Elucidating the Role of Antimony Dopant in Optical Properties of Brightly Luminescent Zero-Dimensional Organic-Inorganic Metal Halides

Doping strategies are regarded as an effective meansto improvethe optical properties of organic-inorganic metal halides andhave attracted widespread attention. Here, we synthesized undopedand Sb3+-doped MA(4)InX(7) (X = Cl, Br;MA(+) = CH3NH3 (+)) singlecrystals. Sb3+-doped samples exhibited bright broadbandemissions of extrinsic self-trapped excitons (STEs). The photoluminescencequantum yields of Sb3+-doped MA(4)InX(7) (X = Cl, Br) are increased by more than 38 and 15 times comparedwith undoped samples, respectively. While a similar behavior in theoptical characteristics was observed before and after introducingSb(3+), explained well by the non-ignorable trace Sb3+ ions in the precursors, which often confused researchers'judgement about the origin of photoluminescence (PL) emission in previousstudies. In addition, an apparent concentration quenching effect wasfound when excessive dopants were fed. The close connection betweenextrinsic STE emissions and the vibrational mode of [SbX6](3-) octahedrons was revealed by temperature-dependentPL spectra and Raman spectra. Our work provides a deep understandingof extrinsic STE emission and thus facilitates the design and developmentof eco-friendly light-emitting metal halides.