Highly Robust, Flexible Top-Emission Organic Light-Emitting Diode Exhibiting Stable Performance under Infolding of Curvature Radius of 0.32 mm

Flexible top-emission organic light-emitting diodes (TOLEDs) with a thin-film encapsulation (TFE) are of increasing attention to improve the flexibility of foldable smartphone organic light-emitting diode (OLED) displays. There are inevitable issues to achieve foldable display with smaller folding radius for the future portable display. Herein, the device flexibility is investigated with infolding and outfolding tests with the curvature radius from 2.5 to 0.32 mm. Parylene (1 μm)/silicon nitride (SiN_x) (X nm)/parylene (1 μm)/SiN_x (X nm) (X = 100, 70, 50, and 30 nm) of TFEs are applied on the TOLEDs. It is found that stable device performances can be achieved at the curvature radius of 0.32 mm after 100 000 cycles infolding testing when the SiN_x thickness is 30 nm. The device has significant degradation upon outfolding of 5000 cycles at the same radius of 0.32 mm. Note that, the water vapor transmission rate (WVTR) of the TFT with 30 nm SiN_x is higher than the TFE with thicker SiN_x (e.g., 50 nm). The flexibility and WVTR can be much improved using four-stacked TFE with 30 nm SiN_x for foldable active-matrix OLED displays.