CsEuCl3 nanocrystals (NCs) are novel lead-free rare-earth perovskite NCs with low toxicity and intrinsic optical activity, exhibiting potential as promising alternatives to lead halide perovskites. However, the limited understanding of their dual-photoluminescence (PL) emission mechanism impedes further material optimization and device integration of CsEuCl3 NCs. In this work, the origin of the dual PL emission peaks in CsEuCl3 NCs is elucidated through comprehensive spectroscopic analyses, including femtosecond transient absorption and temperature-dependent PL spectroscopy. The narrow emission at 435 nm is identified as the band-edge free-exciton recombination, while the broad emission centered at 559 nm arises from extrinsic self-trapped exciton (STE) emission. The excessive Eu suppresses lattice vibrations and facilitates the conversion of the dark STE state into a radiative bright state, thereby enhancing the PL quantum yield (PLQY) to 34.1%, which is record-high for CsEuCl3 NCs. By systematic tuning of the Eu content, the intensity ratio between dual emission bands is regulated. On the basis of the tunable emission, white-light-emitting diodes with correlated color temperatures of 8788 to 4371 K and high operation stability are successfully fabricated. This work unveils the fundamental mechanism governing dual emission behavior in CsEuCl3 NCs, establishes an effective strategy for PL modulation, and highlights their potential as robust, lead-free materials for next-generation solid-state lighting applications.
Zhuang et al. (Sun,) studied this question.
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