Broadband Near-Infrared-Emitting Phosphors with Suppressed Concentration Quenching in a Two-Dimensional Structure

Abstract

For inorganic luminescent materials with activators, the energy yield is usually observed to decrease with an increase in activator concentration, which is known as the concentration quenching effect. To inhibit this phenomenon, a common strategy is to increase the distance between activators. Most previous reports have focused on the three-dimensional crystal lattice, and there have been few reports about two-dimensional layered structure. Herein, we synthesized a novel Cr3+-activated near-infrared (NIR) phosphor Li2Sr2Al­(PO4)3 (LSAPO) with layered structure, and in such a two-dimensional structure, we proved experimentally that the concentration quenching was suppressed. Under 460 nm excitation, LSAPO:Cr3+ gave a broad NIR emission band (700–1200 nm) centered at 823 nm with a full width at half-maximum (fwhm) of 178 nm and a broad absorption band, indicating its potential application in NIR spectroscopy. Moreover, by codoping Cr3+ and Yb3+ ions, we further widened the emission bandwidth to ∼230 nm of fwhm, the internal quantum efficiency increased from 54% to 61%, and the thermal stability was improved. The fabricated NIR device with a LSAPO:Cr3+,Yb3+ phosphor coupled with blue chips can be applied in night-vision technologies and medical fields.

8-Phenylquinoline-Based Tetradentate 6/6/6 Platinum(II) Complexes for Near-Infrared Emitters

“…Near-infrared (NIR) emitters with emission peaks beyond 700 nm have great potential applications in photodynamic therapy, − in vivo bioimaging, − optical signal processing, and night-vision technologies. − However, because the main nonradiative deactivation pathway induces the quenching of NIR emission, which is known as the “energy gap law”, the photoluminescence quantum efficiencies (PLQEs, Φ) of most NIR emitters are low, typically less than 1%, such as phosphorescent d 6 , d 8 , and d 10 transition-metal complexes. − Therefore, the design and development of highly efficient NIR emitters remains a great challenge. In the past decades, Pt­(II) complexes had been demonstrated to act as efficient phosphorescent blue-to-red emitters because of the heavy-atom effect-induced strong spin-orbit coupling, which enabled efficient intersystem crossing (IC) from the lowest singlet (S 1 ) to triplet state (T 1 ) and then radiative decay to the ground state (S 0 ). − Recently, great progress had been made for thermally activated delayed fluorescence (TADF) NIR emitters and Pt­(II)-based NIR emitters through rational molecular design (Figure ).…”

High thermal stability phosphors with a rigid structure similar to the benzene ring and application in plant growth

“…The narrow bands centered at 696 and 719 nm correspond to the 2 E → 4 A 2 electronic spin-forbidden transition, while the broadband is due to the 4 T 2 → 4 A 2 electronic spin-allowed transition of the Cr 3+ ions. 34 The emission intensity of as-synthesized samples increases with the concentration of chromium ions until y = 0.002 and then decreases as a result of the concentration quenching effect caused by the energy transfer between the chromium ions, 35 indicating that the optimum doping concentration of the chromium ions in LiGaGeO 4 and LiAl x Ga 1− x GeO 4 is 0.2% (Fig. 5a).…”

Optical temperature sensing with an Er3+, Yb3+co-doped LaBMoO6single crystal

“…Both samples have a similar profile with the same absorption edge located at about 288 nm, revealing that the doping of Er 3+ and Yb 3+ does not change the band gap of LBMO. According to the Kubelka-Munk theory, 42 it can be deduced that the optical band gap of LBMO is 4.3 eV. Meanwhile, the typical absorption peaks of the dopants appear in the DSR spectra of LBMO-SC: Er 3+ , Yb 3+ .…”