Contact electrification induced mechanoluminescence

Mechanoluminescence (ML) is a luminescence response to mechanical stimuli that shows a variety of significant applications. It is generally believed that ML is due to piezoluminescence in asymmetric piezoelectric materials, but this model encounters difficulties in explaining the ML for centrosymmetric nonpiezoelectric materials, especially the Lu3Al5O12: Ce3+/PDMS elastomer with ultrastrong nonpreirradiation ML. This theoretical problem has become the prominent “dark cloud” in the sky of the ML field. This work reveals for the first time that the ML for the centrosymmetric Lu3Al5O12: Ce3+/PDMS elastomer is essentially induced by contact electrification. According to contact electrification, an electron-cloud model of contact electrification is successfully established to understand the ML mechanism for the elastomer. This demonstrates that contact electrification arising from the interaction of two dissimilar surfaces creates a broadband excitation energy, which directly excites the luminescence levels to emit ML. Accordingly, the unique ML properties of the centrosymmetric Lu3Al5O12: Ce3+/PDMS elastomer that cannot be explained by piezoelectricity can be well understood by contact electrification. Particularly, these results also inspire us to have reasonable new insight into the trap-dependent piezoluminescence mechanism for typical SrAl2O4: Eu2+ and ZnS: Cu/Mn2+ materials.