27‐4:Late‐News Paper:Key Materials for High‐Performance Solution‐Process OLEDs

Abstract

We are accelerating the development of materials for the solution-process OLEDs. High-performance small molecules for EML and platform polymers with reduced the molecular weight for HIL/HTL have been developed as the best practice for highresolution printed OLED panels. Further, no-diffusible pdopants have been successfully developed that are key materials for improving the performances of OLEDs produced by solution processes.

Advances in Solution‐Processed OLEDs and their Prospects for Use in Displays

“…Recent EOLEDs and SOLEDs reported by various mate rial suppliers have a range of efficiencies (Table 1). [27,35,52,53] Regardless of supplier, the blue SOLEDs are less efficient than red or greenemitting SOLEDs. SOLEDs fabricated by the three major SOLED material suppliers (Sumitomo Chem ical (Japan), Mitsubishi Chemical (Japan), and Merck KGaA (Germany)) show CEs that vary depending on the color index (Table 1).…”

“…SOLEDs fabricated by the three major SOLED material suppliers (Sumitomo Chem ical (Japan), Mitsubishi Chemical (Japan), and Merck KGaA (Germany)) show CEs that vary depending on the color index (Table 1). [27,35,53] Bottomemission SOLED devices have CEs (at 1000 cd m −2 ) ≈20 cd A −1 in red emission, ≈80 cd A −1 in green emission, but <10 cd A −1 in blue emission. Furthermore, red and greenemitting devices have >10 times longer lifetimes than blueemitting devices.…”

“…[21,54] Also, SOLEDs still require an evaporated organic layer according to the reports from SOLED materials suppliers. [27,55] The reason for this need may be the limitation in device efficiency and lifetime, and the lack of solvent resist ance of underlying layer. The use of thermal evaporation makes waste of materials inevitable, and the process requires an additional process to flip the substrate before it can be loaded into the evaporator.…”

“…[10,21,22] In contrast, solutionprocessed small to mediumsized SOLEDs are composed of individually driven RGB pixels, which do not need an FMM to isolate each RGB pixel (Figure 1d). [23][24][25][26][27][28] SOLEDs have several advantages over EOLEDs, including simple device structure, availability of topemission structure, low material consumption, and compatibility with largearea manufacturing using 10.5G (2940 mm × 3370 mm) mother glasses. [29] SOLEDs can be produced using inkjet printing (IJP), which uses only the necessary amount of materials to pattern pixels (i.e., drop on demand) (Figure 2a).…”

“…In contrast, SOLEDs can use simple structures, like RGB EOLEDs and therefore can easily be fabricated in topemission structures (Figure 2b, right). [24,25,27,[32][33][34][35] The topemission struc tures amplify light intensity and increase luminous efficiency by using the strong resonancecavity effect between two elec trodes. Also, topemission devices emit light in the opposite direction from thinfilm transistors, so the aperture ratio can also be increased (Figure 1d).…”