Large-Area Flexible Perovskite Light-Emitting Diodes Enabled by Inkjet Printing.

Metal halide perovskite light-emitting diodes (PeLEDs) are attracting increasing attention due to their potential applications in flat panel lighting and displays. The solution process, large-area fabrication, and flexibility are attractive properties of PeLEDs over traditional inorganic LEDs. However, it is still very challenging to deposit uniform perovskite films on flexible substrates using blade or slot-die coating, as the flexible substrate is not perfectly flat. Here, we adopt the inkjet printing technique and overcome the key challenges step-by-step in preparing large-area films on flexible substrates. We first use double hole transporting layers and a wetting interfacial layer to improve the surface wettability so that the printed perovskite droplets can form a continuous wet film. We then manipulate the fluidic and evaporation dynamics of the perovskite wet layer to suppress the coffee ring effect by solvent engineering. We finally obtained uniform perovskite films on flexible substrates with different perovskite compositions. The peak EQE of the inkjet-printed PeLEDs reaches 14.3%. Large-area flexible PeLEDs (4×7 cm 2 ) also show very uniform emission. Our work represents a significant step toward real applications of large-area PeLEDs in flexible flat panel lighting. This article is protected by copyright. All rights reserved.