Growth of Hybrid Perovskite Films via Single‐Source Perovskite Nanoparticle Evaporation

Yadav, Rekha; Roy, Mrinmoy; Banappanavar, Gangadhar; Aslam, M.

doi:10.1002/asia.202200087

Cited by 4 publications

(2 citation statements)

References 88 publications

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“…Alternatively, single-source vapor deposition provides a rapid and relatively simple method to obtain crystalline and smooth thin films of DPs . We have fabricated DP thin films using a single-source vapor deposition technique based on our previous report on the growth of conventional perovskite films …”

Section: Resultsmentioning

confidence: 99%

“…35 We have fabricated DP thin films using a single-source vapor deposition technique based on our previous report on the growth of conventional perovskite films. 36 The single-step vapor deposition technique used here utilizes Cs 2 AgBiX 6 (X = Br and Cl) powder as the precursor (single-source). The process of preparing powder samples of Cs 2 AgBiX 6 (X = Br and Cl) and fabrication of their thin films via vapor-deposition technique is discussed in detail in the experimental section of the ESI.…”

Section: Preparation Methods and Structural And Opticalmentioning

confidence: 99%

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BiOBr Surface-Functionalized Halide Double-Perovskite Films for Slow Ion Migration and Improved Stability

Bhawna

Roy

Kaur

et al. 2023

ACS Appl. Mater. Interfaces

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Surface-tailored lead-free halide double-perovskite (Cs2AgBiX6) thin films are utilized for ion migration studies. A thin surface layer of BiOBr/Cl is grown via intentional annealing of the halide films in ambient conditions. Herein, we physically stacked the two films, viz., Cs2AgBiBr6 and Cs2AgBiCl6, to thermally activate the halide ion migration at different temperatures (room temperature (RT)–150 °C). While annealing, the films’ color changes from orange to pale yellow and transparent brown to yellow as a result of the migration of Br– ions from Cs2AgBiBr6 to Cs2AgBiCl6 and Cl– ions from Cs2AgBiCl6 to Cs2AgBiBr6, respectively. Annealing helps in homogenizing the halide ions throughout the films, consequently leading to a mixed phase, i.e., Cs2AgBiCl x Br6–x /Cs2AgBiBr x Cl6–x (x = 0 to 6) formation. The movement of ions is understood by absorption studies performed at regular time intervals. These investigations reveal a redshift (from 366 to 386 nm) and a blueshift (from 435 to 386 nm) in absorption spectra, indicating the migration of Br– and Cl– toward Cs2AgBiCl6 and Cs2AgBiBr6, respectively. The films characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) reveal the presence of a peak at 2θ = 10.90° and binding energy of 158.1 eV, respectively, corresponding to the formation of Bi–O bonds at the film surface. Also, XRD studies show a lower 2θ shift of the diffraction peak in the case of Cs2AgBiCl6 films and a higher 2θ shift in the case of Cs2AgBiB6 films, which further confirms the migration of Cl– and Br– from one film to the other. XPS investigations confirm the compositional change with a gradual increment in the concentration of Br–/Cl– with an increase in heating time for Cs2AgBiCl6/Cs2AgBiBr6 films. All these studies confirm thermal diffusion of halide ions in double-perovskite films. Further, from the exponential decay of the absorption spectra, the rate constant for halide (Br) ion diffusion is calculated, which shows an increment from 1.7 × 10–6 s–1 at RT to 12.1 × 10–3 s–1 at 150 °C. The temperature-dependent rate constant follows Arrhenius behavior and renders an activation energy of 0.42 eV (0.35 eV) for bromide (chloride) ion mobility. A larger estimated value as compared to the reported values for Cs2AgBiBr6 wafers (∼0.20 eV) reveals a slow mobility of halide ions in thin films of Cs2AgBiBr6/Cl6. The formation of a BiOBr passivation layer at the surface of Cs2AgBiBr6 thin film might be one of the plausible causes of the slow anion diffusion in the present work. Slow ion migration is an indication that the films are stable and of high-quality.

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Section: Resultsmentioning

confidence: 99%

Section: Preparation Methods and Structural And Opticalmentioning

confidence: 99%

BiOBr Surface-Functionalized Halide Double-Perovskite Films for Slow Ion Migration and Improved Stability

Bhawna

Roy

Kaur

et al. 2023

ACS Appl. Mater. Interfaces

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Incremental Feeding of Perovskite Powders: Angstrom‐Precision Growth for Single‐Source Solar Cell Fabrication

Rodkey,

Huisman,

Bolink

2024

Adv Eng Mater

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Vacuum‐based deposition of halide perovskites has received a lot of attention for its proven scalability and conformal depositions. Co‐evaporation has had remarkable success, but efficiencies continue to lag behind their solution‐based counterparts. This is in part attributed to the complex sublimation behavior of some organic ammonium precursor salts and the increased complexity of the absorber materials, requiring the use of four or more sources in a conventional co‐evaporation setup. The latter has driven work into single‐source methods with flash evaporation presented as one such method. However, flash evaporation processes typically evaporate all material in a single batch, leading to short deposition times at high temperatures. Particle sputtering effects seen at these high temperatures drive processes towards low temperatures where prolonged exposure causes degradation. Here, we present a pulse‐driven incremental powder feeding system. This method is capable of stable flash evaporation rates for >1 hour, with controlled rates as low as 1.5 Å per pulse (+‐ 0.89). We demonstrate the feasibility of this method for three different perovskite compositions: FAPbBr3, MAPbI3, and FA1‐xMAxPbSnI3:SnF2. Furthermore, we integrate FAPbBr3 and MAPbI3 into all vacuum‐processed thin‐film solar cells leading to power conversion efficiencies of ∽4% and 10% respectively.This article is protected by copyright. All rights reserved.

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Oxygen and moisture-induced healing of halide double perovskite surface defects

Bhawna,

Alam,

Aslam

2023

The Journal of Chemical Physics

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In this work, we studied the impact of environmental constituents such as oxygen (O2) and moisture on halide double perovskite (HDP) films. The transport measurements indicate that an increment in O2 concentration enhances the resistivity of a Cs2AgBiBr6 film by two orders of magnitude. The adsorption of O2 on the film’s surface helps in passivation of defects (∼50% reduction in defect density on O2 exposure), which inhibits ion migration and results in an increased resistivity of the film. The process of adsorption and desorption of O2 on the film surface is found to be fully reversible. In contrast, the resistivity of double perovskite films decreases by an order of magnitude in the presence of moisture. This is attributed to the generation of free protons as a result of the dissociation of water molecules at the films’ surface, hence exhibiting an increase in current under external bias. The HDP films possess high resistivity (for T < 100 °C) due to the desorption of physisorbed water layers from the surface, which gradually decreases with an increase in the operating temperature. This work demonstrates that O2 and moisture are a good combination for defect passivation in any HDPs, in general.

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Growth of Hybrid Perovskite Films via Single‐Source Perovskite Nanoparticle Evaporation

Cited by 4 publications

References 88 publications

BiOBr Surface-Functionalized Halide Double-Perovskite Films for Slow Ion Migration and Improved Stability

BiOBr Surface-Functionalized Halide Double-Perovskite Films for Slow Ion Migration and Improved Stability

Incremental Feeding of Perovskite Powders: Angstrom‐Precision Growth for Single‐Source Solar Cell Fabrication

Oxygen and moisture-induced healing of halide double perovskite surface defects

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