Effect of Polymer Encapsulation on the Mechanoluminescence of Mn²⁺-Doped CaZnOS

Rare earth and transition metal ion-doped CaZnOS has garnered significant attention for its exceptional mechanoluminescence (ML) performance under mild mechanical stimuli and its capability for multicolor emissions. Since powdered phosphors are not directly usable, they require encapsulation within with polymers to create stable structures. This study investigates Mn²⁺-doped CaZnOS (CaZnOS:Mn²⁺) as the ML phosphor, optimizing its performance by varying the Mn²⁺ content, resulting in bright orange-red emissions from the d-d transitions of the Mn²⁺ activator. A quantum efficiency of 59.08% was achieved through the self-sensitization of the matrix lattice and energy transfer to the Mn²⁺ luminescent centers. The enhancement in ML due to Mn²⁺ doping is attributed to the reduced trap depth and increased trap concentration. Encapsulation with four polymers-PDMS, PU, SIL, and RTV-2-was explored to further optimize ML performance. Among these, PDMS provides the best ML output and sensitivity, owing to its slightly cross-linked structure and good triboelectric properties. The optimized CaZnOS:0.03Mn²⁺/PDMS composite, featuring excellent flexibility and recoverability, shows great potential for applications in anti-counterfeiting encryption, stress sensors, and wearable devices.