Gel permeation chromatography process for highly oriented Cs 3 Cu 2 I 5 nanocrystal film

The emergence of green materials has attracted considerable attention in the field of optoelectronics. Copper-based lead-free metal halide (with a near-unity quantum yield) obtained from Cs 3 Cu 2 I 5 nanocrystals (NCs) can exhibit blue emission with a wavelength of 440 nm and provide outstanding stability for various applications. However, in practical applications, colloidal dispersion purity and film quality are inadequate toward a high-performance device. In this study, antisolvent-free gel permeation chromatography is used to purify Cs 3 Cu 2 I 5 NCs. The purified Cs 3 Cu 2 I 5 NCs exhibit a high photoluminescent quantum yield and provide a highly oriented single-crystal film. Density functional theory calculation results indicate that the iodide-rich surface in the NCs makes them highly stable. In addition, it has been demonstrated for the first time that the mixture of polymethyl methacrylate (PMMA) and Cs 3 Cu 2 I 5 NCs has waterproofing capabilities. The composite film consisting of Cs 3 Cu 2 I 5 NCs and PMMA can survive in water for several days. This result opens up more possibilities for the application of these green material.