Luminance enhancement in quantum dot light-emitting diodes fabricated with Field's metal as the cathode

This work reports the fabrication and characterization of blue–green quantum dot light-emitting diodes (QD-LEDs) by using core/shell/shell Cd1−x Zn x Se/ZnSe/ZnS quantum dots. Poly [(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9–dioctylfluorene)] (PFN) was introduced in order to enhance the electron injection and also acted as a protecting layer during the deposition of the cathode (a Field's metal sheet) on the organic/inorganic active layers at low temperature (63 °C). This procedure permitted us to eliminate the process of thermal evaporation for the deposition of metallic cathodes, which is typically used in the fabrication of OLEDs. The performance of devices made with an aluminum cathode was compared with that of devices which employed Field's metal (FM) as the cathode. We found that the luminance and efficiency of devices with FM was ~70% higher with respect to those that employed aluminum as the cathode and their consumption of current was similar up to 13 V. We also demonstrated that the simultaneous presence of 1,2-ethanedethiol (EDT) and PFN enhanced the luminance in our devices and improved the current injection in QD-LEDs. Hence, the architecture for QD-LEDs presented in this work could be useful for the fabrication of low-cost luminescent devices.