High-Brightness Perovskite Light-Emitting Diodes Based on FAPbBr₃ Nanocrystals with Rationally Designed Aromatic Ligands

Abstract

Despite rapid developments of light-emitting diodes (LEDs) based on emerging perovskite nanocrystals (PeNCs), it remains challenging to achieve devices with integrated high efficiencies and high brightness because of the insulating long-chain ligands used for the PeNCs. Herein, we develop highly luminescent and stable formamidinium lead bromide PeNCs capped with rationally designed short aromatic ligands of 2-naphthalenesulfonic acid (NSA) for LEDs. Compared with commonly used oleic acid ligands, the NSA molecules not only preserve the surface properties of the PeNCs during the purification but also notably improve the electrical properties of the assembled emissive layers, ensuring efficient charge injection/transport in the devices. The resulting champion LED with electroluminescence approaching the Rec. 2020 green primary color demonstrates a high brightness of 67 115 cd cm −2 and a peak external quantum efficiency of 19.2%. More impressively, the device shows negligibly decreased efficiency at an elevated brightness of 20 000 cd cm −2 and a well-retained efficiency of over 10% at around 65 000 cd cm −2 , presenting a breakthrough in LEDs based on PeNCs.

Direct optical patterning of perovskite nanocrystals with ligand cross-linkers

“…The versatility in ligand designs allows NC patterns to incorporate the rich toolbox of surface chemistry developed for improved optical and electrical properties. DOPPLCER also works well for inorganic and organic/inorganic hybrid perovskite NCs synthesized by ligand-assisted reprecipitation (LARP) method ( 43 ), as exemplified by FAPbBr 3 NCs ( 44 ) ( Fig. 4B ).…”

“…A typical device structure includes stacked layers of indium tin oxide cathode (ITO), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS; 25 nm), poly[bis(4-phenyl)(4-butylphenyl)amine] (poly-TPD) (8 nm), NCs, 2,2’,2”-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) (35 nm), and LiF (1 nm)/Al ( Fig. 6A ) ( 44 ). Figure 6B shows the schematic energy level diagram.…”

“…From the device aspect, impressive progress in the performance of perovskite NC–based optoelectronic devices has been made during the past years thanks to the tremendous efforts in the optimization of NC cores, surface states, and device structures. Among them, surface engineering with desirable ligands has been proven effective to achieve high-efficiency and stable perovskite NC LEDs ( 44 , 52 ). The broad applicability of DOPPLCER promises its potential in constructing highly pixelated LEDs and independently addressable photodetector arrays with device characteristics approaching the reported records (e.g., EQE ~ 20% for LEDs).…”

“…The reaction was stopped after 3 min and cooled with an ice water bath. Organic-inorganic hybrid FAPbBr 3 NCs were synthesized by a LARP method reported elsewhere ( 44 ). A precursor solution containing 0.027 g of FABr, 0.0367 g of PbBr 2 , 250 μl of OA, 25 μl of octylamine, and 500 μl of dimethylformamide was loaded in a 2-ml glass vial and then heated at 50°C under stirring until PbBr 2 was completely solubilized.…”

Water-Assisted Perovskite Quantum Dots with High Optical Properties

“…Therefore, not only conventional inorganic perovskites, but also organic-inorganic perovskites, could be synthesized [4,17,18]. In previous studies, various surface treatments have been applied to both inorganic and organic-inorganic perovskites by the LARP method, and the prepared PeQDs via the LARP method could achieve a high PLQY over 70%, similar to that prepared by the HI method [5,19].…”