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

Abstract

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 [PbBr6]4– and suppressing the formation of small-n phases. The CO moiety also coordinated with unsaturated Pb2+ 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.

Spacer cation engineering in Ruddlesden-Popper perovskites for efficient red light-emitting diodes with recommendation 2020 color coordinates

“…For the BZA-and PEA-based films, PB peaks of n2 are quite strong compared with those of n3 and n4, indicating a high proportion of n = 2 phase and wide phase distributions. It has been reported that small-n phases usually suffer from nonradiative recombination induced by strong electronphonon coupling [40]. In contrast, the fraction of n = 2 phase is dramatically reduced in the PPA-and POEA-based films with a high fraction of large-n phases and relatively narrow phase distributions, which is beneficial for radiative recombination and energy funneling.…”

Regulating the phase distribution of quasi-2D perovskites using a three-dimensional cyclic molecule toward improved light-emitting performance

“…On the one hand, such a blue shift can result from its passivation effects at the quasi-2D perovskite grain boundaries. 45 On the other hand, it correlates with the improved quantum well structure in the quasi-2D film arising from the suppression of the bulk phases, which is evident from the gradual decrease in the absorption band edge and the XRD results (discussed later). 46 The X-ray diffraction (XRD) patterns of these films were characterized as follows.…”

Surface Defect Suppression for High Color Purity Light‐Emitting Diode of Free‐Standing Single‐Crystal Perovskite Film

“…[ 15 ] It is worth noting that poor phase purity with wide phase distribution can lead to color impurity, especially for quasi‐2D perovskite with mixed 2D–3D phases. [ 16 ] The small‐n phases ( n = 1, 2, and 3; where n represents the number of inorganic layers) with strong electron‐phonon coupling are dominated by non‐radiative recombination, which may cause homogeneous broadening of FWHM. [ 17 ] Therefore, low defect density and phase‐pure single‐crystal perovskites have the potential to achieve higher color purity.…”