Over 100 cd A−1 Efficient Quantum Dot Light‐Emitting Diodes with Inverted Tandem Structure

Quantum dot light‐emitting diodes (QLEDs) with tandem structure are promising candidates for future displays because of their advantages of pure emission color, long lifetime, high brightness, and high efficiency. To obtain efficient QLEDs, a solution‐processable interconnecting layer (ICL) based on poly(3, 4‐ethylenedioxythiophene)/polystyrene sulfonate/ZnMgO is developed. With the proposed ICL, all‐solution‐processed, inverted, tandem QLEDs are demonstrated with high current efficiency (CE) of 57.06 cd A −1 and external quantum efficiency (EQE) of 13.65%. By further optimizing the fabrication processes and using a hybrid deposition technique, the resultant tandem QLEDs exhibit a very high CE over 100 cd A −1 and an impressive EQE over 23%, which are the highest values ever reported and are comparable with those of the state‐of‐the‐art phosphorescent organic LEDs. Moreover, the efficiency roll‐off, a notorious phenomenon in phosphorescent LEDs, is significantly reduced in the developed QLEDs. For example, even at a very high brightness over 200 000 cd m −2 , the tandem QLEDs can still maintain a high CE of 96.47 cd A −1 and an EQE of 22.62%. The proposed ICL and the developed fabrication methods allow for realization of very efficient tandem QLEDs for next generation display and lighting applications.