The trivalent lanthanides have been broadly utilized as emitting centers in persistent luminescence (PersL) materials due to their wide emitting spectral range, which thus attract considerable attention over decades. However, the origin of the trivalent lanthanides’ PersL is still an open question, hindering the development of excellent PersL phosphors and their broad applications. Here, the PersL of 12 kinds of the trivalent lanthanides with the exception of La3+, Lu3+, and Pm3+ is reported, and a mechanism of the PersL of the trivalent lanthanides in wide bandgap hosts is proposed. According to the mechanism, the excitons in wide bandgap materials transfer their recombination energy to the trivalent lanthanides that bind the excitons, followed by the generation of PersL. During the PersL process, the trivalent lanthanides as isoelectronic traps bind excitons, and the binding ability is not only related to the inherent arrangement of the 4f electrons of the trivalent lanthanides, but also to the extrinsic ligand field including anion coordination and cation substitution. Our work is believed to be a guidance for designing high-performance PersL phosphors.

No abstract

Owing to the forthcoming global energy crisis, the search for energy‐saving materials has intensified. Over the past two decades, mechanically induced luminescent materials have received considerable attention as they can convert waste into useful components, for instance, the conversion from stress into light. However, this material features many constraints that limit its widespread application. Herein, a strategy to improve the mechanoluminescence (ML) of ZnO by embedding it in a ZnF2:Mn2+ matrix is introduced. Upon dynamic excitation via an external stress, the reddish‐yellow ML is confirmed to originate from the 4T1 (4G) → 6A1 (6S) transition of the optically active Mn2+ center. Moreover, the sample with the strongest ML contains the appropriate amount of ZnF2 (ZnF2:ZnO = 7:3). By performing density functional theory calculations, a possible ML‐enhancement mechanism is elucidated, which indicates the formation of a ZnF2/ZnO:Mn2+ heterojunction. Considering the unique characteristics of ML, its promising applications are demonstrated in various mechano‐optics scenarios, including flexible and stretchable optoelectronics, advanced self‐powered displays, e‐skins/e‐signatures, and anti‐counterfeiting, without the use of external light/electric‐incentive sources. The study significantly increases the variety of ML materials and is expected to strengthen the foundation for the future development of smart mechanically controlled devices and energy‐saving systems.

Mechanoluminescence (ML) is used in many areas, in particular for ML-based optical thermometry. However, ML-based thermometry is limited owing to the lack of a strong theoretical foundation. Here, using CaZnOS:Er 3+ and the well-established Boltzmann distribution, a solid and novel ML thermometry framework is established. Upon external force stimulation, CaZnOS:Er 3+ generates bright green ML ascribed to the 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 transitions of Er 3+ . And the populations at the 2 H 11/2 and 4 S 3/2 excited states are confirmed to follow the Boltzmann distribution during the ML process. The utility of this novel ML thermometry framework is demonstrated here on a practical example. Further, potential applications of CaZnOS:Er 3+ to anti-counterfeiting and information encryption are discussed. These results demonstrate that CaZnOS:Er 3+ luminescent materials are promising for multifunctional applications (especially for temperature sensing), and provide the foundation for future ML applications.

Mechanoluminescent materials have attracted considerable attention over the past two decades, owing to the ability to convert external mechanical stimuli into useful photons. Here we present a new, to the best of our knowledge, type of mechanoluminescent material, i.e., MgF2:Tb3+. In addition to the demonstration of traditional applications, such as stress sensing, we show the possibility of ratiometric thermometry using this mechanoluminescent material. Under stimulation of an external force, rather than the conventional photoexcitation, the luminescence ratio of 5D3→7F6 to 5D4→7F5 emission lines of Tb3+ is confirmed to be a good indicator of temperature. Our work not only expands the family of mechanoluminescent materials, but also provides a new and energy-saving route for temperature sensing.