Room Temperature Synthesized Green Perovskite Nanocrystals with Enhanced Thermal Stability Enabled by Fluorinated Ligand Engineering for Light-Emitting Diodes

Abstract

Metal halide perovskite nanocrystals (PeNCs) have shown great promise for display and lighting due to their outstanding optoelectronic properties. However, their practical applications in both of electroluminescent (EL) and photoluminescent (PL) light-emitting diodes (LEDs) are limited by thermal-induced emission quenching. Herein, we synthesized FAPbBr3 and CsPbBr3 PeNCs by a common room-temperature ligand-assisted reprecipitation (LARP) method, and demonstrated that the obtained FAPbBr3 PeNCs showed superior thermal stability compared to the CsPbBr3 PeNCs. By introducing a fluorinated aromatic amine ligand of 2-(4-(trifluoromethyl)phenyl)ethylamine (CF3-PEA) for surface passivation, the modified FAPbBr3 PeNCs exhibited significantly reduced thermal quenching effect, retaining 75% of their initial PL intensity at 380 K and showing complete PL recovery upon cooling to 300 K. The EL devices fabricated using the CF3-PEA-modified FAPbBr3 PeNCs as the emissive layers achieved a maximum external quantum efficiency (EQE) of 20.4%. When deposited together with poly(methyl methacrylate) (PMMA), the CF3-PEA-modified FAPbBr3 PeNCs showed further enhancement in the thermal stability due to the synergistic effect of encapsulation and passivation. By combining the modified FAPbBr3 PeNCs and red phosphor into the PMMA matrix and then assembling with a commercial blue LED chip, we fabricated the down-converting white LEDs with a CIE coordinate of (0.369, 0.355) at 10 mA, covering 127% of the national television system committee (NTSC) color gamut. And the white LEDs possessed high luminance of over 600,000 nits with a peak EQE of 41.8%. This work demonstrates a room-temperature synthetic route for fabricating highly stable FAPbBr3 PeNCs with reduced thermal-induced PL quenching, advancing PeNCs-based optoelectronic device applications.