은 나노와이어 복합 전극이 CdSe/CdZnS 양자점 발광 다이오드의 동작에 미치는 영향

Abstract

A multi-layer QLED with CdSe/CdZnS core/shell/ligand quantum dots as an emission layer was investigated. Tungsten trioxide(WO3), poly(9-vinylcarbazole)(PVK), CdSe/CdZnS quantum dots and zinc oxide (ZnO) were sequentially spin coated on indium tin oxide(ITO) glass. Each layers were used as hole injection layer(HIL), hole transport layer(HTL), emission layer(EML) and electron transport layer(ETL), respectively. The main cathode is silver nanowire(AgNW) for transparent device. To study the effect of sputtering on the cathode, ITO was sputtered on the AgNW electrode. It was observed that the device having only AgNW electrode had a luminance of 91 cd/m2, a transmittance of 76%. AgNW+ITO device exhibited luminance of 69 cd/m2, 63 % transmittance. The operating voltage decreased almost 63 % (11 V to 4 V) after sputtering. Sputtered ITO can be distributed in the void space between the nanowires, therefore the AgNW layer’s imbalance of conductivity could be eliminated. Furthermore, due to ITO, the diameter of the AgNW was increased five times from 20 nm to 100 nm to improve the overlapping location of the AgNW. The lifetime was measured as 7200 seconds for AgNW device and 9300 seconds for AgNW+ITO device. It can be confirmed that sputtering affects the lifetime of the device. As a result, ITO sputtering lowers current density and brightness. However, it has been confirmed that the reduction in the operating voltage and the increase in the lifetime are brought about by eliminating the current imbalance and operating as the oxidation preventing film.