Highly efficient printed quantum dot light-emitting diodes through ultrahigh-definition double-layer transfer printing

Highly efficient and high-definition displays with deformable form factors are highly desirable for next-generation electronic devices. Despite the unique advantages of quantum dots (QDs), including high photoluminescence quantum yield, wide colour range and high colour purity, developing a QD patterning process for high-definition pixels and efficient QD light-emitting diodes (QLEDs) is in its early stages. Here we present highly efficient QLEDs through ultrahigh-definition double-layer transfer printing of a QD/ZnO film. Surface engineering of viscoelastic stamps enables double-layer transfer printing that can create RGB pixelated patterns with 2,565 pixels per inch and monochromic QD patterns with ~20,526 pixels per inch. The close packing of both QDs and ZnO nanoparticles by double-layer transfer printing substantially minimizes the leakage current, enhancing the external quantum efficiency of our devices to 23.3%. Furthermore, we demonstrate highly efficient wearable QLEDs fabricated by our technique. This study paves the way for the development of highly efficient, full-colour QD displays via the transfer printing technique, demonstrating great promise for next-generation display technologies. Transfer printing of a quantum dot–ZnO film with a surface-functionalized viscoelastic stamp enables the realization of RGB QLED pixels with a resolution of 2,500 pixels per inch and a peak external quantum efficiency of 23.3% for green-emitting devices.