Chemically Compatible Sacrificial Layer-Assisted Lift-Off Patterning Method for Fabrication of Organic Light-Emitting Displays Wonsuk Choi, Min-Hoi Kim, and Sin-Doo Lee  School of Electrical Engineering #32, Seoul National University, Seoul 151-600, Korea Received April 4, 2011; accepted June 11, 2011; published online August 5, 2011 We developed a generic platform to pattern combinatorial functional layers composed of different classes of organic materials using a repetitive lift-off method based on a chemically compatible sacrificial layer (SL) for organic light-emitting diodes (OLEDs). The essential features come from the chemically compatible SL of a fluorous-polymer that can be generated by laser-inscription or transfer-printing. The precise registration of lateral patterns of different materials was achieved on a single substrate through a series of SL-assisted lift-off processes. The chemical compatibility of the SL and the stability of the light-emitting characteristics were shown in a fluorous-solvent treated monochrome OLEDs. # 2011 The Japan Society of Applied Physics R ecently, organic light-emitting diodes (OLEDs) have attracted much attention due to their excellent characteristics including fast response, wide view- ing property, and low power consumption for use as high- performance flat panel displays. 1–3) Great progress on the development of new OLED-based devices has been achieved especially towards multi-purpose mobile applications such as smart phones, portable media players, and tablet com- puters. However, there still remains to develop a simple and reliable method of integrating a variety of sensitive organic materials into high-performance OLED elements in a cost- effective manner. Beyond laser-induced thermal imaging, 4) a number of approaches such as ink-jet printing, 5,6) direct laser patterning techniques, 7,8) and soft lithographic tech- niques 9,10) have been recently proposed but they may suffer intrinsically from either the pattern resolution or pattern reliability. In addition, photolithographic 11–13) or elastomeric membrane mask-assisted 14) lift-off methods have also been explored for the OLED applications. In this work, we developed a generic platform to pattern a combinatorial functional layer (CFL) composed of various organic materials through a lift-off process based on a chemically compatible sacrificial layer (SL) for the OLED applications. The key concept of our approach relies on the use of the SL patterns of a fluorous-polymer, complementary to combinatorial functional patterns, produced by either laser-inscription (LI) or transfer printing (TP) which is different from existing photolithographic methods. 12,13) This type of the TP approach was successfully employed for fabricating pentacene-based thin-film transistors and inverters 15) but it has not been explored for the OLEDs with different classes of sensitive organic layers among a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer (EIL) in a stacked structure. Figure 1 shows a schematic diagram showing a repetitive lift-off method based on a chemically compatible SL generated by either LI or TP for fabrication of two-color (green and blue) elements on a substrate through two sequential unit processes (1 and 2). In our case, a fluoruous- polymer (3M NovecÔ EGC-1700) was used as a SL which can be dissolved in a highly fluorous-solvent (3M NovecÔ HFE-7100). Note that the fluorous-solvent is chemically inert to most of organic materials, and is thus definitely able to be used in the process for organic materials. For the LI to produce the SL patterns shown in the top left of Fig. 1, a fluorous-polymer layer was first prepared on a substrate by simple dip-coating and subsequently exposed to ultraviolet (UV) light from a KrF excimer laser through a predefined photomask. This LI process was previously described in multi-level registration of light-emitting polymer patterns within the framework of selective surface wettability. 16) For the TP to directly produce the SL patterns shown in the top right of Fig. 1, a fluorous-polymer solution was coated on the surface of an elastomeric stamp of poly(dimethylsiloxane) (PDMS) having replica shapes of desired color patterns and then transfer-printed onto the substrate. The SL patterns were well-defined by the intimate contact between the surfaces of the PDMS stamp and the substrate surface under ambient conditions without any need to apply high heat/pressure. Then, after blanket-deposition of an organic color layer over the substrate having SL Fig. 1. (Color online) Schematic diagram showing a lift-off process based on a chemically compatible SL generated by either LI or TP for fabrication of two-color (green and blue) elements in an array by simply repeating the unit process.  E-mail address: sidlee@plaza.snu.ac.kr Japanese Journal of Applied Physics 50 (2011) 080219 080219-1 # 2011 The Japan Society of Applied Physics RAPID COMMUNICATION DOI: 10.1143/JJAP.50.080219