Mechanically driven luminescence in a ZnS:Cu-PDMS composite

Abstract

The conventional mechanoluminescence (ML) mechanism of phosphors such as SrAl2O4:Eu and ZnS:Mn is known to utilize carrier trapping at shallow traps followed by stress (or strain)-induced detrapping, which leads to activator recombination in association with local piezoelectric fields. However, such a conventional ML mechanism was found to be invalid for the ZnS:Cu-embedded polydimethylsiloxane (PDMS) composite, due to the absence of luminescence with a rigid matrix and a negligibly small value of the piezoelectric coefficient (d33) of the composite. An alternative mechanism, namely, the triboelectricity-induced luminescence has been proposed for the mechanically driven luminescence of a ZnS:Cu-PDMS composite.

Piezoluminescent devices by designing array structures

“…3d, all the luminance of the PLD during press and release increased with the increasing external pressure within a certain range (0-16 MPa). In addition, embedding the phosphor in the elastic and transparent polymer also protected the phosphor during the stress process to achieve high repeatability of the stress luminescence [9,10,12,17]. As shown in Fig.…”

“…With the requirement to develop green energy, it is highly desired to more efficiently take use of other energy sources such as mechanical energy that can be produced by our body movements every day and is typically released to the environment without harvesting [6][7][8]. Recently, there were some reports in regard to realizing mechanically light-emitting devices under pressing, stretching, vibrating and magnetic field by incorporating the rigid inorganic phosphors particles into elastomers [9][10][11][12][13][14][15][16][17]. However, the mechanoluminescent materials generally exhibited weak brightness and limited color [18][19][20].…”

Force-induced charge carrier storage: a new route for stress recording

“…The friction-induced electric field further excited the phosphors and produced emission. The triboelectricity-induced luminescence answered the questions of why light pre-excitation was not necessary and why a small force load (such as 5N) was sufficient to produce ML 47 . Since the charge carriers had been emptied from traps (at least all the traps with TL temperatures below 600 K), the observed ML without light pre-excitation in Fig.…”

“…On the other hand, when fast friction was produced on the interface, a friction-induced electric field could be established to excite the charge carriers. According to Sohn et al, the electric field around the force-applied ZnS:Cu particle was roughly estimated to be 10 6 –10 7 V/cm 47 , which is much higher than the threshold value required to excite electrons. However, accurate calculation of the resultant electric field in different materials is still very challenging, especially considering the dynamic characteristics and the force distribution.…”

A Review of Mechanoluminescence in Inorganic Solids: Compounds, Mechanisms, Models and Applications

“…New mechanism and models may emerge, for example electroluminescence triggered by triboelectricity was proposed for the peculiar ML behaviour of ZnS:Cu${}^{+}$ [122,334], and they are supposed to reveal common features of ML. Nevertheless, the role of defects is essential.…”