Critical role of mechanochemical synthesis in stabilization and halide engineering of 2D Ruddlesden–Popper Cs2PbI2Cl2

Abstract

Cs2PbI2Cl2 (Ruddlesden–Popper n = 1 phase) is unique among inorganic layered perovskites due to its stability at room temperature and good optoelectronic properties. Solvent-free mechanochemistry was employed to synthesize Cs2PbI2Cl2 and the associated halide modulated compositions through both hand milling and high energy planetary ball milling methods. For anionic modulation, three compositions were considered for investigations among Cs2PbIxCl4−x (x = 0.5 to 3.5), that is, x = 1.5 (Cl-rich), x = 2 (parent), and x = 2.5 (I-rich). The phase constitution and grain morphology in the investigated compositions were sensitive to both the milling method and compositional bias (I-rich or Cl-rich). The compositional bias towards chlorine is comparatively better tolerated than that towards iodine, as the weightage of the RP layered phase dramatically reduced from 94% to 67% from the former to the latter case – even under energetically intensive method of ball milling. The optical characteristics obtained from absorption and photoluminescence studies revealed the synergistic role played by the milling method as well as the phase compositions dealt with in this work. This journal is © The Royal Society of Chemistry, 2026.