All‐Inorganic Perovskite Nanocrystals for High‐Efficiency Light Emitting Diodes: Dual‐Phase CsPbBr₃‐CsPb₂Br₅ Composites

Abstract

A dual‐phase all‐inorganic composite CsPbBr3‐CsPb2Br5 is developed and applied as the emitting layer in LEDs, which exhibited a maximum luminance of 3853 cd m–2, with current density (CE) of ≈8.98 cd A–1 and external quantum efficiency (EQE) of ≈2.21%, respectively. The parasite of secondary phase CsPb2Br5 nanoparticles on the cubic CsPbBr3 nanocrystals could enhance the current efficiency by reducing diffusion length of excitons on one side, and decrease the trap density in the band gap on the other side. In addition, the introduction of CsPb2Br5 nanoparticles could increase the ionic conductivity by reducing the barrier against the electronic and ionic transport, and improve emission lifetime by decreasing nonradiative energy transfer to the trap states via controlling the trap density. The dual‐phase all‐inorganic CsPbBr3‐CsPb2Br5 composite nanocrystals present a new route of perovskite material for advanced light emission applications.

Atomic Characterization of Byproduct Nanoparticles on Cesium Lead Halide Nanocrystals Using High-Resolution Scanning Transmission Electron Microscopy

“…Recent studies have consistently reported the observation of nanoparticles (NPs) with high contrast to LHP nanocrystals (CH 3 NH 3 PbBr 3 [21] and CsPbBr 3 [22][23][24][25][26]) in transmission electron microscopy (TEM) images (i.e., the white dots in Figure 1). However, the structure, chemistry, and forming mechanism of these NPs are still unclear and under debate in these reports.…”

“…Some reports indicate that these NPs are Pb metal, originating from either the precursor material PbBr 2 [26], or the electron damaged CsPbBr 3 lattices [23][24][25]. One report suggests that these NPs are PbBr 2 [21] and another report claims that these NPs are CsPb 2 Br 5 [22].…”

Sequential deposition method fabricating carbonbased fully-inorganic perovskite solar cells

“…In the tetragonal CsPb 2 Br 5 structure, one layer of Cs ions is sandwiched between two layers of Pb-Br coordination polyhedrons [21]. Now the applications of CsPb 2 Br 5 include laser and light-emitting devices [22][23][24]. Compared with the perovskite CsPbBr 3 , the available research on the structure and physical properties of the tetragonal CsPb 2 Br 5 is not very sufficient and many great blanks need to be filled [21].…”

Perovskite Quantum Dot Light-Emitting Diodes

“…Sun's research group found an interesting phenomenon that the introduction of CsPb 2 Br 5 QDs attached on CsPbBr 3 QDs could improve the emission lifetime by decreasing nonradiative energy transfer to the trap states via controlling the trap density [36]. As a result, a high external quantum efficiency of about 2.21% was achieved, and a maximum luminance of 3853 cd/m 2 was obtained.…”

“…Although the device performance of perovskite QD LEDs was promoted greatly in a short time, operation stability has always been criticized for such devices in a continuous current mode, which are the main obstacles hindering the reliable device operation and their future application. In previous reports, conventional carrier injection conducting polymer or small molecules, such as PEDOT:PSS, PCBM, and 1,3,5-tris(2-N-phenylbenzimidazolyl) benzene, have been frequently employed as the carrier injectors in perovskite LEDs [25,33,35,36], but their inherent chemical instability inevitably degrades the device performance; thus, a high-efficiency light emission cannot be sustained over a long running time. More recently, Shi et al present a strategy that addresses simultaneously the emission efficiency and stability issues facing current perovskite LEDs' compromise [30].…”