Single-Layer Sheets of Alkylammonium Lead Iodide Perovskites with Tunable and Stable Green Emission for White Light-Emitting Devices

Recently, metal halide perovskites have attracted considerable interest as highly emissive phosphors for use in white light-emitting diodes (WLEDs). In perovskites, the migration of halide anions between green-emitting bromide (e.g., CsPbBr3) and red-emitting iodide (e.g., CsPbI3) materials is one obstacle to application. Here perovskite WLEDs that do not suffer from the anion exchange problem are reported: this is done by developing green-emitting single-layer sheets of (RNH3)(2)PbI4 (R = C18H35-, C12H25-, and C8H17-) and uniting these with red-emitting CsPbI3 perovskite quantum dots (QDs). It relies on self-assembly from ligand-capped CsPbI3 nanocrystals to form single-layer sheets of (C18H35NH3)(2)PbI4: via judicious selection of alkylamines and alkyl acids, (RNH3)(2)PbI4 single-layer sheets that exhibit bright and stable green emission with well-defined single-layer thickness are produced. Emission from 505, 512 to 536 nm is tuned and a narrow (<20 nm) linewidth is retained. Perovskite LEDs that produce white light with chromaticity coordinates (0.32, 0.33) and color gamut that reaches 117% National Television System Committee (NTSC) in the International Commission on Illumination (CIE) 1931 color space are demonstrated.

Automated summary

This study reports on perovskite white light-emitting diodes (WLEDs) that do not have the issue of anion migration. By developing green-emitting single-layer sheets and combining them with red-emitting perovskite quantum dots, the researchers successfully solved the problem and demonstrated WLEDs with high potential for applications.