The emergence of near-eye displays, such as head-mounted displays, is triggering a requirement for highly enhanced display resolution. High-resolution micro-displays with micro-organic light-emitting diodes (micro-OLEDs) can be a preferential candidate, owing to the mature industrialization of OLEDs along with the advantages of flexibility, light weight, and ease of processing. However, micro-OLEDs with pixel sizes down to micrometers are difficult to be achieved using conventional techniques such as fine metal mask evaporation and lithography. Here, a solution-processing approach to pattern organic semiconductors (OSCs) for micro-OLED arrays with the assistance of templated dewetting is demonstrated. Solvents containing organic functional materials are dewetted on the surface with hydrophobic/hydrophilic patterns to form ordered droplet arrays using dip-coating. Subsequently, patterned OSC films are produced by effectively controlling solvent evaporation. Micro-OLED arrays with a pixel size down to 1 µm are successfully fabricated by further deposition of emitting/electron transport layers and top electrodes. This approach can open an avenue for low-cost manufacturing of flexible and high-resolution micro-displays.
Although organic light-emitting diodes (OLEDs) have been widely employed in displays and flexible electronics, the implementation of micro-OLED arrays still remains a challenge due to the limitations of the mainstream fine metal mask (FMM) technology. Pixel sizes below 30 μm are typically hard to achieve in order to match the requirement (i.e., sub10 μm) of the emerging near-eye displays mainly due to the so-called “screen-door effect”. Conventional lithography used for high-resolution inorganic micro patterns cannot be directly applied owing to the instability of organic materials. Furthermore, damage-free techniques such as inkjet printing also encounter resolution limitations. Self-assembled monolayer (SAM)-assisted patterning and surface-microstructure-assisted patterning techniques, though promising, have so far only been applied to fabricate single-color micro-OLEDs. In this work, high-resolution micro-OLED arrays with dual-color emission were demonstrated using a phase-change material (PCM) or an aggregation-induced emission (AIE) material. Fabricated via the SAM-assisted patterning technique, the PCM dot array exhibits red emission in its amorphous phase and transitions to green emission upon annealing-induced crystallization. Leveraging this unique dual-color capability, micro-OLEDs with 5 μm pixels (2600 PPI) and dual-color emission were achieved after the preparation of other functional layers.
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