Universally applicable small-molecule co-host ink formulation for inkjet printing red, green, and blue phosphorescent organic light-emitting diodes

For organic light-emitting diodes (OLEDs), inkjet printing technology is being developed as an alternative to the traditional vacuum evaporation, because of its precise patterning, high-efficient material utilization, large-area compatibility and low-cost. In this work, we report a universal ink formulation of small-molecule co-host and binary solvents for red, green and blue phosphorescent OLEDs. Moreover, the effect of hole-transporting layers on the ink spreading, film uniformity and exciton confinement ability is investigated. Furthermore, a large-area (170 mm x 170 mm) and homogeneous light-emitting film is inkjet-printed. Finally, red, green and blue OLEDs are successfully constructed using these optimized ink formulations on the solvent resistance hole-transporting layer. This work can reduce the complexity to adjust the host materials and solvents for different color inks, and could be applied in large-area and low-cost OLED displays with high resolution.

Automated summary

In this study, inkjet printing technology is being developed as an alternative to traditional vacuum evaporation for OLEDs, offering advantages such as precise patterning, high efficiency, large area compatibility, and cost-effectiveness. A universal ink formulation was used to successfully print large-area and uniform light-emitting films for red, green, and blue OLEDs. This approach simplifies the adjustment of host materials and solvents for different color inks, making it suitable for high-resolution, large-area, and low-cost OLED displays.