Full-Color Spectrum Coverage by High-Color-Purity Perovskite Nanocrystal Light-Emitting Diodes

Although many synthetic methods such as hot injection and anionic exchange can produce full-color perovskite nanocrystals (PNCs), their emission spectra are broadened by compositional non-uniformity. Here, we propose the synthetic method, hydrogen halide (HX; X = Cl, Br, and I)-mediated uniform halide anion exchange at mild temperatures, for high color-purity PNCs emitters across the full-color spectrum. The HX-mediated exchange reaction produces high-purity PNCs without metallic Pb impurities due to the use of volatile HX as the X source. The blue, green, and red PNCs show narrow emission spectra, with 16, 18, and 18.5 nm of full width at half-maximum, respectively. The red PNC emitter synthesized by the HX-mediated method has a single photoluminescent (PL) peak, with a narrow emission spectrum at low temperature due to compositional uniformity, whereas the PNCs produced by other methods have multiple PL peaks. Accordingly, the red/green/blue electroluminescent devices also have narrow emission spectra.