Anomalous and colossal thermal expansion, photoluminescence, and dielectric properties in lead halide-layered perovskites with cyclohexylammonium and cyclopentylammonium cations

Alberto Cuquejo-Cid; Alberto García-Fernández; Catalin Popescu; Juan Manuel Bermúdez-García; María A Señarís-Rodríguez; Socorro Castro-García; Digna Vázquez-García; Manuel Sánchez-Andújar

doi:10.1016/j.isci.2022.104450

Anomalous and colossal thermal expansion, photoluminescence, and dielectric properties in lead halide-layered perovskites with cyclohexylammonium and cyclopentylammonium cations

iScience. 2022 May 23;25(6):104450. doi: 10.1016/j.isci.2022.104450. eCollection 2022 Jun 17.

Authors

Alberto Cuquejo-Cid¹, Alberto García-Fernández^{1

2}, Catalin Popescu³, Juan Manuel Bermúdez-García¹, María A Señarís-Rodríguez¹, Socorro Castro-García¹, Digna Vázquez-García¹, Manuel Sánchez-Andújar¹

Affiliations

¹ Universidade da Coruña, Quimolmat, Centro de Investigacións Científicas Avanzadas (CICA), Rúa As Carballeiras, 15071 A Coruña, Spain.
² Department of Chemistry, Division of Applied Physical Chemistry, KTH Royal Institute of Technology, SE 100 44 Stockholm, Sweden.
³ CELLS-ALBA Synchrotron Light Facility, Cerdanyola del Vallès, 08290 Barcelona, Spain.

Abstract

A detailed study of lead halide-layered perovskites with general formula A₂PbX₄ (where A is cyclohexylammonium (CHA) or cyclopentylammonium (CPA) cation and X is Cl^- or Br^- anion) is presented. Using variable temperature synchrotron X-ray powder diffraction, we observe that these compounds exhibit diverse crystal structures above room temperature. Very interestingly, we report some unconventional thermomechanical responses such as uniaxial negative thermal expansion and colossal positive thermal expansion in a perpendicular direction. For the polymorphs of (CHA)₂PbBr₄, the volumetric thermal expansion coefficient is among the highest reported for any extended inorganic crystalline solid, reaching 480 MK^-1. The phase transitions are confirmed by calorimetry and dielectric measurements, where the dielectric versus temperature curves show anomalies related with the order-disorder phase transitions. In addition, these compounds exhibit a broad photoluminescence (PL) emission with a large Stokes shift, which is related with an exciton PL emission.

Keywords: Materials science; Nanomaterials; Organic chemistry.