Exciton Localization Engineering in Thermally Evaporated Yb-Doped CsPbCl<sub>3</sub> Near-Infrared Light-Emitting Diodes.

Wang, Shuo; Zhang, Shuhan; Li, Xin; Huang, Dan; Yu, William W; Wang, Liang · Adv Mater · 2026

basic_science · Level V

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Abstract

Near-infrared (NIR) emission underpins biomedical imaging, night vision, and optical communication. Yb<sup>3+</sup>-doped CsPbCl<sub>3</sub> have demonstrated ultrahigh photoluminescence quantum yields via quantum cutting, primarily enabled by a singular defect-assisted energy transfer pathway arising from the substitution of Pb<sup>2+</sup> by Yb<sup>3+</sup>. However, whether additional pathways exist to facilitate visible (VIS)-to-NIR conversion, thereby further enhancing the performance of NIR-emissive devices, remains an open and compelling question. Here, strategic engineering of localized bound excitons (BEs) is proposed in the thermally evaporated CsPbCl<sub>3</sub>:Yb system. Assisted BEs significantly promote energy transfer from CsPbCl<sub>3</sub> matrix to Yb dopants, unveiling a previously unknown excitonic energy transfer channel. Atomic-scale characterization combined with first-principles calculations uncovers a BE-driven excitonic transfer mechanism, specifically implicating Cs-vacancy-induced defects in mediating exciton behavior. These insights lead to the fabrication of high-performance NIR-LEDs with an 8.9% external quantum efficiency and 410 mW·Sr<sup>-1</sup>·m<sup>-2</sup> radiance, marking a breakthrough in thermally evaporated NIR (>950 nm) light-emitting diodes.