Solution-processed fabrication of highly transparent mono- and tri-colored quantum dot-light-emitting diodes

Analogous to organic light-emitting diode (OLED), quantum dot-light-emitting diode (QLED) possesses a high eligibility with respect to device structure for the transformation to transparent device that may be pursued as a next-generation display. We report the fabrication of a series of highly transparent mono-colored blue, green, and red QLEDs with a standard architecture simply by replacing thermally evaporated Al with sputtered indium tin oxide (ITO) film as a top cathode. To alleviate the sputtering damage on the underlying electron transport layer while securing a reasonable sheet resistance of ITO film, a moderate sputtering power is judiciously chosen to attain high device performance. Fabrication of a transparent tri-colored white or full-color-capable QLED, comprising an emitting layer mixed with three primary colored QDs, is also demonstrated and further implemented on a flexible substrate of polyethylene naphthalate to additionally offer its feasibility toward transparent flexible device.