Phase diagram and stability of mixed-cation lead iodide perovskites: A theory and experiment combined study

Xu, Zhengwei; Zhao, Yicheng; Zhang, Jiyun; Chen, Ke‐Qiu; Brabec, Christoph J.; Feng, Yexin

doi:10.1103/physrevmaterials.4.095401

Cited by 24 publications

(23 citation statements)

References 59 publications

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“…Sixty-four kinds of perovskite including over stoichiometric samples with excess halide salts were fabricated through drop-cast and spin-coat methods 3 , as shown in Table S1. The selection for the 64 compositions is mainly based on the phase diagram of mixed-cation perovskites 25 . The selection for the 64 compositions is mainly based on the phase diagram of mixed-cation perovskites 25 .…”

Section: Resultsmentioning

confidence: 99%

“…The selection for the 64 compositions is mainly based on the phase diagram of mixed-cation perovskites 25 . The selection for the 64 compositions is mainly based on the phase diagram of mixed-cation perovskites 25 . Above 300 K, the miscibility gap is at ~25 mol.% for Cs/MA cations in FAPbI3-based perovskites while it is at ~5 mol.% for K/Rb cations.…”

Section: Resultsmentioning

confidence: 99%

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Discovery of temperature-induced stability reversal in perovskites using high-throughput robotic learning

et al. 2021

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Stability of perovskite-based photovoltaics remains a topic requiring further attention. Cation engineering influences perovskite stability, with the present-day understanding of the impact of cations based on accelerated ageing tests at higher-than-operating temperatures (e.g. 140°C). By coupling high-throughput experimentation with machine learning, we discover a weak correlation between high/low-temperature stability with a stability-reversal behavior. At high ageing temperatures, increasing organic cation (e.g. methylammonium) or decreasing inorganic cation (e.g. cesium) in multi-cation perovskites has detrimental impact on photo/thermal-stability; but below 100°C, the impact is reversed. The underlying mechanism is revealed by calculating the kinetic activation energy in perovskite decomposition. We further identify that incorporating at least 10 mol.% MA and up to 5 mol.% Cs/Rb to maximize the device stability at device-operating temperature (<100°C). We close by demonstrating the methylammonium-containing perovskite solar cells showing negligible efficiency loss compared to its initial efficiency after 1800 hours of working under illumination at 30°C.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Discovery of temperature-induced stability reversal in perovskites using high-throughput robotic learning

et al. 2021

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“…While on the incorporation of Cs + into the perovskite crystal lattice, a broad consensus is achieved, ,,,− the question whether Rb + can also be integrated into the mixed perovskite crystal lattice is still discussed. − ,− ,− To address this issue, lattice parameters of the cubic perovskite structure were determined for the different compositions. Figure b depicts the cubic unit cell parameter a as a function of composition.…”

Section: Resultsmentioning

confidence: 99%

“…However, the presence of a segregated PbI 2 phase might negatively affect charge carrier lifetimes and long-term environmental stability of the material . This has been addressed by the addition of Rb + , which has proven beneficial in stabilizing the cubic FAPbI 3 phase ,− and reducing residual PbI 2 , by reacting with the excess material, and has also been explored in quadruple-cation compositions of FA + , MA + , Cs + , and Rb + . ,,,− …”

Section: Introductionmentioning

confidence: 99%

Quantifying Stabilized Phase Purity in Formamidinium-Based Multiple-Cation Hybrid Perovskites

et al. 2021

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A promising approach for the production of highly efficient and stable hybrid perovskite solar cells is employing mixed-ion materials. Remarkable performances have been reached by materials comprising a stabilized mixture of methylammonium (MA + ) and formamidinium (FA + ) as a monovalent cation. We compare and quantify the methods of stabilizing FA-based perovskites involving the additional blending of the smaller inorganic cations cesium (Cs + ) and rubidium (Rb + ), which can lead to an improvement in phase purity of black cubic perovskite modification. Even under excess lead iodide conditions, the presence of a separate PbI 2 phase as well as hexagonal phases, which are very common for formamidinium-containing perovskites, can be drastically reduced or even completely prevented. In this aspect, adding both Cs + and Rb + showed greater effectivity than only adding Cs + , enabling an increase in the percentage of the cubic phase within the material from 45% in the double-cation FA:MA mixture to 97.8% in the quadruple composition. The impact of admixing inorganic cations on the perovskite crystal structure resulted in enlarged homogeneous crystallite sizes and a less pronounced orientational order and indicated also minor modifications of unit cell sizes. Finally, we discuss the impact of the phase purity on charge-carrier recombination dynamics and solar cell performance.

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“…Besides the thermally unstable MA, Cs is a particularly promising smaller cation, enabling Cs x FA 1− x PbI 3 perovskite films with optical and electrical properties suitable for photovoltaics. [ 16,17 ] Another approach for stabilizing the photoactive phase in FA‐based perovskites is introducing different B‐site cations to substitute for Pb. The divalent cation Sr 2+ , as an example, has been used to process FAPb 1− x Sr x I 3 quantum dots with long‐term stability and improved optoelectronic properties, which stem from reduced I and Pb vacancies that lead to the formation of Schottky defects.…”

Section: Introductionmentioning

confidence: 99%

Effects of Alkaline Earth Metal Additives on Methylammonium‐Free Lead Halide Perovskite Thin Films and Solar Cells

et al. 2022

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Organic–inorganic lead halide perovskite solar cells are regarded as one of the most promising technologies for the next generation of photovoltaics due to their high power conversion efficiency (PCE) and simple solution manufacturing. Among the different compositions, the formamidinium lead iodide (FAPbI3) photoactive phase has a bandgap of 1.4 eV, which enables the corresponding higher PCEs according to the Shockley–Queisser limit. However, the photoactive crystal phase of FAPbI3 is not stable at room temperature. The most high‐performing compositions to date have reduced this problem by incorporating the methylammonium (MA) cation into the FAPbI3 composition, although MA has poor stability at high temperatures and in humid environments, which can limit the lifetime of FAxMA1−xPbI3 films. CsxFA1−xPbI3 perovskites are also explored, but despite better stability they still lag in performance. Herein, the additive engineering of MA‐free organic−inorganic lead halide perovskites using divalent cations Sr2+ and Ca2+to enhance the performances of CsxFA1−xPbI3 perovskite compositions is explored. It is revealed that the addition of up to 0.5% of Sr2+ and Ca2+ leads to improvements in morphology and reduction in microstrain. The structural improvements observed correlate with improved solar cell performances at low additive concentrations.

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Phase diagram and stability of mixed-cation lead iodide perovskites: A theory and experiment combined study

Cited by 24 publications

References 59 publications

Discovery of temperature-induced stability reversal in perovskites using high-throughput robotic learning

Discovery of temperature-induced stability reversal in perovskites using high-throughput robotic learning

Quantifying Stabilized Phase Purity in Formamidinium-Based Multiple-Cation Hybrid Perovskites

Effects of Alkaline Earth Metal Additives on Methylammonium‐Free Lead Halide Perovskite Thin Films and Solar Cells

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