Transition metal halide derived phase transition from Cs4PbCl6 to CsPbxM1–xX3 for bright white light-emitting diodes

Abstract

Inorganic perovskite nanocrystals (NCs) have become a research hotspot due to their excellent optical properties. Zero dimensional (0D) Cs₄PbCl₆ NCs are important perovskite derivative structures. Herein, high luminescent and stable CsPb_xM_1–xX₃ NCs were synthesized using a post-processing method. MX₂ (M: Zn and Mn, X: Br and Cl) hexane solutions were used as precursors to treat parent Cs₄PbCl₆ NCs without luminescence. The insertion reaction of cations was promoted during the halogen anion exchange process. After ion exchange, the photoluminescence quantum yields (PLQYs) of samples treated with ZnCl₂ and ZnBr₂ were up to 74.2 and 88.1%, respectively, in which the PLQYs were changed to 70 and 65% after 20 days in air conditions. The MnCl₂ treated sample exhibited a new PL peak at 610 nm because of the insertion of Mn²⁺ ions. The PLQY of the MnCl₂ treated sample was 56%. Namely, CsPb_xZn_1–x(Cl/Br)₃, CsPbBr₃, and CsPb(Br/I)₃ NCs were dispersed in polymethyl methacrylate solutions to prepare PL films. A commercial light-emitting diode (LED) chip was used as an excitation source to prepare white LEDs. From the Commission Internationale de I’Eclairage (CIE) chromaticity diagram, the bright white emission of the film exhibited the corresponding chromaticity coordinates of (0.29, 0.30) which located in the white light area. The white emitting film exhibited high stability.