Title : Homogeneous nucleation and growth for synthesizing highly efficient and stable perovskite quantum dots and their light-emitting diodes
Abstract:
Lead halide chalcogenide nanocrystals are a promising light-emitting material for next-generation display technologies,capable of achieving near-100% photoluminescence quantum yield, narrow light-emitting spectra, and easily tunable light-emitting wavelengths. However, chalcogenide nanocrystals for light-emitting diodes are usually synthesised by difficult-to-control substitution reactions, resulting in low yields, inhomogeneous crystal growth and poor stability. To synthesized high-quality chalcogenide nanocrystals for use in chalcogenide quantum dot light-emitting diodes, we propose a synthetic strategy for uniform growth nucleation. This strategy achieves control of nucleation and growth during synthesis by simultaneously eliminating clusters that affect nucleation and suppressing overgrowth of Ostwald ripening, and synthesises chalcogenide nanocrystals with a narrow size distribution, fewer defects, and highly controllable size. Specifically, we avoided the generation of PbX2 clusters by using Lewis acids and Lewis bases with relatively high dissociation coefficients as precursor ligands. After nucleation, a growth inhibiting reagent was added to the synthesis system, which also regulates the reaction equilibrium and passivates the nanocrystals. The photoluminescence quantum yield and stability of red and green chalcogenide nanocrystals were significantly improved by our synthesis strategy. Stable and efficient green and red lead halide chalcogenide nanocrystals were synthesised. The prepared quantum dot light-emitting diodes achieved an external quantum efficiency of 24.13% at 517/17 nm and 25.80% at 646/40 nm, and achieved pure red emission with 26.04% efficiency at an emitting wavelength and half-height width of 628/33 nm. The green chalcogenide light-emitting diodes operated at a brightness of 10,000 cd/m² with lifetime T50 reached a record 54 minutes, while the operational stability of the red chalcogenide LEDs was improved by a factor of 70, and the pure red chalcogenide quantum dot light-emitting diodes had an operational lifetime of 729 minutes at a brightness of 1,000 cd/m².
