Fabrication of water-resistant fluorescent ink using the near-unity photoluminescence quantum yield of CsPbBr 3 doped with NiBr 2 .

Doping with transition and alkaline earth metal ions into all-inorganic perovskite nanocrystals (NCs) has attracted attention recently for tuning the photoluminescence quantum yield (PLQY). We report on the hot injection synthesis of nickel ion-doped CsPbBr 3 NCs with near-unity PLQYs. Nickel ions were successfully incorporated into the octahedral environment of CsPbBr 3 NCs, replacing the lead ions. The introduction of nickel ions into CsPbBr 3 NCs substantially eliminates intrinsic defects and halide vacancies for improved structural order and near-unity PLQYs. Benefiting from these unique properties, nickel ion-doped CsPbBr 3 NCs were dispersed in a polymer to prepare an efficient fluorescent ink. The fluorescent ink shows excellent thermal and water stability under harsh environmental conditions. Moreover, the usefulness of the fluorescent ink for security purposes was demonstrated by designing and recognizing a fluorescent QR code. This study reveals that doped CsPbBr 3 NCs can be used to prepare efficient water-resistant fluorescent ink for anti-counterfeiting applications, widening the usefulness of doped all-inorganic perovskite NCs.