High-efficiency and high-resolution patterned quantum dot light emitting diodes by electrohydrodynamic printing

The development of quantum dot light-emitting diode (QLED) fabrication technologies for high-definition and low-cost displays is an important research topic. However, commercially available piezoelectric inkjet printing has reached its limit in reducing pixel sizes, which restricts its potential use in high-resolution displays. Here, we exhibit an electrohydrodynamic (EHD) printing method for manufacturing QLEDs with a high resolution of 500 ppi that remarkably surpasses the resolution of conventional inkjet printing displays. By optimizing the EHD printing process, a high-resolution pixelated bottom-emitting passive matrix QLED with a maximal current efficiency of 14.4 cd A⁻¹ in a pixel size of 5 μm × 39 μm was achieved, indicating the capability of the EHD method in superfine printing and high efficiency QLED. Moreover, a top-emitting device is designed using a capping layer; the maximal current efficiency of top-emission passive matrix QLED devices can reach up to 16.5 cd A⁻¹. Finally, a two-color (red and green) bottom-emission QLED device with 500 ppi was fabricated. The successful fabrication of these high-efficiency QLEDs with 500 ppi demonstrated that the EHD printing strategy has numerous potential applications in high-resolution and high-performance QLEDs for a range of applications, such as mobile or wearable devices.