Fluorescent Alloy CsPb(x)Mn(1–x)I(3) Perovskite Nanocrystals with High Structural and Optical Stability

[Image: see text] CsPbI(3) nanocrystals are still limited in their use because of their phase instability as they degrade into the yellow nonemitting δ-CsPbI(3) phase within a few days. We show that alloyed CsPb(x)Mn(1–x)I(3) nanocrystals have essentially the same optical features and crystal structure as the parent α-CsPbI(3) 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(2+) levels fall within the conduction band, thus not strongly altering the optical properties.