Nowadays, the display industry is endeavoring to develop technology to provide large-area organic light-emitting diode (OLED) display panels with 8K or higher resolution. Although the selective deposition of organic molecules through shadow masks has proven to be the method of choice for mobile panels, it may not be so when independently defined high-resolution pixels are to be manufactured on a large substrate. This technical challenge motivated us to adopt the well-established photolithographic protocol to the OLED pixel patterning. In this study, we demonstrate the two-color OLED pixels integrated on a single substrate using a negative-tone highly fluorinated photoresist (PR) and fluorous solvents. Preliminary experiments were performed to examine the probable damaging effects of the developing and stripping processes upon a hole-transporting layer (HTL). No significant deterioration in the efficiency of the develop-processed device was observed. Efficiency of the device after lift-off was up to 72% relative to that of the reference device with no significant change in operating voltage. The procedure was repeated to successfully obtain two-color pixel arrays. Furthermore, the patterning of 15 μm green pixels was accomplished. It is expected that photolithography can provide a useful tool for the production of high-resolution large OLED displays in the near future.

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This article reports photoinduced solubility modulation in copolymer thin films derived from spiropyranyl, perfluoroalkyl, and isobornyl methacrylates. A random copolymer of spiropyranyl methacrylate (SPMA) and 1H,1H,2H,2H-perfluorooctyl methacrylate (FOMA) was first prepared in the absence of isobornyl methacrylate (IBMA). The resulting as-prepared thin film could be dissolved in highly fluorinated or fluorous solvents but became insoluble following exposure to UV light (λ = 365 nm) via the photoisomerization transformation of spiropyran units into merocyanine moieties. On the other hand, the incorporation of IBMA into the copolymer structure above a certain threshold resulted in copolymers exhibiting the opposite dissolution behavior. UV–vis spectroscopic measurements on the copolymer films and solutions indicated that dipolar attraction between the photoisomerized merocyanine moieties contributed to the decrease in solubility. The incorporation of IBMA into the copolymer chains diluted the merocyanine moieties and increased their glass-transition temperature, resulting in the disruption of the intermolecular attraction and an increase in the solubility of the UV-exposed polymer chains. These results suggested that stencils could be developed without additives to generate strong acid molecules or free radicals in polymer thin films. The proposed processing technique for fluoroalkylated copolymers was thus tested in the fabrication of orthogonal copolymer stencils and demonstrated to be a useful tool for the pixel patterning of chemically vulnerable organic light-emitting diodes.