옥타데실아민-그래핀 양자점 기반의 발광 소자의 전기적 및 광학적 특성 연구

Abstract

Graphene quantum dots (GQDs) have currently emerged as excellent candidates for their potential applications in next-generation displays due to the advantages of high quantum efficiency, high chemical stability, and excellent charge carrier mobility, and simple band gap tuning. However, numerous oxygenous functional groups and defects are inherently generated both on the basal plane and at the edges of the GQDs, which significantly affect the dispersion properties of the GQDs, make control of their emission wavelength difficult. Also, this oxidation of the GQDs restrict their florescence quantum yield, resulting in a decrease in the brightness of GQD light emitting devices (LEDs). Therefore, research on graphene quantum dots with low oxygen functional groups is necessary to fabricate highly efficient GQD LEDs. The octadecylamine (ODA)-GQDs are synthesized by using the simple solution method to fabricate the highly efficient GQD LEDs. The content of the oxygen for ODA-GQDs is lower than that of conventional GQDs, resulting in the high quantum yield of ODA-GQDs. The electrical and optical properties of ODA-GQDs have been presented to fabricate the highly efficient GQD LEDs. The electric and optical characteristics of green and blue GQD LEDs were investigated. The current and external quantum efficiencies of the green LEDs with ODA-GQDs were 6.51 cd/A and 2.67 %, respectively, these being the highest values among those reported for LEDs based on GQDs. Finally, the electric and optical properties of blue GQD LEDs were investigated. The luminance and external efficiency values of the blue LEDs with ODA-GQDs were 440.3 cd/m2 and 0.80 %. The efficiency enhancement of the LEDs with the ODA-GQDs was attributed to the optical properties of the high-quality ODA-GQDs, which were improved due to a decrease of oxygen content, an enhancement of the number of holes injected from the hole transport layer to the active layer, and to the efficient energy transfer from the poly(9-vinylcarbazole) to the ODA-GQDs.