Aliovalent Doping and Surface Grafting Enable Efficient and Stable Lead‐Free Blue‐Emitting Perovskite Derivative

Abstract Lead halide perovskites have emerged as superstar semiconductors owing to their superior optoelectronic properties. However, the issues of chemical and thermodynamic instability and toxicity are yet to be resolved. Here, the non‐ and Bi 3+ ‐doped all‐inorganic lead‐free perovskite derivatives are reported. Most remarkable is the successful extending of excitation of Cs 2 ZrCl 6 to match with the commercial near ultraviolet light‐emitting diode chips via deliberate Bi 3+ aliovalent doping. The blue emission, contrary to self‐trapped exciton (STE) emissions amply reported previously, originates from Bi 3+ ionoluminescence with a high photoluminescence quantum efficiency of 50%. The competition for harvesting electrons between STEs and Bi 3+ is studied in detail by steady‐ and transient‐state fluorescence spectroscopy in combination with theoretical calculations. Surface grafting endows Cs 2 ZrCl 6 :Bi 3+ with a robust water‐resistant core–shell‐like structure and abiding emission. Surprisingly, the emission intensity even increases to 115.94% of the initial level after immersing in water for 2 h. The as‐obtained phosphor enables the fabrication of a white light‐emitting diode (w‐LED), achieving CCT = 4179 K and Ra = 81.9. This work not only promotes the step toward development of lead‐free, stable, and high‐efficiency perovskite derivatives for the next‐generation warm w‐LEDs, but also reveals the structure–PL relationship.