Trap-Piezoelectric Synergistic Mechanism in High Intensity Mechanoluminescent Phosphors Ca2GeO4:Tb3+ for Potential Dynamic Multi-Modal Anti-Counterfeiting and Remote Monitoring

As a carrier for mechanical-to-optical conversion, mechanoluminescent (ML) materials are driving innovations in anti-counterfeiting encryption, self-powered sensing, and human-machine interaction, with their core value lying in the transformation of “invisible mechanical forces” into “visible light.” However, current ML materials face challenges, including weak emission intensity, limited luminescence modes, and the absence of a unified mechanism for force-to-light conversion. Here, a high-intensity green ML phosphor, Ca 2 GeO 4 : Tb 3+ , visible under ambient light, is developed. Following pre-irradiation, excellent photoluminescence (PL) and persistent luminescence (PersL) are observed. Notably, tunable emission from blue to green is achieved in the PL through increasing the Tb 3+ doping concentration, and PersL remained detectable after 1 h, suggesting applicability in delayed bioimaging and advanced anti-counterfeiting systems. Furthermore, it is revealed that the synergy between multiple trap levels and the piezoelectric field generated by lattice distortion induced by Tb 3+ substitution for Ca 2+ is identified as a key contributor to high intensity ML in Ca 2 GeO 4 : Tb 3+ , which is of significant importance for clarifying the force-to-light conversion mechanism. Remarkably, owing to its outstanding luminescent properties, the phosphors are integrated with polydimethylsiloxane (PDMS), demonstrating tremendous potential in multi-modal encryption, dynamic anti-counterfeiting, remote monitoring, and human-machine interaction.