Predicting and achieving self-recoverable mechanoluminescence based on contact electrification

Self-recoverable mechanoluminescence (ML), enabling materials to emit light stably under stress, opens applications in intelligent sensors, displays, and wearable devices. However, self-recoverable ML is rare, observed mostly in piezoelectric materials. Here, we propose achieving self-recoverable ML based on contact electrification rather than piezoelectricity. We introduce two key parameters, ΔΦ_s (surface relative work function) and ε_s (surface dielectric constant), to quantify the contact electrification capabilities of phosphors. Using first-principles calculations, we determined the parameters for 114 phosphors. Experimental results for 19 typical commercial phosphors showed a correlation between self-recoverable ML and contact electrification parameters. Notably, active phosphors with high ΔΦ_s and low ε_s exhibit self-recoverable ML, while inactive phosphors do not. Accordingly, we applied interface engineering to enhance contact electrification capabilities of typical inactive phosphors, therefore achieving self-recoverable ML. These findings demonstrate that the realization of self-recoverable ML based on contact electrification can be extended to a wide range of phosphors, providing a general strategy for developing self-recoverable ML materials.