17‐3: An 8.3‐inch 1058‐ppi OLED Display with Side‐by‐Side Pixel Structure Fully Fabricated by Photolithography

Abstract

We developed a patterning technology via photolithography that does not use a fine metal mask to achieve high resolution for all RGB pixels. An 8.3‐inch 1058‐ppi organic light‐ emitting diode (OLED) display was prototyped using the technology for an oxide semiconductor backplane over a glass substrate. Having no restriction on alignment accuracy, metal mask washing, running costs, etc. in the manufacturing process of medium‐ or large‐sized OLED displays, this technology holds promise for enabling the mass production.

New Physics for Better OLEDs

“…To address the brightness and stability obstacles, some industry research has used tandem OLEDs 12,13 and pixels defined via photolithography. [14][15][16] To enable nonplanar form factors, today's state-of-the-art top emission (TE) microcavity designs are fabricated on flexible plastic substrates. A microcavity is an optical path formed between two mirrors (i.e., the OLED's electrodes) that establishes a resonant condition for light in the OLED and results in a narrowed emission spectrum.…”

“…This poses a unique set of challenges for OLEDs, which traditionally are fabricated on rigid substrates and whose efficiency and stability reduce as brightness is increased. To address the brightness and stability obstacles, some industry research has used tandem OLEDs 12,13 and pixels defined via photolithography 14-16 . To enable nonplanar form factors, today's state‐of‐the‐art top emission (TE) microcavity designs are fabricated on flexible plastic substrates.…”

High‐luminance and Highly Reliable Tandem OLED Display Including New Intermediate Connector Designed for Photolithography Applications

“…Therefore, we have succeeded in developing the MML method, which allows pixel patterning by photolithography without damaging the organic layers, without changing constituent materials and device structures of conventional multilayer OLEDs. [5][6][7][8][9][10][11] Figure 1 is the process flowchart for our developed MML, showing an example of employing a tandem OLED. In this process, an RGB-SBS OLED is produced by etching, using a photoresist, excess organic layers (electroluminescence [EL] layers and an intermediate connector) after each deposition of the organic layers for RGB.…”

“…This approach led to the development of our proprietary method known as metal maskless lithography (MML), which allows pixel patterning without damaging an organic layer of an OLED and provides a high-aperture ratio patterned organic semiconductor (HarPOS ® ). [5][6][7][8][9][10][11] Consequently, we successfully created a micro OLED display with a pixel density of 3,207 ppi and a luminance of 5,000 cd/m 2 using the SBS method with a single OLED, maintaining efficiency and reliability comparable to a conventional method of successive formation in a vacuum. [6][7][8][9]11 However, the stringent requirements for higher luminance and reliability in micro OLED displays for XR prompted us to explore alternative solutions.…”

“…Our solution involves utilizing a pixel‐patterning method employing photolithography, not utilizing an FMM, to achieve a microdisplay with both high definition and luminance. This approach led to the development of our proprietary method known as metal maskless lithography (MML), which allows pixel patterning without damaging an organic layer of an OLED and provides a high‐aperture ratio patterned organic semiconductor (HarPOS®) 5–11 . Consequently, we successfully created a micro OLED display with a pixel density of 3,207 ppi and a luminance of 5,000 cd/m 2 using the SBS method with a single OLED, maintaining efficiency and reliability comparable to a conventional method of successive formation in a vacuum 6–9,11 …”