Enhanced luminescence efficiency and stability in deep-blue perovskite quantum dots through synergistic Zn ²⁺ /Ni ²⁺ co-doping

All-inorganic lead halide perovskite quantum dots (PQDs) have emerged as highly promising candidates for next-generation display and lighting owing to their unique optoelectronic properties. However, the achievement of efficient and stable deep-blue emitting PQDs remains a big challenge. Here, we report a bimetallic co-doping strategy to prepare high performance (Rb_0.5Cs_0.5)Pb(Br_0.6Cl_0.4)₃ PQDs via a hot-injection method. Although single Zn²⁺ doping causes an unexpected red-shift in the photoluminescence (PL) peak due to increased average size length, the co-doping of Zn²⁺ and Ni²⁺ leads to a pronounced blue-shift. This beneficial shift is attributed to the synergistic effect of the two dopants, which induces lattice contraction and improves structural homogeneity, effectively passivating defects. As a result, the band gap widens and the emission shifts toward shorter wavelength. By optimizing the Zn²⁺ and Ni²⁺ doping ratios, deep-blue emission at 463 nm with markedly enhanced photoluminescence quantum yield (PLQY) of 61% was achieved, which is nearly three times that of the pristine PQDs. Furthermore, the co-doped PQDs exhibit largely enhanced stability compared to the undoped counterpart. This study provides an effective co-doping approach to develop highly efficient and stable deep-blue emitting perovskite nanomaterials.