Lead‐Free All‐Inorganic Indium Chloride Perovskite Variant Nanocrystals for Efficient Luminescence

Abstract Lead‐free halide perovskites and their variants have attracted great attention due to their non‐toxicity and good photophysical properties. Here, a series of undoped and antimony‐doped all‐inorganic, 0D, indium‐based perovskite variant nanocrystals (NCs): (Rb x Cs 1− x ) 3 InCl 6 and (Rb x Cs 1− x ) 3 InCl 6 :Sb (0 ≤ x ≤ 1) NCs, is reported. Among them, Sb‐doped NCs exhibit green emission. Mixing Rb‐Cs NCs show the higher photoluminescence (PL) quantum efficiency (PLQE) and better stability than unalloyed NCs ( x = 0 or 1). The effect of crystal size on PL property of (Rb 0.75 Cs 0.25 ) 3 InCl 6 :Sb is analyzed in detail. More interestingly, In‐based perovskite variant NCs containing coordinated water are successfully synthesized by a two‐step method (variable temperature hot injection and saturated steam post treatment). The best PLQE of Sb‐doped Cs 2 InCl 5 (H 2 O) NCs reaches 95.5%, which is a new PLQE record for yellow emissive lead‐free perovskite and variant NCs. In addition, the emission mechanism is further clarified by temperature‐dependent PL and femtosecond transient absorption techniques.