Phase Engineering of Cesium Manganese Bromides Nanocrystals with Color‐Tunable Emission

For display applications, it is highly desirable to obtain tunable red/green/blue emission. However, lead‐free perovskite nanocrystals (NCs) generally exhibit broadband emission with poor color purity. Herein, we developed a unique phase transition strategy to engineer the emission color of lead‐free cesium manganese bromides NCs and we can achieve a tunable red/green/blue emission with high color purity in these NCs. Such phase transition can be triggered by isopropanol: from one dimensional (1D) CsMnBr 3 NCs (red‐color emission) to zero dimensional (0D) Cs 3 MnBr 5 NCs (green‐color emission). Furthermore, in a humid environment both 1D CsMnBr 3 NCs and 0D Cs 3 MnBr 5 NCs can be transformed into 0D Cs 2 MnBr 4 ⋅2 H 2 O NCs (blue‐color emission). Cs 2 MnBr 4 ⋅2 H 2 O NCs could inversely transform into the mixture of CsMnBr 3 and Cs 3 MnBr 5 phase during the thermal annealing dehydration step. Our work highlights the tunable optical properties in single component NCs via phase engineering and provides a new avenue for future endeavors in light‐emitting devices.