Spontaneous moisture-driven formation of Cs2Pb1-xMxCl2I2 single crystals with M = Bi, In, Ga and Cr

Abstract

Micrometer to millimeter platelets-like single crystals of the 2D-derivated perovskite structure Cs2PbCl2I2 were synthesized by a very simple route using the humid ambient environment surrounding a DMSO solution containing the salt precursors. Cs2Pb1-xMxCl2I2 formation was also evidenced by single crystal X-ray diffraction, with M = Bi, Ga, In and Cr. X-ray photoelectron spectroscopy (XPS) confirmed the presence of each dopant, with an amount of x  ∼ 5 ato.% for the last three materials. For the Bi-doped sample, XPS showed a larger quantity of dopant that can be due to XPS difficulty to discriminate too close elements for a few nanometers of analysis or higher concentrations in some crystals due to the affinity of both elements to integrate this structure on the same crystallographic site. A decrease of Bi concentration was determined by ion-beam and XPS simultaneous analysis. Finally, a photoluminescence (PL) peak was observed at ∼420 nm for all samples. Peak widening and blue-shift can be ascribed to the doping, and attributed to photon recycling and radiative self-trapped states. These results show the great versatility of ionic substitution and adaptive optoelectronic properties of the 2D phase that is stable in temperature.