Continuous and Controllable Liquid Transfer Guided by a Fibrous Liquid Bridge: Toward High-Performance QLEDs

Solution processing is widely used for preparing quantum dot (QD) films for fabricating QD light-emitting diode display (QLED) devices. However, current approaches suffer from either the coffee-ring effect or a large amount of wasted solution, leading to low performance and high cost. Here, a facile approach guided by a fibrous liquid bridge is developed for the continuous and controllable transfer of QD solution into ultrasmooth films by using a taut fiber with its two ends placed into capillary tubes. Guided along the fiber, a liquid bridge is formed between the horizontal fiber and the substrate, with a large mass of liquid steadily being held within the vertically placed tubes. Directionally moving the liquid bridge generates a high-quality QD film on the substrate. Particularly, the liquid consumption is quantitative, namely, in proportion to the area of the as-prepared film. Moreover, multilayered ultrasmooth red/green/blue QD films are prepared by multiple transfers of liquid onto the same targeted area in sequence. The as-prepared white QLEDs show a rather high performance with a maximum luminance of 57 190 cd m^-2 and a maximum current efficiency of 15.868 cd A^-1 . It is envisioned that this strategy offers new perspectives for the low-cost fabrication of high-performance QLED devices.