Full color quantum dot light-emitting diodes patterned by photolithography technology

Quantum dot light-emitting diodes are promising candidates for next generation displays. For display application, a pixel consists of red (R), green (G), and blue (B) side-by-side sub-pixels, which thereby requires a high resolution patterning of the light-emission layers. In this work, the quantum dot (QD) light-emitting layers are fine patterned by using the photolithography and the lift-off techniques. To facilitate the lift-off process, reverse photoresist AZ5214E is used because of its special inverted trapezoidal structure after developing. To prevent the QDs being washed off during the lift-off process, the ZnMgO layer is treated by the hydrophobic material hexamethyldisilazane. With hexamethyldisilazane treatment, the adhesion between the QDs and the ZnMgO is effectively improved. As a result, side-by-side R/G/B QD with pixel size of 30mx120m is successfully achieved. After patterning, the R, G, and B-quantum dot light-emitting diodes exhibit a maximum current efficiency of 11.6cd/A, 29.7cd/A, and 1.5cd/A, respectively. This work confirms the feasibility of patterning QDs by using the photolithography and the lift-off techniques.