CAS 7787-69-1 | Cesium Bromide CsBr >99.9%

The effect of precursor ratios on the formation of Cs₃Bi₂Br₉ via a re-precipitation synthesis method has been studied thoroughly. X-ray diffraction analysis showed that the precursor ratio was critical for the Cs₃Bi₂Br₉ phase formation. The Cs-rich or Bi-rich precursor ratio resulted in diverse perovskite structure formation of Cs₃BiBr₆ and Cs₃Bi₂Br₆ with micron size platelet and semi-micron size crystal morphology respectively. Unreacted BiBr₃ precursor remains in the supernatant solution under Bi-rich conditions. The synthesized powder dispersed in toluene shows the degradation of the Cs₃Bi₂Br₉ phase at Cs-rich conditions. Photoluminescence quantum yield (PLQY) of 0.73 % was identified in Cs₃Bi₂Br₉ with a large contribution to the exciton-related recombination process. A precursor ratio CsBr:BiBr₃ of 3.0:2.0 is proposed to form a single-phase Cs₃Bi₂Br₉ structure, as the deviation in precursor ratio would promote the Cs₃BiBr₆ structure growth and affect the material's optical performance.