<i>In situ</i> identification of cation-exchange-induced reversible transformations of 3D and 2D perovskites

Huang, Weixin; Sadhu, Subha; Sapkota, Pitambar; Ptasińska, Sylwia

doi:10.1039/c8cc02801j

Cited by 12 publications

(7 citation statements)

References 28 publications

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“…This mechanism reorganizes the surface to form the 2D perovskite. , The greater complexation of Pb 2+ with Br – than with I – justifies the greater bromine/iodine ratio in the 2D phase than in the 3D perovskite . Due to the highly polar nature of IPA, it significantly dissolves FA and MA ions .…”

Section: Resultsmentioning

confidence: 99%

Unraveling the Formation Mechanism of the 2D/3D Perovskite Heterostructure for Perovskite Solar Cells Using Multi-Method Characterization

et al. 2022

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The formation of a two-dimensional (2D) three-dimensional (3D) perovskite heterostructure has lately proved to be a promising way to improve the interface between the perovskite and electron/hole transport layers in perovskite solar cells, which is crucial for better device efficiency and stability. Herein, a spacer cation, 4-fluorophenethylammonium iodide, in isopropyl alcohol was used to form a thin 2D perovskite layer on top of a 3D triple-cation perovskite by a spin-coating deposition process. Therefore, a significant improvement in the device open-circuit voltage is obtained, leading to an enhanced power conversion efficiency. The formation mechanism of the 2D perovskite layer was studied by analyzing the structural, chemical, and optoelectronic properties of the layer, while varying several synthesis parameters. We reveal the presence of bromide inside the 2D phase and conclude with the existence of a concomitant formation mechanism, besides the most commonly described one involving the lead iodide (PbI2) excess contained in the 3D bulk. Therefore, we demonstrate how the stoichiometry of the 2D perovskite is affected by the chemical composition of the 3D layer underneath. This work provides new insights into the synthesis mechanisms of 2D/3D perovskite heterostructures, which could help to optimize their fabrication processes and develop new efficient and functional 2D/3D structures.

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Section: Resultsmentioning

confidence: 99%

Unraveling the Formation Mechanism of the 2D/3D Perovskite Heterostructure for Perovskite Solar Cells Using Multi-Method Characterization

et al. 2022

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“…, where N is the concentration of atoms, I is the peak area of photoelectrons, and S is the atomic sensitivity factor provided by the instrument manufacturer. All spectra were calibrated to their corresponding C 1s which is 285.3 eV, 28,29 and binding energy values for all fitted and assigned spectral peaks are stated with an accuracy of 0.1−0.2 eV. Detailed femtosecond time-resolved transient absorption spectra were described in literature.…”

Section: Methodsmentioning

confidence: 99%

“…The ratios of I/Sn, Br/Sn, N/Sn, and Pb 0 /Pb total were estimated from the following equation: , where N is the concentration of atoms, I is the peak area of photoelectrons, and S is the atomic sensitivity factor provided by the instrument manufacturer. All spectra were calibrated to their corresponding C 1s which is 285.3 eV, , and binding energy values for all fitted and assigned spectral peaks are stated with an accuracy of 0.1–0.2 eV.…”

Section: Methodsmentioning

confidence: 99%

Effect of Light Illumination on Mixed Halide Lead Perovskites: Reversible or Irreversible Transformation

Huang

Yoon

Sapkota

2018

ACS Appl. Energy Mater.

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One intriguing aspect of mixed halide lead perovskites (e.g., CH 3 NH 3 PbBr x I 3−x ) is halide ion segregation when subjected to visible illumination, but this aspect gives rise to the concerns regarding the influence of halide ion movement on the long−term stability and applications. Here, the impact of light illumination on mixed halide hybrid perovskite films was investigated by exposing such films to continuous wavelength laser (25 mW/cm 2 ). It turns out that under illumination the segregated iodide-rich perovskite species further decompose and ultimately form metallic lead (Pb 0 ). The chemical changes in decomposed films were found to cause an irreversible shift of the absorption band edge and a significant change in film morphology, while no decomposition of MAPbI 3 and MAPbBr 3 films was observed after exposure to the same illumination condition. Our results unambiguously demonstrate the deleterious effect of phase segregation on material stability for mixed halide perovskites.

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“…The first two peaks have the same locations as those of the DMEDAI 2 powder, but the last three peaks located at 1021, 857, and 755 cm −1 were not observed in the spectra of DMEDAI 2 or MAPbI 3 , likely corresponding to the newly formed 2D perovskites. These results suggested that DMEDAI 2 did not physically attach to the surfaces of MAPbI 3 but underwent cation exchange with MA in 3D MAPbI 3 or reacted with PbI 2 to form 2D perovskites, 58,59 which changed the structural and optical properties of the pristine MAPbI 3 thin films.…”

Section: Resultsmentioning

confidence: 99%

Facile Formation of 2D–3D Heterojunctions on Perovskite Thin Film Surfaces for Efficient Solar Cells

He¹,

Worku²,

Xu³

et al. 2019

ACS Appl. Mater. Interfaces

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The interfaces between perovskite and charge transport layers greatly impact the device efficiency and stability of perovskite solar cells (PSCs). Inserting an ultrathin wide-bandgap layer between perovskite and hole transport layers (HTLs) has recently been shown as an effective strategy to enhance device performance. Herein, a small amount of an organic halide salt, N,N′-dimethylethylene-1,2-diammonium iodide, is used to create two-dimensional (2D)−three-dimensional (3D) heterojunctions on MAPbI 3 thin film surfaces by facile solution processing. The formation of an ultrathin wide-band-gap 2D perovskite layer on top of 3D MAPbI 3 changes the morphological and photophysical properties of perovskite thin films, effectively reduces the surface defects, and suppresses the charge recombination in the interfaces between perovskite and HTL. As a result, a power conversion efficiency of ∼20.2%, with an open-circuit voltage of 1.14 V, a short-circuit current density of 22.57 mA cm −2 , and a fill factor of 0.78, is achieved for PSCs with enhanced stability.

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In situ identification of cation-exchange-induced reversible transformations of 3D and 2D perovskites

Cited by 12 publications

References 28 publications

Unraveling the Formation Mechanism of the 2D/3D Perovskite Heterostructure for Perovskite Solar Cells Using Multi-Method Characterization

Unraveling the Formation Mechanism of the 2D/3D Perovskite Heterostructure for Perovskite Solar Cells Using Multi-Method Characterization

Effect of Light Illumination on Mixed Halide Lead Perovskites: Reversible or Irreversible Transformation

Facile Formation of 2D–3D Heterojunctions on Perovskite Thin Film Surfaces for Efficient Solar Cells

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