Enhanced 1.54-μm photo- and electroluminescence based on a perfluorinated Er(III) complex utilizing an iridium(III) complex as a sensitizer

Optical Amplification at 1.5 µm in ErIII Coordination Polymer-Doped Waveguides Based on Intramolecular Energy Transfer

9,9-bis (diphenylphosphorylphenyl) fluorene (FDPO) and dibenzotetrathienoacene (DBTTA), are synthesized as the neutral and anionic ligands, respectively, to prepare the ErIII coordination polymer [Er(DBTTA)3(FDPO)]n. Based on the intramolecular energy transfer, optical gains at 1.5 µm are demonstrated in [Er(DBTTA)3(FDPO)]n-doped polymer waveguides under excitations of low-power light-emitting diodes (LEDs) instead of laser pumping. A ligand-sensitization scheme between organic ligands and Er3+ ions under an excitation of an ultraviolet (UV) LED is established. Relative gains of 10.5 and 8.5 dB cm-1 are achieved at 1.53 and 1.55 µm, respectively, on a 1-cm-long SU-8 channel waveguide with a cross-section of 2 × 3 µm2 and a 1.5-µm-thick [Er(DBTTA)3(FDPO)]n-doped polymethylmethacrylate (PMMA) as upper cladding. The ErIII coordination polymer [Er(DBTTA)3(FDPO)]n can be conveniently integrated with various low-loss inorganic waveguides to compensate for optical losses in the C-band window. Moreover, by relying on the intramolecular energy transfer and UV LED top-pumping technology, it is easy to achieve coupling packaging of erbium-doped waveguide amplifiers (EDWAs) with pump sources in planar photonic integrated chips, effectively reducing the commercial costs.

Realization of 1.54-µm Light-Emitting Diodes Based on Er3+ /Yb3+ Co-Doped CsPbCl3 Films

Erbium ions (Er³⁺ , 1.54 µm) electric pumped light sources with excellent optical properties and a simple fabrication process are urgently desired to satisfy the development of silicon-based integration photonics. The previous Er-based electroluminescence devices are mainly based on Er-complexes or Er-doped oxide compounds, which usually suffer from low external quantum efficiency(EQE)or high applied voltage etc. In this work, a novel type of Er³⁺ /Yb³⁺ co-doped lead-halide perovskite films (Er³⁺ /Yb³⁺ :CsPbCl₃ ) with the maximum photoluminescence quantum yield of 30.12% are prepared by a simple two-step solution-coating method and the corresponding light emitting diodes (Er-PeLEDs) are fabricated, which demonstrate an almost pure 1.54-µm emission and a peak EQE up to 0.366% at a low applied voltage of 1.4 V. Strong negative thermal quenching effect may help Er-PeLEDs suppress Joule heating quenching. These excellent LED properties benefit mainly from the outstanding regulatory performance of acetate to perovskite films, the excellent semiconductor behavior and strong ionic property of the perovskite, and the involvement of Yb³⁺ ions, which can directly and efficiently transfer the exciton energy to Er³⁺ through a quantum cutting process. Overall, the realization of 1.54-µm Er-PeLEDs offers new opportunities for silicon-based integrated light sources.

Optical gain at 1.55 µm of Er(TMHD)3 complex doped polymer waveguides based on the intramolecular energy transfer effect

Based on the intramolecular energy transfer mechanism between organic ligand TMHD (2, 2, 6, 6-tetramethyl-3, 5-heptanedione) and central Er³⁺ ions, optical gains at 1.55 µm were demonstrated in three structures of polymer waveguides using complex Er(TMHD)₃-doped polymethylmethacrylate (PMMA) as the active material. With the excitation of two low-power UV light-emitting diodes (LEDs) instead of 980 or 1480 nm lasers, relative gains of 3.5 and 4.1 dB cm^-1 were achieved in a 1-cm-long rectangular waveguide with an active core of Er(TMHD)₃-doped PMMA polymer. Meanwhile, relative gain of 3.0 dB cm^-1 was obtained in an evanescent-field waveguide with cross-section of 4 × 4 µm² using passive SU-8 polymer as core and a ∼1-µm-thick Er(TMHD)₃-doped PMMA as upper cladding. By growing a 100 nm thick aluminum mirror and active lower cladding, the optical gain was doubled to 6.7 dB cm^-1 in evanescent-field waveguides because of the stimulated excitation of Er³⁺ ions in the upper and lower cladding and the improved absorption efficiency.

Enhanced luminescence of erbium silicate: interstitial lithium directly regulates the lattice structure of erbium compound crystals

We prepared high-intensity luminescent films with a high LDP (Er³⁺ luminescence lifetime-concentration product) of 1.54 × 10¹⁹ s × cm^-3, where lithium-doped erbium silicate grains are embedded in cristobalite. The near-infrared and up-conversion luminescence intensities of erbium silicate show ∼55 and 40 times enhancement by lithium-doping, respectively. Lithium-doping directly regulates the lattice structure of erbium silicate to enhance luminescence by reducing the crystal field symmetry around erbium, meanwhile, interstitial lithium does not dilute the concentration of erbium ions. Furthermore, lithium-containing dopants promote silica to crystallize, enhancing the luminescence of erbium silicate by reducing the interface defects. These films are expected to achieve high-gain film waveguide amplifiers in chip-scale optoelectronic integration. And this method opens up possibilities to be universally applicable to erbium compounds for enhancing luminescence by directly regulating the lattice structure.

Achieving Photon Upconversion in Mononuclear Lanthanide Molecular Complexes at Room Temperature

Photon upconversion luminescence at the molecule scale is a rarely observed phenomenon despite possessing colossal potential for basic research and reality applications. Here we show that the eight-coordinate erbium molecular complex composed of Er³⁺ ion, dibenzoylmethane, and 2,2'-bipyridine exhibits upconversion emission. Under direct excitation at the absorption band of Er³⁺ ion at 980 nm, the complex shows upconverted green emissions of Er³⁺ ion at 525 and 545 nm at room temperature. Noticeably, upon the introduction of fluoride ions into this complex, an additional upconverted red emission at 667 nm appears as well, and the luminescence intensities of both the green and red emissions increase by a factor of 13 at most. This study not only provides a strategy to adjust the green and red emissions in mononuclear erbium complexes but also broadens the horizons of designing lanthanide-based molecular upconversion systems.

AIE-active iridium(III) complex integrated with upconversion nanoparticles for NIR-irradiated photodynamic therapy

The integration of an aggregation induced emission (AIE)-active Ir(III) complex and upconversion nanoparticles (UCNPs) has achieved a NIR-irradiated photosensitizer (PS), UCNPs@Ir-2-N. This PS has satisfactory biocompatibility, excellent phototoxicity, good accumulation in cells and high ¹O₂ generation ability, thereby effectively killing 4T1 mouse cancer cells in vitro. This work has potential for future photodynamic therapy (PDT) applications.

Manipulation of Molecular Vibrations on Condensing Er3+ State Densities for 1.5 μm Application

Vibrational modes of chemical bonds in organic erbium (Er³⁺) materials play an important role in determining the efficiency of the 1.5 μm Er³⁺ emission. This work studies the energy coupling of the Er³⁺ intra-4f transitions and vibrational modes. The results demonstrate that the coupling introduces enormous nonradiative internal relaxation, which condenses the excited erbium population on to the ⁴I_13/2 state. This suggests that vibrational modes can be advantageous for optimizing the branching ratio for the 1.5 μm transition in organic erbium materials. Through control of the quenching effect on to the ⁴I_13/2 state and a reliable determination of intrinsic radiative rates, it is found that the pump power for population inversion can be reduced by an order of magnitude at high erbium concentrations compared to conventional inorganic erbium materials.

Synthesis and Biomedical Applications of Lanthanides-Doped Persistent Luminescence Phosphors With NIR Emissions

Persistent luminescence phosphors (PLPs) are largely used in biomedical areas owing to their unique advantages in reducing the autofluorescence and light-scattering interference from tissues. Moreover, PLPs with long-lived luminescence in the near-infrared (NIR) region are able to be applied in deep-tissue bioimaging or therapy due to the reduced light absorption of tissues in NIR region. Because of their abundant election levels and energy transfer channels, lanthanides are widely doped in PLPs for the generation of NIR persistent emissions. In addition, the crystal defects introduced by lanthanides-doping can serves as charge traps in PLPs, which contributes to the enhancement of persistent luminescence intensity and the increase of persistent time. In this paper, the research progress in the synthesis and biomedical applications of lanthanides-doped PLPs with NIR emissions are systematically summarized, which can provide instructions for the design and applications of PLPs in the future.