Although rare-earth tungstates exhibit significant advantages in luminescence, the common problem of charge imbalance in traditional Ln³⁺ doping systems poses a serious challenge for further improving luminescence intensity and color purity. Based on this, a charge self-compensation strategy is proposed by optimizing the charge balance state within the crystal lattice at the atomic scale, which effectively suppresses lattice defects and significantly reduces non-radiative transition processes, thereby greatly improving the luminescence intensity and stability. Detailed calculations and analysis based on density functional theory (DFT) were conducted on the crystal structure, band structure, density of states (DOS), and charge density distribution by constructing different doping structure models. The luminescence efficiency and stability have been improved by enhancing the hybridization of material orbitals. Compared with the corresponding uncompensated samples, the integrated emission peak areas of Ca_1−xSr_xWO₄:Ln³⁺ is enhanced by up to 2.96-fold after charge compensation. In addition, the 3D-printed phosphor-resin composites exhibit robust storage stability, with their integrated emission peak areas remaining above 95% of the initial values after six months of storage. Finally, white light-emitting diodes (WLEDs) manufactured using optimized phosphors achieved better color quality with a color rendering index (CRI) of 95, highlighting their potential in high-quality solid-state lighting and indoor photovoltaic applications.

Although upconversion rare-earth (RE) materials have excellent luminescence properties, the luminescence intensity and thermal stability of phosphors are not favorable due to RE doping induced vacancies. This work focused on enhancing luminescence intensity and stability of phosphor by charge compensation and three-dimensional (3D) printing. The luminescence results showed that Ca_0.697Yb_0.2Er_0.0015Tm_0.0005F₂ with charge compensation exhibited luminescence intensity 3.2 times higher than that of Ca_0.798Yb_0.2Er_0.0015Tm_0.0005F₂ non-charge compensation. The luminescence of resin-coated luminescent materials is still stable after 6 months. The constructed white light-emitting diodes (WLEDs) also exhibit consistent and outstanding color rendering characteristics, with a color rendering index (CRI) of up to 81 and a low color temperature (CCT).

Heterojunction catalysts have been demonstrated to significantly enhance photocatalytic CO₂ reduction activity. However, the direction and rate of charge transfer at the catalyst interfaces remain the primary limiting factors for catalytic performance. In this study, a ternary heterojunction MgTi₂O₅ (MT)/TiO₂/g-C₃N₄ (CN) was prepared via in situ composite synthesis, and rare earth single-atom Ho, with abundant 4f electron energy levels, was utilized as an electron transfer channel within the heterojunction. This approach effectively facilitated electron transfer at the catalyst interface, and its photocatalytic activity and mechanism were thoroughly investigated. Remarkably, the catalyst exhibited distinct charge transport mechanisms under visible light and ultraviolet light. In the absence of a sacrificial agent, the sample MT:CN-1 demonstrated optimal performance under visible light, achieving a CO yield of 31.42 μmol·g⁻¹·h⁻¹, which is 9.8 times higher than that of pristine CN. Under ultraviolet light, the sample MT:CN-2 exhibited the best performance, with a CO yield of 40.61 μmol·g⁻¹·h⁻¹, representing a 4.2-fold enhancement compared to CN. Furthermore, the charge transfer mechanism of the catalyst was elucidated using in situ X-ray photoelectron spectroscopy (XPS) and femtosecond transient fluorescence spectroscopy techniques.