High efficiency, solution processed quantum dot light emitting diode with inorganic charge transport layers

High efficiency all-inorganic quantum dot light emitting diodes with metal oxide charge transport layers are fabricated and characterized. The device is solution processed and active layers are fabricated by using spin coating technique. It consists of patterned FTO anode, nickel oxide thin film hole transport layer, green emitting alloyed CdSe/ZnS quantum dot emissive layer, zinc oxide nanoparticle electron transport layer and Al cathode. The device turn on voltage is 5V with an emission peak at 555 nm. The FWHM of the electroluminescence spectrum is ~42 nm, indicating a highly saturated pure green color emission. The device performance is evaluated by measuring the IV characteristics, luminance, current efficiency, luminous efficiency and quantum efficiency. The maximum current and luminous efficiencies of the device are 144 cd/m² and 14.2 lm/W, respectively. The luminance of the device increases with input voltage to a maximum of ~ 120,000 cd/m² and saturates at 10.5V. The peak external and internal quantum efficiencies of the device are 11.4% and 44.6%, respectively. The superior light output characteristics of the device can be attributed to the efficient charge transport properties of the metal oxide transport layers.