Bright and Efficient Full-Color Colloidal Quantum Dot Light-Emitting Diodes Using an Inverted Device Structure

Abstract

We report highly bright and efficient inverted structure quantum dot (QD) based light-emitting diodes (QLEDs) by using solution-processed ZnO nanoparticles as the electron injection/transport layer and by optimizing energy levels with the organic hole transport layer. We have successfully demonstrated highly bright red, green, and blue QLEDs showing maximum luminances up to 23,040, 218,800, and 2250 cd/m(2), and external quantum efficiencies of 7.3, 5.8, and 1.7%, respectively. It is also noticeable that they showed turn-on voltages as low as the bandgap energy of each QD and long operational lifetime, mainly attributed to the direct exciton recombination within QDs through the inverted device structure. These results signify a remarkable progress in QLEDs and offer a practicable platform for the realization of QD-based full-color displays and lightings.

Optoelectronic Properties in Near‐Infrared Colloidal Heterostructured Pyramidal “Giant” Core/Shell Quantum Dots

“…For many of these potential applications, QDs are required to show efficient exciton (electron–hole pair) generation/separation and further transport with the presence of charge scavengers 2. However, due to the fast exciton recombination, it is still very challenging to fabricate devices with high photon‐to‐current (or fuel) conversion efficiency.…”

Double-heterojunction nanorods

“…In particular, core/shell heterostructures with type I straddling band offset exhibiting high photoluminescence (PL) quantum yields show much promise in imaging 3 , lighting 4,5 and display [6][7][8][9][10][11] applications. Although type II staggered band offset materials have also been achieved and have been shown to allow efficient photoinduced charge separation [12][13][14][15][16] and improved light amplification 17,18 , to date, the highly luminescent type I core/shell heterostructure is the predominant choice in emerging nanocrystal-based products.…”

Interfacial engineering of core/shell heterostructured nanocrystal quantum dots for light-emitting applications

“…Therefore, thick-shell NQDs with engineered interfaces have been extensively studied as light-emitting materials. One representative achievement is thick-shell NQDs with composition gradient interfaces that outperform those of electroluminescence devices ( Figure 5(a,c,d)) [3,5,25]. As a result of the persistent efforts to tailor the formulations at the interfaces, quantum-dot light-emitting diodes with external quantum efficiencies of over 10% with green, blue, and red NQDs have been successfully realized ( Figure 5(b)) [5].…”

“…Nanocrystal quantum dots (NQDs) [1] exhibit narrow emissions upon a broad range of excitation wavelengths and high luminescence efficiencies, making them promising for use in various light-emitting applications, including displays [2][3][4][5][6][7][8][9][10][11], solar concentrators [12][13][14][15], and lasers [16][17][18]. In the last two decades, the structures of NQDs evolved into sophisticated heterostructures, boosting their optical performances and photophysical stabilities [19][20][21][22][23][24][25][26][27].…”