Superior mechanoluminescence of ZnS:Mn/ZnO heterostructure array chip boosted by type II electron transition.

Mechanoluminescence (ML) has garnered considerable attention in widespread applications, including visualized stress detection, electronic signatures, and electronic skin. However, its high stress-threshold and limited emission efficiency fail to satisfy the growing applications. To address these challenges, we propose constructing ZnS:Mn/ZnO heterostructure with type II energy band alignment, aiming to activate the abundant electrons in the valence band for ML emission and introduce additional piezoelectric field as well as built-in electric field. The ZnS: Mn/ZnO heterostructure array chips were fabricated by standard semiconductor techniques, forming regular heterostructures and emission centers in square array. Each emission square functions as a pixel for mapping force and recording dynamic forces. As anticipated, the heterostructure array exhibits a record-low threshold of 0.05 N and a 4-fold increase in ML intensity. In mechano-electro-photon combined study, pulsed electric current were simultaneously observed, directly confirming the generation of non-balanced free carriers upon the mechanical stimulus. Owing to the high electron density in the VB of ML materials, the type II electron transition proposed in this work could dramatically increase the number of non-balanced carriers participating in the ML process, thereby have a revolutionary impact on the efficiency and fundamental understanding of ML emission.