The multi-step ligand exchanged process by silver (Ag)- trioctylphosphine (TOP) reinforce the optical properties (photoluminescence quantum yield, PLQY) of perovskite quantum dots (PeQDs) for storing over one month, and generate highly superior light-emitting diode.
 

Technology Overview
The superior PeQD is based on exchanging of bilateral affinity ligands (Ag-TOP).Ag-TOP ligand exchanging film exhibits solvent and ambient stability over 1 month.LED performance is enhanced by Ag-TOP ligand comparing to TOP or DDAB ligand.The optimized device achieves maximum luminance of 3820 cd cm−2 and EQE 9.43%.

Applications & Benefits
We demonstrated that higher EQE (9.43%) and luminescence (3820 cd/cm2) were produced from PeQDs through facile and scalable exchanges of Ag-TOP ligands. Our studies break new ground in the expansion of PeQDs in high EQE and PLQY, based on double-sided affinity materials.

Abstract：
Perovskite quantum dots (PeQDs) have been under commercial and functional development in recent years since they offer outstanding optoelectronic properties and solution processability. However, both insulating ligands around PeQDs and instability impair the performance of photoelectronic devices. Therefore, we introduce multi-step ligands exchange by silver (Ag)- trioctylphosphine (TOP) as short alkyl ligands to reinforce the optical properties and stability for PeQDs and successfully elevated light-emitting diodes characters. The PeQDs with Ag-TOP ligands (Ag@QD) perform higher photoluminescence quantum yield (PLQY, ~93%), higher exciton binding energy (57.6 meV) with better solvent, temperature, and ambient stability over 1 month presenting better performances on comparison with conventional di-dodecyl dimethyl ammonium bromide (DDAB) or TOP ligands. Nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), and time-resolved photoluminescence (TR-PL) measurement provides clear insight on bilateral affinity in Ag@QD illustrating excellent defect passivation and appropriate steric hindrance. Furthermore, we demonstrate Ag@QD with lower turn-on voltage (~2.8 V), high electroluminescence (~3820 cd/cm−2), and high efficiency (EQE ~ 9.43%).

High luminescence and external quantum efficiency in perovskite quantum-dots light-emitting diodes featuring bilateral affinity to silver and short alkyl ligands
Author：Chen W.-C., Fang Y.-H., Chen L.-G., Liang F.-C., Yan Z.-L., Ebe H., Takahashi Y., Chiba T, Kido J.,Kuo C.-C.
Year：2021
Source publication：Chemical Engineering Journal  Volume 414  128866
Subfield Highest percentage：99%
Industrial and Manufacturing Engineering    #3/336

https://www.sciencedirect.com/science/article/pii/S1385894721004605