Method for monitoring uniformity of perovskite film based on multi-channel in-situ PL spectrum

Abstract

The invention discloses a method for monitoring the uniformity and quality of a perovskite thin film based on a multi-channel in-situ PL spectrum, belongs to the technical field of characterization testing of the perovskite thin film, and reflects the uniformity and crystal quality of the large-area perovskite thin film through multi-channel in-situ PL spectrum monitoring in spin coating and annealing processes in a perovskite preparation process. In the perovskite thin film forming process, PL signals at multiple different positions on the perovskite thin film are synchronously monitored, whether growth of the perovskite thin film at different positions is uniform or not is obtained by comparing the PL signals at different positions, and crystal evolution and uniformity change are dynamically analyzed in real time and in a lossless mode in the perovskite thin film preparation process.

Description

Technical Field

[0001] This invention belongs to the field of characterization and testing technology for perovskite thin films, specifically relating to a method for monitoring the uniformity and quality of perovskite thin films based on multi-channel in-situ PL spectroscopy. Background Technology

[0002] Perovskite materials exhibit strong light absorption in the visible light region (400-800 nm). Furthermore, perovskites have long carrier diffusion lengths, low exciton binding energies, and readily generate free carriers (which are crucial for the formation of effective photocurrent). They also exhibit low nonradiative recombination (which reduces carrier utilization), resulting in superior photoelectric conversion characteristics. Thanks to these numerous unique advantages, perovskite materials have shone brightly in the photovoltaic field in recent years, for example, in solar cells, LED light-emitting devices, and photodetectors.

[0003] The quality (including crystallinity, defect density, and coverage) and uniformity (spatial consistency of thickness, composition, and morphology) of perovskite thin films are core factors determining the performance, stability, and repeatability of optoelectronic devices. Spin coating, commonly used in laboratories, is suitable for small areas (<1 cm²). 2 High-quality films are easily obtained on [a surface], but scaling up to large areas (>100 cm²) is difficult. 2 Maintaining high uniformity in thickness, composition, and morphology is one of the biggest technical bottlenecks in film preparation. Furthermore, film quality is extremely sensitive to preparation conditions (temperature, humidity, solution concentration, spin-coating / coating speed, annealing conditions, timing of antisolvent addition, etc.).

[0004] Steady-state photoluminescence (PL) spectroscopy is one of the core techniques for characterizing the photoelectric properties of perovskite thin films. By analyzing the spectral characteristics emitted by the material under constant illumination, it can directly reflect its crystallinity, defect state density, phase purity, and carrier recombination behavior. An increase in PL peak intensity indicates improved crystallinity and reduced defects (optimal temperature); a decrease in PL peak intensity indicates excessive annealing leading to PbI2 precipitation or volatilization of organic components (phase transition / decomposition). However, traditional characterization methods (SEM, XRD, steady-state PL) can only provide "average" information and cannot reveal nucleation differences caused by interfacial inhomogeneities in real time and with spatial resolution. Summary of the Invention

[0005] This invention provides a method for monitoring the uniformity of perovskite thin films based on multi-channel in-situ PL spectroscopy. By detecting the nucleation and growth of perovskite during spin coating and annealing using multi-channel in-situ PL spectroscopy, the nucleation and growth of perovskite are qualitatively reflected based on the appearance time and intensity changes of the PL peaks. The uniformity of the film is reflected by the nucleation density, thus achieving the characterization of the uniformity and crystal quality of large-area perovskite thin films.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for monitoring the uniformity of perovskite thin films based on multi-channel in-situ PL spectroscopy includes the following steps: During the formation of perovskite thin films, PL signals at multiple different locations on the perovskite thin film are monitored simultaneously. By comparing the PL signals at different locations, the uniformity of the growth of the perovskite thin film at different locations can be determined. In the process of perovskite thin film preparation, the crystallization evolution and uniformity changes can be analyzed in real time, dynamically and non-destructively.

[0007] The intensity of the peak of the detected PL signal reflects the number of nuclei. The stronger the peak, the more nuclei are formed. The more nuclei are formed, the greater the nucleation density, and the fewer defects are formed.

[0008] During the formation of perovskite thin films, the pulse-light (PL) signal at a location reflects the nucleation and crystallization characteristics at that location. During spin coating, the intensity of the PL peak represents the number of nuclei formed; the rate of increase of the PL peak represents the nucleation rate; during annealing, the PL intensity can reflect the number of defects formed. The stronger the PL peak, the fewer the defects, and the better the crystallinity of the film. By processing the signal intensities at different locations and expressing them as percentages, the similarity of the nucleation and crystallization process of the perovskite thin films at different times or locations can be reflected, thereby reflecting the uniformity of the film.

[0009] If the number of channels is n, and the multiple signals are R1, R2, R3, ..., R... n If the average value of all signals is R, then the surface uniformity of the perovskite thin film is... U for: × 100% The perovskite thin film was prepared by solution method, one-step spin coating, with antisolvent assistance and high-temperature annealing, and the composition was FA. 0.85 MA 0.1 Cs 0.05 PbI3 perovskite thin films.

[0010] Beneficial Effects: This invention provides a method for monitoring the uniformity of perovskite thin films based on multi-channel in-situ photoluminescence (PL) spectroscopy. By collecting and comparing multi-channel PL signal results, the repetition rate of PL signal changes over a period of time or at different locations is analyzed. A higher repetition rate indicates more uniform film growth and more consistent film properties. Compared with existing technologies, this invention offers the following advantages: (1) It realizes the instantaneous process of crystallization with second-level resolution (millisecond-level sampling, which can distinguish rapid nucleation within 3 seconds). (2) Single signal interference is eliminated (such as film thickness fluctuations causing PL change ≠ intrinsic quality change). (3) The appearance time and intensity change of the PL peak reflect the nucleation and growth of perovskite, and the uniformity of the film is reflected by the nucleation density, thus realizing the characterization of the uniformity and crystal quality of large-area perovskite films. (4) Spatial resolution: The fiber spacing is approximately 2 mm, which is sufficient to capture micro-uniformities within the substrate at the centimeter level; (5) Label-free, non-contact monitoring, compatible with conventional process lines, mapping “interface chemistry-crystallization kinetics-device yield” one by one to form a closed-loop optimization strategy. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of a dual-channel in-situ PL measurement device used in the method of this embodiment of the invention.

[0012] Figure 2 The in-situ plasma spectral evolution of thin films deposited on substrates with plasma treatment times of 0s (left), 10s (middle), and 20s (right) in this embodiment of the invention is shown during the spin coating process.

[0013] Figure 3 This shows the plasma intensity distribution of the thin films at positions A and B in this embodiment of the invention during thermal annealing (0-120s).

[0014] Figure 4 The PL signal is used to quantify the spatial uniformity during the crystallization process in this embodiment of the invention. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments: A method for monitoring the uniformity of perovskite thin films based on multi-channel in-situ PL spectroscopy employs an apparatus comprising: multiple monochromatic excitation sources (450 nm lasers), multiple Y-shaped fiber optic transmission devices, and multiple spectrometers. The laser source at one end of the Y-shaped fiber transmits the laser light to the probe below, where it strikes the thin film. After the film emits light, it is re-received by the probe and transmitted to the other end of the Y-shaped fiber, which is connected to a long-wavelength filter. The filtered excitation light signal is then received and analyzed by the spectrometers. The multi-channel Y-shaped fiber system can simultaneously analyze multiple different locations, enabling synchronous monitoring of the perovskite crystallization kinetics at different sites.

[0016] The method for monitoring the uniformity of perovskite thin films using the above-mentioned device includes the following steps: During the formation of perovskite thin films, pulse-light (PL) signals at multiple different locations on the perovskite film are monitored simultaneously. By comparing the PL signals at different locations, the uniformity of perovskite film growth at different locations can be determined. During perovskite film formation, the PL signal at a given location reflects the nucleation and crystallization characteristics at that location. During spin coating, a stronger PL peak indicates a higher number of nuclei; the rate of PL peak rise during spin coating reflects the nucleation rate; during annealing, a stronger PL intensity indicates fewer defects. The signal intensities at different locations are processed and expressed as a percentage to reflect the similarity of the nucleation and crystallization process of the perovskite film at different times or locations, thus reflecting the film uniformity. If the number of channels is n, and the multiple signals are R1, R2, R3, ..., R... n If the average value of all signals is R, then the surface uniformity of the perovskite thin film is... U for: × 100%, when U When the content is less than 30%, it can be considered uniform. Example 1

[0017] This embodiment uses dual-channel in-situ PL spectroscopy as an example. A method for monitoring the uniformity and crystal quality of large-area perovskite thin films using dual-channel in-situ PL spectroscopy, with an apparatus such as... Figure 1 As shown, the system integrates two monochromatic excitation sources (450 nm lasers), two Y-shaped fiber optic transmission devices, and two spectrometers. The laser source at the top of the Y-shaped fiber transmits the laser light to the probe below, where it strikes a thin film. After the film emits light, it is received again by the probe and transmitted to the other end of the Y-shaped fiber. This end is connected to a long-wavelength filter, filtering the excitation light before the signal is received and analyzed by the spectrometer. The two-way Y-shaped fiber system can simultaneously analyze two different locations, allowing for synchronous monitoring of the perovskite crystallization kinetics at different sites.

[0018] The method for monitoring the uniformity of perovskite thin films using the above-mentioned device includes the following steps: During the formation of perovskite films, pulse-force (PL) signals at multiple locations on the perovskite film are monitored simultaneously. By comparing the PL signals at different locations, the uniformity of perovskite film growth at different locations can be determined. During perovskite film formation, the PL signal at a given location reflects the nucleation and crystallization characteristics at that location. During spin coating, a stronger PL peak indicates a higher number of nuclei; the rate of PL peak increase during spin coating reflects the nucleation rate; during annealing, a stronger PL intensity indicates fewer defects. The signal intensities at different locations are processed and expressed as a percentage to reflect the similarity of the nucleation and crystallization process of the perovskite film at different times or locations, thus reflecting the film uniformity. For dual-channel monitoring, the difference between the two signals (R1, R2) can be divided by the average of the two signal intensities (R) to express the percentage of the similarity of the nucleation and crystallization process at each time point, i.e., surface uniformity. U ): U = × 100%.

[0019] The perovskite wet film composition is FA 0.85 MA 0.1 Cs 0.05 The specific process for PbI3 is as follows: The ITO glass substrate was sonicated for 30 minutes in a 1:4 mixture of Decon 90 cleaner and deionized (DI) water. The ITO glass was then thoroughly cleaned with DI water and anhydrous ethanol and dried with nitrogen. It was then placed in a 60°C oven to dry for later use. Before fabricating the device, the pre-cleaned ITO glass was treated with an oxygen atmosphere (O2-plasma) for 2 minutes using a plasma cleaner (PT500, LEBO Science).

[0020] NiO prepared by spin coating method x Hole transport layer, 80 μL of NiO is dropped onto an ITO substrate. x The nanoparticle precursor solution (10 mg / ml dissolved in deionized water) was spin-coated at 2000 rpm for 30 s, and annealed at 120℃ for 15 min.

[0021] After preparing NiO x After layering, different NiO x The substrate was treated with O2-plasma for 0s, 10s, and 20s in a glove box under a nitrogen atmosphere, in NiO x 80 μL of Me-2PACz (0.35 mg / ml dissolved in IPA) was dropped onto the substrate, and the mixture was spin-coated at 4000 rpm for 30 seconds. The substrate was then annealed on a hot plate at 100°C for 5 minutes.

[0022] Perovskite absorber layers were prepared using a one-step spin-coating method. The perovskite prepared in this experiment had a composition of FA. 0.85 MA 0.1 Cs 0.05 PbI3. Dissolve 21.2 mg CsI, 237.6 mg FAI, 25.8 mg MAI, 15 mg MACl, and 830 mg PbI2 in 1 mL of DMF / DMSO (volume ratio 4:1) to obtain the perovskite precursor solution. In a glove box under nitrogen atmosphere, add 80 μL of the perovskite precursor solution to a SAM substrate. Spin-coating conditions are: initial spin speed 1800 rpm for 10 s, then spin speed 5000 rpm for 30 s. When the spin-coating reaches approximately 11 s before the countdown ends, add 150 μL of the antisolvent chlorobenzene to the wet perovskite film.

[0023] The instantaneous crystallization process is captured by dual 450nm lasers, two Y-shaped optical fibers, and two synchronous spectrometers. For example... Figure 2 As observed, during spin coating, the photoluminescence intensity increased sharply with the addition of antisolvent, indicating the elimination of solvation and the initiation of perovskite nucleation. After 10 s plasma treatment, the photoluminescence intensity of the film was significantly enhanced, indicating that the film has a high nucleation density under optimal surface coverage.

[0024] Annealing at 100℃ for 30 min, PL signals were collected at "position A" and "position B" of the sample. If the interface SAM coverage is uneven, the perovskite nucleation / crystallization kinetics are different, and the PL evolution trajectories at the two locations will differ; otherwise, it proves uniformity. Figure 3 As the annealing time increased, the PL strength of the samples treated for 0s and 20s further decreased due to the formation of stacking defects. In contrast, the samples treated for 10s showed a significant increase in PL strength during annealing from 50 to 100s, which is attributed to strong secondary crystallization, which promoted crystal growth, reduced defect density, and improved film uniformity.

[0025] Variations in photoluminescence at different locations on the thin film can reveal the coverage and uniformity of the self-assembled film on the substrate. For example... Figure 4 The results show that for 10s plasma-treated films, the minimal difference in PL evolution between measurement locations indicates highly uniform crystallization kinetics, further confirming that 10s plasma treatment of NiOx surfaces leads to the highest degree of SAM molecular homogeneity.

[0026] Dual-channel in-situ PL technology intuitively and quantitatively reveals the regulatory role of NiOx surface hydroxyl chemistry on perovskite nucleation uniformity, providing a key characterization tool and process window for constructing efficient, scalable, and high-yield perovskite photovoltaic devices.

[0027] The above are merely preferred embodiments of the present invention, provided only to enable those skilled in the art to understand and use the invention. Those skilled in the art will readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from its scope should be within the protection scope of the present invention.

Claims

1. A method for monitoring the uniformity of perovskite thin films based on multi-channel in-situ PL spectroscopy, characterized in that, Includes the following steps: During the formation of perovskite thin films, PL signals at multiple different locations on the perovskite thin film are monitored simultaneously. By comparing the PL signals at different locations, the uniformity of the growth of the perovskite thin film at different locations can be determined. In the process of perovskite thin film preparation, the crystallization evolution and uniformity changes can be analyzed in real time, dynamically and non-destructively.

2. The method for monitoring the uniformity of perovskite thin films based on multi-channel in-situ PL spectroscopy according to claim 1, characterized in that, During the formation of perovskite thin films, the PL signal at a certain location reflects the nucleation and crystallization characteristics at that location. The intensity of the detected PL signal peak reflects the number of nuclei. The stronger the peak, the more nuclei are formed. The more nuclei are formed, the greater the nucleation density, and the fewer defects are formed.

3. The method for monitoring the uniformity of perovskite thin films based on multi-channel in-situ PL spectroscopy according to claim 1 or 2, characterized in that, The signal intensity at different locations is processed to reflect the similarity of the nucleation and crystallization process of perovskite films at different times or locations as a percentage, thereby reflecting the uniformity of the film.

4. The method for monitoring the uniformity of perovskite thin films based on multi-channel in-situ PL spectroscopy according to claim 3, characterized in that, If the number of channels is n, and the multiple signals are R1, R2, R3, ..., R... n If the average value of all signals is R, then the surface uniformity of the perovskite thin film is... U for: × 100%。 5. The method for monitoring the uniformity of perovskite thin films based on multi-channel in-situ PL spectroscopy according to claim 4, characterized in that, when U If it is less than 30%, it is considered uniform.

6. The method for monitoring the uniformity of perovskite thin films based on multi-channel in-situ PL spectroscopy according to claim 1 or 2, characterized in that, The perovskite thin film was prepared by a one-step spin coating method and high-temperature annealing.

7. The method for monitoring the uniformity of perovskite thin films based on multi-channel in-situ PL spectroscopy according to claim 6, characterized in that, During spin coating, the intensity of the PL peak represents the number of nuclei formed; the rate at which the PL peak rises represents the rate of nucleation.

8. The method for monitoring the uniformity of perovskite thin films based on multi-channel in-situ PL spectroscopy according to claim 6, characterized in that, During annealing, the PL intensity can reflect the amount of defects formed; the stronger the PL peak, the fewer the defects.

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