Highly efficient flexible quantum-dot light emitting diodes with an ITO/Ag/ITO cathode

Flexible quantum dot light emitting diodes (QLEDs) are highly desired due to their advantages of foldability, lightweight, and potential applications in lighting and displays. In this report, we successfully fabricated high performance red (R), green (G), and blue (B) three primary color QLEDs based on a poly(ethylene-terephthalate)/ITO/Ag/ITO (PET–IAI) cathode. The multilayer flexible IAI electrode shows outstanding stability even after bending over 2000 times with a critical bending radius of 5 mm; the sheet resistance of the IAI film only increases from 12.7 to 14.8 Ω □−1. The maximum current efficiencies are 16.3, 86.5, and 16.1 cd A−1 for RGB QLEDs, respectively, which is the best device performance for flexible RGB QLEDs reported to date. Moreover, to the best of our knowledge, these are also record efficiencies for the green and blue devices in all the reported QLEDs. Furthermore, all the devices show saturated electroluminescence (EL) with the corresponding emission peaks at 606, 530, and 478 nm for three primary color QLEDs. The superior performance is a result of high transmittance and stability of the PET–IAI film. These results signify remarkable progress in flexible QLEDs and suggest that the PET–IAI based flexible QLEDs can offer a practicable platform for foldable applications.