Enhanced Long‐Term Luminescent Stability through Near‐Single‐Dot Passivation and Encapsulation of Perovskite Quantum Dots for Printable Photonics

Metal halide perovskites quantum dots (QDs) stand at the forefront of multifarious photonic applications, including micro‐light‐emitting diode and further augmented reality, virtual reality, and other novel display, lighting technologies. Barriers to applications, however, lie in their toxicity of lead, instability to light, moisture and heat, and processability at the nanoscale‐particle level. Herein, a simple and versatile postprocessing approach is reported for the near‐single‐dot passivation and encapsulation of representative lead‐free double perovskite Cs2Ag0.4Na0.6InCl6:Bi through liquid‐phase processing of perhydropolysilazane and quantum dots colloid with controllable hydrolysis curing. The conventional unstable oleylamine and oleic acid ligands are replaced by ‐NCl bonding on the surface of nanocrystal, accompanied by the resulting compact and robust silica layer without compromising the optical properties of the quantum dots. With the near‐single‐dot protection, the quantum dots do not show fluorescence quenching even when stored for more than 90 days and exhibit remarkably improved stability against heat, ultraviolet irradiation and humidity compared to the raw quantum dots. The strategy offers a versatile way of creating nanoscale‐particle level protection of luminescent quantum dots, and can be universally compatible with solution‐based patterning techniques and photonics applications where quantum dots are used.