80‐3: All Organic Layers Inkjet Printed OLEDs with a Printable Electronic Transport Layer

Abstract

All organic layers inkjet printed OLEDs have been successfully developed with a printable electronic transport layer (ETL). A jettable ETL ink was prepared with a commercially soluble electronic transport material and alcohol solvents. Based on orthogonal solvent systems, the deposition of ETL caused little damage to the emission under-layer. And ETL printed OLEDs show comparable performance with its evaporation ETL counterparts.

20.1: Invited Paper: High Performance Top‐Emission Inkjet Printed OLEDs with Printed Electron Transport Layer

“…There are some requirements for inkjet printed ETL based OLEDs, as mentioned in our previous work [7]. First, soluble ETL materials with good electron transport ability, proper energy level for efficient electron-injection and hole-blocking, high thermal stability and good film uniformity are highly needed.…”

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

“…2023, 35,2207454 SOLEDs produced by IJP is estimated to be ≈25% lower than those of currently used white EOLEDs produced by LG Display Co. [30] However, SOLEDs still have big challenges that must be solved before they are suitable for industrial uses. The most important considerations are regarding solution processing, such as liquidstate processability of materials, [24][25][26]32,35,39,40] intermixing of layers or redissolution of underlying layers in OLEDs, [41,42] limited efficiencies and their severe rolloff, [20] and operational instability caused by molecular aggregation and lessdensely packed solutionprocessed organic film and their SOLEDs [16] compared to the thermally evaporated coun terparts. EOLED devices have been developed to have multiple functional layers including charge injection, transporting, and blocking layers for better charge balance, and therefore have high luminous efficiency and high operational stability.…”

“…[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).…”

“…However, SOLEDs use liquid solutions as starting materials, so other physical properties, including viscosity, vapor pressure, and sur face tension, must also be considered. [24][25][26]32,39,40] These prop erties are important to guarantee inkjet applicability and film flatness after vacuum drying (Figure 2c). Also, the underlying layer in the SOLED must have resistance to the solution that is used to process the upper layer; this resistance is described as solution orthogonality.…”