Triboluminescence of metal halide perovskite films

Metal halide perovskites (MHPs) have shown fantastic properties such as photoelectric conversion, electroluminescence, light amplification, ferroelectricity, and flexoelectricity, becoming versatile materials in diverse fields. Herein, we report a previously undiscovered nature of the MHP film, i.e. triboluminescence (TL), and elucidate its underlying mechanism. The TL response is triggered when an MHP film is scraped by specific materials (like Cu, Au, Pt) with a lower Fermi level than that of the MHP. The friction induces electron transfer from MHP to scraper, generating a positive electrostatic field on the surface of the MHP film, which leads to stretched MHP lattices owing to electrostatic repulsion, consequently enhancing fluorescence and charge carrier lifetime. If the friction material (like Al) has a higher Fermi level, electron transfer process, electrostatic field direction, and lattice structure change are just the opposite, resulting in reduced fluorescence. This work unveils the TL phenomenon of the MHP film and the unique mechanism, opening up new avenues for explorations on the appealing MHPs.