Influence of bilayer resist processing on p-i-n OLEDs: towards multicolor photolithographic structuring of organic displays

Abstract

Recently, bilayer resist processing combined with development in hydrofluoroether (HFE) solvents has been shown to enable single color structuring of vacuum-deposited state-of-the-art organic light-emitting diodes (OLED). In this work, we focus on further steps required to achieve multicolor structuring of p-i-n OLEDs using a bilayer resist approach. We show that the green phosphorescent OLED stack is undamaged after lift-off in HFEs, which is a necessary step in order to achieve RGB pixel array structured by means of photolithography. Furthermore, we investigate the influence of both, double resist processing on red OLEDs and exposure of the devices to ambient conditions, on the basis of the electrical, optical and lifetime parameters of the devices. Additionally, water vapor transmission rates of single and bilayer system are evaluated with thin Ca film conductance test. We conclude that diffusion of propylene glycol methyl ether acetate (PGMEA) through the fluoropolymer film is the main mechanism behind OLED degradation observed after bilayer processing.

Solid-State Lighting Using Side-by-Side White Phosphorescent Organic Light-Emitting Diodes

“…Thus, peel-off enables a flexibility in organic device and process design unavailable to more conventional methods of patterning. In this context, previous work demonstrates a S×S perovskite LED geometry and peel-off patterning exhibiting a >10 3 times increase in leakage current attributed to electrical cross-talk and imperfect edges. , …”

“…Current methods for S×S organic device patterning include vacuum deposition through fine metal shadow masks, direct patterning via organic vapor-jet printing, solution processing using ink-jet printing or microchannels, film transfer via laser-induced thermal imaging, and postdeposition processing via chemical lift-off. − A somewhat less complex and damage-free method that can achieve photolithographic resolution is mechanical peel-off, which has recently been demonstrated for patterning organic photovoltaics and perovskite light-emitting devices. , In this work, we demonstrate two-color, S×S WOLEDs deposited via vacuum thermal evaporation and subsequently patterned using mechanically peeled-off films. This method allows for multilayer patterning with micron-scale resolution while avoiding precise alignment of shadow masks, or exposing the individual color-emitting stripes to destructive solvents used in conventional photolithography.…”

52-2:Invited Paper: OLED Microdisplays - Enabling Advanced Near-to-Eye Displays, Sensors, and Beyond

“…Unfortunately, the high-resolution photolithography commonly adopted in microelectronics cannot easily be applied to OLED, since their photochemistry compounds are going to affect the organic semiconductor materials due to their sensitivity to water. There are potential options to overcome this issue; for example, one way involves the effect of chemical orthogonality to a specifically adapted photochemistry for organic semiconductors [3,4].…”

Two-Color Pixel Patterning for High-Resolution Organic Light-Emitting Displays Using Photolithography

“…This technical benefit motivated several research groups to apply it to OLED pixel patterning. They used a bi-layer resist approach [21][22][23] or photo-crosslinkable electroluminescent polymers as EML [24]. In case of a bi-layer resist approach, the choice of shielding layer and photoresist is important.…”