Brightly luminescent green-emitting halide perovskite light emitting diode by employing the whole single crystal

Halide Perovskite light emitting diodes (LEDs) have attracted enormous attention due to their remarkable optoelectronic properties, facile bandgap tunability and low-cost. Here, we successfully synthesized the centimeter-sized pure non-emissive Cs4PbBr6, hybrid green-emitting Cs4PbBr6@CsPbBr3 (H-Cs4PbBr6) and ligand-induced H-Cs4PbBr6 single crystals (SCs) via the precision-temperature-gradient crystallization method. The detailed formation process of H-Cs4PbBr6 was detected by a real-time optical photograph and ultraviolet lamp during different growth stages ranged from colorless transparent to bright green. Notably, the H-Cs4PbBr6 SC shows the behavior of excellent luminous properties (PLQY = 92 %) owing to the higher exciton binding energy, which is estimated to be ∼439.8 meV. The unusual intense green photoluminescence mechanism is evidenced by the various measurements, which can be attributed to the embedded CsPbBr3 nanocrystals. Interestingly, the excellent long-term stabilities of as-prepared H-Cs4PbBr6 SC against heat, and environment oxygen/moisture degradation are reported, which maintains high fluorescence brightness for 3 years in air, and then for more than 4 days under 80 °C and 80 % relative humidity without additional encapsulation. A larger activation energy of 461.1 meV exhibits the better thermal stability. Furthermore, an adjustment of the PL emission of H-Cs4PbBr6 SCs is first achieved with the addition of ligands. Ultrapure green LED fabricated with the whole large Cs4PbBr6 SC exhibits wonderful performance with luminous efficiency of 20.50 lm·W−1, excellent color purity of ∼90.7 % and external quantum efficiency of 5.43 %, which demonstrate the immense potential and great prospect of H-Cs4PbBr6 perovskite composites to replace conventional phosphors in lighting devices.