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, ΔΦs (surface relative work function) and εs (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 ΔΦs and low εs 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. By quantifying surface work functions and dielectric constants of phosphors via first-principles calculations, this work provides a general strategy for predicting and achieving self-recoverable mechanoluminescence based on contact electrification.