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Updated: May 31, 2025
Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Sign of the Gap Temperature Dependence in CsPb(Br,Cl)3 Nanocrystals Determined by Cs-Rattler-Mediated Electron-Phonon
Shima Fasahat1, Nadesh Fiuza-Maneiro2, Benedikt Schäfer1
1Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193 Bellaterra, Spain.
Abstract:
So far, the striking sign reversal in the near-ambient slope of the gap temperature dependence of colloidal CsPbCl3 perovskite nanocrystals (NCs) compared to its Br counterpart remains unresolved. Pure bromide NCs exhibit a linear gap increase with increasing temperature, to which thermal expansion and electron-phonon interaction equally contribute. In contrast, the temperature slope for the chlorine compound gap is clearly negative. By combining temperature- and pressure-dependent photoluminescence on a series of CsPb(Br1-Cl)3 NCs, we unravel the origin of such inversion. The electron-phonon interaction is solely responsible, undergoing a sudden change in sign and magnitude due to activation of an anomalous electron-phonon coupling mechanism linked to vibrational modes characterized by synchronous octahedral tilting and Cs rattling. This takes place in the shrunken orthorhombic NC lattice for Cl concentrations exceeding ca. 40%. We have thus clarified a puzzling result directly impacting the optoelectronic properties of lead halide perovskite NCs.
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