Improving Photoelectron Localization to Significantly Enhanced Broadband Orange‐Light Emission in Hybrid Antimony Halides with Sb─Cl Secondary Bonding

Abstract Hybrid ns2 metal halides have attracted extensive attention due to the unique photophysical behavior. However, the reasonable improvement of photoluminescence efficiency by accurate structural modulation remains a great challenge. Herein, two kind of antimony halides with formulae as (S)/(R)‐[C6H16N2]3[SbCl5]2·2Cl ((S)/(R)‐1·2Cl) and (S)/(R)‐[C6H16N2]2[SbCl5]2 ((S)/(R)‐2) ([C6H16N2]2+ = 1,2‐Diaminocyclohexane) are developed, in which 0D [Sb4Cl20]8− clusters and 1D infinite [SbCl5]n2n− polyanion chains are adopted, respectively. The stoichiometric tunability enables metastable (S)/(R)‐1·2Cl being transformed to dynamic stable (S)/(R)‐2. All compounds contain a large number of Sb─Cl secondary bonds because of the strong chemical activity of 5s2 electrons. The obtained compounds exhibit broadband orange‐light emission, while photoluminescence quantum yield of (S)/(R)‐2 is significantly enhanced to ≈76% due mainly to the generation of more localized electrons onto 1D chains. Experimental and computational results reveal that efficient broadband emission derives from the synergistic emission of singlet and triplet states, where the presence of shallow trap energy levels leads to anti‐thermal quenching behavior. Furthermore, the highly efficient photoluminescence property allows (S)‐2 to become excellent down‐conversion phosphor for white‐light emitting diode. This work proves that exploring structure‐property relationship in hybrid systems is helpful in promoting the rapid development of high‐performance broadband emission metal halides.