High Luminescence and External Quantum Efficiency in Perovskite Quantum-Dots Light-Emitting Diodes Featuring Bilateral Affinity to Silver and Short Alkyl Ligands

Wei-Cheng Chen, Yu-Han Fang, Lung-Ghih Chen, Fang-Cheng Liang, Zhen-Li, Yan, Hinako Ebe, Yoshihito Takahashi, Takayuki Chiba,* Junji Kido,* Chi-Ching Kuo*

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

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%).