Selective Dispersing Solvent-Assisted Surface Defect Engineering Followed by Time-Resolved Spectroscopy Analysis of Red-Emitting CsPb(Br,I)₃ Nanocrystals for Stable and Bright Light-Emitting Diodes

In the solution process using perovskite nanocrystals (PNCs) as emitting materials for light-emitting diodes (LEDs), solvent orthogonality typically plays a crucial role in preserving stable interfacial conditions between the carrier transport layers on both sides. Unfortunately, there is a lack of clear understanding of which solvent to choose and what effects the solvent has in realizing the photo/electroluminescence (PL and EL) properties of the given PNCs. Here, we investigate the impact of merely changing dispersing solvents on the properties of PNCs, which belong to a family of nonpolar aliphatic hydrocarbons, hexane, octane, and decane. We can realize that by simply postdispersing using longer chain alkane solvents, both the PL/EL properties were improved along with the synthetic yield and uniform PNC particle size distribution, and the suppressed surface defect was found using time-resolved photoluminescence analysis. Samples that underwent dispersion and washing using a decane solvent, which effectively heals the remnant surface defects, were confirmed to have doubled the yield and improved luminous efficiency with superior EL (maximum external quantum efficiency of 14.7%) with reproducible device performances. The given dispersing solvent selection strategy has the potential to enhance the PL and EL properties and thus the reproducibility of perovskite-based LEDs.