Suppressing solvent adducts via coordination competition enables scalable perovskite photovoltaics

Abstract

Scalable coating methods are indispensable for the commercialization of perovskite photovoltaics. However, fundamental divergences in crystallization dynamics hinder the direct adaptation of spin-coating optimization strategies. Furthermore, the limited understanding of crystallization control under scalable conditions constrains the fabrication of high-quality perovskite films. Herein, we identify the solvent-precursor interaction time (τ_int) as the critical, yet previously overlooked, kinetic parameter governing film quality in scalable processes. We demonstrate the prolonged τ_int inherent to blade coating stabilizes solvent-adduct phases, increases solvent retention, and ultimately degrades film crystallinity. To resolve this, we introduce a dynamic coordination competition strategy that modulates the precursor coordination equilibrium, thereby effectively shortening τ_int and yielding high-crystallinity films with enhanced phase purity. Consequently, the blade-coated devices deliver power conversion efficiencies (PCEs) of 26.5% (0.0665 cm²) and 22.9% (728.0 cm²). Our findings provide a kinetic knob for crystallization control and establish a robust protocol for large-area manufacturing of high-quality perovskite films.

Introduction

The scalable fabrication of high-efficiency perovskite photovoltaics represents a critical step toward commercial viability^1,2. Currently, the majority of high-efficiency perovskite solar cells (PSCs) have been achieved predominantly through spin coating^3,4. This is largely attributed to pioneering advancements in precursor chemistry^5,6,7, antisolvent quenching^8,9, and interface engineering^10,11,12. These innovations together facilitate the controlled growth of high-quality perovskite films.

However, the crystallization kinetics of perovskite film formation differ fundamentally between spin coating and scalable coating processes. In spin coating process, wet-film formation is dominated by centrifugal thinning and antisolvent, which enables precise control over nucleation and crystal growth. By contrast, scalable coating techniques depend on capillary flow and natural solvent evaporation^13,14. This inherent dichotomy in fluid dynamics and film formation methods translates into distinct crystallization processes, which ultimately affect the optoelectronic properties of perovskite films. Consequently, crystallization control strategies that succeed for spin-coating systems cannot be directly applied to scalable processes. In turn, the performance of PSCs fabricated via scalable coating has not yet reached the level of aspiration‌ required for commercial deployment. Crucially, our understanding of perovskite film crystallization under scalable deposition conditions remains relatively limited. While the overarching differences in fluid dynamics are appreciated, the fundamental kinetic parameter that dictates final film quality has remained elusive.

Here, we identify the solvent-precursor interaction time (τ_int) in the wet film as the missing link. During blade coating, the slow solvent evaporation rate prolongs τ_int, stabilizing the lead halide•N-methyl-2-pyrrolidone (NMP) adduct, locking in solvent residue, and ultimately compromising film crystallinity. To overcome this bottleneck, we devise a dynamic coordination competition strategy, employing the hydroxyl-terminated molecular bis (2-hydroxyethyl) dimethylammonium chloride (2OH) that outcompetes NMP for Pb²⁺ coordination. This modulation intervention effectively displaces the adduct equilibrium, markedly shortening τ_int. This tailored approach suppresses adducts formation and reduces NMP residue, enabling the formation of high-crystallinity perovskite films with enhanced phase purity and reduced defect density. Consequently, our blade-coated devices achieve power conversion efficiencies (PCEs) of 26.5% (0.0665 cm²), 22.9% (20.8 cm²), and 22.9% (728.0 cm², certified at 22.58%), together with excellent long-term operational stability.

Results

The comparison of perovskite films prepared by spin-coating and blade coating

To evaluate crystallinity differences, we benchmarked blade-coating films against spin-coating references prepared using identical precursor formulations and annealing conditions (see experimental details in Methods). X-ray diffraction (XRD) analysis reveals that the spin-coating films exhibit significantly higher diffraction intensities than their blade-coating counterparts (Fig. 1a).

Fig. 1: The comparison of crystallization and residual-solvent content in perovskite films prepared by spin coating and blade coating.

XRD patterns of annealed (a) and intermediate (b) perovskite films from spin‑coating and blade‑coating. c LC‑MS spectra of the corresponding intermediate films. d The schematic diagram for the solvent-precursor interactions regulation strategy. XRD of blade‑coated films with and without 2OH: annealed (e) and intermediate (f). g LC‑MS spectra of the corresponding intermediate films. arb. units, arbitrary units.

To investigate the reasons behind the considerable crystallinity differences under various processing conditions, we conducted XRD analysis of the intermediate phase films (Fig. 1b). The scattering peak at 2θ = 8.26° corresponds to the PbI₂-NMP solvent phase^15,16. In intermediate wet films (following anti-solvent dripping or gas quenching but prior to annealing), the intensity of the PbI₂-NMP in the blade-coated films was markedly higher than that in the spin-coated ones, which suggests that the intensity of the solvent intermediate phase in the wet film is critical to the final film quality. Subsequently, we measured the NMP content in the intermediate phase wet films prepared by different methods using Liquid Chromatography-Mass Spectrometry (LC-MS, Fig. 1c, Supplementary Fig. 1). This quantification relies on a linear calibration establishing the correlation between integrated signal intensity and NMP concentration (Supplementary Fig. 2a). Cross-sectional SEM imaging of the annealed perovskite films reveals thicknesses of ~592 nm and ~703 nm for spin-coating and blade-coating films, respectively (Supplementary Fig. 2b). Utilization of a standardized extraction protocol ensures that these thickness discrepancies do not bias the LC-MS solvent residue analysis (see the LC-MS in Methods and Supplementary Fig. 2c). Quantitative LC–MS analysis reveals that blade-coated films retain substantially higher NMP concentrations than their spin-coated counterparts processed from the identical precursor (Supplementary Fig. 2d). This difference may arise from the prolonged solvent-precursor interaction time in blade-coating.

The solvent-precursor interaction time and solvent residue in the wet films for different processing methods are illustrated in Fig. 1d. To weaken the solvent-precursor interaction in the blade-coating process, we introduced bis(2-hydroxyethyl) dimethylammonium chloride (named 2OH) molecules into the perovskite precursor. XRD analysis was performed on annealed perovskite films prepared by blade-coating with and without 2OH molecules (Fig. 1e). The results show that the 2OH-treated perovskite films exhibited stronger crystallinity, indicating improved crystallization quality. Subsequently, we conducted XRD analysis on the intermediate phase films (Fig. 1f). The control group displayed an unfavorable PbI₂-NMP solvent phase, while the 2OH-treated wet films showed a suppressed solvent phase. This suggests that the 2OH additive effectively suppresses the interaction between PbI₂ and NMP, thereby reducing NMP residues in the intermediate phase, which in turn promotes better film crystallinity (Fig. 1g, Supplementary Fig. 2e). DFT calculations were performed to analyze the binding energy of the interactions between 2OH, PbI₂, and NMP (Supplementary Table S1). The binding energy between 2OH and PbI₂ (−2.118 eV) is significantly higher than that between PbI₂ and NMP (−1.116 eV), indicating that PbI₂ prefers to bind with 2OH molecules rather than NMP.

Notably, a coherent evidentiary chain validates τ_int as the governing variable. Prolonged solvent residence during spin-coating proves intrinsically detrimental (Supplementary Fig. 3), while gas-quenched spin-coating reproduces kinetic bottlenecks that are specifically resolved by the additive (Supplementary Fig. 4). Moreover, the catastrophic nucleation induced by antisolvent baths confirms that abrupt physical extraction is incompatible with scalable thick films (Supplementary Figs. 5–6, Supplementary Video 1–2). This establishes coordination competition as the essential resolution for kinetic regulation.

Mechanistic origin of the suppressed solvent residue in wet films

We analyzed the transition from the precursor solution to the intermediate phase wet film during the blade-coating process using In-situ Grazing Incidence X-ray Diffraction (In-situ GIXRD) measurements (Fig. 2a). In the control group (blade-coated films without any additives), a distinct PbI₂-NMP solvent peak appeared in the intermediate phase (Supplementary Fig. 7). In contrast, the 2OH-treated group did not exhibit PbI₂-NMP solvent peak at the initial stage, showing only an amorphous solvent phase. This suggests that the introduction of 2OH effectively weakens the interaction between PbI₂ and NMP.

Fig. 2: The Interactions between 2OH additives, solvents, and perovskite.

a In-situ GIXRD intensity maps of control and 2OH perovskite films during the gas quenching process. The orange circle highlights the PbI₂-NMP solvent phase. b FTIR spectra of pure PbI₂, 2OH, and the PbI₂-2OH complex. c FTIR spectra of pure FAI, 2OH, and FAI-2OH complex. d FTIR spectra of pure NMP, 2OH, PbI₂-NMP, and the PbI₂-2OH-NMP complexes. e The k³-weighted Fourier transforms in R-space of the EXAFS at the Pb L_III-edge of the PbI₂-NMP, and 2OH-PbI₂-NMP. f XRD patterns of the pure PbI₂, 2OH and the PbI₂-2OH complex (left), pure FAI, 2OH and FAI-2OH complex (right). Left panel: diamonds mark the PbI₂ (001) reflection at 12.74°, whereas circles indicate the 9.91° peak of the PbI₂–2OH one‑dimensional phase. Right panel: the bottom green trace is the simulated FAI reference, and squares denote the FAI (040) reflection at 25.69°. arb. units arbitrary units.

To further investigate how the additive alters solvent-precursor interactions, we performed Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy. Upon mixing 2OH with PbI₂, the stretching vibration peak of the OH functional group (3278 cm⁻¹) shifted to a higher wavenumber of 3398 cm⁻¹, indicating strong coordination between the OH group and Pb²⁺ (Fig. 2b). In addition, mixing 2OH with FAI induces discernible shifts in both the C = N stretching vibration of FAI and the O–H stretching vibration of 2OH, indicating an interaction between the two species (Fig. 2c). The C = O stretch in pure NMP at 1692 cm⁻¹ shifted to 1625 cm⁻¹ upon the addition of PbI₂, whereas it shifted to 1637 cm⁻¹ in the 2OH-PbI₂-NMP complex. A free NMP peak appeared at 1688 cm⁻¹ (Fig. 2d). These observations further confirm that 2OH competes with NMP for PbI₂ coordination and thereby weakens the PbI₂–NMP interaction. Tracking ʋ_C=O evolution across PbI₂:2OH ratios (500:1–5:1) reveals a concentration-dependent coordination shift (Supplementary Fig. 8 and Table S1). The additive competitively displaces NMP, progressively weakening the Pb···O = C interaction to restore the free solvent population. Notably, a distinct feature emerges at 1613 cm⁻¹ in the high-concentration regime, attributable to robust hydrogen bonding (Pb-O-H···O = C) driven by the polarization-enhanced acidity of the coordinated hydroxyl group.

To further elucidate how 2OH attenuates the coordination between PbI₂ and NMP, we collected Pb L_III-edge absorption spectra using extended X-ray absorption fine spectroscopy (EXAFS) (Fig. 2e). The peak in the R-space at approximately 2.2 Å corresponds to the Pb…O bond in the PbI₂-NMP^17,18, which shifts to 2.45 Å in the PbI₂-2OH-NMP complex, indicating an elongated Pb–O distance and confirming that 2OH effectively weakens the interaction between PbI₂ and NMP. Building on this, we performed XRD measurements to further investigate the interactions between 2OH, FAI, and PbI₂ (Fig. 2f). The peak of pure PbI₂ at 12.78° corresponds to its (001) reflection. After adding 2OH, the PbI₂ peak vanishes, and a new diffraction peak appeared at 9.97°, which is attributed to the diffraction peak of the one-dimensional perovskite structure of PbI₂-2OH. The peak of FAI at 25.56° corresponds to its (040) reflection¹⁹. The intensity of this peak increases in the presence of 2OH, suggesting that 2OH enhances the crystallinity of FAI, which may play a role in the subsequent oriented growth of the perovskite film.

To demonstrate that the OH functional group serves as a tool for 2OH to compete with NMP for coordination with PbI₂, we designed molecules without OH groups (Tetramethylammonium chloride, 0OH) and molecules with reduced OH number (Choline chloride, 1OH). The chemical structures of these three molecules are illustrated in Supplementary Fig. 9. To investigate the influence of additives with varying numbers of OH groups on the interaction between the solvent and the precursor, we monitored the precursor solution to the intermediate phase transition using in-situ GIXRD (Fig. 3a). In the control group, the PbI₂-NMP solvent phase emerged at 32 s, while in the 0OH group, it appeared slightly earlier (30 s). By contrast, the PbI₂-NMP peak was progressively delayed in the 1OH groups, and was not detected within the observation window for the 2OH group. These results indicate that OH-terminated molecules effectively compete with NMP for PbI₂ coordination, and that the coordination ability strengthens as the number of OH groups increases.

Fig. 3: The Interactions among additives with varying numbers of hydroxyl groups, the solvents, and the perovskite.

a In-situ GIXRD intensity maps of control, 0OH, 1OH, 2OH perovskite films during the gas quenching process. FTIR spectra of pure 0OH, 1OH, 2OH, and their interaction with PbI₂ (b), FAI (c) and PbI₂-NMP (d). e XPS spectra of Pb 4 f for the control, 0OH, 1OH, 2OH films. f XRD patterns of the pure PbI₂, and the PbI₂-xOH complex (left), pure FAI and FAI-xOH complex (right). Left panel: Diamonds denote the PbI₂ (001) reflection at 12.74°, whereas circles at 10.54°, 10.19°, and 9.91° mark the one‑dimensional PbI₂–0OH, PbI₂–1OH, and PbI₂–2OH phases, respectively. Right panel: the bottom green trace is the simulated FAI reference, and squares denote the FAI (040) reflection at 25.69°. a.u., arbitrary units. g Corresponding PL intensity maps for the Control, 0OH, 1OH, and 2OH perovskite films. arb. units arbitrary units.

To compare the strength of interactions between molecules with varying numbers of OH groups and the solute/solvent, as well as their impact on the PbI₂-NMP interaction, we conducted FTIR measurements. For the neat additives, the C-N stretching vibration of 0OH is located at 950 cm⁻¹, while the O-H stretching vibrations of 1OH and 2OH appear at 3149 cm⁻¹ and 3170 cm⁻¹, respectively. Upon coordination with PbI₂, these peaks shift to 947 cm⁻¹, 3250 cm⁻¹, and 3499 cm⁻¹, respectively, indicating a progressive enhancement in coordination ability with PbI₂ as the number of OH groups increases (Fig. 3b). A similar trend is observed with FAI. The C = N stretching vibration of FAI in 0OH, 1OH, and 2OH shifted from 1699 cm⁻¹ to 1701 cm⁻¹, 1705 cm⁻¹, and 1710 cm⁻¹, respectively, while the N–H stretching vibration shifted from 3455 cm⁻¹ to 3456 cm⁻¹, 3462 cm⁻¹, and 3465 cm⁻¹, respectively. These systematic shifts further demonstrate that, with the increasing number of OH groups, the coordination ability with both PbI₂ and FAI is also enhanced. (Fig. 3c).

Furthermore, the C = O stretching vibration peak of PbI₂-NMP at 1625 cm⁻¹ shifts to 1626 cm⁻¹ (PbI₂-0OH-NMP), 1633 cm⁻¹ (PbI₂-1OH-NMP), and 1636 cm⁻¹ (PbI₂-2OH-NMP) upon the introduction of additives with varying numbers of OH groups (Fig. 3d). These shifts indicate that, as the number of OH groups increases, the stronger additive–PbI₂ coordination progressively weakens the PbI₂–NMP interaction. The full FTIR spectra of ternary PbI₂-xOH-NMP are shown in Supplementary Fig. 10a–c. This conclusion is further corroborated by the EXAFS spectra. The Pb-O atomic distances at the Pb L_III-edge for PbI₂-NMP, 0OH-PbI₂-NMP, 1OH-PbI₂-NMP, and 2OH-PbI₂-NMP (Supplementary Fig. 11) are 2.18 Å, 2.19 Å, 2.32 Å, and 2.42 Å, respectively. These results indicate that, as the number of OH groups increases, the Pb-O bond length gradually elongates, thereby weakening the interaction between PbI₂ and NMP. The density functional theory (DFT) calculations optimized structures of various molecular systems and their corresponding binding energies, as shown in Supplementary Fig. 12 and Supplementary Table 2, further support this conclusion.

Additionally, X‑ray photoelectron spectroscopy (XPS) corroborates the enhanced coordination imparted by the OH functional groups. The Pb 4 f binding energy shifts to higher binding energies as the number of OH groups increases, further supporting the notion of stronger coordination between the OH groups and PbI₂ (Fig. 3e). Moreover, the XPS spectra of I 3 d and N 1 s (Supplementary Fig. 13a–b) reveal enhanced coordination with FAI as the number of OH groups increases. Taken together, these results provide compelling evidence that the introduction of OH-containing molecules outcompetes NMP for coordination with PbI₂, thereby weakening the interaction between PbI₂ and NMP.

To further elucidate the interactions between molecules with varying numbers of OH groups, PbI₂, and FAI, we performed XRD analysis. Upon mixing PbI₂ with 0OH, peaks appeared at 12.75° and 10.56°, assigned to the (001) plane of PbI₂ and the one-dimensional structure of PbI₂-0OH, respectively (Fig. 3f). When mixed with 1OH/2OH, peaks appeared at 9.56° and 9.45°, characteristic of the corresponding one-dimensional structures of PbI₂-1OH/2OH phases²⁰. Additionally, the original PbI₂ peak disappears, indicating that the presence of OH-containing molecules strengthens the interaction with PbI₂. When FAI is mixed with 1OH or 2OH, the intensity of the FAI (040) reflection increases, indicating that OH-containing molecules enhance the crystallinity of FAI. Interestingly, in the FAPbI₃-xOH complexes, FAPbI₃-0OH exhibited a weak peak at 10.56° (PbI₂-0OH one-dimensional perovskite peak), while a pronounced peak at 11.9° corresponded to δ-FAPbI₃ (Supplementary Fig. 14a)²¹. By contrast, the peaks at 6.47° and 6.65° identify the one-dimensional PbI₂-1OH and PbI₂-2OH phases, respectively. Notably, the δ-FAPbI₃ peak at 11.9° significantly decreased (Supplementary Fig. 14b–c). These results suggest that OH-containing molecules preferentially interact with PbI₂, forming complexes that delay the reaction between FAI and PbI₂. FTIR further confirms the interactions between xOH and FAI/PbI₂. For the 0OH molecule, it shows negligible interaction with either PbI₂ or FAI (Supplementary Fig. 15a), whereas 1OH and 2OH molecules exhibit interactions with both species (Supplementary Fig. 15b–c). These observations provide additional evidence for the role of OH-containing molecules in preferentially forming intermediate complexes that delay the reaction between FAI and PbI₂, thus influencing the crystallization process.

LC-MS analysis of the intermediate phase wet films after gas quenching (Supplementary Fig. 16) indicated that the residual NMP content falls steadily as the number of introduced OH groups increases. This suggests that the introduction of OH-containing molecules weakens the interaction between PbI₂ and the solvent, thereby reducing solvent residue and setting the stage for higher-quality perovskite film formation.

To confirm how this modulation strategy translates into the perovskite film quality, we conducted spatially resolved photoluminescence mapping (PL mapping) tests (Fig. 3g). Consistent with the LC-MS results, the PL intensity becomes progressively higher as the number of OH groups increases, signaling the reduced non-radiative recombination and improved crystallinity of the perovskite films, which also correlates with the weaker interaction between PbI₂ and NMP. Subsequently, we performed in-situ GIXRD measurements to monitor the perovskite crystallization process (Supplementary Fig. 17a–d). The peaks at 11.9° and 14.2° correspond to the δ phase and α-phase of FAPbI₃²², respectively. The evolution of the α and δ phases of perovskite films with different OH additives over time is shown in Supplementary Fig. 17e. Compared to the other samples, the δ-FAPbI₃ phase in the 0OH sample decays most slowly, with its conversion to α-FAPbI₃ proceeding at the slowest rate and exhibiting the weakest diffraction peak intensity. As the number of OH groups increased, the conversion rate to α-FAPbI₃ accelerated and amplified the intensity of α phase. This suggests that the progressively weakened solvent-solute interaction promotes more efficient conversion to the α-FAPbI₃ phase and higher film crystallinity.

Device performance and stability

We fabricated devices with an ITO/NiOx/2-(pyren-1-yl)ethyl) phosphonic acid (Py3)/ Cs_0.02FA_0.98PbI₃/LiF/C₆₀/BCP/Ag structure using the blade-coating configuration detailed in Supplementary Fig. 18 and Supplementary Video 3, and assessed their performance using additives with varying numbers of OH groups. Relative to the control one, the devices with 0OH molecules exhibited a slight decrease in performance, whereas those with 1OH/2OH additives showed significant improvements, primarily due to enhanced fill factor (FF) and open-circuit voltage (V_OC) (Supplementary Fig. 19, Table S3). We also optimized the concentration of 2OH molecules, with the optimal concentration determined to be 0.3% mol (Supplementary Fig. 20, Table S4). As shown in Fig. 4a, the J-V curves show that the highest PCE for the control device is 25.3% (V_OC = 1.15 V, J_SC = 26.2 mA/cm², FF = 84.0%), while the 2OH device achieves a PCE of 26.5% (V_OC = 1.18 V, J_SC = 26.3 mA/cm², FF = 85.5%). The stabilized PCE for the control and 2OH devices is 25.2% and 26.2%, respectively (Fig. 4b). The integrated current density (J_SC) values derived from the EQE spectra were 25.1 mA/cm² for the control and 25.4 mA/cm² for the 2OH treated PSCs, which match well with the J-V measurement (Supplementary Fig. 21). Figure 4c presents the statistical comparison of PCE for 15 devices under each condition, further highlighting the significant improvements in both FF and V_OC upon the addition of the 2OH (Supplementary Fig. 22). Extending the strategy to triple-cation and mixed-halide compositions (Supplementary Figs. 23, 24), alongside alternative 2-pyrrolidone solvent systems (Supplementary Fig. 25), yields consistent performance enhancements that validate its broad applicability.

Fig. 4: The effect of 2OH on the performance and stability of PSCs.

J–V curves (a) and the steady-state power output (SPO) (b) of perovskite solar cell devices fabricated with and without 2OH. The inset shows the detailed photovoltaic parameters. c PCE distribution of perovskite solar cells with and without 2OH. d I–V curves of the champion perovskite mini-modules (aperture area: 20.8 cm²) for control and 2OH treated devices. Inset, a photograph of the mini-module. e I–V curves of the champion 30 × 30 cm sub-module (aperture area: 728.0 cm²) with 52 series-connected subcells under reverse and forward scans. Inset, a photograph of a 30 × 30 cm sub-module. f MPP tracking of perovskite devices fabricated with and without 2OH under continuous one-sun light soaking at ~50 °C.

To evaluate the scalability, we fabricated perovskite mini-modules with an active area of 20.8 cm² featuring precise laser-scribed interconnects with a total dead-area width of approximately 280 µm (Supplementary Fig. 26a). Electroluminescence (EL) mapping captures the contrast in macroscopic homogeneity; the unmodified blade-coated module exhibits subdued, speckled luminescence indicative of widespread non-radiative defects, whereas the 2OH-treated counterpart displays a consistently bright and uniform emission profile (Supplementary Fig. 26b). Infrared thermography (IRT) under forward bias further distinguishes the electrical integrity. Distinct localized hot spots revealing low-resistance shunt paths in the control are effectively eliminated in the modified module, which maintains a homogeneous thermal distribution (Supplementary Fig. 26c).

Furthermore, statistical analysis of ten mini-modules (20.8 cm²) substantiates scalability, where 2OH-modified devices achieve 22.6 ± 0.8% efficiency versus the 20.9 ± 1.0% for control (Supplementary Fig. 27). The champion PCE of modules was improved from 21.5% to 22.9% (Fig. 4d and Supplementary Table 5). We next translated the strategy to a pre‑pilot sub‑module (30 × 30 cm², an aperture area of 728.0 cm²), which yielded a PCE of 22.9% under reverse scan and 21.9% under forward scan (Fig. 4e and Supplementary Table 6). A record certified PCE of 22.58% was also achieved (Supplementary Fig. 28), demonstrating the suitability of this strategy for commercial‑scale production. A statistical summary of efficiencies across scalable fabrication methods is presented in Supplementary Fig. 29 (Supplementary Tables 7, 8). Our method achieved champion PCEs of 26.5% for small-area cells, 22.9% for 20.8 cm² mini-modules, and 22.9% for 728.0 cm² sub-modules, surpassing state-of-the-art benchmarks for blade- and slot-die coating. These results reveal the efficacy of our strategy for scalable manufacturing.

To elucidate the origins of the improved V_OC and FF afforded by the 2OH additive, we first conducted current-flow microscopy (CFM) characterization. CFM maps revealed an increase in surface current after 2OH treatment, suggesting a reduction in defect state density (Supplementary Fig. 30a,c)²³. We further measured the surface potential of the perovskite films using Kelvin Probe Force Microscopy (KPFM). After 2OH treatment, the films exhibited a reduced surface contact potential difference, indicating an increased work function and a more p-type surface (Supplementary Fig. 30b,d)²⁴. This result is consistent with the UPS data, which showed a better alignment of the energy levels, facilitating efficient charge transfer and improving the overall FF (Supplementary Fig. 31a–b). Furthermore, the perovskite films treated with 2OH displayed enhanced photoluminescence (PL) intensity and longer transient photoluminescence (TRPL) carrier lifetimes, indicating a reduction in defect state density and non-radiative recombination, as well as an overall improved film quality (Supplementary Fig. 31c–d)⁵.

The charge transfer and recombination dynamics in the PSCs were investigated using transient photocurrent (TPC) and transient photovoltage (TPV) measurements. The observed reduction in TPC photocurrent decay time and the extension of TPV decay time further confirm efficient carrier extraction and reduced recombination (Supplementary Fig. 32a–b)²⁵. A smaller energy disorder (E_U = 12.07 meV) was observed in the devices with 2OH, compared to the control devices (E_U = 14.05 meV). This indicates that the introduction of 2OH effectively reduced energy disorder and mitigated the energy loss associated with the reduction of the V_OC deficit (Supplementary Fig. 32c)²⁶. Additionally, the overall saturation dark current of the devices decreased, as evidenced by the dark J-V curve, which suggests a reduction in shallow energy level defects (Supplementary Fig. 32d)³. The plot of V_OC versus the logarithm of light intensity is shown in Supplementary Fig. 32e. The deviation of the slope from unity (kT/q) suggests trap-assisted recombination in the solar cells, where k is the Boltzmann constant, T is the absolute temperature, and q denotes the elementary charge. The slope for the 2OH-based device is 1.31 kT/q, significantly smaller than the slope of 1.58 kT/q for the control device. This indicates that defect-assisted charge recombination is substantially reduced²⁷. Moreover, the lower trap density of states (tDOS) characterization revealed a lower trap density across the energy range (0.30–0.49 eV) (Supplementary Fig. 32f), which is expected to minimise nonradiative recombination and voltage deficit²⁸.

Finally, we evaluated the stability of small-area devices under continuous 1 sun illumination while tracking the maximum power point (MPP). After 920 h, the PCE of the control devices decreased to 80% of their initial efficiency, while the 2OH devices maintained 92% (Fig. 4f). The devices at 85 °C thermal stress (ISOS-D-2 protocol) was also performed. The 2OH treated devices maintained over 92% of their initial efficiency after 550 h, whereas the device based on control remained only 85% (Supplementary Fig. 33). The enhanced stability may be attributed to the reduced NMP residue and improved crystallinity in the 2OH perovskite films.

Discussion

We identify the prolonged solvent-precursor contact interaction time (τ_int) as a fundamental bottleneck limiting the performance of scalable blade coating devices, and present a crystallization strategy that circumvents this limitation, enabling scalable production of highly crystalline α-FAPbI₃ films. This strategy involves introducing hydroxyl-terminated molecules into the precursor, which they preferentially coordinate with Pb²⁺, displace the coordinating solvent, and effectively shorten the τ_int. This modulation suppresses the formation of undesired solvent intermediate phases within our observational window and reduces the solvent residue, yielding perovskite films with superior crystallinity, high phase purity, and low trap densities. By offering a simple and manufacturing-compatible solution, this strategy establishes a practical pathway toward the scalable, cost-effective production of high-performance perovskite photovoltaics and paves the way for their commercial deployment across a wide range of applications.

Methods

Materials

All materials used in this work were obtained commercially and used without further purification unless otherwise specified. The transparent ITO glass substrates (ITO, 10 Ω per square, transmittance 88%) were purchased from Shenzhen Huayu United Technology Co., Ltd. The perovskite raw materials including lead iodide (PbI₂, purity 99.999%), cesium iodide (CsI, purity 99.999%), formamidinium iodide (FAI, purity 99.99%), methylammonium chloride (MACl, purity 99.9%), lithium fluoride (LiF, purity 99.99%) and C₆₀ (purity 99.9%) were all purchased from Advanced Election Technology Co., Ltd. Bathocuproine (BCP, purity 99%), Piperazine Dihydriodide (PDI, purity 99.5%), Propylammonium chloride (PACl, purity 99.8%) and 1,8-Octanediamine dihydriodide (ODADI, purity 99%) were purchased from Xi’an Polymer Light Technology Corp. Inc. L-α-phosphatidylcholine (LP, purity 99%) was obtained from Shanghai Macklin Biochemical Technology Co., Ltd. The NiOx nanoparticles (~10 nm diameter) were sourced from Advanced Election Technology. We employed in-house synthesized (2-(pyren-1-yl)ethyl)phosphonic acid (Py3) as the hole selective contact material³. The required solvent including N, N-Dimethylformamide (DMF, extra dry, purity 99.8%), dimethyl sulfoxide (DMSO, anhydrous, ≥99.9%), isopropanol (IPA, extra dry, purity 99.5%), methanol (extra dry, purity 99.8%), 2-methoxyethanol (2-ME, extra dry, purity 99.9%), N-Methyl-2-pyrrolidone (NMP, extra dry, purity 99.9%), isopropanol (IPA, extra dry, purity 99.5%), 2-pyrrolidone (PDI, purity 99%) and silver (Ag, purity 99.99%) were purchased from Sigma-Aldrich Inc.

Preparation of perovskite precursors and films

For the preparation of perovskite films with a composition Cs_0.02FA_0.98PbI₃, 1.65 M perovskite precursor solution was prepared by dissolving FAPbI₃ and CsPbI₃ powder in mixed solvent of 2-Me and NMP at volume ratio 10:1. Additional, 10 mol% PACl and 15 mol% MACl, 2 mg/mL LP and 0.2 mg/mL ODADI were added to the precursor solution as additives. Then, the filtered perovskite precursor was blade-coated onto the substrates with a gap of 140 μm at a coating speed of 25 mm/s under dry air quenching. The blade-coating processes were performed under ambient conditions (25 ± 1 °C) with controlled humidity (~30%). The wet perovskite films were then transferred onto a hot plate and annealed at 130 °C for 5 min in air.

For the preparation of perovskite films with a composition MA_0.05Cs_0.02FA_0.93PbI₃, 1.65 M perovskite precursor solution was prepared by dissolving MAI, FAPbI₃ and CsPbI₃ powder in mixed solvent of 2-Me and NMP at volume ratio 10:1. Additional 10 mol% PACl and 15 mol% MACl, 2 mg/mL LP and 0.2 mg/mL ODADI were added to the precursor solution as additives. Then the filtered perovskite precursor was blade-coated onto the substrates with a gap of 140 μm at a coating speed of 25 mm/s under dry air quenching. The blade-coating processes were performed under ambient conditions with controlled humidity (~30%). The wet perovskite films were then transferred onto a hot plate and annealed at 130 °C for 5 min in air.

For the preparation of perovskite films with a composition (Cs_0.02FA_0.98PbI₃)_0.98(MAPbBr₃)_0.02, 1.65 M perovskite precursor solution was prepared by dissolving FAPbI₃, CsPbI₃ and MAPbBr₃ powder in mixed solvent of 2-Me and NMP at volume ratio 10:1. Additional 10 mol% PACl and 15 mol% MACl, 2 mg/mL LP and 0.2 mg/mL ODADI were added to the precursor solution as additives. Then the filtered perovskite precursor was blade-coated onto the substrates with a gap of 140 μm at a coating speed of 25 mm/s under dry air quenching. The blade-coating processes were performed under ambient conditions with controlled humidity (~30%). The wet perovskite films were then transferred onto a hot plate and annealed at 130 °C for 5 min in air.

For the preparation of perovskite films with a composition Cs_0.02FA_0.98PbI₃, 1.65 M perovskite precursor solution was prepared by dissolving FAPbI₃ and CsPbI₃ powder in mixed solvent of 2-Me and PDI at volume ratio 12:1. Additional, 10 mol% PACl and 15 mol% MACl, 2 mg/mL LP and 0.2 mg/mL ODADI were added to the precursor solution as additives. Then, the filtered perovskite precursor was blade-coated onto the substrates with a gap of 140 μm at a coating speed of 25 mm/s under dry air quenching. The blade-coating processes were performed under ambient conditions with controlled humidity (~30%). The wet perovskite films were then transferred onto a hot plate and annealed at 130 °C for 5 min in air.

Fabrication of perovskite solar cells by blade-coating

The pre-patterned ITO glass substrates were cleaned by sequentially washing with detergent, deionized water, acetone, and isopropanol (IPA), followed by drying with a pure nitrogen flow. Before use, the ITO was cleaned with ultraviolet ozone for 20 min. Then the substrate was spin-coated with a thin layer of NiOx nanoparticle film (20 mg/ml NiOx water solution) at 1500 rpm for 30 s, and annealed in ambient air at 125 °C for 10 min. 0.5 mg/ml Py3 in mixed solvent of methanol and DMF at a volume ratio 2:1 was deposited on the NiOx at 3000 rpm for 40 s. Afterwards, the film was annealed at 115 °C for 20 min. After cooling down to room temperature, perovskite films were coated on these layers following the above-mentioned method. For the surface passivation layer, PDI was dissolved in isopropyl alcohol (IPA) to form a saturated solution. The PDI solution was spin-coated on top of the as-prepared perovskite at 5000 rpm for 30 s, and then transferred to the hotplate and annealed at 100 °C for 5 min. After cooling down to room-temperature, the whole device was transferred to a vacuum chamber under a base pressure of <5.0 × 10⁻⁶ Pa. 0.6 nm LiF at a rate of 0.1 Å/s, 30 nm C₆₀ at a rate of 0.3 Å/s and 6 nm BCP at a rate of 0.1 Å/s were thermally evaporated on the perovskite thin film sequentially (Angstrom Engineering Inc, Beijing technol science co., ltd.) respectively, without breaking vacuum. Finally, a 120 nm thick Ag electrode at a rate of 1.5 Å/s was deposited to complete the devices for current density-voltage (J-V) measurements.

Fabrication of perovskite solar cells by spin-coating

The perovskite precursor solution was prepared using the composition detailed previously, dissolved in a 10:1 (v/v) solvent mixture of DMF and NMP, and stirred overnight. The preparation of the NiO_X and Py3 based SAM layers follows the aforementioned procedures. The filtered perovskite precursor solution was spin-coated onto the prepared substrate at 4000 rpm for 40 seconds. During the spinning process, 150 µL of ethyl acetate (EA) was rapidly dispensed as an anti-solvent at the 20 s during the spinning step. Subsequently, the film was annealed at 130 °C for 5 min. To complete the device, the remaining functional layers were then deposited using the methodologies described above.

Experimental groups definition

In this study, the intermediate phase films/wet films are defined as the films immediately after antisolvent/gas-quenching activation but prior to the thermal annealing. The Control group refers to perovskite devices/films fabricated via the blade-coating process without any additives.

Fabrication of blade-coated perovskite solar modules

Mini-modules (20.8 cm²) with ten subcells connected in series were fabricated on ITO glass with a size of 6.5 × 8.0 cm². The series interconnection of the module was realized by P1, P2 and P3 lines, which were patterned using a laser scribing system (HANSPV PV-HL0303) with a wavelength of 532 nm, a power of 30 W and pulse width of 15 ps. The ITO substrate was pre-patterned for P1 (18 μm wide) at 7.5% laser power and a speed of 300 mm/s with a frequency of 269 kHz. The following steps were the same as the fabrication of small-area PSCs. For the preparation of Cs_0.02FA_0.98PbI₃ thin film, the precursor concentration is 1.45 M. Additional 10 mol% PACl and 15 mol% MACl, 2 mg/mL LP, and 0.2 mg/mL ODADI were added to the precursor solution as additives. The perovskite precursor solution was then blade-coated on the substrate at 15 mm/s with the blade gap of 180 μm under dry air quenching. The films were annealed at 130 °C for 5 min. The blade-coating processes were performed under ambient conditions with controlled humidity (~30%). The passivation layer, LiF (0.6 nm), C₆₀ (40 nm), BCP layer (6 nm) were prepared by the same method as listed above. The P2 lines (48 μm wide) were patterned with 1.6% laser power at a speed of 500 mm/s and frequency of 500 kHz. After Ag electrode (120 nm) was deposited, the P3 lines (37 μm wide) were patterned with an average laser power of 2.8% at a speed of 500 mm/s and frequency of 500 kHz. The distance between the P1 and P3 lines is about 280 μm, the width of a single sub-cell (including dead area) is about 5.2 mm. the geometric fill factor is around 97.5%.

Device characterization

J-V characteristics of small-area photovoltaic cells were taken using a Keithley 2400 source measure unit under a simulated AM 1.5 G illumination from an SS-X100R solar simulator (Enli Technology). The illumination light was calibrated to 100 mW/cm² AM 1.5 G using a silicon reference cell (Enli Technology). Typically, the devices were measured in reverse scan (1.20 V → 0 V, step 0.02 V). All the devices were measured without pre-conditioning, such as light-soaking, and a bias voltage was applied. Steady-state power conversion efficiency was calculated by measuring stabilized photocurrent density under a constant bias voltage. A black metal mask (0.0665 cm²) was applied to define the testing area of PSCs.

Large area mini-modules were measured using an Oriel solar simulator equipped with a Keithley 2400 source meter at a light intensity of 100 mA/cm², calibrated using a Si reference solar cell (Newport). PSMs were measured in forward and reverse scan modes with a bias voltage from 0 to 12 V at a scanning step of 50 mV and a delay time of 200 ms.

External quantum efficiencies (EQEs) were measured using an integrated system (Enlitech Technology) and a lock-in amplifier with a current preamplifier under short-circuit conditions.

Device stability tests

The stability test following the ISOS-L-2 protocol was conducted with continuous heating at ~50 °C and under continuous AM 1.5 G illumination (100 mW/cm², white LED) at open-circuit condition. The PCEs of the devices were tracked over time, and the J-V measurements were performed after cooling the devices down to room temperature. The maximum power point tracking (MPPT) of the devices was conducted under AM 1.5 G illumination at ~50 °C. The voltage at the maximum power point was automatically adjusted and applied, and the power output of the devices was tracked over time. For the temperature control, we employed the Solar Cell Stability Test System PR-SCCS-C24Q from PURI Materials, in which the devices were placed on a heating stage, with a temperature detector attached and connected to an external proportional-integral-derivative (PID) controller. The stability test following the ISOS-D-2 protocol was conducted in the nitrogen atmosphere with continuous heating at ~85 °C at open-circuit condition for the unencapsulated devices. For all the stability measurements, the films were then transferred to the atomic layer deposition (ALD) system for SnO₂ layer deposition to replace the BCP layer.

Materials characterization

X-Ray Diffractometer (XRD): To evaluate the diffraction intensity of the intermediate solvate phase and crystallinity of perovskite films, perovskite layers were deposited on NiOx/SAM substrates following the spin- and blade-coating protocols described above based on the exact same DMF/NMP (10:1) precursor formulation. X-ray diffraction patterns were acquired upon antisolvent or gas quenching to capture the characteristic solvate peaks in the as-cast films and the crystallinity of the annealing films. The signals were collected in reflection mode at room temperature on a D8 advance diffractometer equipped with a 1D LynxEye detector using monochromated Cu-Ka (λ = 1.5418 Å) radiation. Prior to XRD analysis, all samples were positioned at the same height, aligned with the edge of the holder’s top surface. The samples were subjected to a spin rate of 10 r/min to ensure averaged results.

Liquid chromatography-mass spectrometry (LC-MS): The NMP content in the perovskite wet films and annealed films was semi-quantified using an ultra-performance liquid chromatography (UPLC) system. Three substrates were placed into a 20 mL brown vial, followed by the addition of 2 mL of ACN. The perovskite films were detached from the ITO substrates through ultrasonic exfoliation and subsequently dissolved in ACN for UPLC analysis. All samples were prepared at a concentration of 1 mg/mL. The perovskite wet film samples were diluted 100 times prior to injection. Quantification analysis of NMP was carried out by an ultra-performance liquid chromatography instrument (ACQUITY UPLC, H-Class, Waters) coupled with a photodiode array detector (PDA) with BEH T3 column (1.8 μm, 2.1*100 mm, Waters). The mobile phase A is a water solution (0.1% formic acid, v/v) and mobile phase B is acetonitrile. The initial mobile phase is 20% B, increasing to 100% B in 2 min and maintaining for 2 min later. The post running time is 3.0 min. The elution is performed at 40 °C with a flow rate of 0.4 mL/min. Single PDA channels at 330 nm were used for NMP. All data were collected and processed with Empower 3 software.

In-situ Grazing-incidence X-ray diffraction (In-situ GIXRD): The measurement was performed using a Bruker D8 Venture device. The samples were illuminated with a Cu Kα radiation source (λ  =  1.5418 Å) at an incident angle of 0.2°. The scattered X-rays were detected using a Dectris Pilatus 2 M photon-counting detector. To record the gas quenching and annealing process of the perovskite films, the perovskite precursor was first dipped onto the ITO substrate. Wet perovskite precursor films were then mounted on an in situ heating holder at 130 °C and observed with a microscope (DM2500P, Leica) equipped with a hot stage (LTSE420, Linkam) and a camera (MicroPublisher 5.0 RTV, QImaging).

Fourier Transform infrared spectroscopy (FTIR): For FTIR measurements, samples without NMP were dissolved in a mixed solvent of 2-Me and NMP at a volume ratio of 1:2. The resulting solutions were then deposited onto high-resistance silicon substrates and dried at 130 °C in a nitrogen glove box to remove the solvent before measurements. For samples containing NMP, the solution was spin-coated onto high-resistance silicon substrates and annealed at 80 °C for 1 min before analysis. The FTIR spectra were collected at room temperature by an FTIR spectrometer (ThermoFisher Nicolet iS50) equipped with a DTGS KBr detector. Spectral resolution was set to 1 cm⁻¹, aperture to 4 mm, and spectra were acquired by averaging 64 scans.

The XAFS spectra at the Pb L_III-edge were characterized using a Rapid 2 M instrument (Anhui Absorption Spectroscopy Analysis Instrument Co., Ltd.), equipped with a double Si (111) monochromator to monochromatize the X-ray white beam. Fourier-transformed radial distribution functions of k³-weighted Pb L_III-edge EXAFS spectra (k³χ(k)) were obtained in the k range of 3.0 to 9.0 Å⁻¹ using a standard XAFS data analysis protocol. Energy calibration was performed with a Pb foil reference, and data processing and analysis were carried out using the Athena package.

Photoluminescence (PL) mapping: The measurement was performed using an alpha 300 R (WITec GMBH, Germany) confocal Raman system. A diode-pumped solid-state laser (532 nm, cobalt laser) was focused on samples with a diffraction-limited beam size of 590 nm by a 50x long-focus objective (NA = 0.55). The collected PL signal was dispersed using a UHTS 600 mm spectrometer and detected using an electron-magnified charge-coupled-device (EMCCD) thermoelectrically cooled to −60 °C. Ultrafast PL imaging comprised a 200 nm step size and 10 ms integration time.

High-resolution X-ray photoelectron spectroscopy (XPS): The samples were loaded into the XPS instrument (ThermoFisher ESCALAB Xi + ), and an Al Kα (1486.6 eV) X-ray was used as the excitation source. For the ultraviolet photoelectron spectroscopy (UPS) measurements, a He discharge lamp, emitting ultraviolet energy at 21.2 eV, was used for excitation. All UPS measurements were performed using standard procedures with a −10 V bias applied between the samples and detectors. Clean gold was used as a reference.

Atomic force microscope (AFM) and its variants: For the AFM, conductive atomic force microscope (c-AFM) and Kelvin probe force microscope (KPFM) measurements of the Control and 2OH-based blade-coating perovskite films. The as-prepared samples were subsequently sent out for the c-AFM and KPFM measurements using the Jupiter XR Oxford Instruments. For all c-AFM measurements, a bias of 400 mV was applied.

Time-resolved photoluminescence (TRPL): For TRPL measurements, the perovskite layers were deposited onto the functional layers using the method indicated above. The sample was excited with a picosecond-pulsed diode laser (Pico-quant LDH 450), with a ∼70 ps pulse width and 20 MHz repetition rate, focused on the sample with a 100x objective (NA = 0.90). The photoluminescence signal was acquired through the TCSPC strobelock system. The total instrument response function (IRF) for the photoluminescence decay was less than 200 ps, and the temporal resolution was less than 30 ps. The energy density of the laser for TRPL measurements was set to be 26.46 nJ/cm².

Transient photovoltage (TPV) and transient photocurrent (TPC) measurements: TPV and TPC measurements were performed by a photo-electrochemical measurement system (CIMPS-abs) and a high-power white light source (1000 W/m²) as a bias light source. A strongly attenuated laser pulse (550 nm) was used to generate a transient voltage (ΔV) of less than 20 mV.

Thermal admittance spectroscopy (TAS): The measurements were conducted using an impedance spectroscopy analyser (ZENNIUM, Zahner, Germany). The d.c.bias was set to 0 V, and the a.c.bias amplitude was fixed at 20 mV. The frequency range for the a.c. signal was scanned from 0.02 kHz to 2000 kHz, allowing for a detailed analysis of the frequency-dependent capacitance and corresponding trap state dynamics.

Electroluminescence (EL) Characterization: EL imaging was performed using a commercial EL inspection system (GSOLA). The perovskite modules were placed on a motorized translation stage and scanned using a 4 K line-scan camera equipped with a custom optical lens module. The detection window was optimized for the 750–850 nm range to capture the perovskite emission. The devices were electrically driven by an integrated programmable DC source meter (Voltage: 0–300 V, Current: 0–5 A, Precision: ±0.01 V/A) in a constant current mode. The images were reconstructed from the line-scan data with a spatial resolution of better than 0.5 mm. To evaluate the macroscopic uniformity, the modules were scanned with a 5 ms exposure time (integration time) while being driven at a constant injection current of 0.2 × Isc.

Infrared Thermography (IRT): To investigate the thermal distribution and identify potential shunts or defects, thermal imaging was performed under dark conditions. The portable HIKMICRO P09 thermal imaging camera (smartphone-integrated module) featuring an infrared resolution of 96 × 96 pixels and a temperature range of −20 to 400 °C was employed. We performed infrared thermography under a 6 V forward bias under dark conditions, where the voltage was supplied by a Keithley 2400 source meter.

DFT calculations

The binding energies of various systems were computed using density functional theory within the Gaussian 16 software package²⁹. Geometry optimizations were performed employing the B3LYP hybrid functional³⁰ paired with the def2TZVP basis set and supplemented with DFT-D3 dispersion correction³¹ to account for long-range dispersion interactions. The binding energy $({E}_{{{\rm{binding}}}})$ was calculated by the following equation:

$${E}_{{{\rm{binding}}}}={{E}}_{{{\rm{system}}}}-{E}_{{{\rm{molecule}}}1}-{E}_{{{\rm{molecule}}}2}$$

(1)

where ${E}_{{{\rm{system}}}}$ is the total energy of the system, and ${E}_{{{\rm{molecule}}}1}$ and ${E}_{{{\rm{molecule}}}2}$ are the energies of molecules 1 and 2, respectively. All calculated energies are shown in Table S1.

Reporting summary

Further information on research design is available in the Nature Portfolio Reporting Summary linked to this article.