Rearranging the Phase Distribution of Quasi-2D Perovskite for Efficient and Narrow Emission Perovskite Light-Emitting Diodes.

Quasi-2D perovskite light-emitting diodes (PeLEDs) have attracted significant attention for their promising light-emitting applications. However, quasi-2D perovskite films typically consist of a broad phase distribution and small grains with a large surface area to volume ratio, leading to inferior color purities and higher defect densities. Herein, a bifunctional additive ((l)-tryptophan bromide, l-TrpBr) was introduced into a quasi-2D perovskite film. The C═O moiety of l-TprBr formed hydrogen bonds with S-MBA + , retarding the coordination between S-MBABr and [PbBr 6 ] 4- and suppressing the formation of small- n phases. The C═O moiety also coordinated with unsaturated Pb 2+ sites to passivate the defects. Finally, the PeLEDs with l-TrpBr exhibited a significantly improved EQE of 14.32% compared to the control devices (7.88%) and the narrowest fwhm (17 nm) for green quasi-2D PeLEDs reported to date. Our work provides a practical approach to controlling the phase distribution and passivating the defects in quasi-2D perovskite films, toward high-efficiency and color-pure quasi-2D PeLEDs.