title: Enhanced Performance of Light-Emitting Diodes by Surface Ligand Modification on Quantum Dots.
abstract: The electrical characteristics of quantum dots (QDs) can vary depending on the surface modulation, which can change the luminance and efficiency of electroluminescent devices. Thus, understanding surface ligand is essential in improving the performance of QDs-based light-emitting diodes (LEDs). We analyzed the performance of QDs-based LEDs with respect to the QD surface volume. On the QD surfaces, the 1.1 nm-long tryoctylphosphine oxide (TOPO) ligand with three neck-type structure was replaced with a 1.7 nm-long oleic acid (OA) ligand with a one neck-type structure to evaluate the dependence of the LED properties on the ligand length. With all other conditions being identical, the luminance and efficiency of the QDs-based LEDs with an OA ligand were approximately 1,000 cd/m2 greater and 1.5 times higher, respectively, than those of the QDs-based LEDs with a TOPO ligand. These results show that if the physical length of the surface ligand is relatively long, decreasing the surface area would result in increased injection of electrons and holes into the QDs, increasing the luminance and efficiency.
authors.forename: Byoung-Ho
authors.initials: BH
authors.lastname: Kang
authors.forename: Sang-Won
authors.initials: SW
authors.lastname: Lee
authors.forename: Sung-Woo
authors.initials: SW
authors.lastname: Lim
authors.forename: Ju-Seong
authors.initials: JS
authors.lastname: Kim
authors.forename: Gopalan
authors.initials: G
authors.lastname: Sai-Anand
authors.forename: Seung-Ha
authors.initials: SH
authors.lastname: Lee
authors.forename: Dae-Hyuk
authors.initials: DH
authors.lastname: Kwon
authors.forename: Shin-Won
authors.initials: SW
authors.lastname: Kang