Pressure- and Rate-Dependent Mechanoluminescence with Maximized Efficiency and Tunable Wavelength in ZnS: Mn2+, Eu3+

Mechanoluminescence (ML) has received widespread attentionbecauseof potential application in stress sensors and imaging. However, pursuinghighly efficient ML remains a challenge due to multifactorial limitationssuch as pressure and loading rate. Here, we systematically investigatepressure- and rate-dependent ML in Mn2+ and Eu3+ co-doped ZnS in a gigapascal pressure range by using a high-pressuredynamic diamond anvil cell and microsecond time-resolved fluorescentmethods and demonstrate the giant tunability in both ML efficiencyand wavelength. Compressed from ambient pressure to 11 GPa at differentcompression rates, ZnS: Mn2+, Eu3+ exhibitsa volcano shape in ML emission efficiency with an optimum at similar to 3.5GPa and similar to 211.1 GPa/s, at least 1000-fold higher than that measuredin the MPa range. The pressure-dependent ML is accompanied with atunable yellow-to-red emission color change. A combination of high-pressureX-ray diffraction and photoluminescence measurements reveals thatthe pressure- and rate-dependent ML behavior derives from pressure-inducedstrengthening of the crystal piezoelectric field and enhanced interactionbetween the host lattice and doped ions with a significant changeof the energy level of the Mn ion. Significantly, the highly efficientML of ZnS: Mn2+, Eu3+ at the GPa level is reproducibleunder a compression-decompression process and can be manipulated ona micron scale, implying great potential in mechanical-optical energyconversion and application in dynamic pressure imaging, stress sensors,and multicolor displays.