Understanding the Origins of Self-Recoverable Mechanoluminescence for Rational Materials Design.

Mechanoluminescent materials represent an emerging class of optoelectronic systems that convert mechanical stimuli into light, yet their rational design remains limited by an incomplete understanding of stress-responsive electronic processes. Here we reveal that stress-induced electronic-state transitions at dopant centers govern self-recoverable mechanoluminescence (ML) through a closed defect-redox cycle. Mechanical loading transiently converts the ground-state luminescent center into a charged intermediate by driving electron transfer to nearby native defects; upon unloading, electron recapture populates the excited state, followed by radiative relaxation and restoration of the initial ground-state configuration. Based on this mechanism, we identify a stress-induced half-occupied dopant-ligand antibonding state as a general electronic descriptor for predicting ML activity. Thermodynamic control of synthesis conditions, including annealing temperature and precursor concentrations, further enhances ML performance, with carrier densities increasing by more than an order of magnitude. Guided by this descriptor, we computationally screen candidate systems and experimentally validate four new self-recoverable ML materials. This work establishes a unified mechanistic framework and a predictive design strategy for the discovery and optimization of next-generation ML materials.