Influence of Au nanoparticles for enhanced performance of quantum dot light-emitting diodes

1. INTODUCTION Colloidal quantum dots (QDs) emit vivid light with narrow full width half maximum and their wavelength is tunable due to quantum confinement effect. From these unique optical/electrical properties, various... [ view full abstract ]

1. INTODUCTION

Colloidal quantum dots (QDs) emit vivid light with narrow full width half maximum and their wavelength is tunable due to quantum confinement effect. From these unique optical/electrical properties, various display applications using QDs, therefore, have been spotlighted as a post OLED display technology. One of advantages of quantum dot light-emitting diodes (QLEDs) is a low fabrication cost, because it is based on a solution process. However, the lower current efficiency compared to OLED is still a weakness. Many researchers have been constantly tried various materials for efficient charge transport within device, at last, they came to agreement the use of inorganic nanoparticles (NPs) as an electron transport layer to improve the performance of QLEDs. 

2. METHODS

The blended PEDOT:PSS:Au NPs were spin-coated on the cleaned ITO substrate. To observe the effect of the Au NPs density, the density of the Au NPs in blended solution was increased up to 0.01, 0.02, 0.03 mg/ml respectively. TFB dissolved in chlorobenzene was spin-coated on the blended PEDOT:PSS:Au NPs layer. For the light emission layer, QDs were dispersed in Heptane and spin-coated on the TFB layer. Then, ZnO NPs was spin-coated as an ETL. After finishing solution process, the Al cathode was deposited by thermal evaporation on the ZnO NPs layer. 

3. RESULTS AND DISCUSSION

The light extraction technology is one of the well-known technologies to increase the optical efficiency of the light emitting devices. Among them, localized surface plasmon resonance (LSPR) is a technology that can improve the luminance by controlling refraction and scattering of light using metal NPs in the device. Here, we investigated the LSPR effect on the device performance by dispersing the Au NPs in the hole transport layer (HTL) and hole injection layer (HIL) (Figure 1). The result indicates that the optical enhancement of the QLEDs is attributed to strong resonance coupling between excitons in the QDs and LSP in the Au NPs in the HIL. Further optimization using Au NPs will help make highly efficient QLEDs for future display application.