Rate-Dependent Mechanoluminescence in SrZn2S2O:Mn2+ for Time-Characterized Optoelectronic Devices

Self-recoverable mechanoluminescence (ML) has demonstrated broad applications in mechanosensory optoelectronic devices based on pressure- and rate-dependent emission performance. However, understanding the coupled effect of pressure and rate on the ML kinetics remains elusive, limiting the design of time-characterized ML-based optoelectronic devices. Here, we show that SrZn₂S₂O:Mn²⁺ exhibits an oscillatory ML behavior with a series of sharp emission peaks in a time-dependent ML curve under rapid compression from 0.1 to 11.0 GPa at critical rates of ∼1.7–4.7 GPa/s, distinct from the ML kinetics under decompression in which the ML curve presents broad emission peaks. The X-ray diffraction measurement shows that the SrZn₂S₂O matrix is stable up to ∼14.6 GPa above which it transforms to a new structure. Photoluminescence spectroscopy shows that SrZn₂S₂O changes monotonically in emission intensity and wavelength in the pressure range of 0.1–8.2 GPa. By combining the experimental results with the piezoelectric detrapping model, we suggest that the oscillatory ML behavior under rapid compression may result from the multiple-cyclic processes of the piezoelectrically induced excitation of the luminescent activators, indicating the intrinsic response to rapid compression. The rate-dependent distinct ML kinetics may be conducive to the design of ML devices with temporal characteristics.