Solid Ligand-Assisted Storage of Air-Stable Formamidinium Lead Halide Quantum Dots via Restraining the Highly Dynamic Surface toward Brightly Luminescent Light-Emitting Diodes

Although organometal halide perovskites have garnered enormous interest in solar cells, scarce attention has been paid to light-emitting devices using formamidinium lead halide perovskite as the emitting layer. Highly luminescent and air-stable formamidinium lead halide perovskite quantum dots using high-melting-point ligands have been synthesized. Through compositional engineering, the emission spectra are readily tunable over the entire visible spectral region of 409-817 nm. The photoluminescence of FAPbX₃ nanocrystals has narrow emission line widths of 21-34 nm, high quantum yields of up to 88%, and a photoluminescence lifetime of 54.6-68.6 ns for single halide FAPbBr₃, which could be stable for several months. We have demonstrated the fabrication of highly efficient formamidinium lead halide perovskite quantum dot-based green-light-emitting diodes with a moderately high luminance of 33993 cd m^-2, current efficiency of 20.3 cd A^-1, and moderately high maximum external quantum efficiency of 4.07%.