Wavelength‐Tunability and Multiband Emission from Single‐Site Mn²⁺ Doped CaO Through Antiferromagnetic Coupling and Tailored Superexchange Reactions

Abstract

In modern phosphor materials, in contrast to single‐band emission, simultaneous photoluminescence through two or more emission bands enables broad and tailorable emission color, but requires fine control of activator precipitation on specific crystallographic sites. This presents a major obstacle in the design of tunable emitters, since dedicated control of site occupancy is rarely possible. Here, a new paradigm of tunability is considered, which overcomes this limitation. It is demonstrated in CaO:Mn2+ that single‐ and dual‐band emission can be generated by involving only a single type of crystallographic sites. This enables tailoring of the emission color alone through dopant concentration. The two emission bands exhibit different spectral, dynamic, and thermal characteristics, but very similar excitation spectra. While the variations in thermal quenching provide a tool for tunability, the variations in decay behavior suggest interesting potential for lifetime‐multiplexing and coding. Energy transfer is observed between the two emission bands, using time‐resolved emission spectra. From the analysis of crystal structure, spectral data, electron paramagnetic resonance analyses, and density functional theory calculations analyses, it is found that the emission bands at ≈600 and 660 nm originate from isolated Mn2+ ions and superexchange reactions in Mn2+ Mn2+ dimers, respectively.

Cation Substitution Induced Adjustment on Lattice Structure and Photoluminescence Properties of Mg14Ge5O24:Mn4+: Optimized Emission for w‐LED and Thermometry Applications

“…The above luminescence improvement and variation are possibly attributed to the resonance emission enhancement (REE) effect. According to a previous report, the emission of Mn 4+ is usually dominated by vibronic transitions. As the vibronic transition occurs, the energy travels in the form of wave in the lattice during the vibronic transition process.…”

“…The MGTO:Mn 4+ sample was chosen as the representative red phosphor to combine with Y 3 Al 5 O 12 :Ce 3+ (YAG) yellow phosphor and 440 nm blue chips for forming w‐LED devices (LED1). To obtain an intuitive evaluation, the CASN (LED2) and CSF (LED3) red phosphors were also employed to fabricate w‐LED devices for parallel comparisons. The electroluminescence (EL) spectra corresponding to the w‐LED devices with different compositions are demonstrated in Figure a.…”

Mn2+–Mn2+ Magnetic Coupling Effect on Photoluminescence Revealed by Photomagnetism in CsMnCl3

“…Mn 2+ is a vital transition-metal ion with unique visible emission, which is usually used in pc-WLEDs when being doped in semiconductors with an appropriate bandgap or codoped with Eu 2+ in inorganic phosphors with a wide bandgap. − However, the emission of Mn 2+ is easily saturated owing to its rather long decay lifetime, which results from a spin-forbidden transition of 4 T 1 → 6 A 1 . The long decay time of Mn 2+ may result in the depletion of ground energy level, causing PL saturation of Mn 2+ -doped phosphor under intense irradiation. − The saturation would lead to quenching and, hence, results in lower efficiency .…”

Photon energy conversion and management in SrAl12O19: Mn2+, Gd3+ for rewritable optical information storage

“…Notably, the corresponding emission intensity in the OSL decay curve after switching-off the laser is always higher than that in the normal decay one. All these results indicate that deep traps can be release through the conduction band by 980 nm photons and there is a trap redistribution as part of these traps are recaptured by the shallow traps while others recombine at Mn 2+ emitting centers [34,35].…”