Unraveling Size‐Dependent Ion‐Migration for Stable Mixed‐Halide Perovskite Light‐Emitting Diodes

Abstract

Mixed‐halide perovskites show tunable emission wavelength across the visible‐light range, with optimum control of the light color. However, color stability remains limited due to the notorious halide segregation under illumination or an electric field. Here, a versatile path toward high‐quality mixed‐halide perovskites with high emission properties and resistance to halide segregation is presented. Through systematic in and ex situ characterizations, key features for this advancement are proposed: a slowed and controllable crystallization process can promote achievement of halide homogeneity, which in turn ensures thermodynamic stability; meanwhile, downsizing perovskite nanoparticle to nanometer‐scale dimensions can enhance their resistance to external stimuli, strengthening the phase stability. Leveraging this strategy, devices are developed based on CsPbCl1.5Br1.5 perovskite that achieves a champion external quantum efficiency (EQE) of 9.8% at 464 nm, making it one of the most efficient deep‐blue mixed‐halide perovskite light‐emitting diodes (PeLEDs) to date. Particularly, the device demonstrates excellent spectral stability, maintaining a constant emission profile and position for over 60 min of continuous operation. The versatility of this approach with CsPbBr1.5I1.5 PeLEDs is further showcased, achieving an impressive EQE of 12.7% at 576 nm.

Energy Transfer-Dominated Quasi-2D Blue Perovskite Light-Emitting Diodes

“…This change by the strong quantum confinement effect may result from the two Br atoms on the DBA molecule reducing the formation energy of the low-dimensional phase and increasing the nucleation site or steric hindrance due to their stronger electronegativity. 18,47,48 The grain sizes of SFB-modified and DBA@SFB-modified perovskite films were calculated using the Scherrer equation from the XRD pattern to be approximately 220 and 130 nm, respectively (Figures 3b and S10), which is consistent with the observations of blue shifts. In addition to altering the phase distribution, there is also an enhanced PL intensity for the DBA@SFB-modified perovskite films.…”

“…The most common strategy for achieving blue emission in PeLEDs is to replace some bromide (Br) ions by chlorine (Cl) ions in the crystal structure, which allows the tunable to be tuned. − However, too high Cl content can lead to the formation of deep trap states for Auger recombination, and cause spectral instability due to ion segregation under an external electrical bias. − Therefore, bromide–chlorine (Br/Cl) mixed perovskite systems combined with the quantum confinement effect have become a mainstream strategy for developing high-efficiency blue PeLEDs. The quasi-two-dimensional (2D) perovskites with natural quantum wells can be obtained by inserting large organic cations, such as phenethylammonium (PEA), phenylmethylamine (PMA), 1,3-diammonium (PDA), and butylammonium (BA), into the parent structure, breaking it up into low-dimensional structures of more layers of Pb­(Br/Cl) 6 octahedra.…”

Amphoteric Chelating Ultrasmall Colloids for FAPbI3 Nanodomains Enable Efficient Near-Infrared Light-Emitting Diodes

“…Finally, Cs-based blue PeLEDs with record efficiencies were achieved and were expanded to long-wavelength visible emissions by halide substitution. In brief, selecting reasonable agents for the growth of small-sized, well-confined perovskite domains is the most promising path toward superior device performance. , However, near-infrared perovskite emitters, such as FAPbI 3 , still face difficulties in being in situ fabricated down to tens of nanometers on the substrate due to the lack of suitable agents, restricting their full potential on further efficiency improvement.…”

Structure-Guided Approaches for Enhanced Spin-Splitting in Chiral Perovskite

“…Hybrid organic–inorganic perovskite has demonstrated intriguing optical and electrical properties, which prompted extensive development of such a material family within the realm of multiple optoelectronics including photovoltaics, light emitting diodes, and photodetectors. − Following the progress in perovskite-based optoelectronic devices, the exploration and evolution of chiral perovskite with various chirality transfer mechanisms from organic components to inorganic lattice also quickened research interest of these compounds in the field of spintronics applications. , …”