Dynamic CPL switching realized in chiral Mn-based metal halides with reversible thermochromism

Abstract

Circularly polarized luminescence (CPL) active materials have attracted much attention due to their extensive applications in 3D optical displays and encrypted transmission. The switchable regulation of CPL is of great importance for applications such as spintronics. However, the study of intelligent regulation is scarce, especially the simultaneous regulation of the color and direction of polarization. In this paper, we have successfully prepared switchable CPL active Mn-based metal halides (R-/S-Br-MBA)₃MnBr₅, whose single crystal displays orange CPL at 634 nm at room temperature. With the increase of temperature, the CPL displayed by single crystals gradually turns into green at 520 nm and the CPL signal flips, variable emission color and CPL switch in +/− are achieved in the prepared chiral manganese halides. This emission switch of wavelength and handedness is reversible. The reversible transition of CPL emission wavelength is attributed to the change of emission with temperature. However, the sign reversal of CPL with temperature is due to the change of spin polarization during the transition from self-trapped emission to Mn²⁺ d–d transition emission. The CPL materials with switchable handedness and emission wavelength have great potential applications in information processing and intelligent sensors.