Strong Electron–Phonon Coupling and Self-Trapped Excitons in the Defect Halide Perovskites A3M2I9 (A = Cs, Rb; M = Bi, Sb)

McCall, Kyle M.; Stoumpos, Constantinos C.; Kostina, Svetlana S.; Kanatzidis, Mercouri G.; Wessels, Bruce W.

doi:10.1021/acs.chemmater.7b01184

Cited by 556 publications

(762 citation statements)

References 106 publications

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“…Because of the photoinduced Jahn-Teller distortion, which causes substantial octahedral distortion upon photoexcitation, the STE usually acts as a state with a large Stokes shift. The formation of a localized STE is critically dependent on the dimensionality of the crystalline systems, and a more reduced dimensionality makes exciton self-trapping easier 29 .…”

Section: Resultsmentioning

confidence: 99%

Pressure-induced emission of cesium lead halide perovskite nanocrystals

et al. 2018

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Metal halide perovskites (MHPs) are of great interest for optoelectronics because of their high quantum efficiency in solar cells and light-emitting devices. However, exploring an effective strategy to further improve their optical activities remains a considerable challenge. Here, we report that nanocrystals (NCs) of the initially nonfluorescent zero-dimensional (0D) cesium lead halide perovskite Cs4PbBr6 exhibit a distinct emission under a high pressure of 3.01 GPa. Subsequently, the emission intensity of Cs4PbBr6 NCs experiences a significant increase upon further compression. Joint experimental and theoretical analyses indicate that such pressure-induced emission (PIE) may be ascribed to the enhanced optical activity and the increased binding energy of self-trapped excitons upon compression. This phenomenon is a result of the large distortion of [PbBr6]4− octahedral motifs resulting from a structural phase transition. Our findings demonstrate that high pressure can be a robust tool to boost the photoluminescence efficiency and provide insights into the relationship between the structure and optical properties of 0D MHPs under extreme conditions.

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Section: Resultsmentioning

confidence: 99%

Pressure-induced emission of cesium lead halide perovskite nanocrystals

et al. 2018

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“…TheL O phonon energy obtained from the fitting corresponds to af requency of 105 cm À1 ,w hich is well within the range of PbCl stretching frequencies,a se videnced by Raman spectroscopy ( Figure S21 (b)). [28] In addition, temperaturedependent band gap behavior was also observed in TJU-4 with ab lue shift of the absorption edge as the temperature decreased from 233 Kt o9 3K( Figure S22). [28] In addition, temperaturedependent band gap behavior was also observed in TJU-4 with ab lue shift of the absorption edge as the temperature decreased from 233 Kt o9 3K( Figure S22).…”

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confidence: 82%

Intrinsic Broadband White‐Light Emission from Ultrastable, Cationic Lead Halide Layered Materials

et al. 2017

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We report a family of cationic lead halide layered materials, formulated as [Pb X ] [ O C(CH) CO ] (X=F, Cl, Br), exhibiting pronounced broadband white-light emission in bulk form. These well-defined PbX-based structures achieve an external quantum efficiency as high as 11.8 %, which is comparable to the highest reported value (ca.9 %) for broadband phosphors based on layered organolead halide perovskites. More importantly, our cationic materials are ultrastable lead halide materials, which overcome the air/moisture-sensitivity problems of lead perovskites. In contrast to the perovskites and other bulk emitters, the white-light emission intensity of our materials remains undiminished after continuous UV irradiation for 30 days under atmospheric conditions (ca.60 % relative humidity). Our mechanistic studies confirm that the broadband emission is ascribed to short-range electron-phonon coupling in the strongly deformable lattice and generated self-trapped carriers.

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“…[120] The VBM consists mainly of I 5p orbitals slightly hybridized with Bi 6s orbitals, while the CBM is derived from the antibonding states of Bi 6p and I 5p orbitals. [118,[123][124][125][126] Figure 11c shows the Tauc plot of Cs 3 Bi 2 I 9 crystals at 10 K. Notably, the sharp excitonic peak at 2.56 eV is well separated from the electronic bandgap at 2.86 eV, corresponding to an excitonic binding energy, E b X = 300 meV. [118,121,122] The 0D structure also causes large exciton binding energies.…”

Section: A 3 B(iii) 2 X 9 Nonperovskites (Dimer Phases)mentioning

confidence: 99%

From Lead Halide Perovskites to Lead‐Free Metal Halide Perovskites and Perovskite Derivatives

2019

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serious challenges due to the inclusion of toxic Pb and instability against moisture, heat, and irradiation. In recent years, significant efforts have been paid to develop Pb-free halide perovskite and perovskite derivative absorber materials. However, so far, solar cells based on these materials show significantly inferior performances as compared to their Pb halide perovskite counterparts. Herein, we provide reviews on the fundamental understandings of the photovoltaic properties from Pb halide perovskites to Pb-free metal halide perovskites and perovskite derivatives as well as the experimental results reported in the literature. The results suggest that replacing Pb by nontoxic elements may degrade the superior photovoltaic properties seen in Pb halide perovskites, explaining the fact that all reported solar cells based on Pb-free perovskites or perovskite derivatives show performances significantly lower than Pb halide perovskite solar cells. Overview: Approaches and Consequences of Pb ReplacementWe first provide an overview of the approaches and consequences of Pb replacement reported in the literature, as shown in Figure 1. In general, there are two categories for Pb replacement: using either homovalent elements such as Sn and Ge or heterovalent elements such as Bi and Sb. The heterovalent replacement category can be divided into two subcategories based on the ways to maintain the charge neutrality: ion-splitting and ordered vacancy. The ion-splitting subcategory can be further divided into mixed anion compounds with the formula of AB(Ch,X) 3 , where Ch represents a chalcogen element, and X represents a halogen element, and mixed cation compounds with a formula of A 2 B(I)B(III)X 6 , which are commonly called double perovskites. The ordered vacancy subcategory can also be divided into the B(III) compounds with a formula of A 3 ◻B(III)X 9 and the B(IV) compounds with a formula of A 2 ◻ B(IV)X 6 (the sign of ◻ indicates vacancy). Figure 1 also summarizes the photovoltaic properties and the stabilities of each group of materials, which provides a clear overview of the consequences of Pb replacement. While the homovalent replacement by Sn or Ge leads to instability, the heterovalent Pb replacement leads to degraded electronic properties mainly due to the reduction on electronic dimensionality. As a result, all the reported Pb-free perovskite and perovskite derivative solar Despite the exciting progress on power conversion efficiencies, the commercialization of the emerging lead (Pb) halide perovskite solar cell technology still faces significant challenges, one of which is the inclusion of toxic Pb. Searching for Pb-free perovskite solar cell absorbers is currently an attractive research direction. The approaches used for and the consequences of Pb replacement are reviewed herein. Reviews on the theoretical understanding of the electronic, optical, and defect properties of Pb and Pb-free halide perovskites and perovskite derivatives are provided, as well as the experimental results available in the literature....

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Strong Electron–Phonon Coupling and Self-Trapped Excitons in the Defect Halide Perovskites A₃M₂I₉ (A = Cs, Rb; M = Bi, Sb)

Cited by 556 publications

References 106 publications

Pressure-induced emission of cesium lead halide perovskite nanocrystals

Pressure-induced emission of cesium lead halide perovskite nanocrystals

Intrinsic Broadband White‐Light Emission from Ultrastable, Cationic Lead Halide Layered Materials

From Lead Halide Perovskites to Lead‐Free Metal Halide Perovskites and Perovskite Derivatives

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