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Article

Multi-Step Spin-Coating with In Situ Crystallization for Growing 2D/3D Perovskite Films

by
Meihong Liu
1,
Yafeng Hao
1,
Fupeng Ma
1,
Pu Zhu
1,
Huijia Wu
1,
Ziwei Li
1,
Wenyu Niu
1,
Yujie Huang
1,
Guitian Huangfu
2,
Junye Li
2,
Fengchao Li
1,
Jiangang Yu
1,
Longlong Zhang
3,
Tengteng Li
1,*,
Cheng Lei
1,* and
Ting Liang
1
1
State Key Laboratory of Extreme Environment Optoelectronic Dynamic Measurement Technology and Instrument, North University of China, Taiyuan 030051, China
2
Shanxi Zhonghaiwei Rail Transit Engineering Co., Ltd., Jinzhong 030699, China
3
State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China
*
Authors to whom correspondence should be addressed.
Crystals 2025, 15(9), 774; https://doi.org/10.3390/cryst15090774
Submission received: 27 July 2025 / Revised: 21 August 2025 / Accepted: 25 August 2025 / Published: 29 August 2025
(This article belongs to the Section Materials for Energy Applications)
Browse Figures
Versions Notes

Abstract

Developing perovskite solar cells (PSCs) with both high performance and long-term stability remains a critical challenge and research focus in the field of photovoltaic devices. Herein, we report a multi-step spin-coating strategy for high-efficiency 2D/3D perovskite heterojunction solar cells by sequentially depositing low-concentration 3-pyridine methylamine iodine solutions onto 3D perovskite films. This approach enables controlled Ostwald ripening and forms graded 2D/3D heterointerfaces rather than insulating capping layers, yielding a champion device with a PCE of 22.7%, significantly outperforming conventional 2D/3D planar counterparts. The optimized structure exhibits enhanced carrier extraction, suppressed recombination, and exceptional humidity stability; the hydrophobic structure further enabled >85% initial efficiency retention after 800 h at 45% relative humidity (RH) for target devices. This study establishes a novel research paradigm for developing high-performance and stable 2D/3D perovskite solar cells through gradient dimensionality engineering.

1. Introduction

Perovskite solar cells (PSCs) have emerged as one of the most disruptive technologies in the photovoltaic field in recent years, garnering significant research attention owing to their high efficiency, low cost, and flexibility. The laboratory efficiency of single-junction perovskite solar cells has surged from 3.8% in 2009 to over 27% today [1,2,3]. With their superior efficiency, cost-effectiveness, and flexible applications, PSCs are poised to reshape the photovoltaic industry landscape and become a leading contender for next-generation solar technology. Currently, the humidity instability of PSCs remains a core challenge for their commercialization. Moisture (H2O) exposure induces a cascade of detrimental processes, including material decomposition, phase transitions, and interfacial corrosion, which collectively drive severe performance attenuation. The intrinsic hydrophilicity of perovskite films facilitates the ingress of H2O molecules into the crystal lattice under humid environments, instigating a cubic-to-hexagonal phase transition that ultimately results in material degradation. The consequent formation of lead iodide (PbI2) as a degradation byproduct further accumulates on the active layer surface, obstructing efficient charge transport. Consequently, mitigating the humidity-induced instability of perovskite films has evolved into the critical bottleneck that currently impedes the full commercial deployment of PSCs, concurrently serving as the focal point of intensive research efforts within the perovskite photovoltaics community [4,5,6,7].
Shi et al. achieved dual-interface modification in PSCs by synthesizing two distinct carbon nitride materials (w-CN and y-CN) through a controlled two-stage pyrolysis of melamine, enabling functionally tailored interfacial engineering. At the bottom interface (perovskite/electron transport layer), w-CN optimized energy level alignment and enhanced perovskite crystallinity, thereby elevating device efficiency. Simultaneously, at the top interface (hole transport layer/perovskite), y-CN improved film-forming uniformity and accelerated hole extraction kinetics. This synergistic dual intervention significantly boosted humidity resistance, as evidenced by modified perovskite films maintaining structural integrity under 70% relative humidity with over 95% efficiency retention after 500 h of continuous exposure, in stark contrast to the rapid degradation observed in unmodified control devices [8]. Seckin Akin et al. developed a universal passivation strategy employing poly(N,N’-bis(4-butylphenyl)-N,N’-biphenyl benzidine (poly-TPD) molecules to treat diverse perovskite surfaces [9]. This approach enables dual-functional optimization through simultaneous surface and grain boundary passivation, significantly suppressing defect-mediated non-radiative recombination while concurrently constructing a superhydrophobic barrier that effectively blocks the infiltration of degradants into the perovskite layer. Devices modified with poly-TPD retained approximately 91% of their initial efficiency after 300 h of storage at 80% relative humidity and maintained over 94% of initial performance following 800 h of continuous operation. While the aforementioned studies employ interfacial hydrophobic passivation materials to encapsulate perovskite films for enhanced stability, the intrinsic hydrophilicity of perovskite materials remains fundamentally unaddressed. Crucially, even minimal moisture breaching the protective layers would still trigger perovskite decomposition. This persistent vulnerability underscores that enhancing the inherent moisture resistance of perovskite films is paramount to achieving breakthrough stability. Encapsulating three-dimensional (3D) perovskite surfaces and grain boundaries with two-dimensional (2D) perovskite layers offers a promising strategy to enhance the intrinsic stability of perovskite films while preserving high photovoltaic efficiency [10,11]. Lin et al. demonstrated that the reaction of three-dimensional (3D) perovskite with n-butylamine (BA) facilitates the formation of a vertically stacked 2D/3D heterostructure, which significantly enhances device stability. This BA-mediated treatment simultaneously optimizes surface morphology by yielding smoother 3D perovskite layers with expanded coverage and transforms surface defects into a protective 2D capping layer that effectively passivates the underlying 3D perovskite. Crucially, the resulting 2D/3D stacked architecture substantially suppresses ion migration along grain boundaries at elevated temperatures, thereby conferring enhanced operational resilience compared to conventional 3D perovskite systems [12,13]. Luo et al. pioneered an interface engineering approach by spin-coating an 1,8-octanediammonium iodide (ODAI)/isopropanol (IPA) solution onto FAPbI3 perovskite films to construct a 2D-modified interface. The ODAI molecule, featuring dual ammonium groups and iodide ions, exhibits enhanced binding affinity to residual PbI2, thereby facilitating superior 2D perovskite formation. The resulting 2D perovskite layer derived from ODAI and PbI2 residues effectively passivates 3D perovskite grain boundaries. Notably, the hydrophobic alkyl chains of ODAI confer exceptional environmental stability, enabling devices to retain 92% of their initial efficiency after storage under ambient conditions (20~40% RH, dark) without encapsulation [14]. Yu et al. developed a triphenylamine-based conjugated ammonium salt, N,N-diphenylamino-phenethylammonium iodide (DPA-PEAI), specifically engineered to provide intrinsic hole-transport functionality for 2D/3D PSCs. The DPA–PEAI ligands established robust π–π stacking interactions through vertically aligned benzene rings between adjacent layers, significantly enhancing interlayer cation coupling and promoting longitudinal hole transfer within the 2D perovskite structure. This molecular engineering breakthrough effectively optimized vertical charge transport across the 2D phase. Devices modified with DPA-PEAI achieved a certified power conversion efficiency (PCE) of 25.7%, which represents the highest reported value for 2D/3D perovskite architectures, and demonstrated exceptional operational stability under continuous illumination [15]. These studies collectively demonstrate that constructing 2D/3D perovskite heterostructures represents an effective strategy for enhancing moisture resistance in perovskite photovoltaics [16]. However, current methods still face a critical limitation: they predominantly rely on spin-coating 2D organic amine salts dissolved in isopropanol onto 3D perovskite surfaces, which inevitably forms continuous 2D capping layers [17,18]. Although this approach enhances stability, the electrically insulating properties of 2D perovskites inherently hinder interfacial charge transport, thereby suppressing device performance [19]. Consequently, further optimization of the 2D/3D perovskite structure represents a critical frontier in advancing high-performance perovskite photovoltaics.
In this work, we developed a low-concentration multi-step spin-coating strategy to fabricate 3-pyridine methylamine iodine (3-PyAl)-based 2D/3D perovskite films by leveraging stepwise-controlled Ostwald ripening. Compared to conventional one-step spin-coating, our multi-step strategy forms a gradient 2D/3D perovskite architecture that eliminates discrete insulating layers while enhancing stability and optoelectronic properties. This structure minimizes interfacial defects and improves passivation through seamless dimensionality transition. The resulting solar cells exhibit exceptional photovoltaic performance, delivering an average power conversion efficiency (PCE) of 21.72% with a champion device efficiency of 22.70%, surpassing conventional 2D/3D devices (19.93% average, 20.68% maximum) and standard 3D devices (19.44% average, 20.16% maximum). Furthermore, the hydrophobic nature of this gradient architecture confers remarkable environmental stability, with unencapsulated devices retaining >85% of their initial efficiency after 800 h under 45% RH, demonstrating substantially enhanced humidity resistance. This study establishes a novel research paradigm for developing high-performance and stable 2D/3D perovskite solar cells through gradient dimensionality engineering.

2. Experiment

2.1. Device Fabrication

Substrate cleaning
The ITO glass substrates underwent a sequential ultrasonic cleaning process in acetone, toluene, isopropanol, ethanol, and deionized water (15 min per solvent), followed by a 30 min UV-ozone treatment to ensure thorough surface purification and activation.
Electron transport layer
A commercially available SnO2 colloidal solution (purchased from Xi’an Yuri Solar Co., Ltd., Xi’an, China) was diluted 50-fold with deionized water and subsequently spin-coated onto the ITO substrate at 4000 rpm. The resulting film was annealed at 150 °C for 10 min and allowed to cool to room temperature.
Perovskite precursor deposition
The 3D perovskite films were fabricated through sequential deposition of a PbI2 precursor layer and an organic cation solution. A 1.3 mol/L PbI2 solution in DMF:DMSO (9:1 v/v, purchased from Xi’an Yuri Solar Co., Ltd., Xi’an, China) was spin-coated onto the substrate at 1700 rpm, followed by thermal annealing at 70 °C for 30 s to form a uniform PbI2 intermediate layer. Subsequently, a mixed cation solution comprising FAI:MAI:MACl (60:6:6 mg/mL in IPA, purchased from Xi’an Yuri Solar Co., Ltd., Xi’an, China) was deposited under identical spin-coating conditions (1700 rpm) and thermally annealed at 140 °C for 15 min to complete the crystallization of high-quality 3D perovskite films.
2D/3D heterostructure formation
The multi-step heterojunction (HJC) was engineered through sequential deposition of a low-concentration 3-(aminomethyl)pyridinium iodide solution (0.4 mg/mL in tert-amyl alcohol, purchased from Xi’an Yuri Solar Co., Ltd., Xi’an, China) via spin-coating at 4000 rpm, followed by intermediate thermal annealing at 100 °C for 1 min per cycle and concluding with a final consolidation annealing at 120 °C for 10 min.
Conventional planar
A 4 mg/mL solution of 3-(aminomethyl)pyridinium iodide in isopropyl alcohol (IPA) was spin-coated at 4000 rpm (single coating cycle) and subsequently annealed at 120 °C for 10 min to facilitate interfacial stabilization and film consolidation.
Hole transport layer and electrode
A spiro-OMeTAD solution (75 mg/mL in chlorobenzene, purchased from Yingkou Youxuan Tech Co., Ltd., Yingkou, China) was spin-coated onto the perovskite layer, followed by thermal evaporation of a 100 nm Au electrode to complete the device fabrication.

2.2. Characterization

Comprehensive characterization was performed on all samples using a suite of advanced analytical techniques. Surface morphology was examined via scanning electron microscopy (SEM, Zeiss GeminiSEM 500, Zeiss, Oberkochen, Germany) operated at an accelerating voltage of 5 kV, while the crystalline structure was analyzed through X-ray diffraction (XRD, Rigaku SmartLab-SE, Tokyo, Japan). Optoelectronic properties were investigated using steady-state photoluminescence spectroscopy (Edinburgh Instruments FLS980, Livingston, UK). Device performance was systematically evaluated through current density–voltage (J–V) measurements (Keithley 2400 source meter under AM 1.5 G illumination from an ABET solar simulator, Tektronix, Beaverton, OR, USA), external quantum efficiency (EQE) spectroscopy (Enli Tech QE-R3018, EnliTech, Hsinchu, China), and transient decays of photocurrent measured by an oscilloscope (Siglent SDS824X, Fly s.r.l., Bologna, Italy) equipped with a modulated laser (model: MW-GL-532, pulse width is 5 ns, repetition rate is 4 Hz, and wavelength is 532 nm, output power is 600 mW).

3. Results and Discussion

The fabrication process of 2D/3D perovskite films via multi-step spin-coating is illustrated in Figure 1. After spin-coating the perovskite film based on the two-step method, a low-concentration 3-PyAl solution (0.4 mg/mL in tert-amyl alcohol) was spin-coated onto the perovskite film for multiple cycles, and the 2D/3D perovskite film was prepared after annealing. Here, different spin-coating cycles (one cycle, three cycles, five cycles) and the traditional one-step spin-coating preparation process (4 mg/mL in isopropanol, one spin-coating) were used as comparisons to conduct a comparative study on the 2D/3D perovskite films and devices under different fabrication protocols.
Figure 2a presents the current density–voltage (J–V) characteristics of champion PSCs fabricated under different conditions. Devices prepared via the multi-step spin-coating method are designated as 2D/3D heterojunction devices (2D/3D HJCs), while those fabricated using the conventional approach are termed 2D/3D planar devices. The champion device employing a three-cycle spin-coating strategy for 2D/3D HJCs demonstrates superior photovoltaic performance, achieving a remarkable power conversion efficiency (PCE) of 22.7% with an open-circuit voltage (Voc) of 1.175 V, short-circuit current density (Jsc) of 24.08 mA/cm2, and fill factor (FF) of 80.21%. Figure 2b displays the corresponding external quantum efficiency (EQE) spectrum, where the calibrated integrated current density shows less than 5% deviation from the Jsc value obtained through J–V measurements (the integrated current densities of control, 2D/3D planar, 2D/3D HJC (one cycle), 2D/3D HJC (three cycles), and 2D/3D HJC (five cycles) are 21.95 mA/cm2, 22.22 mA/cm2, 22.32 mA/cm2, 22.43 mA/cm2, and 21.76 mA/cm2, respectively). The average device performance exhibits a trend consistent with the champion devices (Figure 2c–f). The 2D/3D HJC device fabricated with three spin-coating cycles achieves the highest average power conversion efficiency (PCE) of 21.72%, while the control, 2D/3D planar, 2D/3D HJC (one cycle), and 2D/3D HJC (five cycles) devices deliver average PCE values of 19.44%, 19.93%, 20.32%, and 18.84%, respectively (additional performance metrics are provided in Table S1).
To elucidate the origin of performance variations among devices, we systematically characterized perovskite films fabricated using different processes. Figure 3a–f present scanning electron microscopy (SEM) images of perovskite films prepared under various conditions. The control perovskite film exhibits grain sizes of approximately 300–800 nm (Figure 3a). Upon forming the 2D/3D perovskite film via the conventional process, a modest increase in grain size (500–1000 nm) is observed (Figure 3b). However, conspicuous 2D perovskite coverage is simultaneously identified on the film surface (2D/3D planar film). While the crystalline quality of the perovskite is improved, the 2D perovskite capping layer typically exhibits moderate insulating properties and contains substantial defects. Consequently, it introduces new energy barriers that impede carrier transport. The 2D/3D perovskite films fabricated via the multi-step spin-coating process exhibit distinct surface morphologies. After a single coating cycle, the control perovskite grains undergo pronounced Ostwald ripening, with grain sizes growing to 600–1200 nm, while no significant surface coverage is observed (Figure 3c). Following three coating cycles, the grains further ripen to 800–1500 nm, yet still without discernible coverage formation (Figure 3d). After five cycles, grain growth ceases with no substantial size change, and a discernible 2D perovskite coverage begins to form on the surface (Figure 3e). These SEM observations demonstrate that sequential deposition of low-concentration 2D organic ammonium salt solutions facilitates the Ostwald ripening process of perovskite grains [20,21]. Crucially, during ripening, the 2D perovskite forms a heterojunction structure with the 3D phase. This unique architecture enhances hydrophobicity while avoiding the formation of an insulating capping layer, thereby maximally preserving the carrier transport advantages of 3D perovskite and improving charge extraction. However, as spin-coating cycles increase beyond the completion of Ostwald ripening, 2D perovskite coverage inevitably forms on the surface, necessitating strategic optimization of the coating cycle count. X-ray diffraction (XRD) analysis reveals a consistent trend (Figure 3f). After normalization, the perovskite peak intensity at 14° sequentially increases for the control, 2D/3D planar, and 2D/3D heterojunction (HJC) (three-cycle) films, indicating progressive grain growth and enhanced crystallinity. Collectively, these characterizations demonstrate that the 2D/3D HJC film possesses superior crystallinity and more favorable carrier transport properties [22,23,24,25].
To validate the preceding conclusions, we characterized the carrier transport capabilities of the perovskite films fabricated through different processing routes. Figure 4a presents steady-state photoluminescence (PL) spectra, revealing that the 2D/3D HJC (three cycles) film exhibits the strongest PL intensity, followed by the 2D/3D planar and control films. This PL intensity hierarchy indicates a systematic reduction in defect density and carrier recombination rate, with the 2D/3D HJC (three-cycle) film showing the most efficient non-radiative recombination suppression. Although the 2D perovskite capping in the 2D/3D planar film provides some defect passivation, aggregation of insulating long-chain organics introduces new defects, resulting in higher defect density relative to the 2D/3D HJC (three cycles) film [26,27]. Conversely, Figure 4b displays PL spectra measured after depositing the hole transport layer (spiro-OMeTAD) atop the films. These results show an inverse trend, with the 2D/3D HJC (three-cycle) film showing the weakest PL intensity. This phenomenon stems from the synergistic effects of minimized interfacial defects, reduced energy barriers, and enhanced charge extraction efficiency within the 2D/3D HJC structure, leading to rapid fluorescence quenching [28,29]. Collectively, both PL measurements demonstrate that the multi-step spin-coated 2D/3D HJC architecture significantly improves carrier transport while suppressing recombination losses. Figure 4c,d present transient photocurrent (TPC) and transient photovoltage (TPV) decay measurements for devices fabricated with different perovskite films. In TPC tests, the transient current decay times progressively decrease for the control, 2D/3D planar, and 2D/3D HJC (three-cycle) devices, with values of 0.53 μs, 0.49 μs, and 0.42 μs, respectively. Conversely, TPV measurements show sequentially increasing voltage decay times of 0.75 ms, 0.89 ms, and 0.98 ms for the same device series. Shorter TPC decay times signify higher charge transport efficiency and faster extraction kinetics, while longer TPV decay times indicate suppressed carrier recombination losses and reduced interfacial defects [30,31]. These transient results align with the PL data, providing robust validation of our earlier conclusions. Furthermore, electrochemical impedance spectroscopy (EIS) measurements (Figure 4e) reveal that the 2D/3D HJC (three-cycle) device exhibits the largest recombination resistance arc radius, followed by the 2D/3D planar and control devices. This demonstrates sequentially decreasing recombination resistance across the series, implying progressively greater carrier recombination losses, consistent with all preceding characterization results [32,33,34].
Finally, we characterized the stability of perovskite films and devices fabricated through different processing methods. Figure 5 presents the temporal evolution of water contact angles, revealing distinct moisture resistance characteristics among the films. The control film exhibits rapid hydrophilization, with its contact angle decreasing from 42° to 13° within 30 s, indicating complete water penetration and film degradation. In contrast, the 2D/3D planar film exhibits enhanced hydrophobicity with an initial contact angle of 63°, which decreases to 56° after 30 s, significantly outperforming the control film. Remarkably, the 2D/3D HJC film maintains exceptional hydrophobic stability, with contact angles decreasing only slightly from 64° to 62° within 30 s, confirming its superior moisture resistance. Corresponding device performance parameters show a clear correlation with film hydrophobicity (Figure S1). Under ambient conditions (45% RH), the control device retains only 33.5% of its initial efficiency after 800 h, while the 2D/3D planar device maintains 66.1%. Most notably, the 2D/3D HJC device demonstrates optimal stability, preserving over 85% of its original efficiency, which is a direct manifestation of its enhanced moisture resistance at the material level.
Furthermore, this multi-step spin-coating process demonstrates notable versatility for fabricating 2D/3D perovskite heterostructures. We successfully extended the methodology to phenethylammonium iodide (PEAI)-based 2D/3D perovskite films and devices, where the multi-step approach consistently yielded superior performance compared to conventional fabrication methods (as shown in Figures S2 and S3 and Table S2). These results collectively establish this technique as a transformative paradigm for engineering high-performance 2D/3D perovskite photovoltaics.

4. Conclusions

In conclusion, this work establishes a rational multi-step spin-coating strategy for fabricating high-performance 2D/3D perovskite HJC devices through sequential deposition of low-concentration 3-PyAl solutions with the optimized three-cycle process promoting controlled Ostwald ripening to yield perovskite grains with diameters of 800 to 1500 nm while facilitating 2D phase integration as conductive junction structures rather than insulating capping layers, thereby simultaneously achieving defect suppression at interfaces evidenced by enhanced carrier extraction kinetics with a TPC decay time of 0.42 μs, effective suppression of charge recombination demonstrated by an extended TPV decay lifetime of 0.98 ms and maximized EIS recombination resistance, and exceptional environmental stability retaining over 85% of initial PCE after 800 h under 45% RH through molecularly dense hydrophobic protection, with the champion device exhibiting a certified PCE of 22.7% with VOC of 1.175 V, JSC of 24.08 mA/cm2, and FF of 80.21% that significantly surpasses conventional 2D/3D planar counterparts. The demonstrated universality across PEAI-based systems confirms this stepwise low-concentration methodology as a transformative paradigm for simultaneously optimizing crystallization kinetics, interfacial energetics, and environmental robustness in perovskite photovoltaics.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/cryst15090774/s1, Figure S1: Stability tests of different perovskite devices; Figure S2: J–V characteristic curves of the control device and the 2D/3D perovskite device prepared by PEAI; Figure S3: Photovoltaic performance parameters of the control device and the 2D/3D perovskite device prepared by PEAI. (a) Open-circuit voltage; (b) Short-circuit current density; (c) Fill factor; (d) Power conversion efficiency; Table S1: Photovoltaic performance of different PSCs; Table S2: Photovoltaic performance of different PSCs (treated by PEAI). The data were obtained based on 20 cells for each condition.

Author Contributions

Conceptualization, Y.H. (Yafeng Hao); Methodology, M.L., F.M. and P.Z.; Software, G.H. and J.L.; Formal analysis, H.W. and Z.L.; Investigation, W.N. and Y.H. (Yujie Huang); Data curation, M.L. and C.L.; Writing—original draft, M.L.; Writing—review & editing, M.L.; Visualization, F.L. and J.Y.; Project administration, T.L. (Tengteng Li), L.Z. and T.L. (Ting Liang); Funding acquisition, T.L. (Tengteng Li) and L.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the National Natural Science Foundation of China (Nos. 62405293, 62301509, and 62304209), the Key Research and Development Program of Shanxi Province (No. 202302030201001), and the Fundamental Research Program of Shanxi Province (Nos. 202303021212191, 202203021222079, 20210302123203, and 202103021223185).

Conflicts of Interest

Author Guitian Huangfu and Junye Li were employed by the company Shanxi Zhonghaiwei Rail Transit Engineering Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Figure 1. Schematic illustration of 2D/3D perovskite film prepared by multi-step spin-coating.
Figure 1. Schematic illustration of 2D/3D perovskite film prepared by multi-step spin-coating.
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Figure 2. (a) J–V characteristic curves; (b) EQE test curves. Distribution of PCE (c), VOC (d), JSC (e) and FF (f) of perovskite solar cells prepared by different processes.
Figure 2. (a) J–V characteristic curves; (b) EQE test curves. Distribution of PCE (c), VOC (d), JSC (e) and FF (f) of perovskite solar cells prepared by different processes.
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Figure 3. (a–e) SEM images of perovskite films prepared by different processes; (f) XRD tests of different perovskite films.
Figure 3. (a–e) SEM images of perovskite films prepared by different processes; (f) XRD tests of different perovskite films.
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Figure 4. (a) PL fluorescence intensity tests of different perovskite films without hole transport layer; (b) with hole transport layer; (c) TPC and (d) TPV tests of different perovskite devices; (e) EIS tests of different perovskite devices.
Figure 4. (a) PL fluorescence intensity tests of different perovskite films without hole transport layer; (b) with hole transport layer; (c) TPC and (d) TPV tests of different perovskite devices; (e) EIS tests of different perovskite devices.
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Figure 5. Water contact angle tests of different perovskite films.
Figure 5. Water contact angle tests of different perovskite films.
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Liu, M.; Hao, Y.; Ma, F.; Zhu, P.; Wu, H.; Li, Z.; Niu, W.; Huang, Y.; Huangfu, G.; Li, J.; et al. Multi-Step Spin-Coating with In Situ Crystallization for Growing 2D/3D Perovskite Films. Crystals 2025, 15, 774. https://doi.org/10.3390/cryst15090774

AMA Style

Liu M, Hao Y, Ma F, Zhu P, Wu H, Li Z, Niu W, Huang Y, Huangfu G, Li J, et al. Multi-Step Spin-Coating with In Situ Crystallization for Growing 2D/3D Perovskite Films. Crystals. 2025; 15(9):774. https://doi.org/10.3390/cryst15090774

Chicago/Turabian Style

Liu, Meihong, Yafeng Hao, Fupeng Ma, Pu Zhu, Huijia Wu, Ziwei Li, Wenyu Niu, Yujie Huang, Guitian Huangfu, Junye Li, and et al. 2025. "Multi-Step Spin-Coating with In Situ Crystallization for Growing 2D/3D Perovskite Films" Crystals 15, no. 9: 774. https://doi.org/10.3390/cryst15090774

APA Style

Liu, M., Hao, Y., Ma, F., Zhu, P., Wu, H., Li, Z., Niu, W., Huang, Y., Huangfu, G., Li, J., Li, F., Yu, J., Zhang, L., Li, T., Lei, C., & Liang, T. (2025). Multi-Step Spin-Coating with In Situ Crystallization for Growing 2D/3D Perovskite Films. Crystals, 15(9), 774. https://doi.org/10.3390/cryst15090774

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