The research team led by Professor Jaeuk Kang of Jeonbuk National University (JBNU)'s Graduate School of Flexible Printed Electronics demonstrated, through an inkjet printing (inkjet printing)-based process technology, both large-area, uniform thin-film fabrication and eco-friendly process scalability for next-generation display light-emitting devices and solar cells.

Professor Kang's team, in collaboration with Professor Seongho Jin's group at Pusan National University, developed a high-performance organic light-emitting device (PHOLED) based on inkjet printing that combines eco-friendly solvent design and interface engineering. The study was published in the internationally renowned journal Materials Today.

The research team used non-chlorinated eco-friendly solvents and applied self-assembled monolayer (SAM) interface engineering to implement the entire process by inkjet printing under room-temperature, ambient conditions. In particular, they significantly improved the uniformity of the printed thin films by adopting a binary solvent system to suppress the coffee-ring effect and a dual SAM interface treatment. As a result, the ambient-processed inkjet-printed PHOLED achieved an external quantum efficiency (EQE) of 16.8%.

The team also reported extended research results. Through collaboration with Dr. Dohyung Kim's group at the Korea Electric Power Research Institute, they extended the inkjet printing process platform to large-area perovskite solar cells. They improved the uniformity of large-area films and secured module-level solar cell performance. The paper reporting these results was subsequently published in Advanced Functional Materials.

In collaboration with Professor Jeonghwan Lee's team at Inha University, they proposed a new ligand-exchange strategy to overcome the light-outcoupling limits of perovskite nanocrystal-based LEDs (PeQLEDs).

By using a dual-functional ligand (NDSA) to improve the alignment of the transition dipole moment (TDM) in the emissive layer, they increased light-outcoupling efficiency from 16.15% to 20.09% and achieved a maximum external quantum efficiency of 22.63%. This research was published in Advanced Materials.

This research is significant in that it integrates precise patterning, large-area uniformity, and solvent eco-friendliness—key process elements for displays and solar cells—into a single inkjet printing process platform.

The research team explained that they have, in effect, been the only group in the country to accumulate research capabilities that holistically optimize materials, interfaces, inks, and equipment conditions centered on inkjet printing process technology.

Professor Jaeuk Kang said, "Inkjet printing is a next-generation process technology capable of eco-friendliness, low cost, non-contact processing, and large-area manufacturing," adding, "We have systematically studied inkjet-based optoelectronic device fabrication processes domestically, and collaboration with the Korea Electric Power Research Institute has further advanced their practical applicability."

Meanwhile, this research was carried out with support from the Mid-Career Researcher Support Program of the Ministry of Science and ICT and research funding from Korea Electric Power Corporation.