Mn-derived Cs4PbX6 nanocrystals with stable and tunable wide luminescence for white light-emitting diodes

Abstract

Cs₄PbX₆ nanocrystals (NCs) are perovskite derivatives with a wide band gap, but their application is limited because of their non-luminescence characteristics in the visible range. In this paper, the band gap of Cs₄PbX₆ NCs was adjusted via Mn doping (Mn:Cs₄PbX₆). Mn doping changes the photoluminescence (PL) properties of the NCs. A PL peak at 610 nm is observed at λ_ex = 289 nm, which confirms that Mn ions are introduced in the lattice of the Cs₄PbX₆ NCs. The effect of Mn ions on the PL properties of the Cs₄PbX₆ NCs is investigated by changing the Pb : Mn molar ratio. When the Pb : Mn ratio is 1 : 1, the PL quantum yield of the NCs reaches 23.1%. Transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction (XRD) analysis indicate that Mn ions were successfully introduced in the Cs₄PbCl₆ NCs. Raman spectroscopy further proves that the Cs₄PbCl₆ NCs possess high crystallinity. Two PL peaks at 355 and 610 nm are observed for the Mn:Cs₄PbX₆ NCs. The PL decay plots of the Mn:Cs₄PbCl₆ NCs show that the lifetime at λ_em = 355 nm reduces with increasing Pb : Mn molar ratio while the lifetime at λ_em = 610 nm increases, suggesting that the process of photo exciton transfer occurs from Pb to Mn ions. Due to their high stability, white light-emitting diodes (LEDs) were fabricated using CsPb(Cl/Br)₃, CsPbBr₃ and Mn:Cs₄PbCl₆ NCs as color conversion layers using a 280 nm commercial LED chip as the excitation source. The Internationale de I’Eclairage chromaticity coordinates of the white LED are located at (0.3229, 0.3037).