High-quality single-component white phosphors are instrumental in realizing high-efficiency devices. Rare earth fluorides and carbon quantum dots have great potential in the white light-emitting diode (WLED) field due to their unique advantages. Here, Rare-earth single atom based NaGdF₄:Tb³⁺/Eu³⁺@C:N/Eu³⁺ single phosphor with tunable full-color luminescence was reported. The results of density functional theory (DFT) calculation and experimental characterization show that C atoms cannot be replaced by Eu³⁺, but C atoms are more favorable for anchoring Eu³⁺ single atoms. The DFT was employed to optimize the structures of the C:N/Eu³⁺ and NaGdF₄:Tb³⁺/Eu³⁺, and calculate the work function, optical properties, and charge density difference. The obtained tunable full-color single phosphor can emit stable light from blue to red or even white. The constructed WLED devices also have stable and excellent color performance, that is, a color rendering index of up to 95 and a lower color temperature, and it has broad application possibilities in WLEDs.

A novel host-guest luminous system with enhanced near-UV light absorption thereby enhanced luminescence are designed based on the synergism of quantum confinement, spatial confinement, and antenna effect, where ultrasmall Y₂O₃:Eu³⁺ nanocrystals are fixed inside MOF (Eu/Y-BTC) as supporting structure. The Eu/Y-BTC not only limits the size and leads to lattice distortion of Y₂O₃:Eu³⁺ nanocrystals and controls the distance between nanocrystals, but also promotes the light absorption and emission. The significantly red-shifted and broadened charge transfer band of Y₂O₃:Eu³⁺/(Eu/Y-BTC) leads to the excellent applications of Y₂O₃:Eu³⁺ in white light-emitting diodes (LEDs). Our results show that white light with superior color quality (CRI>90) and extremely high luminous efficacy (an LER of 335 lm/W) could be achieved using Y₂O₃:Eu³⁺/(Eu/Y-BTC) as red phosphor. The Y₂O₃:Eu³⁺/ (Eu/Y-BTC) also improves the photoelectric performance of dye-sensitized solar cells (DSSCs), not only because Y₂O₃:Eu³⁺/(Eu/Y-BTC) has a large specific surface area and the adsorption amount of the dye is increased, but also because the valence band position of Y₂O₃:Eu³⁺/(Eu/Y-BTC) is 2.41 eV, which can provide an additional energy level between the TiO₂ and dye, promoting electron transfer. For these advantageous features, the multifunctional Y₂O₃:Eu³⁺/(Eu/Y-BTC) composite product will open new avenues in white LEDs and DSSCs.