Influence of Lead Thiocyanate on the Optical Properties and Stability of All-Inorganic Lead Halide Perovskite Nanocrystals for Lighting Applications

All-inorganic lead halide perovskite (CsPbX₃, X = Cl⁻, Br⁻, I⁻) nanocrystals (NCs) are promising materials for illumination and display applications because of low-cost, high photoluminescence quantum yields (PLQYs), as well as narrow and tunable emission spectra. However, the low stability issue of these NCs in the presence of air and moisture impedes their practical utilization. In this study, we reported that the addition of lead thiocyanate [Pb(SCN)₂] during the synthesis of CsPbX₃ NCs helps to improve the stability and optical properties of the resulting NCs. With an increasing concentration of Pb(SCN)₂, the thiocyanate (SCN⁻)-based NCs demonstrate narrower and tunable emission spectra with a substantial increase in PLQYs. Besides, the SCN⁻-based NCs retain higher photoluminescence intensity (three times higher) compared to the host NCs, when stored in an ambient environment for several days. This suggests the betterment in the stability of as-grown NCs against air and moisture. Finally, the implications of these different colors (green, yellow, and red) emitting NCs as the color conversion layer results in bright neutral white light with a correlated color temperature of 5148 K and a high color rendering index of 91.