Oriented Growth of Highly Emissive Manganese Halide Microrods for Dual-Mode Low-Loss Optical Waveguides

Zero-dimensional (0D) structured lead-free metal halides have recently attracted widespread attention due to their high photoluminescence quantum yield (PLQY) and negligible self-absorption, showing enormous potential as optical waveguides towards miniaturized photonic devices. However, due to the great difficulty in growth of rod-like nano/micro-sized morphologies, such applications have been less explored. Herein, a new-type emissive organic-inorganic manganese (II) halide crystal (TPS₂MnCl₄, TPS=C₁₈H₁₅S, triphenylsulfonium) in the form of microrods is synthesized via a facile chloride ion (Cl^-) induced oriented growth method. Due to a combination of attractive features such as a high PLQY of 86 %, negligible self-absorption and smooth crystal surface, TPS₂MnCl₄ microrods are well suited for use in optical waveguide with an ultra-low optical loss coefficient of 1.20 ⋅ 10^-4 dB μm^-1, superior to that of most organic-inorganic metal halide hybrids, organic materials, polymers and metal nanoclusters to the best of our knowledge. Importantly, TPS₂MnCl₄ microrods can further work as dual-mode optical waveguides, combining active and passive light transmission functionalities in one single crystal. In addition, TPS₂MnCl₄ microrods also display remarkable performance in lighting and anti-counterfeiting due to their distinct optical properties and commendable stability.