Thermodynamic Origin of Photoinstability in the CH3NH3Pb(I1–xBrx)3 Hybrid Halide Perovskite Alloy

Brivio, Federico; Caetano, Carla; Walsh, Aron

doi:10.1021/acs.jpclett.6b00226

Cited by 339 publications

(527 citation statements)

References 42 publications

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“…These results are consistent with our observation that formation of PbI 2 was suppressed for increasing FA content with only trace amounts of PbI 2 found aer 10 days for x ¼ 0.6. We note that Brivio et al 38 nd very small entropy terms for halide ion mixing in MAPI-based perovskites, which would further increase the stability of 1 À A), where the A is peak area under the PbI 2 (001) reflections in the X-ray diffraction patterns and t is time in hours. Similar plots were produced for each value of x.…”

Section: -36mentioning

confidence: 76%

Understanding the stability of mixed A-cation lead iodide perovskites

et al. 2017

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The routes and kinetics of the degradation of thin films of methylammonium (MA)/formamidinium (FA) lead iodide perovskites (MA 1Àx FA x PbI 3 , 0 # x # 1) under dry atmospheric conditions have been investigated. MA-rich phases decompose to the precursor iodide salts and PbI 2 , while FA-rich phases convert mainly to the yellow hexagonal phase. The reactivity is strongly inhibited for mixed cation phases of MA 1Àx FA x PbI 3 , for x ¼ 0.4 to 0.6, where the decomposition routes available to end member phases become less favourable. It is shown that for pristine films with x ¼ 0.6, PbI 2 formation can be completely suppressed for up to 10 days. Kinetic analysis reveals that the rate of PbI 2 formation decays exponentially with increasing FA content until x ¼ 0.7, beyond which the FA containing perovskite transforms rapidly to the hexagonal phase. Ab initio simulations of the decomposition reaction energies fully support the increased kinetic stability found experimentally for the mixed A-cation perovskites.Hybrid lead halide perovskites have recently risen to prominence as highly versatile materials for optoelectronic technologies, particularly high efficiency, solution processed solar cells.1-4 They display near optimal band gap for solar light absorption, high absorption coefficients, steep absorption onsets and signicant charge carrier lifetimes (and thus diffusion lengths).2,5 These properties, combined with the processability of these materials, 6,7 have resulted in solar cell device efficiencies rising rapidly to over 22%.8 However, the commercial applicability of these materials is hampered by their relative lack of stability compared to established inorganic and organic semiconductors.9-11 By chemical site-substitution at any of the A, B or X sites of the ABX 3 perovskite structure, it has been found that it is possible to tune the properties and, most pertinently, the stability of the resultant material. 12-14The archetypal hybrid perovskite methylammonium (MA) lead iodide (CH 3 NH 3 PbI 3 ), MAPI, crystallises in the tetragonal space group I4/mcm at room temperature.15 Formamidinium (FA) lead iodide (CH(NH 2 ) 2 PbI 3 ), FAPI, by contrast preferentially crystallises in the yellow, 2H hexagonal perovskite type polymorph at room temperature, which can be driven to transform to the black cubic perovskite polymorph (required for photovoltaic applications) by heating above room temperature. 16-19Such varying phase behaviour can be accounted for by the different sizes and hydrogen bonding mechanisms of these dissimilar organic cations, MA and FA.Both MA and FA cations display directional hydrogen bonding, a factor of increasing importance in controlling phase behaviour as the system temperature is reduced and also for dening the relative stability of the two polymorphs of FAPI. 20Stabilisation of mixed A site compounds relative to the end members of the series can be rationalised using geometrical arguments in which the perovskite tolerance factor is tuned using differently sized cations, as well as an entrop...

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Section: -36mentioning

confidence: 76%

Understanding the stability of mixed A-cation lead iodide perovskites

et al. 2017

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“…46 In addition, our solid phase synthesis requires no solvent(s) so that no single precursor or major component is lost during sample isolation and purification.…”

Section: U P P O R T T H E I D E a T H A T T H E N O N S T O I C H Imentioning

confidence: 99%

Persistent Dopants and Phase Segregation in Organolead Mixed-Halide Perovskites

Rosales¹,

Men

Cady³

et al. 2016

Chem. Mater.

142

218

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O r g a n o l e a d m i x e d -h a l i d e p e r o v s k i t e s s u c h a s CH 3 NH 3 PbX 3−a X′ a (X, X′ = I, Br, Cl) are interesting semiconductors because of their low cost, high photovoltaic power conversion efficiencies, enhanced moisture stability, and band gap tunability. Using a combination of optical absorption spectroscopy, powder X-ray diffraction (XRD), and, for the first time, 207 Pb solid state nuclear magnetic resonance (ssNMR), we probe the extent of alloying and phase segregation in these materials. Because 207 Pb ssNMR chemical shifts are highly sensitive to local coordination and electronic structure, and vary linearly with halogen electronegativity and band gap, this technique can provide the true chemical speciation and composition of organolead mixed-halide perovskites. We specifically investigate samples made by three different preparative methods: solution phase synthesis, thermal annealing, and solid phase synthesis. 207 Pb ssNMR reveals that nonstoichiometric dopants and semicrystalline phases are prevalent in samples made by solution phase synthesis. We show that these nanodomains are persistent after thermal annealing up to 200 °C. Further, a novel solid phase synthesis that starts from the parent, single-halide perovskites can suppress phase segregation but not the formation of dopants. Our observations are consistent with the presence of miscibility gaps and spontaneous spinodal decomposition of the mixed-halide perovskites at room temperature. This underscores how strongly different synthetic procedures impact the nanostructuring and composition of organolead halide perovskites. Better optoelectronic properties and improved device stability and performance may be achieved through careful manipulation of the different phases and nanodomains present in these materials.

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“…The halogen ions locate at the corners of Pb-X octahedron, and the iodine ions locate at the top and/or bottom sites of each octahedron. These two ordered structures provide the structural freedom to separate the Pb-I (longer) and Pb-Br (shorter) interatomic separation along distinct directions, so that the internal strain is minimized and the architecture is most stable [60].…”

Section: Mixed X Halide Anionsmentioning

confidence: 99%

Perovskite-Based Solar Cells: Materials, Methods, and Future Perspectives

Zhou

Tian

et al. 2018

Journal of Nanomaterials

277

148

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A novel all-solid-state, hybrid solar cell based on organic-inorganic metal halide perovskite (CH 3 NH 3 PbX 3 ) materials has attracted great attention from the researchers all over the world and is considered to be one of the top 10 scientific breakthroughs in 2013. The perovskite materials can be used not only as light-absorbing layer, but also as an electron/hole transport layer due to the advantages of its high extinction coefficient, high charge mobility, long carrier lifetime, and long carrier diffusion distance. The photoelectric power conversion efficiency of the perovskite solar cells has increased from 3.8% in 2009 to 22.1% in 2016, making perovskite solar cells the best potential candidate for the new generation of solar cells to replace traditional silicon solar cells in the future. In this paper, we introduce the development and mechanism of perovskite solar cells, describe the specific function of each layer, and focus on the improvement in the function of such layers and its influence on the cell performance. Next, the synthesis methods of the perovskite light-absorbing layer and the performance characteristics are discussed. Finally, the challenges and prospects for the development of perovskite solar cells are also briefly presented.

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Thermodynamic Origin of Photoinstability in the CH₃NH₃Pb(I_1–xBr_x)₃ Hybrid Halide Perovskite Alloy

Cited by 339 publications

References 42 publications

Understanding the stability of mixed A-cation lead iodide perovskites

Understanding the stability of mixed A-cation lead iodide perovskites

Persistent Dopants and Phase Segregation in Organolead Mixed-Halide Perovskites

Perovskite-Based Solar Cells: Materials, Methods, and Future Perspectives

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