We report highly efficient inverted quantum-dot light emitting diodes (QLEDs) using an Al doped ZnO (AZO)/Li doped ZnO (LZO) stack electron transport layer (ETL). An introduction of the LZO layer on AZO improved the current and power efficiencies of the green (G-) QLEDs from 10.5 to 34.0 cd A and from 5.4 to 29.6 lm W, respectively. The red (R-), G-, and blue (B-) QLEDs fabricated in this work exhibited the maximum external quantum efficiencies (EQEs) of 8.4, 12.5, and 4.3%, respectively. It is found from time-resolved photoluminescence (PL) and transient electroluminescence (EL) decay that exciton loss at the interface between the ETL and the emission layer can be significantly reduced by introducing LZO.

No abstract

Charge generation junction (CGJ) is widely used in tandem organic light emitting diodes (OLEDs), mainly fabricated by vacuum deposition. But solution processed CGJs are used for quantum-dot light emitting diodes (QLEDs). It is demonstrated in this work that the QLEDs with top and bottom CGJs have similar device performance with conventional QLED. The current and power efficiencies of the QLED with top and bottom CGLs are almost independent on the work function of cathode metal, which demonstrates the effectiveness of the CGJs. Double stack QLED is designed and fabricated with the same three CGJs with 3 kinds of materials and two different quantum-dots materials.

We report in this wok the improvement of current efficiency (CE) roll‐off and power efficiency (PE) roll‐off of QLED by shell engineering of quantum‐dots (QDs). The inverted QLEDs using the green QDs (G‐QDs) with optimized shell exhibited the extremely reduced CE roll‐off of 9% at 10,000 cd/m2 and also 10 times longer lifetime compared with the QLED with conventional G‐QDs.