Enhancing the Performance and Stability of Perovskite Nanocrystal Light‐Emitting Diodes with a Polymer Matrix

Abstract

efficiency (EQE) values of the devices have increased from 0.12% to 3.8% for green emission and to 5.7% for red emission. [10][11][12][13][14][15][16][17][18] Recently, bulk film-based perovskite LEDs have been reported to reach high EQEs of 8.53% for green emission and 11.7% for near-infrared emission; however, the issues of long-term device stability and photoluminescence (PL)/electroluminescence (EL) blinking emission should be resolved before the commercial application of these materials can be realized. [19][20][21][22][23][24][25][26][27][28] Fortunately, CsPbX 3 perovskite nanocrystals exhibit lower levels of PL blinking and greater device stability compared to bulk film-based perovskite. For these reasons, they hold great potential in LED applications despite their low device efficiency. [29,30] In previous reports related to colloidal nanocrystal quantum dots (QDs), the use of nonuniform CdSe (ZnS) nanocrystal QD film has led to imbalanced charge injections and low luminance efficiency of QD-based LEDs. [31] Stan et al. dispersed nanocrystal QDs within a polymer matrix of polystyrene or poly(methyl methacrylate) (PMMA), [32] with the nanocrystal QD:polymer composite film showing a uniform morphology with excellent properties, such as good electrical and optical properties, robust chemical resistance, good thermal stability and easy processability, leading to improved stability and performance of devices. [33][34][35][36] Much effort has been made to obtain uniform nanocrystal QD film using an adequate deposition method, such as drop-casting, dip-or spray-coating, the Langmuir-Blodgett method, and the doctor-blade method. These deposition methods can be used to obtain highly uniform nanocrystal film, thus increasing device performance levels. [37][38][39][40] Recently, Pan et al. reported a high efficiency CsPbBr 3 -based PeNLED with an EQE of 3.0% for green emission using a ligand exchange process to passivate CsPbBr 3 nanocrystals. [41] The passivation of the CsPbBr 3 nanocrystals through the ligand exchange also exhibited stable amplified spontaneous emission. [42] These reports demonstrate that the ligand exchange method in nanocrystals can enhance the performance and stability of perovskite nanocrystal-based optoelectronic devices through the passivation of the perovskite nanocrystals.Here, we successfully fabricate efficient CsPbBr 3 -based PeNLEDs using a monolayered CsPbBr 3 nanocrystal film with All-inorganic perovskite nanocrystal materials exhibit excellent light-emitting properties in the visible range with narrow-band emissions, relatively high stability levels, and high photoluminescence quantum efficiency. A uniform morphology of perovskite nanocrystal film is necessary to realize highly efficient light-emitting devices, but the morphology of CsPbX 3 nanocrystal films has not been intensively studied. Here, a novel method is presented to obtain uniform and stable CsPbBr 3 nanocrystal film through a drop-casting method with a poly(methyl methacrylate) (PMMA) matrix. The introduction of CsPbB...

Facile synthesis of 1D organic–inorganic perovskite micro-belts with high water stability for sensing and photonic applications

“…To date, although numerous efforts have been made to achieve water-stable perovskite micro- and nano-particles with low dimension (0D, 1D and 2D),4a,7,9,13 most are focused on the external encapsulation of metal oxides,14,15 polymers,16,17 mesoporous inorganic oxides18,19 and metal–organic framework20 matrixes. Only recently, Han's and Yang's groups demonstrated that pyridine additives with various alkyl-chain substituents or alkyl ammonium cations on the perovskite surface can substantially improve the stability of perovskite solar cells 21,22.…”

Improved Stability and Photodetector Performance of CsPbI3 Perovskite Quantum Dots by Ligand Exchange with Aminoethanethiol

“…CsPbI 3 perovskite can easily lose its structural integrity under humidity or under UV illumination, leading to decomposition or unwanted phase transformation from cubic to orthorhombic phase 3d,4. Considerable efforts have thus been devoted to improve stability of perovskite QDs, such as adding encapsulation using silica, silica spheres, mesoporous silica or polyhedral oligomeric silsesquioxanes, coating by lipid layers, fabrication of AlO x ‐passivated perovskite QD films by atomic layer deposition, and protection within hydrophobic phosphate glasses and polymethyl methacrylate polymer . However, such insulating coatings would also hinder the charge transport between QDs, leading to poor conductivity of such embedded perovskite QD films.…”

Stability of electroluminescent perovskite quantum dots light‐emitting diode

“…Many literatures have demonstrated that the morphology of the emission layer determines the performance of device. [80][81][82] Improper processing methods will bring about the clustering of nanocrystal and lead to the rough thin film, which deteriorates not only the optical performance but also long-term stability of the device [83] (Figure 2A). On the one hand, this may result in a turn-on voltage (Von) much higher than the band gap energy of the nanocrystals, suggesting that poor contact between the functional layers and the carrier injection from chargetransporting layers (CTL) into nanocrystals was inefficient.…”