Fabrication of Large-Area Uniform Nanometer-Thick Functional Layers and Their Stacks for Flexible Quantum Dot Light-Emitting Diodes.

Large-area fabrication and stacking of various nanometer-thick functional layers from solutions is essentially important for the construction of flexible thin-film optoelectronic devices, but very challenging. The existing fabrication methods suffer from either non-uniformity caused by the coffee-ring effect or serious solution waste (excess of 90% for spin coating), and are hard to scale up and create stacks. Here, it is shown that centrifugal casting is a universal, scalable, and efficient method to fabricate uniform nanometer-thick films and their stacks of various materials. The coffee-ring effect is effectively suppressed, the solution utilization ratio is higher than ≈61%, and the films/stacks show a smooth surface/high-quality interface. Using this method, flexible quantum dot light-emitting diode displays with uniform luminance in a large lighting area of ≈115 cm that have not been achieved even on rigid substrates by the existing methods, are realized. This efficient and low-cost solution processing method paves a way for large-area fabrication of various flexible thin-film optoelectronic devices.