Room‐Temperature Triple‐Ligand Surface Engineering Synergistically Boosts Ink Stability, Recombination Dynamics, and Charge Injection toward EQE‐11.6% Perovskite QLEDs

Abstract

Developing low-cost and high-quality quantum dots (QDs) or nanocrystals (NCs) and their corresponding efficient light-emitting diodes (LEDs) is crucial for the next-generation ultra-high-definition flexible displays. Here, there is a report on a room-temperature triple-ligand surface engineering strategy to play the synergistic role of short ligands of tetraoctylammonium bromide (TOAB), didodecyldimethylammonium bromide (DDAB), and octanoic acid (OTAc) toward "ideal" perovskite QDs with a high photoluminescence quantum yield (PLQY) of >90%, unity radiative decay in its intrinsic channel, stable ink characteristics, and effective charge injection and transportation in QD films, resulting in the highly efficient QD-based LEDs (QLEDs). Furthermore, the QD films with less nonradiative recombination centers exhibit improved PL properties with a PLQY of 61% through dopant engineering in A-site. The robustness of such properties is demonstrated by the fabrication of green electroluminescent LEDs based on CsPbBr QDs with the peak external quantum efficiency (EQE) of 11.6%, and the corresponding peak internal quantum efficiency (IQE) and power efficiency are 52.2% and 44.65 lm W , respectively, which are the most-efficient perovskite QLEDs with colloidal CsPbBr QDs as emitters up to now. These results demonstrate that the as-obtained QD inks have a wide range application in future high-definition QD displays and high-quality lightings.

White Photoluminescent Ti3C2 MXene Quantum Dots with Two‐Photon Fluorescence

“…An absolute PLQY of 9.36% was also observed under 360 nm excitation. [43,44] As for the white-emission perovskite QDs, combinations of a self-trapped excitons associated with the octahedra distortion upon irritation were responsible for the photoluminescence mechanism. A representative two-photon luminescence spectrum of the MQDs is shown in Figure 3b, and is similar to the single-photon fluorescence spectrum.…”

Metal halide perovskite nanocrystals and their applications in optoelectronic devices

“…Zhong's group used a method combining multiple phases (DMF as “aqueous phase,” n‐hexane as “oil phase,” OA as “surfactant,” and tert‐butanol as demulsifier) to synthesize MAPbBr 3 colloidal QDs by adding a certain amount of tert‐butanol into the DMF solution to form a suspension and then centrifuged and dissolved them in toluene. This method could better control the size of the as‐prepared QDs from 2 to 8 nm and achieved high PL QYs of 80%‐92% . Brabec et al utilized chloroform as an antisolvent to synthesize FAPbX 3 NCs .…”

Ligand‐Exchange of Low‐Temperature Synthesized CsPbBr3 Perovskite toward High‐Efficiency Light‐Emitting Diodes

“…In recent years, all‐inorganic CsPbX 3 (X = Br, Cl, or I) nanoacrystals (NCs) have shown great potential for the next‐generation lighting and display applications due to their low material cost, high defect tolerance, tunable emission wavelength with narrow bandwidth, and high photoluminescence quantum yield (PLQY) . The external quantum efficiency (EQE) of light‐emitting diodes (LEDs) incorporating CsPbX 3 NCs as the active layer has increased abruptly from 0.12% to 11.6% in the last 3 years.…”

“…Those ligands that remain on the surface of CsPbX 3 NCs have been identified as playing a crucial role in determining the device performance of LEDs . For example, Sargent and co‐workers prepared CsPbX 3 quantum dots (QDs) capped with a relatively short ligand, namely didodecyl dimethyl ammonium bromide (DDAB) and found that DDAB resulted in efficient charge injection and better charge transport.…”

“…Zwitterionic ligands possess several anchoring groups, which showed stronger adhesion to the surface of NCs via the chelating effect, and enable the retention of 65% of PLQY even after two cycles of solvent washing using ethanol . Whilst the short‐chain ligands on the surface of CsPbX 3 have been found to lead to poor dispersion (as they fail to provide steric or electrostatic stabilization), a triple‐ligand strategy has led to the successful synthesis of CsPbBr 3 QDs, with the resulting CsPbBr 3 LEDs exhibiting an excellent current efficiency (CE) of 45.4 Cd A −1 and a record EQE of 11.6% . In this approach, the ligand tetraoctylammonium bromide was used to increase the solubility of PbBr 2 .…”