Accommodative Organoammonium Cations in A‐Sites of Sb─In Halide Perovskite Derivatives for Tailoring BroadBand Photoluminescence with X‐Ray Scintillation and White‐Light Emission

Abstract Broadband emissive perovskites are next‐generation materials for solid‐state lighting and radiative detection. However, white‐emitting perovskites are generally synthesized by regulating B/X sites, while not enough attention is paid to the A‐site, which is thought to hardly affect the band‐edge structures and optoelectronic properties. Here, a series of Sb 3+ ‐doped In‐based 0D halide perovskite derivatives are described with various organoammonium cations in A‐sites. Warm‐white light emitting across the visible spectrum (450–850 nm), large Stokes shifts, and high photoluminescence quantum yields are easily tunable by molecularly tailoring A‐site cations. These features enable a light yield up to 60976 Photons/MeV as X‐ray scintillator, and a detection limit of 90 nGy air /s that is ≈60 times lower than the medical requirement. It is proved that A‐site plays a critical role in determining the degree of distortion of polyhedra, which influences the broadband photoluminescence and self‐trapped exciton (STE) dominates the emission process. Moreover, for the first time, via the incorporation of 2,6‐dimethylpiperazine, a mixed A‐site regulating strategy produces a standard white‐light emission, which originates from the blue‐light and yellow‐light related to various STE emission centers. It is foreseen that this strategy highlights the expanded role of A‐site and the importance of rethinking A‐sites in perovskites.