스크린 인쇄법으로 제작된 전극을 가지는 전기화학발광 셀(LECs)의 제작에 관한 연구

Abstract

Since organic light emitting diode (OLED) technology has been applied to display panel and successfully commercialized, large-area flexible lighting is highlighted for the next application of OLED technology. However, for the fabrication of large-area display panel the more complex and multi-stacked structure of OLED for more efficient charge-injection process increased the fabrication cost and thus make an implantation of OLED technology to the large-area flexible lighting required to the low-cost fabrication process somewhat challenging. Light-emitting electrochemical cells (LECs) are electrochemically luminescent devices through the oxidation-reduction reaction of mobile ions in their active layer sandwiched the top and bottom electrodes. Aside from the mobile ions, their structure is very similar to that of the OLED but they have many advantages over the OLED. In particular, their simple structure without buffer layers for charge injection and independent performance on the thickness of the active layer allow the LECs to use relatively inexpensive large-area printing processes for their fabrication. In this study, we have investigated the electrical and optical properties of the LECs having screen-printed electrodes. For the experiment, the active layer is composed of an ionic transition metal complex, Ru(bpy)3(PF6)2 ((Tris(2,2'-bipyridine)ruthenium(II) hexafluorophosphate)), and an electrolyte material to assist in the redox reaction, ionic liquid EMIM-TFSI(1-Ethyl-3-methyl Imidazolium bis)Imide) at a ratio of 1:16 wt%. Importantly, the electrodes were prepared by using screen printing process and thermal evaporation to compare the electrical property. According to the result of a series of electrical property measurements, the resistivity value of the screen-printed electrode is about 6.68×10-7Ωm, and it was confirmed that the screen printed electrodes have sufficient electric property to fabricate the LEC devices in terms of turn-on voltages and J-V characteristics, although the screen printed electrodes have relatively higher resistance value than that of the conventionally evaporated metal electrodes.