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## Anharmonicity in Hybrid and Inorganic Perovskite Materials used for Photovoltaics Applications References

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Arthur Marronnier
• Function : Correspondent author
• PersonId : 1028242

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Heejae Lee
Denis Tondelier
Bernard Geffroy
• Function : Author
• PersonId : 832974
Jean Eric Bourée
Yvan Bonnassieux
Guido Roma

#### Abstract

Hybrid organic-inorganic perovskite materials have emerged over the past five years as absorber layers for new high-efficiency yet low-cost solar cells that combine the advantages of organic and inorganic semiconductors. Despite this sky rocketing evolution, the physics behind the electronic transport in these materials is still poorly understood. Here, employing the linear response (DFPT) approach of Density Functional Theory (DFT) and frozen phonon calculations, we reveal strong anharmonic effects in the inorganic CsPbI$_3$ perovskite structure compared to the hybrid CH$_3$ NH$_3$ PbI$_3$ (MAPbI$_3$) material, and found a double-well instability at the center of the Brillouin Zone. We show that previously reported soft modes are stabilized at the actual lower symmetry equilibrium structure, which occurs in a very flat energy landscape. These findings highlight the crucial role played by temperature in these materials, showing that this perovskite structure can oscillate between two equilibrium states at room temperature. Taking into account these low energy-highly occupied phonon states into the models used for electron-phonon interactions and band gap calculations could lead to a better understanding of the electrical transport properties of perovskite solar cells.

#### Domains

Chemical Sciences Material chemistry

### Dates and versions

cea-02340988 , version 1 (31-10-2019)

### Identifiers

• HAL Id : cea-02340988 , version 1

### Cite

Arthur Marronnier, Heejae Lee, Chloé Dindault, Denis Tondelier, Bernard Geffroy, et al.. Anharmonicity in Hybrid and Inorganic Perovskite Materials used for Photovoltaics Applications References. Journées Perovskites Hybrides, May 2017, Angers, France. ⟨cea-02340988⟩

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