잉크젯 프린팅을 이용한 OLED의 정공수송층 제작과 특성에 관한 연구

Abstract

The use of display and solid state lighting applications based on organic light-emitting diode(OLED) is an emerging technology. Since Tang and Vanslyske demonstrated stable and efficient double-layered OLED in 1987, various efforts have been made to enable their practical application to flat panel display and lighting devices. Efficient OLED based on small molecular organic materials or polymers have received intensive research interest because of their promising application to full-color flat panel displays. OLED using either small molecules or polymers, have attracted considerable interest due to their easy processability, flexibility, low cost, low operating voltages, wide viewing angles, tunability of the color emission, fast response time, and ease of forming large area. Another of the advantage of OLED is that because OLED were fabricated by wet process such as spin-coating and ink-jet printing from solution, it brings the benefits of cost-effective mass production. Therefore, this paper studied about manufacture of hole transport layer in OLED by ink-jet printing technology. OLED with ink-jet printed hole transport layer was fabricated as the following structure: ITO glass, hole injection layer, hole transport layer, emitting layer and cathode. The hole transport layer for ink-jet printing was formulated with TPD (N,N'- diphenyl-N,N'-bis(3-methy lphenyl)1-1'biphenyl-4,4'-diamine), PC(polycabonate) and solvent of high boiling point [DCB(1,2-dichlorobenzene, BP 180 ℃), NMP(N-methyl-2-pyrrolido ne, BP 202 ℃)] and THF(tetrahydrofuran, BP 65℃). Ink-jet printing method used with the manufactured solvent ink has proper properties which are viscosity, density, surface tension, is possible to make hole transport layer of OLED. As a result, the luminescence efficiency and light-current-voltage curve of OLED with ink-jet printed hole transport layer were measured. We expect the spin coating method and inkjet method to make hole transport layer will be shortening a process time and cost down.