Blue photoluminescence enhancement achieved by zero-dimensional organic indium halides via a metal ion doping strategy

Abstract

Low-dimensional organic–inorganic metal halide hybrids exhibit promising optical properties for light emitting applications. However, developing lead-free blue-light emitters with high photoluminescence quantum efficiency (PLQE) remains an ongoing challenge. In our work, a novel zero-dimensional (0D) indium hybrid compound (MA)₄InCl₇ (MA = CH₃NH₃⁺) was developed which exhibited broadband blue emission with a PLQE of 11.2% when excited by ultraviolet (UV) light. More interestingly, upon Cs⁺ or Mn²⁺ doping, the emission of the 0D compound further blue-shifted and became narrower, while the PLQE was significantly enhanced to 18.8% (Cs⁺) or 20.7% (Mn²⁺). More prominent PLQE enhancement to 74.7% was observed after Sb³⁺ doping, which also altered the emission spectrum to the orange region. According to experimental characterization and theoretical calculations, we attribute the PLQE enhancement upon Cs⁺ and Mn²⁺ doping to defect passivation and the orange emission upon Sb³⁺ doping to altered emission centers. We have demonstrated that multiple metal ions possess the ability to improve the light emitting properties of 0D organic–inorganic metal halides, and (MA)₄InCl₇ could be utilized as a Sb³⁺ heavy metal ion sensor with high selectivity and sensitivity.