The model of developing luminescent materials has transferred from the conventional “trial and error” to “experience-guided experiments”, and further to a novel paradigm of “theoretical prediction and experimental verification”. Efficient theoretical prediction and rapid experimental verification are a key to this transformation. The theoretical prediction methods such as high-throughput calculations and machine learning are becoming more and more mature, and the corresponding experimental methods such as single-particle diagnosis are more efficient, laying a theoretical and experimental foundation for the development of novel luminescent materials. This review briefly summarizes recent research progresses on discovering new rare earth-activated luminescent materials based on single-particle diagnosis and high-throughput computation approaches.

Mini-LED backlights, combining color conversion materials with blue mini-LED chips, promise traditional liquid crystal displays (LCDs) with higher luminance, better contrast, and a wider color gamut. However, as color conversion materials, quantum dots (QDs) are toxic and unstable, whereas commercially available inorganic phosphors are too big in size to combine with small mini-LED chips and also have strong size-dependence of quantum efficiency (QE) and reliability. In this work, we prepare fine-grained Sr₂Si₅N₈:Eu²⁺-based red phosphors with high efficiency and stability by treating commercially available phosphors with ball milling, centrifuging, and acid washing. The particle size of phosphors can be easily controlled by milling speed, and the phosphors with a size varying from 3.5 to 0.7 μm are thus obtained. The samples remain the same QE as the original ones (~80%) even when their particle size is reduced to 3.2–3.5 μm, because they contain fewer surface suspension bond defects. More importantly, SrBaSi₅N₈:Eu²⁺ phosphors show a size-independent thermal quenching behavior and a zero thermal degradation. We demonstrate that red-emitting mini-LEDs can be fabricated by combining the SrBaSi₅N₈:Eu²⁺ red phosphor (3.5 μm in size) with blue mini-LED chips, which show a high external quantum efficiency (EQE) of above 31% and a super-high luminance of 34.3 Mnits. It indicates that fine and high efficiency phosphors can be obtained by the proposed method in this work, and they have great potentials for use in mini-LED displays.