Important Progress on “near-perfect” Perovskite QDs in Advanced Materials

Recently, Song Jizhong and Zeng Haibo group made important progress in high quality perovskite quantum-dot (QDs), which was published in Advanced Materials. Perovskite QDs with high ink stability and ideal emissive properties were prepared via a room-temperature triple-ligand surface engineering strategy. The triple-synergistic-ligand including octanoic acid, tetraoctylammonium bromide, and didodecyldimethylammonium bromide, makes QDs with high PLQY of >90% and unity radiative decay (single exponential decay with the best value for a goodness-of-ft (χ2) of 0.986) in the intrinsic channel. Meanwhile, the use of short ligands enables the production of thin films with effective charge injection and transportation features. The Room-Temperature Triple-Ligand Surface Engineering synergistically boosts ink stability, recombination dynamics, and charge injection towards EQE-11.6% perovskite QLEDs.

Besides, this facile room-temperature synthetic method does not require the protection of inert gas, and is readily usable to scale up QDs production without any obvious change in material properties or device performances. The proposed low-cost strategy for synthesizing high-quality QDs demonstrates promising applications in future novel high-definition displays and high-quality lightings. The link to the article is: https://doi.org/10.1002/adma.201800764.

 

Figure. Room-temperature triple-ligands for ideal perovskite QD emitters.

Refresh the Efficiency of Green Perovskite QLEDs in Advanced Materials

Recently, Song Jizhong and Zeng Haibo group achieved a breakthrough in efficiency of green Pe-QLEDs, which was published in Advanced Materials. The link to the article is: https://doi.org/10.1002/adma.201805409.

 

Figure. Highly efficient perovskite QLEDs

In this work, an organic-inorganic hybrid ligand (OIHL) strategy was developed to passivate perovskite QDs for controlling the surface state and then constructing highly efficient QLEDs. The hybrid ligands adhered to the QD surface evidenced by infrared spectra and X-ray photoelectron spectroscopy. The remaining organic ligands enable the QDs with high colloidal ink stabilization for preparing the high-quality films. The introduced short metal bromide inorganic ligands could enhance the luminescent features and effective carrier injection originated from increase of radiative recombination, and their intrinsic high conductivity. Thus, simultaneously conductive and bright QD-emitting layers make QLEDs with a peak EQE of 16.48%, which is the highest efficiency among perovskite-based QLEDs reported thus far. Furthermore, various metal bromides, such as MnBr2, GaBr3, and InBr3, could feasibly be used to passivate perovskite QDs through the proposed OIHL strategy to enhance device performance with a nearly 40% improvement. The proposed OIHL passivation strategy for highly efficient LEDs makes perovskite QD emitters closer to industrialization.

Improving the Stability of Red Perovskite LEDs in Advanced Functional Materials

Song Jizhong and Zeng Haibo group made important progress in red perovskite light-emitting diodes (PeLEDs), which was published in Advanced Functional Materials. The link to the article is: https://doi.org/10.1002/adfm.201804285.

 

Figure. Highly stable and efficient red perovskite LEDs.

This work reported the achievement of stable α­CsPbI3 by using long­chain cation (e.g., 2­(naphthalene­1­yl)ethanamine (NEA)) in phase engineering. First, density functional theory (DFT) calculations reveal that the incorporation of NEA can efficiently reduce formation energy of α­CsPbI3. Systematic measurement including X­ray diffraction, photoluminescence, transient absorption, and time­resolved photoluminescence implies that the NEA covers on the as­fabricated α­CsPbI3 grain surface and protects CsPbI3 grain from humidity and oxygen. Finally, the NEA-incorporated α­CsPbI3 films were adapted in PeLEDs as the emitters. The peak EQE of 8.65% was obtained for the typical red band emission ≈682 nm, which represents the highest value among the Cs­based red PeLEDs up to now. More importantly, the corresponding PeLEDs exhibit outstanding stability retaining 90% of the EQE after 3 months. The half­time of the devices is about 6 h, which is the best operational lifetime of red PeLEDs. These results provide the deep understanding of additive on phase stability and make an important progress toward highly efficient and stable PeLEDs for the desired practical applications.