Fluorescent Alloy CsPb Mn I Perovskite Nanocrystals with High Structural and Optical Stability.

CsPbI nanocrystals are still limited in their use because of their phase instability as they degrade into the yellow nonemitting δ-CsPbI phase within a few days. We show that alloyed CsPb Mn I nanocrystals have essentially the same optical features and crystal structure as the parent α-CsPbI system, but they are stable in films and in solution for periods over a month. The stabilization stems from a small decrease in the lattice parameters slightly increasing the Goldsmith tolerance factor, combined with an increase in the cohesive energy. Finally, hybrid density functional calculations confirm that the Mn levels fall within the conduction band, thus not strongly altering the optical properties.