Holy Water: Photo‐Brightening in Quasi‐2D Perovskite Films under Ambient Enables Highly Performing Light‐Emitting Diodes

Abstract

Quasi‐2D perovskites provide new opportunities for lighting and display applications due to their high radiative recombination and excellent stability. However, seldom attention has been placed on their self‐stability/working operation under ambient storage. Herein, quasi‐2D perovskites/Polyethylene oxide (PEO) films are studied, showing an unforeseen photo‐brightening effect under ambient storage (i.e., an increase of the photoluminescence quantum yield from 55% to 74% after 100 days). In stark contrast, those stored under a dark/inert atmosphere show a significant decrease down to 38%. This counterintuitive phenomenon responds to the increasing radiative recombination rate caused by the passivation of the surface Br vacancies in the presence of physically adsorbed water molecules, as corroborated by in situ/ex situ X‐ray photoelectron spectroscopy and density functional theory calculations. Capitalizing on this surprising effect, stable light‐emitting diodes (LEDs) using quasi‐2D perovskites/PEO color filters are fabricated, realizing high stabilities of ≈400 h@10 mA under operating ambient conditions, representing a 20‐fold enhancement compared to LEDs with 3D counter partners. Hence, this study reveals a unique insight into the impact of water passivation on the optical/structural properties of quasi‐2D perovskite films, broadening their applications under operating ambient conditions.

Air‐Processed Blue Perovskite Light‐Emitting Diodes Enabled by Manipulation of Adsorbed‐Moisture‐Dominated Crystallization Kinetics

“…[22][23][24] Additionally, it has been reported that the optical properties and stability of perovskite films in ambient air are significantly affected by light illumination. [25][26][27][28] We thus investigated the stability of these airprocessed blue perovskite films with varying times of light illumination and darkness (Figure S8, Supporting Information). It can be found that in the dark, the films retained their initial PLQY value or PL intensity over 80%; however, when illuminated by white light, they degraded to about 50% of their original values.…”

Performance Enhancement of Quasi-Two-Dimensional Perovskite Light-Emitting Diodes by Constructing an Efficient Energy Funnel via Ionic Liquid Doping

“…Here, n defines the number of (PbX 6 ) 4– octahedron stacks, where n = ∞ stands for the 3D perovskite . Recently, quasi-2D perovskites have attracted more attention in light-emitting device research due to their strong exciton binding energies and functional cation modification in electroluminescence devices. , The external quantum efficiency has achieved over 25% in red light-emitting devices . However, it has been found that quasi-2D perovskites generate more surface deep defects than 3D perovskites, which could severely influence the radiative recombination process .…”

Silver Ions Assisted Inversion Temperature Crystallization of 2D Cs3Bi2Br9 Nanoflakes for Highly Sensitive X‐Ray Detection

“…[1][2][3][4] This structure-tunable traits of 2D perovskites are beneficial to control their structural distortion, exciton-phonon coupling and quantum confinement, which in turn, attune their electronic and optical properties. [5][6][7][8][9] Nevertheless, most currently 2D perovskites were synthesized by separating compact 3D structure of traditional ABX 3 (A is cation with large radius, B is cation with smaller radius, X is anion) perovskites with organic cation groups, leading to low purity and mixtures of various layered compounds. [10,11] Different from the 2D perovskites composed of organic spacer molecules, allinorganic A 3 B 2 X 9 perovskites were transformed through replacing divalent B with trivalent cations such as Bi 3+ , showing much higher chemical and structure stability to thermal, moisture and oxidation.…”