Understanding the photoionic mechanism in optoelectronic
materials
offers significant potential for various applications in the fields
of laser, data/energy storage, signal processing, and ionic batteries.
However, the research on such light-matter interaction using photons
of sub-bandgap energy is scarce, especially for those transparent
materials with photoactive centers that would generate a local field
upon photoillumination. This research investigates the photoionic
effect in Yb3+/Er3+ doped tellurate glass with
Ag nanoparticles (NPs) embedded. It is found that the photogenerated
electric dipole of Yb3+/Er3+ ions and local
field of Ag NPs could block the Ag+ migration in an external
electric field. The blocking phenomenon of Ag NPs is the so-called
Coulomb blocking effect (ascribed to its quantum confinement effect),
which would be further enhanced by the additional photoinduced localized
surface plasmon resonance (LSPR) effect. Interestingly, the photoresponsive
electric dipole of lanthanide ions could cause plasmon oscillation
of Ag NPs, resulting in a partial release of the blockade of lanthanide
ions and enhanced blockade via quantum confinement of Ag NPs. A model
device is proposed according to the photoresistive behavior. The research
gives another perspective on the photoionic effect via the photoresponsive
local field generated by photoactive centers in optofunctional materials.
Defects are common in inorganic materials and not static
upon annealing
of the heat effect. Antithermal quenching of luminescence in phosphors
may be ascribed to the migration of defects and/or ions, which has
not been well-studied. Herein, we investigate the antithermal quenching
mechanism of upconversion luminescence in Sc2(MoO4)3: 9%Yb1%Er with negative thermal expansion via a fresh
perspective on thermodynamics and kinetics, concerning the thermally
activated movement of defects and/or ions. Our results reveal a second-order
phase transition taking place at ∼573 K induced by oxide-ion
migration. The resulting variation of the thermodynamics and kinetics
of the host lattice owing to the thermally induced oxide-ion movement
contributes to a more suppressed nonradiative decay rate. The dynamic
defects no longer act as quenching centers with regard to the time
scale during which they stay nearby the Yb3+/Er3+ site in our proposed model. This research opens an avenue for understanding
the antithermal quenching mechanism of luminescence via thermodynamics
and kinetics.
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