Liquid Nitrogen Temperature Mechanoluminescence and Persistent Luminescence

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 BaSi2O2N2:Eu2+ (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 & AP;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.