High-efficiency deep-blue organic light-emitting diodes (OLEDs) play a crucial role in realizing ultra-high-definition (UHD) flat-panel displays and reducing power consumption. Generally, most reported OLEDs with a Commission Internationale de L’Eclairage (CIE) y coordinate < 0.06 are achieved by traditional fluorescent deep-blue emitters. However, it is challenging to obtain deep-blue fluorescent OLEDs with a high external quantum efficiency (EQE) (reaching the theoretical limit of 5%). In this work, we have successfully employed a hole-transporting material for an emitter, which can increase the efficiency in deep-blue OLEDs. The device employed with the proposed hole-transporting material exhibits deep-blue emission peaks at 427.0 nm with CIE coordinates of (0.155, 0.051), a turn-on voltage (Von) of 4.5 V, and an EQE of 4.5%. The performance of the OLED can be improved by 5.0% by optimizing the device structure. Finally, the flexible display when using the OLED devices exhibited a high image quality.

Ion beam-assisted deposition (IBAD) has been proposed as a promising texturing technology that uses film epitaxy method to obtain biaxial texture on a non-textured metal or compound substrate. Magnesium oxide (MgO) is the most well explored texturing material. In order to obtain the optimal biaxial texture, the actual thickness of the IBAD-MgO film must be controlled within 12 nm. Due to the bombardment of ion beams, IBAD-MgO has large lattice deformation, poor texture and many defects in the films. In this work, an additional homogeneous epitaxy MgO (epi-MgO) layer has been deposited on the IBAD-MgO layer by electron-beam evaporation. The biaxial texture can be optimized by the deposition of additional epi-MgO layer. The effects of growth temperature, film thickness, deposition rate and oxygen flux on the texture and morphology of the epi-MgO film were systematically studied. After the research of epi-MgO process, the best full width at half maximum (FWHM) values were 2.2 for the out-of-plane texture and 4.8° for the in-plane texture, respectively. Subsequently, the LaMnO3 cap layer and YBa2Cu3O7-x (YBCO) functional layer was deposited on the epi-MgO layer to test the quality of MgO layer. Finally, the critical current density of YBCO films is 6MA/cm2 (77K, 500nm, self-field), indicating that this research provides a high-quality MgO substrate for the YBCO layer.