Self-recoverable near-infrared mechanoluminescence from ZnS:Mn by controlling manganese clusterization

Near-infrared (NIR)-emitting mechanoluminescence (ML) materials are highly desirable since they are biological transparency and suitable for deep-imaging inside biological tissues. So far, NIR emission can be found in very limited number ML materials. Moreover, reported NIR ML materials suffer from limitations associated with the incompetence in self-reproducibility. Herein, we observe sustainable and self-recoverable NIR ML emission in pulsed laser deposition (PLD) method grown ZnS:Mn film, for the first time. ML emission in ZnS:Mn can be explained by the piezoelectricity-induced detrapping model. Broad ML emission covering both red and NIR ranges arises from the presence of (Mn)n clusters, which facilitates the energy transfer from excited Mn2+ ions to them. During the PLD growth, high laser fluence and deposition rate contribute to the formation of (Mn)n clusters, which was verified by electron paramagnetic resonance EPR and X-ray photoelectron spectroscopy XPS analysis. The device exhibits durable NIR ML over 105 repeated mechanical stresses, suggesting new possibilities aiming for constructing self-recoverable NIR ML materials.