Liquid Nitrogen Temperature Mechanoluminescence and Persistent Luminescence

Abstract As novel stress‐sensing materials, the reported mechanoluminescence (ML) phosphors work only at or above room temperature. Herein, the ML response to low temperatures (77 K) is extended by employing ultra‐shallow traps. Strong ML stimulated by handwriting force followed by persistent luminescence is observed in BaSi 2 O 2 N 2 :Eu 2+ (BSON) at 77 K. The UV pre‐irradiated BSON can still keep the characteristics of ML with 45% intensity after 300 min. Abundant ultra‐shallow traps with depth of ≈0.19 eV are found and revealed to be responsible for the low‐temperature ML and persistent luminescence. Manipulation of the ultra‐shallow traps is realized by doping Ge, Er, and Ce ions in BSON, leading to significant ML enhancement at 77 K. Together with ML, the ultra‐shallow traps also exhibit force memory ability to replicate the pre‐applied force pattern simply by afterglow. The finding advances the state‐of‐the‐art in force sensing under low temperature conditions.