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. 2026 Mar 11;11(11):17644–17651. doi: 10.1021/acsomega.5c11480

Enhancing the Optical Properties of MAPbI3 Perovskites Passivated with Coordinating and Hydrogen Bond Donor Ligands

Matthieu Gamarde †,§,⊥, Abdelaziz Jouaiti †, Daniel Chartrand ‡, Mohan Raj Anthony Raj §,⊥, W G Skene §,⊥,*, Sylvie Ferlay †,*
PMCID: PMC13019396  PMID: 41908442

Abstract

MAPbI 3 (MA; methylammonium) perovskite films were treated with both fluorinated (trifluoroacetamidine, TFA, and trifluoroacetamide, TFAM) and nonfluorinated (oxamide, Oxa) hydrogen bond donors as additives. The corresponding films named Oxa-MAPbI 3 , TFA-MAPbI 3 , and TFAM-MAPbI 3 were thoroughly characterized to evaluate the influence of the type of additive on the structure, morphology, thermal stability, and optical properties of the resulting films. Powder X-ray diffraction (PXRD) studies confirmed the preservation of the MAPbI 3 perovskite structure for the three types of additives. The decomposition kinetics at 100 °C in air highlight the high thermal stability of the TFAM-MAPbI 3 film, compared to the behavior of films treated with other additives. An increase in binding energy was observed by XPS for the additives owing to their perturbation of Pb2+. MAPbI3 perovskite films containing different additives exhibited similar emissions as the MAPbI3 pristine films; however, their excited-state lifetimes were increased by roughly 40%.

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Introduction

In the past decade, perovskite solar cells (PSCs) have garnered attention because of their collective properties, including broadly harvesting sunlight for its sustainable conversion to electricity. , The unique properties of metal halide perovskites (ABX3) make them ideal candidates to be used for solar energy conversion in solar cells, offering high-power conversion efficiency (PCE) to effectively convert sunlight into electrical energy. Furthermore, ABX3 perovskites have low production costs, and their preparation can be scaled up with affordable solution processing methods that are suitable for the quantities required in industrial solar cell manufacturing. Despite the many advantages of the metal halide perovskites, they face challenges related to their thermomechanical and chemical stability: they are indeed affected by moisture, UV light, and temperature, and these conditions have a detrimental effect on the perovskite PCE. Degradation alters perovskite crystallinity, affecting grain size and morphology, and can lead to decomposition or reformation of precursors, such as PbI2. These collective constitutional and morphological changes influence the charge generation and dissociation at the interfacial charge recombination, generally resulting in poor optical properties.

Several strategies have successfully been adopted to overcome the performance-limiting PCE, particularly the sensitivity to the above-mentioned parameters. One strategy consists of changing the anions (X) and cations (A and B) within the metal halide perovskite structure. For example, the introduction of organic cations (A) can improve the charge carrier mobilities by increasing the interfacial charge transfer as a result of innocuous shallow states. Adding UV filtering layers and moisture barriers to the solar cell device is another approach to prevent unwanted degradation.

Additives − and passivating agents − dedicated to metal halides have further been developed to suppress crystallization imperfections, thus improving the crystallinity of perovskites, along with increasing their grain sizes. By modification of the crystallinity of the perovskite, it is possible to suppress the otherwise detrimental trap states that usually arise at grain boundaries. This, in turn, increases (i) the charge generation and dissociation efficiencies by reducing the interfacial charge recombination and nonradiative recombination and (ii) the photoluminescence lifetime and carrier diffusion length toward boosting solar cell performance.

Additives for the metal halide perovskites that interact with both the inorganic (BX n ) n−2 and the organic component (A) of the metal halide can further improve the performance, similar to the morphological changes and optical aspects. For example, coordinating additives to metallic cations (B), such as Pb2+, can be favored with either hydrogen- or halogen-bonded networks, − along with weaker π–π interactions. Interactions of the organic additives at the surface of the perovskite are desired for deactivating both the electronic and the chemical reactivity of the defect site. Various passivating agents have also been used to promote supramolecular interactions like salt additives and also organic molecules functionalized with amines, , hydroxyls, , thiols, carboxyls, amides, − thioamides, , guanidines, and imidazoles, together with chlorinated, brominated, and fluorinated additives. − ,,− Trifluoroacetamide (TFA; Figure ) has been used as such a perovskite additive, because it forms strong intermolecular hydrogen bonds via the donor–acceptor amide, due to its strong electron-withdrawing −CF3 group. For example, FASnI3 and lead halide perovskites have been treated with TFA additives. In the case of CsPbI3–x Br x (x = 0.15), CsPbI3 and also FA0.85MA0.15PbI3 perovskites, supramolecular interactions with the TFA additive clearly increased their PCE.

1.

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Neutral molecular hydrogen bond donor/acceptor additives used for interacting with the MAPbI3 perovskite in films.

We explored the effect of three unimolecular multifunctional hydrogen bond donor/acceptor species on MAPbI3 perovskite films (MA = methylammonium) by leveraging the hydrogen bonding and Pb2+-coordination of amides and acetamides to tune the molecular organization. The aim was to address the lack of understanding of the effect of hydrogen bonds on the crystallization and grain size of films of MAPbI3 perovskites. This was complemented by understanding whether the hydrogen bonding with TFA is universal and applicable to other unimolecular hydrogen bond donors and acceptors with the same shape but differing in their electron density. Both the neutral additives oxamide (Oxa; Figure ) and trifluoroacetamidine (TFAM) were chosen to provide this key information by benchmarking against known TFA. Oxa was chosen because it is a well-known hydrogen bond donor/acceptor and, to the best of our knowledge, has not been reported as a perovskite passivating agent. TFAM is an acetamidine counterpart of TFA, and has also not been reported yet as an additive. MAPbI3 films treated with a series of amide and amidine hydrogen bond additives and their effect on the grain size, spectroscopic properties, and thermal stability of the additive integrated perovskites (Oxa-MAPbI 3 , TFA-MAPbI 3 , and TFAM-MAPbI 3 ) are presented herein.

Experimental Section

Materials

Lead iodide (PbI2), hydrogen iodide aqueous solutions (57%), methylammonium iodide, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), IPA (isopropanol), hydroiodic acid (HI), and additives were purchased from Acros Organics. The chemicals were used as received without further purification. Conductive glass was obtained from Delta Technologies Limited, Loveland, CO.

Stepwise Synthesis of Thin-Film Perovskites

ITO-coated glass (indium tin oxide) was consecutively cleaned using deionized water, acetone, and ethanol by sonication for 20 min for each solvent. After the mixture was dried with compressed air, UV–ozone was applied for further cleaning.

Methylammonium iodide (MAI) was synthesized as previously reported: Methylamine was mixed with a hydrogen iodide aqueous solution (57%, 1 mL, 7.7 mmol) and stirred at 0 °C for 2 h. The resulting solution was concentrated, and the solvent was removed under reduced pressure. The resulting white solid was washed with diethyl ether three times to yield a white crystalline final product (420 mg, 80%).

The pure perovskite precursor solution was prepared by dissolving a mixture of lead iodide (PbI2, 460 mg, 1 mmol), methylammonium iodide (150 mg, 1 mmol), and a mixed solution (1 mL) of DMF and DMSO [DMF (v):DMSO (v) = 4:1]. Additives (TFA, TFAM, and Oxa) were added (3 mg/mL), and the solution was heated at ∼70 °C to dissolve. The perovskite active layer was deposited using an antisolvent method (IPA): one step or two-step spin-coating method was used for the deposition on the freshly prepared substrate. The first step was performed at 1000 rpm with an acceleration rate of 200 rpm for 10 s. The second step was followed at 5000 rpm at an acceleration rate of 2000 rpm/s for 30 s. IPA (70 μL) was added after 20 s. After spin coating, the substrate was annealed at 100 °C for 10 min. This procedure is illustrated in Scheme S1 in the Supporting Information.

Characterization

Powder X-ray Measurements

Powder X-ray diffraction (PXRD) patterns were obtained in 60 min scans with a range of 3° ≤ 2θ ≤ 50° with a Malvern Panalytical Empyrean diffractometer 3 instrument equipped with a PIXcel3D detector, Icore and Dcore optics set to automatic slits set at 10 mm irradiated length, and a Cu Kα radiation source in Bragg–Brentano (ϑ–ϑ) geometry (λ = 1.541874 Å).

For in situ decomposition (at T = 100 °C or T = 70 °C), MoKα radiation was used (λ = 0.71073 Å) collecting a 1 min scan in fixed mode centered at ω = 3.5° (range 3.4° ≤ 2θ ≤ 10.55°) with a Malvern Panalytical Empyrean diffractometer 3 instrument equipped with a GaliPIX3D detector and 1/2° antiscatter slit.

DFT Calculations

Gaussian version G16 C.01 was used to extract the interaction energies and optimize the different structures using the 6.31G basis set and the LanL2DZ basis set (with lead atoms). DFT and PBEPBE were used. The Amsterdam modeling suite with the Quantum Espresso package was used for the solid-state geometry optimization calculations using PBESol.

Fluorescence Measurements

Fluorescence measurements were performed on an FLSP-920 spectrometer with a Xenon 900 lamp combined with a detector working between 300 and 900 nm. All the measurements were performed with an excitation wavelength λexc = 440 nm.

Atomic Force Microscopy Measurements

A Dimension Icon microscope with a Nanoscope V controller (Bruker, Santa Barbara, CA, USA) was used for capturing the topography AFM images. PeakForce tapping mode and a Si probe (Scan Asyst Air) were used for acquiring the images with a spring constant of 0.4 Newton/m. Force–distance curves were recorded at 2 kHz rate, and the peak force set point was adjusted by the ScanAsyst Auto control. Grain size distribution was deduced using ImageJ free software.

X-ray Photoelectron Spectroscopy Measurements

Measurements were made with a Thermo Scientific ESCALAB 250Xi XPS microprobe in ultrahigh vacuum with a 1486.680054 eV. An Al/Kα source gun type was used with the standard lens mode. The CAE Pass Energy of 150.0 eV was used for the analyzer mode for the survey scan, while 20.0 eV was used for the Pb4f scans. The energy step size was contingent on the sample varying between 0.100 and 1 eV. See the SI for additional details.

Results and Discussion

Structural Study

Mixtures with a defined amount of additive (3 mg/mL, 3% of additive) were prepared as thin films using a two-step procedure (see the Experimental Section for details and also Scheme S1 in the Supporting Information for a schematic representation) on an ITO-coated glass substrate. First, the solution was prepared from methylammonium iodide (MAI) and PbI2 in DMF:DMSO (4:1). The additives were added, and an antisolvent (IPA, isopropanol) was then deposited on the substrate, followed by spin coating. X-ray diffraction measurements of the films were made to assess the 3D phase of MAPbI3 after additive incorporation. The diffraction peaks at 2θ of 14.02°, 19.9°, 24.4°, 28.3°, 31.7°, 34.8°, 41.4°, and 42.98° (using Cu Kα radiation) for the three compounds (Oxa-MAPbI 3 , TFA-MAPbI 3 , and TFAM-MAPbI 3 ) corresponded, respectively, to the crystalline (110) and (002), (200) and (112), (202), (004), (310), and (114), (312), (400) and (224), and finally (330) and (402) planes of the MAPbI 3 phase. The diffractograms revealed that the three compounds contained the well-known MAPbI 3 phase (Figure S1 in the Supporting Information), and according to the position of the (001) peak for all of the compounds (Figure S2 in the Supporting Information), they all displayed the same cell parameters as those of the MAPbI 3 phase. The lattice of the films also did not expand with the addition of the three additives (TFA, TFAM, and Oxa). The least stable compound TFA-MAPbI3 exhibited small amounts of PbI2, as shown in the PXRD diagrams (Figure S1 in the Supporting Information), matching the observations reported in Figure .

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2θ powder X-ray diffractograms of films of pristine MAPbI 3 (A), Oxa-MAPbI 3 (B), TFA-MAPbI 3 (C), and TFAM-MAPbI 3 (D) contingent on the heating time at 100 °C under air. The zoomed region corresponds to the MAPbI 3 and PbI2 representative peaks: (110), 2θ = 6.5° (MAPbI3) and (001), and 2θ = 5.9° (PbI2), respectively. A MoKα radiation is used here.

Decomposition Kinetics of the MAPbI3 Films

To mimic the decomposition of the perovskites under ambient conditions, PXRD diffractograms of the films were recorded at regular intervals while heating the films at both 70 and 100 °C under air. The increased temperature relative to room temperature was required to accelerate the aging of the films and for differences in the diffractograms to occur within a reasonable time. The corresponding results are presented in Figure . The analysis window was focused on the [5–10] 2θ range (using a MoKα radiation). This region was chosen because it contained the most intense peaks of the MAPbI 3 perovskite phase ((110), 2θ = 6.5°) and of the PbI2 precursor ((001), 2θ = 5.9°) (Figure S3 in the Supporting Information). The data showed that the kinetics of decomposition for both MAPbI 3 and Oxa-MAPbI 3 are comparable. Meanwhile, the decomposition kinetics of TFAM-MAPbI 3 were slower: it was thermally stable for more than 8 h with little noticeable decomposition in the measured time frame. This contrasted with that of TFA-MAPbI 3 , whose decomposition kinetics were the fastest among the three evaluated additives involved in the MAPbI 3 phase.

The decomposition kinetics of the perovskites were determined by plotting the intensity of 2θ = 6.5° (MAPbI3) and 5.9° (PbI2) peaks as a function of time. The decomposition of the MAPbI 3 phase mirrored the formation rate of PbI2 at both 70° and 100 °C (Figures S4 and S5 in the Supporting Information), respectively. It is worth noting that there is an induction period at 70 °C prior to perovskite decomposition, which was not observed at 100 °C. The MAPbI 3 phase slowly degraded to 11% of the original intensity during 16 h of heating at the lower temperature. Afterward, the MAPbI 3 phase was entirely degraded in less than 6 h of subsequent heating. This contrasted with heating at 100 °C, with the decomposition occurring < 1 h and degradation completed around 8 h. The additives influenced the stability of the perovskite at the concentrations examined. This was enhanced at lower temperatures according to the slow decomposition kinetics of TFAM-MAPbI 3 with TFAM that prevented the thermal degradation of the perovskite, whereas TFA-MAPbI 3 was less thermally stable as per its faster decomposition kinetics.

Morphological Aspects

The morphology of the thin films of the MAPbI 3 perovskites containing the additives, formed on the surface of the ITO substrate, was evaluated by using atomic force microscopy (Figure ). While SEM images were also acquired to complement the AFM micrographs, they were of poor quality (not presented here). Nonetheless, the AFM images qualitatively reveal that the grain size of the MAPbI 3 perovskite is affected by the nature of the additive. The aggregations are less intense for TFA-MAPbI 3 than those for TFAM-MAPbI 3 and Oxa-MAPbI 3 . TFA-MAPbI 3 had the smoothest grains, and they were consistent with the ones observed for MAPbI 3 . This aside, the average grain surface was within the 100 and 150 nm2 range. Large variances in the grain size for the additives were also observed. MAPbI 3 displayed the most homogeneous grain size distribution (Figure , bottom panel) along with the smallest roughness (11.8 nm). The grain size distribution is reported in Figure S6 in the Supporting Information, along with the corresponding roughness (Table S1 in the Supporting Information). TFAM-MAPbI 3 had the largest grain size variation according to the Gaussian fitting of the size histograms and its corresponding variance ((1.28 ± 3.2) × 10–2 μm2), along with the largest surface roughness of 39.6 mm. The size distribution of Oxa-MAPbI 3 was similarly large, with three discrete populations observed with a global mean of (1.36 ± 1.88) × 10–2 μm2 corresponding to 0.05, 0.15, and 0.035 μm2 in decreasing abundance.

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AFM topography (top) and roughness (bottom) images of perovskite films of MAPbI 3 (A) TFA-MAPbI 3 (B), TFAM-MAPbI 3 (C), and Oxa-MAPbI 3 (D). Scale bar is 200 nm, and the height scales for both the topography (top) and roughness (bottom) images are identical. For more details, see the SI.

Interactions between MAPbI3 and the Additives

X-ray photoelectron spectroscopy (XPS) analyses were conducted on the films to explore the interaction between the additives and MAPbI 3 , especially by probing the 4f Pb energy level that is sensitive to interaction (coordination) with the additive. The underlying substrate on which the perovskite is prepared, as well as its oxidation state, further affects the Pb 4f binding energy. , The surface effects can be negated by using a common substrate and fabricating the perovskites with consistent protocols. Acquiring XPS measurements under identical experimental conditions further ensures that the samples can be directly compared. Any shifts in its binding energy arise uniquely from changes in its environment induced by the Lewis base or hydrogen-bonding additive. Of note were noticeable variations in the adventitious carbon used to reference the binding energies, necessary to directly compare the Pb 4f7/2 peak of the samples with the different additives (Table S3 in the Supporting Information). Taking the predominant peak with the lowest binding energy of adventitious carbon as the reference, the trend of increasing binding energies with additives could be established (Figures S12 and S15 in the Supporting Information). The shifts were <1.3 eV relative to the pristine MAPbI 3 and are representative, increasing in binding energy according to TFAM > TFA > Oxa (Figure S16 in the Supporting Information). The increase in binding energy is consistent with a decrease in electron density of Pb2+ with the donor effect of the additive, making the removal of the 4f electron more difficult. Similarly, the coordination of Oxa with Pb2+ perturbs the electron density, resulting in increased energy ionization of lead. While the exact mechanism responsible for increasing the binding energy cannot be unequivocally assigned, whether it be Lewis base interaction, hydrogen bonding, or screening, the additives indeed perturb the lead electronic density in varying degrees.

Unfortunately, the H-bond network could not be confirmed by FT-IR (Figure S8 in the Supporting Information).

Theoretical calculations provided further insight into the interaction of additives with MAPbI 3 . The calculations from the chosen level of theory and functional were validated by the geometries of the lattices that were consistent with calculations of other fluorinated passivating agents used with MAPbI 3 . The calculations confirmed intramolecular hydrogen bonds and interactions between the additives and the (PbI3) n n– 3D network (see Figure S7 in the Supporting Information). They also support the coordination between CO and Pb2+ for the Oxa and TFA additives, which were not directly confirmed by XPS. For TFAM-MAPbI 3 , the interactions were stronger than the corresponding interactions in TFA-MAPbI 3 (see Table S2 in the Supporting Information), in accordance with what was observed by XPS measurements. The calculated energy for Oxa-MAPbI 3 was higher, although the distances were shorter than those of the other additives: this is owing to the lack of fluorine atoms in the Oxa additive, thus forming the strongest hydrogen bond network among the additives.

Time-Resolved Photoluminescence

Photoluminescence (PL) and time-resolved photoluminescence (TRPL) tests were measured to explore how the additives affected the dynamics of carrier transport in the perovskite films. Nonradiative recombination, closely associated with defects in perovskite films, is a predominant mode that deteriorates device performance. This pathway can be evaluated by excited-state kinetics. The absorption spectra of thin films deposited on glass of MAPbI 3 containing the additives were first measured (Figure S9 in the Supporting Information) to determine the ideal excitation wavelength (λ = 440 nm) for emission studies. No obvious shift in the NIR emission was observed with the three analyzed compounds (Figure a). The exception was oxa-MAPbI 3 , whose emission was slightly red-shifted by ca. 5 nm.

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Steady-state (a) and time-resolved emission (b) of perovskite films of MAPbI 3 (black) TFA-MAPbI 3 (red), TFAM-MAPbI 3 (blue), and Oxa-MAPbI 3 (green). Lifetimes were fitted to biexponential decay using the tail-fit model.

Steady-state photoluminescence (PL) analysis of the thin films of MAPbI 3 containing the additives was measured, as shown in Figure b. Although the absolute emission could not be obtained owing to differences in the film thickness, qualitatively, the emission was more pronounced for oxa-MAPbI 3 , while the emission of TFA-MAPbI 3 and TFAM-MAPbI 3 was muted.

Time-resolved photoluminescence was then measured by single-photon counting. The excited-state kinetics could be fitted with a biexponential decay (see corresponding equations in the SI), providing insights into the charge carrier dynamics. According to Table , the additives efficiently suppress the nonradiative recombination in the MAPbI 3 perovskite films. Lifetime measurements, along with biexponential fitting tables (Table ), highlight an increase in average lifetime for all MAPbI3 phases with additives.

1. Excited-State Lifetimes of the MAPbI 3 Perovskite without and with Additive, Along with the Weighted Signal Composition.

  MAPbI3 TFA-MAPbI3 Oxa-MAPbI3 TFAM-MAPbI3
τ1 fast (ns) 0.720 114.5 101.3 137.9
τ2 slow (ns) 185.5 426.6 442.4 608.1
average lifetime τ (ns) 27.6 133.8 123.6 176.2
Χ2 0.83 0.980 0.98 0.94
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a

Weighted signal contribution given in parentheses of either biexponential fit (see equations in the SI).

The carrier lifetimes can be divided into two mechanisms, and these can be assigned according to the perovskite excited-state lifetime: surface and bulk recombination. − Long-lived intermediate lifetimes (>0.5 ms) are attributed to bulk recombination, while shorter lifetimes are ascribed to surface effects. The additive plays a role in shifting the intrinsic surface recombination of the carriers to bulk according to the increased lifetime with the additive. Fast decay in all cases is assigned to rapid trap filling. The most marked increase in excited lifetime was observed with the use of TFAM, indicating that both electronic and hydrogen bonding affect the carrier kinetics. Direct comparison between the additives is possible, given that the samples were evaluated under similar conditions. This is relevant and important because of the variability of the reported absolute emission lifetime owing to different perovskite preparation. The trend in the increased lifetime with additives is nonetheless real. This trend is also consistent with known additives such as formamide and TFA.

Conclusions

Films of perovskite phases with three different additives were studied. The additives were chosen for their fluorination (TFAtrifluoroacetamide and TFAMtrifluoroacetamidine) and coordination (TFA and oxaoxamide) to form (i) hydrogen bonds and/or (ii) coordination bonds. The structural study (PXRD) of the resulting films confirmed that loading the additives (3%) did not alter the MAPbI 3 phase (nature and cell parameters). However, AFM microscopy revealed that the morphology of the resulting films was contingent on the type of additive. For example, Oxa-MAPbI 3 had the largest grain size. XPS confirmed interactions of the additives with PbI3 –, probably leading to 3D networks, and this was stronger for the TFAM-MAPbI 3 films. These results were supported by the theoretical calculations. Collectively, the measurements confirmed that the type of additive can be used to modulate the perovskite properties. TFA gave the best morphology, resembling the pristine MAPbI 3 perovskite, while conferring thermal stability and accelerating the excited-state lifetime. This contrasted with the TFAM-MAPbI 3 film having larger grain sizes and being more thermally stable with a much desired longer excited lifetime. The properties of the Oxa-MAPbI 3 film were between those of its trifluoroamide/amidine counterparts, confirming that the strong electron-withdrawing group is not required to positively affect the perovskite. While only a subset of additives was evaluated with the well-used MAPbI 3 perovskite, the type of additive and its hydrogen bonds and halogen interactions can be leveraged to tweak the perovskite morphology and its resulting properties. By expanding both the ensemble of additives to include other intermolecular contacts, along with their integration into different perovskites, design rules can be established for tuning the desired properties. Such rules are of importance for ultimately rationally designing perovskites having given properties and further improving the performance of perovskite solar cells.

Supplementary Material

ao5c11480_si_001.pdf (2.7MB, pdf)

Acknowledgments

Financial support from the University of Strasbourg and the CNRS is acknowledged. Dr. Y. Cornaton (IC, UMR 7177, Strasbourg) is warmly acknowledge for the support in the modelling. The Natural Sciences and Engineering Council Canda (NSERC) and the Canada Foundation for Innovation are acknowledged for operating funds and providing equipment, respectively, that supported this collaborative research. The Quebec Center for Advanced Materials (CQMF) is also acknowledged for providing access to vital equipment. P. Moraille and the Laboratoire de characterization des matériaux (LCM) are acknowledged for assistance with the AFM measurements. The Digital Alliance of Canada and its regional partners (Compute Ontario and the BC DRI Group) are acknowledged for providing access to computational resources. M.G. also thanks both MITACS and the Université de Montréal for graduate scholarships. J. Lefebvre is thanked for assistance with XPS measurements.

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.5c11480.

  • Synthetic procedure, PXRD data, grain size distribution, modeling, spectroscopic measurements, TPRL measurements, and detailed XPS measurements (PDF)

¶.

Université de Bordeaux, CNRS, Bordeaux INP, IMS, UMR 5218, F-33400 Talence, France

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

NSERC Canada. CFI. MITACS. CQMF. Unistra. CNRS.

The authors declare no competing financial interest.

References

  1. Bush K. A., Palmstrom A. F., Yu Z. J., Boccard M., Cheacharoen R., Mailoa J. P., McMeekin D. P., Hoye R. L. Z., Bailie C. D., Leijtens T., Peters I. M., Minichetti M. C., Rolston N., Prasanna R., Sofia S., Harwood D., Ma W., Moghadam F., Snaith H. J., Buonassisi T., Holman Z. C., Bent S. F., McGehee M. D.. 23.6%-efficient monolithic perovskite/silicon tandem solar cells with improved stability. Nat. Energy. 2017;2:17009. doi: 10.1038/nenergy.2017.9. [DOI] [Google Scholar]
  2. Yoo J. J., Seo G., Chua M. R., Park T. G., Lu Y., Rotermund F., Kim Y. K., Moon C. S., Jeon N. J., Correa-Baena J. P., Bulovic V., Shin S. S., Bawendi M. G., Seo J.. Efficient perovskite solar cells via improved carrier management. Nature. 2021;590:587–593. doi: 10.1038/s41586-021-03285-w. [DOI] [PubMed] [Google Scholar]
  3. Kojima A., Teshima K., Shirai Y., Miyasaka T.. Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc. 2009;131:6050–6051. doi: 10.1021/ja809598r. [DOI] [PubMed] [Google Scholar]
  4. Wang Z., Shi Z., Li T., Chen Y., Huang W.. Stability of Perovskite Solar Cells: A Prospective on the Substitution of the A Cation and X Anion. Angew. Chem., Int. Ed. 2017;56:1190–1212. doi: 10.1002/anie.201603694. [DOI] [PubMed] [Google Scholar]
  5. Wafee S., Liu B. H., Leu C.-C.. Lewis bases: promising additives for enhanced performance of perovskite solar cells. Mater. Today Energy. 2021;22:100847. doi: 10.1016/j.mtener.2021.100847. [DOI] [Google Scholar]
  6. Li Y., Dailey M., Lohr P. J., Printz A. D.. Performance and stability improvements in metal halide perovskite with intralayer incorporation of organic additives. J. Mater. Chem. A. 2021;9:16281–16338. doi: 10.1039/D1TA05252G. [DOI] [Google Scholar]
  7. Jiang Q., Tong J. H., Xian Y. M., Kerner R. A., Dunfield S. P., Xiao C. X., Scheidt R. A., Kuciauskas D., Wang X. M., Hautzinger M. P., Tirawat R., Beard M. C., Fenning D. P., Berry J. J., Larson B. W., Yan Y., Zhu K.. Surface reaction for efficient and stable inverted perovskite solar cells. Nature. 2022;611:278–283. doi: 10.1038/s41586-022-05268-x. [DOI] [PubMed] [Google Scholar]
  8. Jiao S., Wang T., Zhou Z.. Additive Engineering Toward Suppression of Sn2+ Oxidation in Sn–Pb Perovskite Solar Cells: Mechanisms, Advances, and Outlook. ChemSusChem. 2025;18:e202500333. doi: 10.1002/cssc.202500333. [DOI] [PubMed] [Google Scholar]
  9. Teale S., Degani M., Chen B., Sargent E. H., Grancini G.. Molecular cation and low-dimensional perovskite. Nat. Energy. 2024;9:779–792. doi: 10.1038/s41560-024-01529-3. [DOI] [Google Scholar]
  10. Wang J., Bi L., Fu Q., Jen A. K.-Y. Methods for Passivating Defects of Perovskite for Inverted Perovskite Solar Cells and Modules. Adv. Energy Mater. 2024;14:2401414. doi: 10.1002/aenm.202401414. [DOI] [Google Scholar]
  11. Zhang F., Guo R., Zeng H., Wang L.. Role of Small Organic Molecules in Perovskite Light-Emitting Diodes: Applications, Mechanisms and Prospects. Adv. Funct. Mater. 2025;35:2500348. doi: 10.1002/adfm.202500348. [DOI] [Google Scholar]
  12. Li T., Zhu T., Li S., Zhang X., Tang H., Zhang K., Zhu X., Ma W., Yu J.. Stable and efficient perovskite solar cells via hydrogen bonding and coordination. Nanoscale. 2023;15:19557–19568. doi: 10.1039/D3NR04207C. [DOI] [PubMed] [Google Scholar]
  13. Yong T., Choi S., Kim S.-K., Han S., Seo G., Kim H. J., Park J. Y., Yu H. N., You H. R., Lee E. J., Lee G., Lee W., Kim S., Yun S., Lee Y., Lee J., Kim D.-H., Lim S. J., Nam D.-H., Kim Y., Lim J., Moon B. J., Choi J.. Hydrogen bond-mediated pseudo-halide complexation for stable and efficient perovskite precursors and solar cells. Energy Environ. Sci. 2024;17:9443–9454. doi: 10.1039/D4EE02793K. [DOI] [Google Scholar]
  14. Ahmed R., Rheman S., Chen Z., Ye F., Ren X.. Ligand Assisted Hydrogen Bonding: A Game-Changer in Lead Passivation and Stability in Perovskite Solar. Angew. Chem., Int. Ed. 2025;64:e202418763. doi: 10.1002/anie.202418763. [DOI] [PubMed] [Google Scholar]
  15. He A., Wang M., Gong X., Tang P., Wu L., Hao X., Wang W., Xia G., Jiang Y., Zhang J.. pi–pi stacking small molecules enable high performance perovskite solar cells. J. Mater. Chem. A. 2024;12:16901–16909. doi: 10.1039/D3TA07997J. [DOI] [Google Scholar]
  16. Boopathi K. M., Mohan R., Huang T.-Y., Budiawan W., Lin M.-Y., Lee C.-H., Ho K.-C., Chu C.-W.. Synergistic improvements in stability and performance of lead iodide perovskite solar cells incorporating salt additives. J. Mater. Chem. A. 2016;4:1591–1597. doi: 10.1039/C5TA10288J. [DOI] [Google Scholar]
  17. Dong H., Xi J., Zuo L., Li J., Yang Y., Wang D., Yu Y., Ma L., Ran C., Gao W., Jiao B., Xu J., Lei T., Wei F., Yuan F., Zhang L., Shi Y., Hou X., Wu Z.. Conjugated Molecules “Bridge”: Functional Ligand toward Highly Efficient and Long-Term Stable Perovskite Solar Cell. Adv. Funct. Mater. 2019;29:1808119. doi: 10.1002/adfm.201808119. [DOI] [Google Scholar]
  18. Dong T., Tan L., Li Z., Li J., Li H., Liao J., Chen X., Zhang W., Li H.. Enhanced Efficiency and Intrinsic Stability of Wide-Bandgap Perovskite Solar Cells Through Dimethylamine-Based Cation Engineering. Chem. – Eur. J. 2025;31:e202403527. doi: 10.1002/chem.202403527. [DOI] [PubMed] [Google Scholar]
  19. Li X., Ke S., Feng X., Zhao X., Zhang W., Fang J.. Enhancing the stability of perovskite solar cells through cross-linkable and hydrogen bonding multifunctional additives. J. Mater. Chem. A. 2021;9:12684–12689. doi: 10.1039/D1TA01572A. [DOI] [Google Scholar]
  20. Choi M.-J., Lee Y.-S., Cho I. H., Kim S. S., Kim D.-H., Kwon S.-N., Na S.-I.. Functional additives for high-performance inverted planar perovskite solar cells with exceeding 20% efficiency: Selective complexation of organic cations in precursors. Nano Energy. 2020;71:104639. doi: 10.1016/j.nanoen.2020.104639. [DOI] [Google Scholar]
  21. Yang Y., Wei T., Shai X., Song Q., Zeng C., He D., Zhang H., Chen J.. Improving Photovoltaic Performance and Stability of Perovskite Solar Cells via Molecular Bridge Strategy. Adv. Opt. Mater. 2023;11:2300684. doi: 10.1002/adom.202300684. [DOI] [Google Scholar]
  22. Zheng H., Zhu L., Hu L., Yang S., Chen S., Alsaedi A., Hayat T., Huang Y., Pan X., Dai S.. Promoting perovskite crystal growth to achieve highly efficient and stable solar cells by introducing acetamide as an additive. J. Mater. Chem. A. 2018;6:9930–9937. doi: 10.1039/C8TA02121J. [DOI] [Google Scholar]
  23. Cheng W., He X., Wang J.-G., Tian W., Li L.. N -(2-aminoethyl) Acetamide Additive Enables Phase-Pure and Stable α-FAPbI3 for Efficient Self-Powered Photodetectors. Adv. Mater. 2022;34:2208325. doi: 10.1002/adma.202208325. [DOI] [PubMed] [Google Scholar]
  24. Wang W.-T., Holzhey P., Zhou N., Zhang Q., Zhou S., Duijnstee E. A., Rietwyk K. J., Lin J.-Y., Mu Y., Zhang Y., Bach U., Wu C.-G., Yip H.-L., Snaith H. J., Feng S.-P.. Water- and heat-activated dynamic passivation for perovskite photovoltaics. Nature. 2024;632:294–300. doi: 10.1038/s41586-024-07705-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Xu C., Zhang Z., Zhang S., Si H., Ma S., Fan W., Xiong Z., Liao Q., Satter A., Kang Z., Zhang Y.. Manipulation of Perovskite Crystallization Kinetics via Lewis Base Additives. Adv. Funct. Mater. 2021;31:2009425. doi: 10.1002/adfm.202009425. [DOI] [Google Scholar]
  26. Zhao W., Xu J., He K., Cai Y., Han Y., Yang S., Zhan S., Wang D., Liu Z., Liu S.. et al. Effective lewis base additive with S-donor for efficient and stable CsPbI2Br based perovskite solar cells. J. Chem. Eng. 2021;420:129931. doi: 10.1016/j.cej.2021.129931. [DOI] [Google Scholar]
  27. Zhou W., Tai S., Li Y., Fu H., Zheng Q.. Achieving High-Quality Perovskite Films with Guanidine-Based Additives for Efficient and Stable Methylammonium-Free Perovskite Solar Cells. Adv. Funct. Mater. 2024;34:2407897. doi: 10.1002/adfm.202407897. [DOI] [Google Scholar]
  28. Wang Y., Ye J., Song J., Chu L., Zang Y., Li G., Zhou Q., Yang G., Tu Y., Jin Y., Li Z., Yan W.. Modulation of Buried Interface by 1-(3-aminopropyl)-Imidazole for Efficient Inverted Formamidinium-Cesium Perovskite Solar Cell. Small. 2024;20:2304273. doi: 10.1002/smll.202304273. [DOI] [PubMed] [Google Scholar]
  29. Liu X., Guo Y., Cheng Y., Lu S., Li R. J., Chen. Advances in chloride additives for high-efficiency perovskite solar cells: multiple points of view. Chem. Commun. 2023;59:13394–13405. doi: 10.1039/D3CC04177H. [DOI] [PubMed] [Google Scholar]
  30. Wang Q., Chen Y., Chen X., Tang W., Qiu W., Xu X., Wu Y., Peng Q.. Tailored Succinic Acid-Derived Molecular Structures toward 25.41%-Efficiency and Stable Perovskite Solar Cells. Adv. Mater. 2024;36:2307709. doi: 10.1002/adma.202307709. [DOI] [PubMed] [Google Scholar]
  31. Liu Y., Akin S., Pan L., Uchida R., Arora N., Milić J., Hinderhofer A., Schreiber F., Uhl A. R., Zakeeruddin S. M., Hagfeldt A., Dar M. I., Grätzel M.. Ultrahydrophobic 3D/2D fluoroarene bilayer-based water-resistant perovskite solar cells with efficiencies exceeding 22% Sci. Adv. 2019;5:eaaw2543. doi: 10.1126/sciadv.aaw2543. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Li N., Tao S., Chen Y., Niu X., Onwudinanti C. K., Hu C., Qiu Z., Xu Z., Zheng G., Wang L., Zhang Y., Li L., Liu H., Lun Y., Hong J., Wang X., Liu Y., Xie H., Gao Y., Bai Y., Yang S., Brocks G., Chen Q., Zhou H.. Cation and anion immobilization through chemical bonding enhancement with fluorides for stable halide perovskite solar cells. Nature Energy. 2019;4:408–415. doi: 10.1038/s41560-019-0382-6. [DOI] [Google Scholar]
  33. Ouedraogo N. A. N., Yan H., Han C. B., Zhang Y.. Influence of Fluorinated Components on Perovskite Solar Cells Performance and Stability. Small. 2021;17:2004081. doi: 10.1002/smll.202004081. [DOI] [PubMed] [Google Scholar]
  34. Zhao W., Xu J., He K., Cai Y., Han Y., Yang S., Zhan S., Wang D., Liu Z., Liu S.. A Special Additive Enables All Cations and Anions Passivation for Stable Perovskite Solar Cells with Efficiency over 23% Nano-Micro Lett. 2021;13:169. doi: 10.1007/s40820-021-00688-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Zhang H., Xiang W., Zuo X., Gu X., Zhang S., Du Y., Wang Z., Liu Y., Wu H., Wang P., Cui Q., Su H., Tian Q., Liu S.. Fluorine-Containing Passivation Layer via Surface Chelation for Inorganic Perovskite Solar Cells. Angew. Chem., Int. Ed. 2023;62:e202216634. doi: 10.1002/anie.202216634. [DOI] [PubMed] [Google Scholar]
  36. Jiang X., Yang G., Zhang B., Wang L., Yin Y., Zhang F., Yu S., Liu S., Bu H., Zhou Z., Sun L., Pang S., Guo X.. Understanding the Role of Fluorine Groups in Passivating Defects for Perovskite Solar Cells. Angew. Chem., Int. Ed. 2023;62:e202313133. doi: 10.1002/anie.202313133. [DOI] [PubMed] [Google Scholar]
  37. Yadav D., Das Adhikari R., Baishya H., Patel M. J., Lyer P. K.. Enhancing the efficiency and stability of inverted perovskite solar cells by using 6-(trifluoromethyl)­nicotinic acid as a potent defect passivator. J. Mater. Chem. C. 2024;12:14561–14571. doi: 10.1039/D4TC02432J. [DOI] [Google Scholar]
  38. Gurumallappa G., Lu N., Chen Y.-D., Lin Y.-C., Hsiao Y.-F., Liu P.-Y., Tsai M.-L.. A trifluoromethyl group-incorporated spacer in 2D perovskite-based photodetectors with good responsivity and a big Pb–I–Pb bond angle: the first example of an aliphatic linearly-chained spacer forming non-classical hydrophobic hydrogen bonding. J. Mater. Chem. C. 2025;13:7912–7917. doi: 10.1039/D5TC00443H. [DOI] [Google Scholar]
  39. Li P., Dong H., Li J., Cao X., Xi J., Wang D., Jiao B., Hou X., Yang Y., Wu Z.. Synergistic trifluoroacetamide regulating crystal orientation and energy alignment for tin-based perovskite solar cells. Org. Electron. 2023;113:106707. doi: 10.1016/j.orgel.2022.106707. [DOI] [Google Scholar]
  40. Li X., Wang P., Guo R., Chen Y., Chen C., Yang W., Zeng Q., Ye C., Huang Y., Zhang J.. Printable mesoscopic perovskite solar cells with performance tuning via trifluoroacetamide. Sustainable Energy Fuels. 2025;9:1765–1772. doi: 10.1039/D4SE01801J. [DOI] [Google Scholar]
  41. Huang J., Wang H., Chen C., Liu S.. Multifunctional Passivator Trifluoroacetamidine for Improving the Performance of All-Inorganic CsPbI3 Perovskite Solar Cells. Sol. RRL. 2022;6:2200809. doi: 10.1002/solr.202200809. [DOI] [Google Scholar]
  42. Liu L., Li Y., Zheng C., Liu Z., Yuan N., Ding J., Wang D., Liu S.. Collaborative Strategy of Multifunctional Groups in Trifluoroacetamide Achieving Efficient and Stable Perovskite Solar Cells. Sol. RRL. 2022;6:2200284. doi: 10.1002/solr.202200284. [DOI] [Google Scholar]
  43. Grätzel M.. The Rise of Highly Efficient and Stable Perovskite Solar Cells. Acc. Chem. Res. 2017;50:487–491. doi: 10.1021/acs.accounts.6b00492. [DOI] [PubMed] [Google Scholar]
  44. Jeon N. J., Noh J. H., Kim Y. C., Yang W. S., Ryu S., Seok S. I.. Solvent Engineering for High-Performance Inorganic-Organic Hybrid Perovskite Solar Cells. Nat. Mater. 2014;13:897–903. doi: 10.1038/nmat4014. [DOI] [PubMed] [Google Scholar]
  45. Gaussian 16, Rev. C.01; Gaussian Inc.: Wallingford, CT, 2016. [Google Scholar]
  46. Hay P. J., Wadt W. R.. Ab initio effective core potentials for molecular calculations. Potentials for K to Au including the outermost core orbitals. J. Chem. Phys. 1995;82:299–310. doi: 10.1063/1.448975. [DOI] [Google Scholar]
  47. Perdew J. P., Burke K., Ernzerhof M.. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996;77:3865–3868. doi: 10.1103/PhysRevLett.77.3865. [DOI] [PubMed] [Google Scholar]
  48. Rüger, R. ; Trnka Franchini, M. T. ; Yakovlev, A. ; van Lenthe, E. ; Philipsen, P. ; van Vuren, T. ; Klumpers, B. ; Soini, T. . Theoretical Chemistry; Vrije Universiteit: Amsterdam, The Netherlands, http://www.scm.com. [Google Scholar]
  49. Giannozzi P., Baroni S., Bonini N., Calandra M., Car R., Cavazzoni C., Ceresoli D., do L Chiarotti G., Cococcioni M., Dabo I., Corso A. D., de Gironcoli S., Fabris S., Fratesi G., Gebauer R., Gerstmann U., Gougoussis C., Kokalj A., Lazzeri M., Martin-Samos L., Marzari N., Mauri F., Mazzarello R., Paolini S., Pasquarello A., Paulatto L., Sbraccia C., Scandolo S., Sclauzero G., Seitsonen A. P., Smogunov A., Umari P., Wentzcovitch R. M.. QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials. J. Phys.: Condens. Matter. 2009;21:395502. doi: 10.1088/0953-8984/21/39/395502. [DOI] [PubMed] [Google Scholar]
  50. Perdew J. P., Ruzsinszky A., Csonka G. I., Vydrov O. A., Scuseria G. E., Constantin L. A., Zhou X., Burke K.. Restoring the Density-Gradient Expansion for Exchange in Solids and Surfaces. Phys. Rev. Lett. 2008;100:136406. doi: 10.1103/PhysRevLett.100.136406. [DOI] [PubMed] [Google Scholar]
  51. Olthof S., Meerholz K.. Substrate-dependent electronic structure and film formation of MAPbI3 perovskites. Sci. Rep. 2017;7:40267. doi: 10.1038/srep40267. [DOI] [PMC free article] [PubMed] [Google Scholar]
  52. Zhidkov I. S., Gerasimov M. F., Ozerova V. V., Frolova L. A., Ustinova M. I., Akbulatov A. F., Kukharenko A. I., Troshin P. A., Kurmaev E. Z.. XPS Visualization of Soft and Hard Lewis Base Passivation of Defects in MAPbI3 Perovskite. Physica B: Condensed Matter. 2025;711:417268. doi: 10.1016/j.physb.2025.417268. [DOI] [Google Scholar]
  53. Li C., Zhang N., Gao P.. Lessons Learned: How to Report XPS Data Incorrectly About Lead-Halide Perovskites. Mater. Chem. Front. 2023;7:3797–3802. doi: 10.1039/D3QM00574G. [DOI] [Google Scholar]
  54. Yang W., Long H., Sha X., Sun J., Zhao Y., Guo C., Peng X., Shou C., Yang X., Sheng J., Yan Z., Ye J.. Unlocking Voltage Potentials of Mixed-Halide Perovskite Solar Cells via Phase Segregation Suppression. Adv. Funct. Mater. 2022;32:2110698. doi: 10.1002/adfm.202110698. [DOI] [Google Scholar]
  55. Chen X., Lu H., Yang Y., Beard M. C.. Excitonic Effects in Methylammonium Lead Halide Perovskites. J. Phys. Chem. Lett. 2018;9:2595–2603. doi: 10.1021/acs.jpclett.8b00526. [DOI] [PubMed] [Google Scholar]
  56. Yang Y., Yang M., Moore D. T., Yan Y., Miller E. M., Zhu K., Beard M. C.. Top and Bottom Surfaces Limit Carrier Lifetime in Lead Iodide Perovskite Films. Nat. Energy. 2017;2:16207. doi: 10.1038/nenergy.2016.207. [DOI] [Google Scholar]
  57. Shi D., Adinolfi V., Comin R., Yuan M., Alarousu E., Buin A., Chen Y., Hoogland S., Rothenberger A., Katsiev K., Losovyj Y., Zhang X., Dowben P. A., Mohammed O. F., Sargent E. H., Bakr O. M.. Low Trap-State Density and Long Carrier Diffusion in Organolead Trihalide Perovskite Single Crystals. Science. 2015;347:519–522. doi: 10.1126/science.aaa2725. [DOI] [PubMed] [Google Scholar]
  58. Jain S. M., Qiu Z., Häggman L., Mirmohades M., Johansson M. B., Edvinsson T., Boschloo G.. Frustrated Lewis Pair-Mediated Recrystallization of CH3NH3PbI3 for Improved Optoelectronic Quality and High-Voltage Planar Perovskite Solar Cells. Energy Environ. Sci. 2016;9:3770–3782. doi: 10.1039/C6EE02544G. [DOI] [Google Scholar]
  59. Xie J., Zhou Z., Qiao H., Chen M., Wang L., Yang S., Hou Y., Yang H.. Modulating MAPbI3 Perovskite Solar Cells by Amide Molecules: Crystallographic Regulation and Surface Passivation. J. Energy Chem. 2021;56:179–185. doi: 10.1016/j.jechem.2020.07.050. [DOI] [Google Scholar]

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