Multicolor colloidal quantum dot based light emitting diodes using a solution processed electron transporting layer

We report a multilayered Quantum Dot (QD) based Light Emitting Diode structure with a solution processed zinc oxide nanoparticle based electron transporting layer, with subsequent patterning of the anode and cathode on the same substrate. The solution processed electron transporting layer improves the robustness of the device as compared to the use of sputtered thin films, resulting in LEDs with longer lifetimes. The use of spin coated zinc oxide layer and an insulating aluminum oxide layer allows for fabrication of LEDs using spin coating of quantum dots while patterning the anode and cathode. Zinc oxide shows low CB and VB edge energy levels, efficiently suppressing the hole leakage current. We have shown successful electroluminescence at 580nm and 600nm wavelengths, with a typical turn on voltage of about 12V. An array of individually addressable LEDs was fabricated on a single substrate, with the average size of each element of 800um × 200um. A potential application of such compact multicolor light source for cell characterizations is demonstrated by imaging of HEMA 3 stained MDA-MB 231 breast cancer cells on-chip.