Ternary phase diagram of all-inorganic perovskite CsPbClaBrbI3−a−b nanocrystals

All-inorganic lead halide perovskite CsPbX3 (X = Cl, Br, and I) nanocrystals (NCs) have shown great application prospects in optoelectronic fields. Their properties can be feasibly tuned by the ratio of different halide ions. Post-synthesis halide anion exchange of Cl—Br or Br—I in CsPbX3 NCs allows getting any desired composition of CsPbClxBr3−x and CsPbBrxI3−x (0 ≤ x ≤ 3). However, due to the large difference of the Cl and I radii, they can only substitute each other in a limited ratio to form CsPbClyI3−y (0 < y < δ or 3 − δ < y < 3). To date, little has been known on the phase diagram of the ternary halide perovskite of CsPbClaBrbI3−a−b (0 < a + b < 3). In this work, the ternary halide perovskite phase diagram is constructed by the strategy of halide anion exchange between perovskite NCs. From the diagram, the composition and proportion of the perovskite NC final phases from any starting perovskite NC mixture can be calculated. Specifically, a two-phase perovskite NC system showing stable dual photoluminescence (PL) peaks is achieved.