In situ inclusion of thiocyanate for highly luminescent and stable CH₃NH₃PbBr₃ perovskite nanocrystals

In this work, an in situ thiocyanate inclusion method for the fabrication of highly luminescent and stable CH₃NH₃PbBr₃ perovskite nanocrystals (NCs) is developed, employing Pb(SCN)₂ as the lead precursor to partially or totally replace PbBr₂ in the ligand-assisted reprecipitation (LARP) process. The in situ approach not only avoids the introduction of impurity elements, but also more interestingly incorporation of thiocyanate can control the crystallinity, particle size, luminescence and stability of CH₃NH₃PbBr₃ NCs in a simple and effective manner. By adjusting the thiocyanate concentration, the photoluminescence (PL) of the synthesized CH₃NH₃PbBr₃ NCs can be tuned in a range of 473-526 nm, as characterized by narrow emission line widths of 21-28 nm and outstanding photoluminescence quantum yields (PLQYs) of 73% to 96%. Meanwhile, the stability of CH₃NH₃PbBr₃ NCs can be greatly improved as the amount of thiocyanate increases. The improvement in the optical performance and stability of CH₃NH₃PbBr₃ NCs is mainly due to the contribution of higher crystallinity and, more stable and defect-free surface passivation induced by the presence of thiocyanate. This work paves a novel way for preparing highly luminescent and stable CH₃NH₃PbBr₃ NCs.