Effects of the hole injection on InP colloidal quantum dot-based electroluminescent devices

Abstract

Since quantum dots (QDs) have fascinating properties that they can control emission wavelength according to their size, have narrow linewidth and be capable of a solution process, researches have been conducted to use QDs as a light-emitting materials of a next-generation electroluminescent device. However, since Cd-based QDs have harmfulness to humans, development of Cd-free QDs based light-emitting devices is required. This thesis shows the effects of hole injection on the InP-based quantum dot light-emitting diodes (QD-LEDs). In order to analyze the device characteristics according to the carrier injection barrier between hole transport layers (HTLs) and the QD layer, the HTLs with various energy levels were introduced on the InP-based QD-LEDs. As a result of analysis of the current density-voltage-luminance (J-V-L) characteristics of the devices, it was found that the HTL material having the highest external quantum efficiency was TCTA which has excellent carrier injection balance with ZnO electron transport layers. In addition, in order to analyze the carrier injection barrier between HTL and anode, the hole-only devices (HODs) were fabricated and the hole current density was analyzed. The hole current density was greatly increased by introducing the C60 thin film at the interface between HTL and anode. By applying the anode with C60 to InP-based QD-LEDs, the driving voltage of InP-based QD-LEDs was decreased and power efficiency was increased.