental valence states: Four perovskite films obtained in Example 1, treated with oxygen plasma for different times, were subjected to X-ray photoelectron spectroscopy (XPS) to observe changes in the negative valence state of iodine and the generation of iodine in new valence states. Results are as follows: Figure 2 and Figure 5 As shown in b, according to Figure 2 As can be seen, a new peak appears for iodine, which corresponds to pentavalent iodine, indicating that interstitial iodine was oxidized and produced pentavalent iodide ions; Figure 5 b shows the trend of iodine changes with the extension of treatment time; pentavalent iodine shows a trend of first increasing and then decreasing over time.
[0038] Test Example 3
[0039] UV-Vis absorption detection: Four perovskite films obtained in Example 1, treated with oxygen plasma for different times, were subjected to UV-Vis light detection to determine the absorption peak wavelengths and the Raman excitation source. The results are as follows: Figure 3As shown, the absorption peak around 750nm remained unchanged before and after the treatment. Irradiation with a Raman light source of similar wavelength will produce obvious charge transfer and enhance the Raman signal. Therefore, 785nm excitation light was selected to test Raman.
[0040] Test Example 4
[0041] Raman detection: Two probe molecule solutions were dropped onto the surface of the perovskite thin film treated with oxygen plasma at 0s, 20s, 40s, and 60s, respectively, to deposit the probe molecules. After drying, Raman detection was performed using a 785nm Raman excitation source with a wavelength similar to the absorption peak wavelength, and the changes in Raman intensity were observed.
[0042] Probe molecule solution 1: Take 5.76 mg of copper phthalocyanine (CuPc) and 10 ml of anhydrous ethanol, mix them to prepare a 10⁻³ M copper phthalocyanine solution, and stir at room temperature for at least 12 hours. Before use, sonicate for 30 minutes to ensure uniform distribution of probe molecules.
[0043] Probe molecule solution 2: Take 4.79 mg of Rhodamine 6G (R6G) and 10 ml of anhydrous ethanol, mix them to prepare a 10⁻³ M copper phthalocyanine solution, and stir at room temperature for at least 12 hours. Before use, sonicate for 30 minutes to ensure uniform distribution of probe molecules.
[0044] Comparison of Raman intensities before and after oxidation (20s) Figure 4 As shown, Figure 4 (a) shows the Raman results for the probe molecule CuPc. The Raman signal is significantly enhanced after partial oxidation treatment. Figure 4 (b) shows the Raman results of the probe molecule R6G. Oxidation treatment also improved the Raman signal of perovskite, and the enhancement was observed after oxidation for different probe molecules.
[0045] Taking CuPc as an example, the Raman intensity variation trend at different treatment times is as follows: Figure 5 As shown in (a), the Raman enhancement of perovskites first increases and then decreases, reaching its maximum at 20 s. Furthermore, perovskites treated for 60 s all showed a significant overall increase in Raman enhancement compared to untreated perovskites. Finally, we conducted repeatability tests, measuring Raman signals at 15 randomly selected points. The results are as follows... Figure 6 As shown, the Raman spectroscopy of oxidized perovskite exhibits a general enhancement.
Claims
1. A method for enhancing Raman signals on a perovskite substrate, characterized in that, Specifically, the ITO conductive glass coated with a perovskite precursor solution is heated and annealed to crystallize into a film, and then subjected to oxygen plasma treatment. The oxygen plasma treatment has a power of 20W, an oxygen flow rate of 0.2mL / min, and a time of 10-60s. The perovskite precursor solution is prepared by adding methylamine lead iodide and lead iodide in a molar ratio of 1:1 to a mixed solution of dimethyl sulfoxide and butyrolactone, stirring and heating to prepare a perovskite precursor solution, stirring for more than 12 hours, and heating at 60°C. The heating annealing process specifically involves placing an ITO conductive glass coated with a perovskite precursor solution onto a heating stage, annealing at 110 °C for 15 min to allow the perovskite to crystallize into a film, and then cooling at room temperature for 30 min after annealing.
2. The method according to claim 1, characterized in that, The method for preparing the ITO conductive glass with a perovskite thin film spin-coated is as follows: S1. The ITO conductive glass is ultrasonically cleaned with acetone and anhydrous ethanol in sequence, and then dried with nitrogen for later use. S2. After treating the ITO conductive glass obtained in step S1 with ultraviolet ozone, spin-coating a perovskite precursor solution is performed to obtain the ITO conductive glass with a perovskite film spin-coated.