TY - JOUR
T1 - Complete Suppression of Detrimental Polymorph Transitions in All-Inorganic Perovskites via Nanoconfinement
AU - Kong, Xiaoqing
AU - Shayan, Kamran
AU - Hua, Sophia
AU - Strauf, Stefan
AU - Lee, Stephanie S.
N1 - Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/4/22
Y1 - 2019/4/22
N2 - Reducing the size of metal halide perovskite crystals to the nanoscale has been demonstrated to stabilize high-performance metastable polymorphs at room temperature. Cesium lead iodide (CsPbI3), for example, typically exists as the insulating δ-phase at room temperature but can adopt the narrow-bandgap γ-phase when the crystal size is reduced to the nanometer length scale. Here we advance a fundamental understanding of the role of nanoconfinement in CsPbI3 polymorph stabilization through a combination of X-ray diffraction and temperature-dependent photoluminescence. Using a wet annealing method to directly form γ-CsPbI3 from solution in the cylindrical nanopores of anodized aluminum oxide, we discovered that nanoconfinement lowers the δ-γ solid-state phase transition temperature from 448 K in the bulk to 370 K. Once formed, nanoconfined γ-CsPbI3 crystals were found to be stable across the temperature range of 4-610 K and upon an unprecedented one year of air exposure at room temperature. Taking advantage of the nanoconfinement-induced suppression of phase transitions, we report for the first time a detailed analysis of electron-phonon interactions in γ-CsPbI3 via temperature-dependent photoluminescent measurements. In-depth analysis of the temperature-dependent peak broadening revealed electron-phonon interactions to be dominated by Fröhlich scattering, similar to that observed in inorganic-organic hybrid perovskite systems. Photoluminescence mapping further confirmed that nanoconfined γ-CsPbI3 crystals exhibit spatial uniformity on the tens of micrometers length scale, suggesting nanoconfinement as a promising strategy to form stable, high-performance perovskite films from solution for light-emitting and light-harvesting applications.
AB - Reducing the size of metal halide perovskite crystals to the nanoscale has been demonstrated to stabilize high-performance metastable polymorphs at room temperature. Cesium lead iodide (CsPbI3), for example, typically exists as the insulating δ-phase at room temperature but can adopt the narrow-bandgap γ-phase when the crystal size is reduced to the nanometer length scale. Here we advance a fundamental understanding of the role of nanoconfinement in CsPbI3 polymorph stabilization through a combination of X-ray diffraction and temperature-dependent photoluminescence. Using a wet annealing method to directly form γ-CsPbI3 from solution in the cylindrical nanopores of anodized aluminum oxide, we discovered that nanoconfinement lowers the δ-γ solid-state phase transition temperature from 448 K in the bulk to 370 K. Once formed, nanoconfined γ-CsPbI3 crystals were found to be stable across the temperature range of 4-610 K and upon an unprecedented one year of air exposure at room temperature. Taking advantage of the nanoconfinement-induced suppression of phase transitions, we report for the first time a detailed analysis of electron-phonon interactions in γ-CsPbI3 via temperature-dependent photoluminescent measurements. In-depth analysis of the temperature-dependent peak broadening revealed electron-phonon interactions to be dominated by Fröhlich scattering, similar to that observed in inorganic-organic hybrid perovskite systems. Photoluminescence mapping further confirmed that nanoconfined γ-CsPbI3 crystals exhibit spatial uniformity on the tens of micrometers length scale, suggesting nanoconfinement as a promising strategy to form stable, high-performance perovskite films from solution for light-emitting and light-harvesting applications.
KW - all-inorganic perovskites
KW - nanoconfinement
KW - photophysics
KW - polymorph phase transition
KW - stability
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U2 - 10.1021/acsaem.9b00322
DO - 10.1021/acsaem.9b00322
M3 - Article
AN - SCOPUS:85064812571
VL - 2
SP - 2948
EP - 2955
JO - ACS Applied Energy Materials
JF - ACS Applied Energy Materials
IS - 4
ER -