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Unusual Pressure‐Driven Phase Transformation and Band Renormalization in 2D vdW Hybrid Lead Halide Perovskites
Author(s) -
Li Han,
Qin Ying,
Shan Bohan,
Shen Yuxia,
Ersan Fatih,
Soignard Emmanuel,
Ataca Can,
Tongay Sefaattin
Publication year - 2020
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201907364
Subject(s) - halide , materials science , perovskite (structure) , van der waals force , phase transition , band gap , chemical physics , octahedron , phase (matter) , anisotropy , semiconductor , molecule , condensed matter physics , crystallography , crystal structure , optics , chemistry , optoelectronics , inorganic chemistry , physics , organic chemistry
The application of high pressure allows control over the unit cell and interatomic spacing of materials without any need for new growth methods or processing while accessing their materials properties in situ. Under these extreme pressures, materials may assume new structural phases and reveal novel properties. Here, unusual phase transition and band renormalization effects in 2D van der Waals Ruddlesden−Popper hybrid lead halide perovskites, which have shown extraordinary optical properties and immense potential in light emission and conversion technologies, are reported. The results show that (CH 3 (CH 2 ) 3 NH 3 ) 2 (CH 3 NH 3 )Pb 2 Br 7 ( n = 2) layers undergo two distinct phase transitions related to PbBr 6 octahedra, butylammonium (BA), and methylammonium (MA) molecule tilting motion that leads to rather unique/anomalous bandgap variation with pressure. In contrast, (CH 3 (CH 2 ) 3 NH 3 )PbBr 4 ( n = 1) lacks MA molecules and possesses only one pressure‐induced phase transition related to PbBr 6 octahedra and BA tilting. In this range, the bandgap reduces monotonically, much similar to other inorganic semiconductors and display surprisingly large redshift from 3 to 2.4 eV. Together with theoretical calculations, this study offers unique insights into these pressure‐induced changes and extends the understanding of these highly anisotropic layered soft organic perovskite materials under extreme conditions.