Engineering of Annealing and Surface Passivation toward Efficient and Stable Quasi-2D Perovskite Light-Emitting Diodes

Abstract

Solution-processed quasi-two-dimensional (quasi-2D) perovskites with selfassembled multiple quantum well (QW) structures exhibit enhanced exciton binding energy, which is ideal for use as light emitters. Here, we have found that postannealing is important to promoting the QWs' composition transfer, and we explored the correlation among the annealing time, the external quantum efficiency (EQE), and the operational stability of the device. During thermal annealing, the low-n QWs will gradually convert to high-n phases, accompanied by an increase in grain size. The EQE and working stability of the device exhibit different annealing-time dependences; that is, with the extension of the annealing time, the EQE gradually decreases while the working stability improves. By introducing trimethylolpropane trimethacrylate (TPTA) to passivate the emitting-region defects, the annealing-time dependence of the EQE was effectively eliminated due to the reduction of the nonradiative recombination rate, wherefore high efficiency and stability can be achieved simultaneously. Our research provides an effective way to develop highly efficiency and stable perovskite light-emitting diodes.

Phase rearrangement for minimal exciton loss in a quasi-2D perovskite toward efficient deep-blue LEDs via halide post-treatment

“…The enhancement in the operating stability and device efficiency has been attributed to the population of high- n phases for HPR-treated perovskite films. 58…”

Reduced Confinement Effect by Isocyanate Passivation for Efficient Sky‐Blue Perovskite Light‐Emitting Diodes

“…Defect passivation is a widely used strategy to reduce the density of defect states on grain boundary and surface. [19][20][21][22][23] The Lewis base molecules containing CO or PO functional groups have been reported to effectively eliminate halide vacancies in perovskite films by sharing lone pair electrons with empty orbitals of lead ions to saturate the undercoordinated lead sites, thus leading to high PLQYs for perovskite films. [19,[24][25][26][27][28] Herein, the electrostatic potential (ESP) of 2, 4-TDI was calculated to evaluate its interaction with perovskite based on density functional theory.…”

Ultra‐Stable and Highly Efficient White Light Emitting Diodes through CsPbBr3 Perovskite Nanocrystals−Silica Composite Phosphor Functionalized with Surface Phenyl Molecules

“…This prominent enhancement in PLQY of the film can be attributed to the thermal curing (annealing) and aging effect of the confined P NCs, as previously reported for spin-coated perovskite layers. [43][44][45][46] It is well-documented that annealing of the perovskite layer brings about an increase in grain size, which suppresses halide ion migration and hysteretic behavior resulting in increased operational stability at the expense of decreased PLQY due to decreased radiative recombination rate relative to the non-radiative recombination. [43] Meanwhile, subsequent aging of the perovskite layer under dark ambient conditions yields a prominent self-enhancement in PLQY as a result of homogenized composition through halide ion redistribution and deactivation of defect states by atmospheric O 2 .…”

“…[43][44][45][46] It is well-documented that annealing of the perovskite layer brings about an increase in grain size, which suppresses halide ion migration and hysteretic behavior resulting in increased operational stability at the expense of decreased PLQY due to decreased radiative recombination rate relative to the non-radiative recombination. [43] Meanwhile, subsequent aging of the perovskite layer under dark ambient conditions yields a prominent self-enhancement in PLQY as a result of homogenized composition through halide ion redistribution and deactivation of defect states by atmospheric O 2 . [44][45][46] The fundamental understanding of the mechanism behind annealing and aging of the perovskite layers should be also pertinent to the perovskite NCs confined in the silica (incorporated in the film), given that atmospheric O 2 can reach the NCs.…”