Calcium-Assisted in Situ Formation of Perovskite Nanocrystals for Luminescent Green and Blue Emitters

Organometal halide perovskite nanocrystals show near-unity photoluminescence quantum yield which decrease dramatically in thin films because of nonradiative losses. Here, we demonstrate a solution-processed highly luminescent perovskite film by confining the MAPbBr(3) nanocrystals into the inorganic CaBr2 matrix in situ. The confinement of the exciton in small nanograins facilitates radiative recombination. Meanwhile, part of the lattice-incorporated calcium ions could alter the electronic band structures and then increase the exciton binding energy of MAPbBr(3) perovskite. The synergism of morphology control and structural regulation leads to efficient radiative recombination and the enhancement of photoluminescence quantum yield from 4.2% to 45.6%. Moreover, the chloride could also be introduced and stabilized into the perovskite lattice through the calcium incorporation. Desirable pure blue (<480 nm) emission was obtained in situ through manipulating the calcium and chloride ions in the precursor solutions without the assistance of bulky ligands. Our strategies of locally creating luminescent color-tunable perovskite films are promising for further improving the performance of organic-inorganic hybrid perovskite electroluminescence devices.