A method for monitoring the quality and uniformity of perovskite thin films

Abstract

The present application relates to the technical field of perovskite photoelectric devices and flat plate optical waveguide, and particularly relates to a method for monitoring the quality and uniformity of perovskite thin film. The method comprises: providing a device to be measured comprising at least a glass substrate and a perovskite layer; coupling light from a wide-spectrum light source into the glass substrate through a multimode optical fiber to excite a loss mode resonance (LMR) effect; collecting a transmission spectrum after a polarizer through a spectrometer; extracting the peak position, intensity and half-peak width of the LMR characteristic peak. The red shift of the peak position indicates thickness change, the intensity decay and the half-peak width broadening indicate quality decline. Multi-point scanning can evaluate uniformity. The present application does not require vacuum equipment, is non-destructive, fast, low-cost, can be integrated into the production line, and solves the problem that the existing detection method cannot meet the needs of large-scale production.

Description

Technical Field

[0001] This invention relates to the field of perovskite optoelectronic devices and planar optical waveguides, specifically to a method for monitoring the quality and uniformity of perovskite thin films. Background Technology

[0002] Perovskite materials, with their excellent light absorption coefficient, tunable optical constants, low cost, and solution-processability, have shown great potential in optoelectronic devices such as solar cells, photodetectors, and light-emitting diodes. However, the quality and uniformity of perovskite materials are key factors affecting device performance during thin film preparation. Commonly used industrial film-forming processes (such as spin coating, evaporation, or spraying) easily lead to uneven film thickness, uneven grain distribution, or local defects. These problems directly reduce photoelectric conversion efficiency and increase batch-to-batch variability. Existing research shows that film degradation often starts at the interface or edge and is affected by factors such as light, heat, and humidity, leading to changes in the material's optical properties and thus affecting overall yield. Traditional evaluation methods include scanning electron microscopy, X-ray diffraction, ultraviolet-visible absorption spectroscopy, and photoluminescence spectroscopy. While these methods can provide structural or optical information, they are cumbersome to operate, rely on specialized instruments, and have long evaluation cycles, making it difficult to provide timely feedback for production parameter adjustments. Furthermore, these methods rely on point measurements to assess film uniformity, making it difficult to cover large-area samples, resulting in delayed quality feedback during production and affecting overall yield and efficiency optimization. This is particularly pronounced in large-scale production, leading to high defect rates, low production efficiency, and an inability to meet commercial demands. With the increasing demand for large-scale perovskite thin film fabrication, existing monitoring technologies are no longer sufficient for industrial requirements.

[0003] For example, the existing technology has the following shortcomings: (1) The evaluation process is complicated and the equipment is expensive (such as SEM or XRD which require a vacuum environment and high-resolution equipment), and cannot provide a simple and convenient means of thin film detection, which makes it difficult to screen quickly on the production line and prolongs the overall production cycle; (2) It is difficult to fully quantify the uniformity of the thin film. The existing methods are mostly point sampling or local scanning, ignoring the thickness gradient, defect distribution or optical inhomogeneity of large-area thin films, resulting in large batch quality fluctuations and unstable productivity; (3) The evaluation index is single and cannot simultaneously capture the multi-dimensional optical characteristics of the thin film (such as wavelength shift caused by refractive index change and intensity attenuation caused by absorption coefficient change), and it is difficult to directly correlate with production process parameters (such as annealing temperature and solution concentration); (4) The feedback mechanism is lagging. The current technology is mostly post-analysis and cannot guide process optimization in real time, which increases material waste and energy consumption. Existing loss mode resonance (LMR) technology is primarily maturely applied to stable inorganic oxide thin films. However, its application to perovskite photovoltaic devices presents significant technical challenges. Perovskite photovoltaic devices need to simultaneously achieve both high-efficiency photoelectric conversion and LMR sensing, requiring the bottom electrode and electron transport layer to balance low refractive index (facilitating LMR excitation) with good electron transport capabilities. This necessitates a significant trade-off between these two aspects in material selection and performance optimization. Furthermore, perovskite optoelectronic devices have complex structures, requiring the perovskite layer to be placed in the center as a high-refractive-index loss layer. Traditional metal oxide LMR often employs a simple structure where the loss layer is deposited directly on the waveguide, leading to structural and optical incompatibility between the traditional LMR optical mode and the photovoltaic charge transport path. Therefore, directly transferring LMR technology to perovskite optoelectronic devices is not straightforward and requires overcoming multiple structural and functional compatibility challenges.

[0004] Therefore, there is an urgent need to develop a simple and non-destructive thin film evaluation method that can achieve large-area, efficient detection and parameter adjustment through rapid spectral acquisition and analysis, thereby optimizing production efficiency and increasing yield. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for monitoring the quality and uniformity of perovskite thin films. This method utilizes a planar optical waveguide structure based on the LMR effect for non-destructive evaluation of the quality and uniformity of perovskite thin films. The in-situ optical monitoring system of this invention meets both the normal operation requirements of perovskite optoelectronic devices and the optical monitoring requirements of internal perovskite functional materials. It can be used for in-situ monitoring of the quality and uniformity of internal thin films in perovskite optoelectronic devices, thereby promoting their industrialization.

[0006] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a method for monitoring the quality and uniformity of perovskite thin films, comprising the following steps: S1. A perovskite photovoltaic device to be tested is provided, the device comprising at least a glass substrate and a perovskite layer formed on the transparent glass substrate; S2. The incident light emitted by the broadband light source is coupled into the glass substrate through a multimode optical fiber; S3. The emitted light from the glass substrate is collected through another multimode fiber and a polarizer, and then sent to a spectrometer to obtain the transmission spectrum. S4. Extract the peak position wavelength, peak intensity value, and full width at half maximum (FWHM) value of the loss mode resonance characteristic peak generated by the perovskite layer from the transmission spectrum.

[0007] Preferably, the perovskite photovoltaic device further includes a bottom electrode and a first charge transport layer located between the glass substrate and the perovskite layer, and the refractive indices of the glass substrate and the first charge transport layer are both lower than the refractive index of the perovskite layer.

[0008] In this structure, the perovskite layer becomes the loss layer with the highest refractive index. The optical waveguide mode mainly propagates in the lower refractive index bottom layer and effectively extends to the upper high-refractive-index perovskite layer through the evanescent field, generating a strong loss mode resonance. If the refractive index of the first charge transport layer is higher than or close to that of the perovskite layer, a low-high-low refractive index distribution structure will be formed, causing light to be strongly confined in the first charge transport layer and unable to effectively enter the perovskite layer. Consequently, the LMR resonance peak is significantly weakened or even unobservable.

[0009] More preferably, the material of the bottom electrode includes ITO, FTO, or PEDOT:PSS.

[0010] More preferably, the broadband light source includes a halogen lamp, a white LED, or a supercontinuum laser.

[0011] Preferably, the glass substrate has a refractive index of 1.51±0.1 and a thickness of 150-500 μm.

[0012] Specifically, a glass substrate that is too thin is prone to breakage during device fabrication, which is detrimental to actual fabrication and subsequent applications. Secondly, the effective range of the waveguide in the substrate is limited, while a substrate that is too thick weakens the interaction between the waveguide and the loss layer, thereby reducing the depth and deteriorating the peak shape of the LMR resonance, which is not conducive to subsequent testing. Within this thickness range, sufficient mechanical strength can be ensured while maintaining a strong evanescent field, making the LMR resonance peak more obvious and clear.

[0013] Preferably, the core diameter of the multimode optical fiber is 50.0±2.5 μm and the cladding diameter is 25±2 μm; the wavelength range of the light source is 300-1200 nm.

[0014] Preferably, in step S3, the TE mode transmission spectrum and the TM mode transmission spectrum are obtained by rotating the polarizer.

[0015] Preferably, step S4 further includes: repeating steps S2 and S3 at at least two different locations in the perovskite layer to obtain the peak wavelength, peak intensity, and full width at half maximum (FWHM) of the loss mode resonance characteristic peaks in the transmission spectra at multiple locations.

[0016] Preferably, the perovskite photovoltaic device further includes a second charge transport layer and a back electrode located on the perovskite layer; and the refractive index of the second charge transport layer is lower than the refractive index of the perovskite layer.

[0017] Specifically, by making the perovskite layer the loss layer with the highest refractive index and forming a low-high-low refractive index distribution structure, light leakage in the substrate is facilitated and strongly confined in the perovskite layer, making the LMR resonance peak more obvious and clear.

[0018] Preferably, an interface layer is further provided between the second charge transport layer and the back electrode, and the material of the interface layer includes BCP.

[0019] Preferably, the material of the first charge transport layer includes SnO2, PCBM, PEDOT:PSS, or PTAA.

[0020] More preferably, SnO2 and PCBM serve as electron transport layers in a positive (nip) structure; or PEDOT:PSS and PTAA serve as hole transport layers in a negative (pin) structure.

[0021] Preferably, the material of the perovskite layer includes MAPbI3 or MAPbBr3.

[0022] More preferably, the perovskite layer has a positive real part of dielectric constant and a real part of refractive index that is greater than the imaginary part, serving as a loss layer in the waveguide.

[0023] Specifically, the device obtained by this invention is a perovskite optoelectronic device with optical monitoring capability of loss mode resonance effect in the perovskite layer; wherein the low refractive index functional layer between the perovskite layer and the glass substrate is used to enhance the phase matching between the evanescent wave and the loss mode, optimize the peak shape of the perovskite material, and improve the resolution; the method of this invention is applicable to positive (nip) or inverse (pin) structures, ensuring that the refractive index of the charge transport layer is lower than that of the perovskite to enhance the LMR effect.

[0024] Preferably, before step S2, a step of spectral correction with a blank glass substrate as a reference is included: turning off the light source to collect the dark spectrum and turning on the light source to collect the bright spectrum.

[0025] Specifically, this invention assesses the thin film state by analyzing the LMR resonance valleys (peak position, peak intensity, full width at half maximum, and quality factor) in the transmission spectrum, and can be extended to multi-point scanning to map uniformity. The peak positions of the LMR characteristic peaks of perovskite materials redshift with the increase of perovskite film thickness. The thickness and uniformity of the film can be determined based on the peak positions of characteristic peaks generated at different locations of the device.

[0026] Furthermore, high-quality, highly crystalline, and dense perovskite films possess stronger optical absorption and a more stable high refractive index, enabling strong loss resonance in the LMR mode within the film. This results in characteristic peaks with large depths, narrow full width at half maximum (FWHM), and high quality factors. Conversely, low-quality or partially damaged perovskite films, due to their small grain size, numerous pinholes, and high defect density, exhibit reduced effective optical absorption, significantly increased light scattering, and localized refractive index fluctuations. Consequently, the interaction between the LMR mode and the film is weakened, ultimately manifesting as shallower LMR characteristic peaks, significantly broader peak widths, or even complete disappearance. Therefore, by comparing the shape and parameters of the LMR characteristic peaks at different locations in perovskite films, the quality of the film in that region can be effectively determined.

[0027] Compared with the prior art, the advantages of the present invention are as follows: (1) This invention provides a simple, fast and non-destructive thin film evaluation method that only requires collecting and analyzing transmission spectra to quantify quality indicators; by extracting multiple parameters of the transmission spectrum (such as perovskite characteristic peak position, characteristic peak intensity, half peak width, etc.), the thin film quality can be comprehensively evaluated and production parameter optimization can be guided.

[0028] (2) The device of the present invention has a simple structure and low cost, and is easy to integrate into the thin film preparation process to achieve efficient quality feedback and significantly reduce the defect rate.

[0029] (3) The present invention has strong applicability and will not damage the perovskite film at all. It can quickly identify local non-uniformity, thereby improving the overall production efficiency and the consistency of device performance. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the online in-situ monitoring system based on perovskite thin films for photovoltaic devices according to the present invention; Figure 2The images show the LMR transmission spectra (TE / TM mode) of perovskite films of different masses in Example 1; where (a) and (b) are the initial high-quality films; (c) and (d) are the films after degradation at 100 °C for 5 h; and (e) and (f) are the films after degradation at 100 °C for 10 h. Figure 3 The images show LMR transmission spectra and location diagrams of different parts of the perovskite thin film in Example 1; where (a) and (b) are region ①; (c) and (d) are region ②; (e) and (f) are region ③; (g) and (h) are region ④; and (i) is a schematic diagram of different test locations.

[0032] In the figure, 1-light source, 2-multimode optical fiber, 3-glass substrate, 4-bottom electrode, 5-first charge transport layer, 6-perovskite layer, 7-second charge transport layer, 8-back electrode, 9-perovskite photovoltaic device, 10-polarizer, 11-spectrometer. Detailed Implementation

[0033] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0034] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0035] In this document, the terms “containing,” “comprising,” or “including” are open-ended expressions, meaning they include the contents specified in this invention but do not exclude other aspects.

[0036] In this document, the terms “optional,” “optionally,” or “optional” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0038] Unless otherwise specified, all reagents used in this invention can be purchased from the market. Indium tin oxide (ITO) conductive glass was purchased from Liaolin Youxuan; commercial carbon paste was purchased from Maitowei Chemical New Materials.

[0039] Example 1 This embodiment provides a perovskite photovoltaic device and a method for monitoring its quality and uniformity. The device structure includes a glass substrate (150 µm, refractive index 1.51) 3 / ITO bottom electrode 4 / SnO2 first charge transport layer (refractive index 1.8-2.0) 5 / MAPbI3 perovskite layer (refractive index 2.0-2.55) 6 / carbon back electrode 8.

[0040] (1) The photovoltaic device fabrication steps include: First, indium tin oxide (ITO) conductive glass (with ITO bottom electrode 4 pre-deposited on glass substrate 3) is provided. The ITO conductive glass is ultrasonically cleaned sequentially with detergent, deionized water, acetone, isopropanol and anhydrous ethanol for a total of 30 min. Then, the ITO conductive glass is dried with a nitrogen gun. Subsequently, the dried ITO conductive glass is treated with ultraviolet light-ozone in a plasma cleaner for a total of 15 min to remove organic matter on the surface and increase the hydrophilicity of the ITO conductive glass surface. Next, tin oxide (SnO2) colloidal dispersion (5 wt%, diluted with deionized water) was dropped onto ITO conductive glass and coated by spin coating at 5000 rpm for 60 s. After spin coating, the coating was annealed at 60 °C for 30 min to obtain the first charge transport layer 5 of SnO2. Next, the perovskite precursor solution (838.2 mg PbI2 and 286.1 mg MAI dissolved in 900 µL DMF and 100 µL LDMSO, stirred overnight at room temperature 25 °C, concentration 1.8 M) was dropped onto the SnO2 first charge transport layer 5, and spin-coated at 4000 rpm for 30 s. 20 s after the spin-coating started, 200 µL of chlorobenzene (CB) was dropped in. After spin-coating, the mixture was annealed at 100 °C for 10 min to obtain a uniform and dense MAPbI3 perovskite layer 6. Finally, a commercial carbon paste (10 Ω / cm) was coated onto the surface of the perovskite layer 6 using a scraper. After annealing at 100 °C for 10 min, a carbon back electrode 8 was obtained, completing the fabrication of the perovskite photovoltaic device 9.

[0041] (2) The optical signal testing device includes: The broadband light source 1 is a halogen lamp with a wavelength of 300-1200 nm; the spectrometer 11 is a fiber optic spectrometer with a resolution of 0.05 nm and a wavelength range of 300-1200 nm; two multimode optical fibers 2 with a core diameter of 50.0 μm and a cladding diameter of 25 μm are connected to the light source 1 and the spectrometer 11 respectively. according to Figure 1 Assembly as shown: Two multimode optical fibers 2 are placed vertically on both sides of the glass substrate 3, and a polarizer 10 is added between the multimode optical fiber 2 connected to the spectrometer 11 and the glass substrate 3; the coupling efficiency is calibrated by a power meter, and the positions of the multimode optical fiber 2 and the glass substrate 3 are adjusted until the coupling rate reaches the optimal level. Then the positions of each component are fixed to obtain the optical fiber coupling assembly. First, the optical fiber coupling assembly is spectrally calibrated, with a blank glass substrate 3 placed as a reference. Then, the light source 1 is turned off, and the dark spectrum is collected using the spectrometer 11 to subtract background noise. Next, the light source 1 is turned on, and the bright spectrum is collected using the spectrometer 11 to subtract systematic errors such as light source spectral shape, optical fiber transmission loss, and substrate absorption / reflection.

[0042] (3) Monitoring methods include: S1. Place the prepared perovskite photovoltaic device 9 in the above-mentioned optical fiber coupling assembly, specifically: remove the blank glass substrate 3, place the glass substrate 3 of the device 9 in the original position of the blank glass substrate 3, so that the two multimode optical fibers 2 are located on both sides of the glass substrate 3 of the device 9 respectively. S2. Turn on the broadband light source 1 and couple the incident light emitted by it into the transparent glass substrate 3 through the first multimode fiber 2. Use the glass substrate 3 as the waveguide layer and the perovskite layer 6 as the loss mode support layer to excite the loss mode resonance (LMR) effect. S3. The emitted light from the transparent glass substrate 3 is collected through the second multimode fiber 2 and the polarizer 10, and sent to the spectrometer 11 to obtain the transmission spectrum; the transmission spectra in TE mode and TM mode are recorded by rotating the polarizer 10 respectively. S4. Extract the peak position wavelength, peak intensity value and full width at half maximum (FWHM) value of the LMR characteristic peak generated by the perovskite layer 6 from the transmission spectrum.

[0043] like Figure 2 As shown, the initial high-quality MAPbI3 perovskite layer 6 in TE mode ( Figure 2 a) and TM mode ( Figure 2 In b), sharp, high-intensity LMR characteristic peaks were produced; after thermal degradation at 100 °C for 5 hours, the TE mode ( Figure 2 c) and TM mode ( Figure 2 In the d) mode, the intensity of the characteristic LMR peaks decreased and the full width at half maximum (FWHM) increased; after 10 hours of degradation, the TE mode ( Figure 2 (e) and TM mode ( Figure 2 The LMR characteristic peak under f) gradually weakens.

[0044] The above results indicate that as the MAPbI3 perovskite layer 6 undergoes thermal degradation, the peak intensity of the LMR characteristic peaks in the transmission spectrum collected by the monitoring device decreases, the full width at half maximum (FWHM) increases, and the peak quality factor decreases. Therefore, the quality of the perovskite film can be monitored and determined using the method of this invention.

[0045] like Figure 3 As shown, at different locations of device 9 ( Figure 3 In the diagram, i represents ① the central region, ② the secondary central region, ③ the inner edge region, and ④ the edge region, respectively, and spectra are collected in these regions. The central region ① is in TE mode ( Figure 3 a) and TM mode ( Figure 3 In b), the LMR characteristic peaks are sharp and have high intensity; the edge region ④ in TE mode ( Figure 3 g) and TM mode ( Figure 3 The intensity of the characteristic LMR peaks in region h is significantly reduced and the full width at half maximum (FWHM) is increased; the middle regions ② and ③ ( Figure 3 The cf in the text exhibits a gradual change characteristic.

[0046] The above results indicate that the perovskite films prepared by spin coating are not completely uniform. In this test, the LMR characteristic peaks generated by the film in the central region are sharp, indicating high film quality. However, in the edge region, the intensity of the LMR characteristic peaks is significantly weakened, the half-width is increased, the overall peak shape is broadened, and the peak value is reduced, reflecting poor film quality and more defects in the edge region. The decreasing trend of film quality is more obvious as the position is closer to the edge, which is highly consistent with the radial non-uniformity commonly seen in the actual preparation process of spin coating. Therefore, the method of this invention can monitor and determine the uniformity of perovskite films in perovskite solar cells.

[0047] In summary, this system uses an optical signal generated by a light source, which is incident on the glass substrate 3 of the device through a multimode fiber. The glass substrate 3 acts as a waveguide layer to generate waveguide modes, while the perovskite thin film on top acts as a loss mode support layer to generate loss modes. Together, they produce the LMR effect. The output light is transmitted through the multimode fiber to a spectrometer for collection in the form of transmission spectra. The low-refractive-index layer between the perovskite thin film and the glass substrate 3 in the device can optimize the peak shape of characteristic peaks in the transmission spectrum, and the carbon layer on the perovskite thin film can protect the perovskite thin film and improve the stability of the device. The polarizer is used to distinguish the characteristic peaks in the TE and TM modes in the LMR characteristic peaks and optimize the resolution of the characteristic peaks. Damage to the perovskite thin film will affect its thickness, refractive index, dielectric constant, composition, etc., thereby changing the peak position, full width at half maximum (FWHM), and peak depth of the LMR characteristic peaks in the transmission spectrum. By recording and analyzing the information of characteristic peaks in the transmission spectrum collected by the spectrometer, the quality and uniformity of the perovskite thin film in the device can be monitored.

[0048] Example 2 This embodiment provides a perovskite photovoltaic device and a method for monitoring its quality and uniformity. The device structure includes a glass substrate (150 µm, refractive index 1.50) 3 / ITO bottom electrode 4 / SnO2 first charge transport layer (refractive index 1.8-2.0) 5 / MAPbI3 perovskite layer (refractive index 2.0-2.55) 6 / P3HT second charge transport layer (refractive index 1.55-1.90) 7 / Ag back electrode 8.

[0049] (1) The difference between the photovoltaic device fabrication steps and those in Example 1 is as follows: After obtaining the MAPbI3 perovskite layer 6, the P3HT precursor solution (20 mg P3HT dissolved in 10 mL CB, stirred at 70 °C for 2 h until completely dissolved, and filtered through 0.22 µm PTEE) was further spin-coated onto the perovskite surface, and the second charge transport layer 7 of P3HT was obtained by spin coating at 4000 rpm for 30 s. Finally, a 100 nm thick Ag back electrode 8 was deposited on the P3HT second charge transport layer 7 to complete the fabrication of the perovskite photovoltaic device 9; the remaining steps were the same as in Example 1.

[0050] (2) The optical signal testing device includes: The broadband light source 1 is a halogen lamp with a wavelength of 300-1200 nm; the spectrometer 11 is a fiber optic spectrometer with a resolution of 0.05 nm and a wavelength range of 300-1200 nm; two multimode optical fibers 2 with a core diameter of 47.5 μm and a cladding diameter of 23 μm are connected to the light source 1 and the spectrometer 11 respectively. according to Figure 1 Assembly as shown: Two multimode optical fibers 2 are placed vertically on both sides of the glass substrate 3, and a polarizer 10 is added between the multimode optical fiber 2 connected to the spectrometer 11 and the glass substrate 3; the coupling efficiency is calibrated by a power meter, and the positions of the multimode optical fiber 2 and the glass substrate 3 are adjusted until the coupling rate reaches the optimal level. Then the positions of each component are fixed to obtain the optical fiber coupling assembly. First, the optical fiber coupling assembly is spectrally calibrated, with a blank glass substrate 3 placed as a reference. Then, the light source 1 is turned off, and the dark spectrum is collected using the spectrometer 11 to subtract background noise. Next, the light source 1 is turned on, and the bright spectrum is collected using the spectrometer 11 to subtract systematic errors such as light source spectral shape, optical fiber transmission loss, and substrate absorption / reflection.

[0051] (3) The monitoring method is consistent with that in Example 1.

[0052] Using the complete formal device structure of this embodiment, the P3HT second charge transport layer 7 and Ag back electrode 8 protect the perovskite layer 6 and reduce light leakage. Monitoring results show that the LMR characteristic peaks generated by the high-quality MAPbI3 perovskite layer 6 are sharp and have high intensity. When the perovskite layer 6 degrades or has uneven thickness, the characteristic peaks show red shift, intensity decay, and broadening of the full width at half maximum (FWHM).

[0053] By performing multi-point scanning at different locations on the device, the differences in LMR characteristic peaks between the central and edge regions can be clearly distinguished, thereby assessing the uniformity of the thin film. This embodiment verifies the applicability of this method in devices with a complete second charge transport layer and a metal back electrode.

[0054] Example 3 This embodiment provides a perovskite photovoltaic device and a method for monitoring its quality and uniformity. The device structure includes a glass substrate (150 µm, refractive index 1.52) 3 / ITO bottom electrode 4 / PEDOT:PSS first charge transport layer (refractive index 1.5-1.6) 5 / MAPbI3 perovskite layer (refractive index 2.0-2.55) 6 / PCBM second charge transport layer (refractive index 1.7-2.2) 7 / Ag back electrode 8.

[0055] (1) The difference between the photovoltaic device fabrication steps and those in Example 1 is as follows: First, an indium tin oxide (ITO) conductive glass is provided (an ITO bottom electrode 4 is pre-deposited on a glass substrate 3), and the cleaning steps are the same as in Example 1; Next, a PEDOT:PSS solution was dropped onto an ITO conductive glass and coated by rotating at 3000 rpm for 30 s to obtain the first charge transport layer 5 of PEDOT:PSS. Next, the perovskite precursor solution (same as in Example 1) was dropped onto the first charge transport layer 5 of PEDOT:PSS and spin-coated at 4000 rpm for 30 s. 200 µL of chlorobenzene (CB) was dropped in 20 s after the spin coating started. After spin coating was completed, the layer was annealed at 100 °C for 10 min to obtain a uniform and dense MAPbI3 perovskite layer 6. Then, the PCBM precursor solution (30 mg PCBM dissolved in 10 mL CB solvent, stirred at room temperature 25 °C until completely dissolved, and filtered through 0.22 µm PTEE) was spin-coated onto the surface of the perovskite layer 6 at a speed of 3000 rpm for 30 s. After spin-coating, the layer was annealed at 100 °C for 10 min to obtain the PCBM second charge transport layer 7. Finally, a 100 nm thick Ag back electrode 8 was deposited on the second charge transport layer 7 of the PCBM to complete the fabrication of the perovskite photovoltaic device 9.

[0056] (2) The optical signal testing device includes: The broadband light source 1 is a halogen lamp with a wavelength of 300-1200 nm; the spectrometer 11 is a fiber optic spectrometer with a resolution of 0.05 nm and a wavelength range of 300-1200 nm; two multimode optical fibers 2 with a core diameter of 52.5 μm and a cladding diameter of 27 μm are connected to the light source 1 and the spectrometer 11 respectively. according to Figure 1 Assembly as shown: Two multimode optical fibers 2 are placed vertically on both sides of the glass substrate 3, and a polarizer 10 is added between the multimode optical fiber 2 connected to the spectrometer 11 and the glass substrate 3; the coupling efficiency is calibrated by a power meter, and the positions of the multimode optical fiber 2 and the glass substrate 3 are adjusted until the coupling rate reaches the optimal level. Then the positions of each component are fixed to obtain the optical fiber coupling assembly. First, the optical fiber coupling assembly is spectrally calibrated, with a blank glass substrate 3 placed as a reference. Then, the light source 1 is turned off, and the dark spectrum is collected using the spectrometer 11 to subtract background noise. Next, the light source 1 is turned on, and the bright spectrum is collected using the spectrometer 11 to subtract systematic errors such as light source spectral shape, optical fiber transmission loss, and substrate absorption / reflection.

[0057] (3) The monitoring method is consistent with that in Example 1.

[0058] This embodiment describes an inverted perovskite device. Monitoring results show that the peak position, intensity, and full width at half maximum (FWHM) of the LMR characteristic peaks are sensitive to changes in the quality of the perovskite layer 6. When the perovskite layer 6 is uniform and dense, the characteristic peaks are sharp and symmetrical; when defects or uneven thickness exist in the film, the characteristic peaks broaden and their intensity decreases. Radial non-uniformity caused by the spin-coating process can be detected through multi-point testing. This demonstrates that this method is also applicable to inverted device structures using PEDOT:PSS as the hole transport layer and PCBM as the electron transport layer.

[0059] Example 4 This embodiment provides a perovskite photovoltaic device and a method for monitoring its quality and uniformity. The device structure includes a glass substrate (500 µm, refractive index 1.51) 3 / ITO bottom electrode 4 / PTAA first charge transport layer (refractive index 1.55-1.65) 5 / MAPbI3 perovskite layer (refractive index 2.0-2.55) 6 / PCBM second charge transport layer (refractive index 1.7-2.2) 7 / BCP layer (refractive index 1.65-1.85) / Ag back electrode 8.

[0060] (1) The difference between the photovoltaic device fabrication steps and those in Example 1 is as follows: First, an indium tin oxide (ITO) conductive glass is provided (an ITO bottom electrode 4 is pre-deposited on a glass substrate 3), and the cleaning steps are the same as in Example 1; Next, PTAA solution (20 mg PTAA dissolved in 10 mL toluene solvent, stirred at room temperature 25 °C until completely dissolved, filtered through 0.22 µm PTEE) was added dropwise onto ITO conductive glass, and the solution was coated by rotating at 4000 rpm for 40 s to obtain the first charge transport layer 5 of PTAA. Next, the perovskite precursor solution (same as in Example 1) was dropped onto the first charge transport layer 5 of PTAA and spin-coated at a speed of 4000 rpm for 30 s. 200 µL of chlorobenzene (CB) was dropped in 20 s after the spin coating started. After spin coating was completed, the layer was annealed at 100 °C for 10 min to obtain a uniform and dense MAPbI3 perovskite layer 6. Then, the PCBM precursor solution (20 mg PCBM dissolved in 10 mL CB solvent, stirred at room temperature 25 °C until completely dissolved, and filtered through 0.22 µm PTEE) was spin-coated onto the surface of the perovskite layer 6 at a speed of 2000 rpm for 30 s. After spin-coating, the layer was annealed at 100 °C for 10 min to obtain the PCBM second charge transport layer 7. A BCP solution (0.5 mg / mL, 0.5 mg BCP powder dissolved in 1 ml isopropanol solvent, stirred at room temperature 25 ℃ until completely dissolved, and filtered through 0.22 µm PTEE) was spin-coated onto the surface of the second charge transport layer 7 of the PCBM at a speed of 4000 rpm for 30 s. After spin-coating, the layer was annealed at 100 ℃ for 10 min to obtain the BCP layer. Finally, a 100 nm thick Ag back electrode 8 was deposited on the second charge transport layer 7 of the BCP to complete the fabrication of the perovskite photovoltaic device 9.

[0061] (2) The optical signal testing device and its assembly are consistent with those in Example 1.

[0062] (3) The monitoring method is consistent with that in Example 1.

[0063] This embodiment demonstrates a multilayer structure with a PTAA hole transport layer, a PCBM electron transport layer, and a BCP cathode interface layer. Monitoring results show that the variation pattern of the LMR characteristic peaks is consistent with that of the previous embodiment, namely, the quality degradation of the perovskite layer 6 leads to a decrease in characteristic peak intensity and an increase in full width at half maximum (FWHM), and changes in thickness cause peak position shifts. By comparing the LMR characteristic peaks at different locations of the device, the uniformity of large-area thin films can be effectively quantified. The BCP interface layer helps improve electron extraction efficiency and device stability without affecting the basic principle of LMR monitoring. This method remains effective for devices with multiple interface modification layers, demonstrating good universality.

[0064] Example 5 This embodiment provides a perovskite photovoltaic device and a method for monitoring its quality and uniformity. The device structure includes a glass substrate (150 µm, refractive index 1.51) 3 / ITO bottom electrode 4 / SnO2 first charge transport layer (refractive index 1.8-2.0) 5 / MAPbI3 perovskite layer (refractive index 2.0-2.55) 6.

[0065] (1) The difference between the photovoltaic device fabrication steps and those in Example 1 is as follows: After obtaining the MAPbI3 perovskite layer 6, no further preparation is carried out, that is, the second charge transport layer 7 and the back electrode 8 are not prepared, resulting in an incomplete device; the rest is consistent with Example 1.

[0066] (2) The optical signal testing device and its assembly are consistent with those in Example 1.

[0067] (3) The monitoring method is consistent with that in Example 1.

[0068] This embodiment demonstrates that even in intermediate processes where not all electrode fabrication is complete, this method can still independently monitor the quality and uniformity of the perovskite layer 6. Monitoring results show that a high-quality perovskite layer 6 produces distinct LMR characteristic peaks, while a poor-quality film results in weakened characteristic peak intensity and broadened full width at half maximum (FWHM). Non-uniform distribution of the film can also be detected through multi-point scanning. Therefore, this technology is applicable not only to complete optoelectronic devices but also to intermediate monitoring during the fabrication process, facilitating timely feedback for process parameter adjustments and enabling rapid screening on the production line.

[0069] In summary, Examples 1-4 are all complete device structures, applicable to various optoelectronic device fields such as solar cells, photodetectors, and light-emitting diodes. Example 5 is a non-complete device, representing a necessary step in the fabrication of a complete device. This technology is applicable not only to monitoring the quality and uniformity of perovskite thin films in simple non-complete devices but also to monitoring the quality and uniformity of perovskite thin films in complex perovskite optoelectronic devices.

[0070] Comparative Example 1 This comparative example provides a perovskite photovoltaic device that is not applicable to the quality and uniformity monitoring method of the present invention. The device structure includes a glass substrate (150 µm, refractive index 1.51) 3 / ITO bottom electrode 4 / TiO2 (refractive index 2.2-2.6) first charge transport layer 5 / MAPbI3 perovskite layer 6 / Spiro-OMeTAD second charge transport layer (refractive index 1.55-1.75) 7 / Ag back electrode 8.

[0071] (1) The difference between the photovoltaic device fabrication steps and those in Example 1 is as follows: First, an indium tin oxide (ITO) conductive glass is provided (an ITO bottom electrode 4 is pre-deposited on a glass substrate 3), and the cleaning steps are the same as in Example 1; Next, a titanium dioxide (TiO2) precursor solution (370 μL of isopropyl titanate dissolved in 2.5 mL of anhydrous isopropanol, stirred at room temperature (25 °C) for 12 h, and filtered through 0.22 µm PTEE) was added dropwise onto ITO conductive glass. The solution was then spin-coated at 2000 rpm for 60 s. After spin-coating, the solution was sintered at 500 °C for 30 min to obtain the first charge transport layer 5 of TiO2. Next, the perovskite precursor solution (same as in Example 1) was dropped onto the TiO2 first charge transport layer 5 and spin-coated at a speed of 4000 rpm for 30 s. 200 µL of chlorobenzene (CB) was dropped in 20 s after the spin coating started. After spin coating was completed, the layer was annealed at 100 °C for 10 min to obtain a uniform and dense MAPbI3 perovskite layer 6. Then, the Spiro-OMeTAD precursor solution (72.3 mg Spiro-OMeTAD, 28 µL 4-tert-butylpyridine (tBP) and 17 µL Li-TFSI acetonitrile solution (520 mg / mL) dissolved in 1 mL chlorobenzene, stirred at room temperature (25 °C) until completely dissolved, and filtered through 0.22 µm PTEE) was spin-coated onto the surface of the perovskite layer 6 at a speed of 2000 rpm for 40 s to obtain the Spiro-OMeTAD second charge transport layer 7; Finally, a 100 nm thick Ag back electrode 8 was deposited on the Spiro-OMeTAD second charge transport layer 7 to complete the fabrication of the perovskite photovoltaic device 9.

[0072] (2) The optical signal testing device and its assembly are consistent with those in Example 1.

[0073] (3) The monitoring method is consistent with that in Example 1.

[0074] In the transmission spectroscopy test, no obvious perovskite characteristic peaks were found in the wavelength range of 300-1200 nm. This is because the refractive index of TiO2 is close to and higher than that of perovskite. Light leaking from the substrate will enter TiO2 and will have difficulty entering the perovskite layer, thus failing to effectively excite the LMR phenomenon of perovskite.

[0075] The embodiments described above are some, but not all, of the embodiments of the present invention; the detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention; all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for monitoring the quality and uniformity of perovskite thin films, characterized in that, Includes the following steps: S1. Provide a perovskite photovoltaic device (9) to be tested, the device (9) including at least a glass substrate (3) and a perovskite layer (6) formed on the glass substrate (3). S2. The incident light emitted by the broadband light source (1) is coupled into the glass substrate (3) through the multimode optical fiber (2); S3. The emitted light from the glass substrate (3) is collected through another multimode fiber (2) and via a polarizer (10) and sent to a spectrometer (11) to obtain the transmission spectrum. S4. Extract the peak position wavelength, peak intensity value and full width at half maximum value of the loss mode resonance characteristic peak generated by the perovskite layer (6) from the transmission spectrum.

2. The method according to claim 1, characterized in that, The perovskite photovoltaic device (9) further includes a bottom electrode (4) and a first charge transport layer (5) located between the glass substrate (3) and the perovskite layer (6), and the refractive indices of the glass substrate (3) and the first charge transport layer (5) are both lower than the refractive index of the perovskite layer (6).

3. The method according to claim 1, characterized in that, The glass substrate (3) has a refractive index of 1.51±0.1 and a thickness of 150-500 μm.

4. The method according to claim 1, characterized in that, The multimode fiber (2) has a core diameter of 50.0±2.5μm and a cladding diameter of 25±2 μm; the light source (1) has a wavelength range of 300-1200 nm.

5. The method according to claim 1, characterized in that, In step S3, the TE mode transmission spectrum and the TM mode transmission spectrum are obtained by rotating the polarizer (10).

6. The method according to claim 1, characterized in that, Step S4 further includes repeating steps S2 and S3 at at least two different locations in the perovskite layer (6) to obtain the peak wavelength, peak intensity and full width at half maximum (FWHM) of the loss mode resonance characteristic peaks in the transmission spectra at multiple locations.

7. The method according to claim 1, characterized in that, The perovskite photovoltaic device (9) further includes a second charge transport layer (7) and a back electrode (8) located on the perovskite layer (6); the refractive index of the second charge transport layer (7) is lower than that of the perovskite layer (6).

8. The method according to claim 7, characterized in that, An interface layer is further provided between the second charge transport layer (7) and the back electrode (8), and the material of the interface layer includes BCP.

9. The method according to claim 2, characterized in that, The material of the first charge transport layer (5) includes SnO2, PCBM, PEDOT:PSS or PTAA; the material of the perovskite layer (6) includes MAPbI3 or MAPbBr3.

10. The method according to claim 1, characterized in that, Before step S2, there is also a step of spectral correction with a blank glass substrate as a reference: turn off the light source (1) to collect the dark spectrum, and turn on the light source (1) to collect the bright spectrum.

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