Polarity-Mediated Antisolvent Control Enables Efficient Lanthanide-Based near-Infrared Perovskite LEDs

Alloying lanthanide ions (Yb³⁺) into perovskite quantum dots (Yb³⁺:CsPb(Cl_1-Br)₃) is an effective method to achieve efficient near-infrared (NIR) luminescence (>950 nm). Increasing the Yb³⁺ alloying ratio in the perovskite matrix enhances the luminescence intensity of Yb³⁺ emission at 990 nm. However, high Yb³⁺ alloying (>15%) results in vacancy-induced inferior material stability. In this work, we developed a polarity-mediated antisolvent manipulation strategy to resolve the incompatibility between a high Yb³⁺ alloying ratio and inferior stability of Yb³⁺:CsPb(Cl_1-Br)₃. Precise control of solution polarity enables increased uniformity of the perovskite matrix with fewer trap densities. Employing this strategy, we obtain Yb³⁺:CsPb(Cl_1-Br)₃ with the highest Yb³⁺ alloying ratio of 30.2% and a 2-fold higher electroluminescence intensity at 990 nm. We lever the engineered Yb³⁺:CsPb(Cl_1-Br)₃ to fabricate NIR-LEDs, achieving a peak external quantum efficiency (EQE) of 8.5% at 990 nm: this represents the highest among perovskite NIR-LEDs with an emission wavelength above 950 nm.