White CsPbBr<sub>3</sub>: Characterizing the One‐Dimensional Cesium Lead Bromide Polymorph
Marcel Aebli, Bogdan M. Benin, Kyle M. McCall, Viktoriia Morad, Debora Thöny, Hansjörg Grützmacher, Maksym V. Kovalenko
Abstract
Abstract Inorganic lead halide perovskites have gained immense scientific interest for optoelectronic applications. In this work, we present a one‐dimensional polymorph of cesium lead bromide ( δ ‐CsPbBr 3 ) synthesized through a simple anion‐exchange reaction, wherein distorted edge‐sharing PbBr 6 octahedra form 1D chains isolated by Cs ions. δ ‐CsPbBr 3 was characterized by Raman spectroscopy, X‐ray diffraction, 207 Pb and 133 Cs solid‐state NMR, and by optical emission and absorption spectroscopies. This non‐perovskite material irreversibly transforms into the well‐known three‐dimensional perovskite phase ( γ ‐CsPbBr 3 ) upon heating to above 151 °C. The indirect bandgap was determined by absorption measurements and calculation to be 2.9 eV. δ ‐CsPbBr 3 exhibits broadband yellow photoluminescence with a quantum yield of 3.2 %±0.2 % at room temperature and 95 %±5 % at 77 K, and this emission is attributed to the recombination of self‐trapped excitons. This study emphasizes that the metastable δ ‐CsPbBr 3 may be a persistent, concomitant phase in Cs−Pb‐Br‐containing materials systems, such as those used in solar cells and LEDs, and it showcases the characterization tools used for its detection.