Mechanochemical engineering of chiroptical properties in indium-based chiral metal halides by grinding.

Circularly polarized luminescence is crucial for optoelectronics, bioimaging, and three-dimensional display, yet most of current materials suffer from complex synthesis and limited tunability. Herein, we show the regulation of chiroptical properties in metal halides through mechanochemical engineering. Specifically, phosphorescent indium-based chiral metal halides exhibit blue circularly polarized luminescence, along with antimony-doped indium-based metal halides emit orange circularly polarized luminescence. A grinding strategy using bromide salts like potassium bromide induces bright yellow fluorescence and enables versatile circularly polarized luminescence modulation. When antimony-doped indium-based metal halides are ground with five different bromide salts, it exhibits intriguing and tunable properties: (i) enhanced circularly polarized luminescence, with a luminescence dissymmetry factor value up to 10⁻²; (ii) inversion of the circularly polarized luminescence signal; (iii) generation of near-infrared circularly polarized luminescence with a substantial Stokes shift of 370 nm; and most notably, (iv) a 29.71-fold improvement in second-harmonic generation efficiency. This approach also realizes applications in circularly polarized light-emitting diodes.