Methylammonium-formamidinium reactivity in aged organometal halide perovskite inks

Valenzano, Vitantonio; Cesari, Andrea; Balzano, Federica; Milella, Antonella; Fracassi, Francesco; Listorti, Andrea; Gigli, Giuseppe; Rizzo, Aurora; Uccello‐Barretta, Gloria; Colella, Silvia

doi:10.1016/j.xcrp.2021.100432

Cited by 37 publications

(68 citation statements)

References 26 publications

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“…With respect to the organic cation mixtures, the perovskites incorporating GA, FA and EA show the higher stability. This is in line with reported improvements in the overall stability of the PSCs for GA-MA mixtures [48], EA-MA mixtures as revealed by first-principles calculations [46], while FA-MA mixtures with additional Cs also demonstrate stability enhancement [66]. Triple cations systems have been also evaluated starting with the base composition of MA 0.5 FA 0.25 Cs 0.25 PbI 3 and subsequently the highest proportion among the cations is varied along with halogen composition.…”

Section: Resultssupporting

confidence: 89%

Investigation of Opto-Electronic Properties and Stability of Mixed-Cation Mixed-Halide Perovskite Materials with Machine-Learning Implementation

et al. 2021

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The feasibility of mixed-cation mixed-halogen perovskites of formula AxA’1−xPbXyX’zX”3−y−z is analyzed from the perspective of structural stability, opto-electronic properties and possible degradation mechanisms. Using density functional theory (DFT) calculations aided by machine-learning (ML) methods, the structurally stable compositions are further evaluated for the highest absorption and optimal stability. Here, the role of the halogen mixtures is demonstrated in tuning the contrasting trends of optical absorption and stability. Similarly, binary organic cation mixtures are found to significantly influence the degradation, while they have a lesser, but still visible effect on the opto-electronic properties. The combined framework of high-throughput calculations and ML techniques such as the linear regression methods, random forests and artificial neural networks offers the necessary grounds for an efficient exploration of multi-dimensional compositional spaces.

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Section: Resultssupporting

confidence: 89%

Investigation of Opto-Electronic Properties and Stability of Mixed-Cation Mixed-Halide Perovskite Materials with Machine-Learning Implementation

et al. 2021

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“…After most MA + was consumed, resonances from the MFA + and DMFA + CH 3 groups exhibited a 9:1 peak area ratio in both solvent systems, indicating a 9:1 M ratio of MFA + to DMFA + . Aging MA + /FA + inks in the DMSO/DMF cosolvent has previously been shown to result in the formation of similar ratios of MFA + and DMFA + . , …”

Section: Resultsmentioning

confidence: 97%

“…The 3.05 and 8.30 ppm signals appeared with a peak area ratio of 3:1, from the CH 3 and CH protons of N -methyl formamidinium (“MFA + ”), respectively. , The 3.20 ppm resonance is from a CH 3 group in N , N -dimethyl formamidinium (“DMFA + ”). , The appearance of several low intensity resonances with aging times greater than 1 day (Figures S9–S14) can be attributed to the formation of different stereoisomers of MFA + and DMFA + . No resonance from dimethylamine (Figure S21), a product of DMF hydrolysis, , was observed.…”

Section: Resultsmentioning

confidence: 99%

“…The formation of these degradation products is thought to be initiated by neutral MA, which affects aminolysis of FA + to produce MFA + and ammonia, followed by a second aminolysis reaction between MA and MFA + to produce DMFA + and ammonia (Figure D). , Both MA and FA could participate in these reactions and are always present in the perovskite ink at low concentrations as the conjugate bases in their respective acid–base equilibria . Based on the initial concentrations of 0.38 M MA + and 1.2 M FA + in fresh MC-NMP ink and their aqueous p K a values (), which are strongly correlated and similar in magnitude to their p K a values in polar aprotic solvents such as DMSO, NMP, and DMF, the approximate initial concentrations of MA and FA in MC-NMP ink are 3 × 10 –6 and 2 × 10 –6 M, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…The oxidation of I – to I 2 and reactions of the organic components including MA + , FA + , and solvent are major contributors to perovskite ink decomposition. ,− Proposed organic reactions begin with the deprotonation of MA + or FA + to produce methylamine (MA) or formamidine (FA), which then undergo further reactions. ,,,,− , In perovskite inks containing FA + or MA + /FA + in dimethyl sulfoxide (DMSO) and N , N -dimethylformamide (DMF) cosolvent, the presence of water in solvents from exposure to air accelerates these degradation processes ,, and in some cases, results in the hydrolysis of the DMF solvent to produce dimethylamine and formic acid . Although inhibiting the deprotonation of MA + or FA + with sulfur, triethyl borate, or phenylboric acid significantly improved the stability of DMSO/DMF inks, the characteristics of an additive required to confer moisture stability remain to be investigated.…”

Section: Introductionmentioning

confidence: 99%

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Inhibition of Amine–Water Proton Exchange Stabilizes Perovskite Ink for Scalable Solar Cell Fabrication

et al. 2022

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Ambient air processing is desirable for the industrial fabrication of perovskite solar cells. Here, we show that perovskite ink containing methylammonium and formamidinium in Nmethyl-2-pyrrolidone and N,N-dimethylformamide, a cosolvent composition that satisfies prerequisites for upscaling solar cell fabrication, degrades within a day in ambient air. From 1 H NMR spectroscopic analysis, we find that water proton exchange with methylammonium and formamidinium facilitates the aminolysis of formamidinium by methylamine. The addition of elemental sulfur inhibits this proton exchange process via sulfur−amine reactions, resulting in a stable perovskite ink with an extrapolated half-life of 6300 h. The control ink aged for 1 day does not form perovskite films for solar cell fabrication, while the sulfur-stabilized ink is reproducibly used to make devices with efficiencies >15% when aged for over 1 month. The stabilized ink is suitable for upscaling perovskite solar cell fabrication, with efficiencies up to 17% for blade-coated devices.

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Volatile 2D Ruddlesden‐Popper Perovskite: A Gift for α‐Formamidinium Lead Triiodide Solar Cells

Liang

Zhang

Huang

et al. 2022

Adv Funct Materials

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Perovskite solar cells with increasingly pure composition of α-formamidinium lead triiodide (α-FAPbI 3 ) perovskite are utilized to set more and more record-breaking efficiencies. However, pure α-FAPbI 3 perovskite is unstable and difficult to prepare. Here, a series of bulky alkylammoniums known as the spacer cations (RP cations) of 2D Ruddlesden-Popper perovskites (2D perovskites) are used to prepare α-FAPbI 3 perovskite films. The deprotonation process of RP cations during annealing removes the in situ generated 2D perovskites from the film, which determines the phase and compositional purity, crystallinity, and stability of α-FAPbI 3 perovskite films and depends on the design of RP cations. Only a small number of residual RP cations (0.3-2.3%) are found anchoring at grain boundaries. As a result, α-FAPbI 3 perovskite solar cells prepared from RP cations, especially 2-thiophenemethylammonium, show higher efficiency and stability than control devices prepared from the most commonly used methylammonium. It is believed that in situ generated 2D perovskites are ideal additives for α-FAPbI 3 perovskite, because a large addition (20%) of 2D perovskites ensures the preparation of high-quality phase-pure α-FAPbI 3 perovskite films, while a small number of residual RP cations anchored at grain boundaries guarantee the performance and stability of α-FAPbI 3 perovskite solar cells.

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Methylammonium-formamidinium reactivity in aged organometal halide perovskite inks

Cited by 37 publications

References 26 publications

Investigation of Opto-Electronic Properties and Stability of Mixed-Cation Mixed-Halide Perovskite Materials with Machine-Learning Implementation

Investigation of Opto-Electronic Properties and Stability of Mixed-Cation Mixed-Halide Perovskite Materials with Machine-Learning Implementation

Inhibition of Amine–Water Proton Exchange Stabilizes Perovskite Ink for Scalable Solar Cell Fabrication

Volatile 2D Ruddlesden‐Popper Perovskite: A Gift for α‐Formamidinium Lead Triiodide Solar Cells

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