Thin-film transistor-driven vertically stacked full-color organic light-emitting diodes for high-resolution active-matrix displays

Sukyung Choi,Chi-Sun Hwang,Hee-Ok Kim,Jun-Han Han,Chun-Won Byun,Jin-Wook Shin,Nam Sung Cho,Byoung-Hwa Kwon,Hyunkoo Lee,Eungjun Kim,Seunghyup Yoo,Hyunsu Cho,Kang Me Lee,Chan-Mo Kang,Jong-Heon Yang

doi:10.1038/s41467-020-16551-8

Abstract

Thin-film transistor (TFT)-driven full-color organic light-emitting diodes (OLEDs) with vertically stacked structures are developed herein using photolithography processes, which allow for high-resolution displays of over 2,000 pixels per inch. Vertical stacking of OLEDs by the photolithography process is technically challenging, as OLEDs are vulnerable to moisture, oxygen, solutions for photolithography processes, and temperatures over 100 °C. In this study, we develop a low-temperature processed Al2O3/SiNx bilayered protection layer, which stably protects the OLEDs from photolithography process solutions, as well as from moisture and oxygen. As a result, transparent intermediate electrodes are patterned on top of the OLED elements without degrading the OLED, thereby enabling to fabricate the vertically stacked OLED. The aperture ratio of the full-color-driven OLED pixel is approximately twice as large as conventional sub-pixel structures, due to geometric advantage, despite the TFT integration. To the best of our knowledge, we first demonstrate the TFT-driven vertically stacked full-color OLED.

Highlights

Thin-film transistor (TFT)-driven full-color organic light-emitting diodes (OLEDs) with vertically stacked structures are developed using photolithography processes, which allow for high-resolution displays of over 2,000 pixels per inch
Materials used in OLEDs are generally susceptible to damage by moisture, oxygen, organic solvents, and high temperatures[28,29,30,31,32,33]; developing a low-temperature process for forming intermediate electrodes and via holes without damaging the OLEDs, is an important advance required for making thin-film transistor (TFT)-driven, vertically stacked fullcolor OLEDs, using photolithography process
A schematic of the vertically stacked full-color OLED with the R, G, and B primary colors is presented in Fig. 1a, with detailed layer information depicted in Supplementary Fig. 1

Summary

Introduction

Thin-film transistor (TFT)-driven full-color organic light-emitting diodes (OLEDs) with vertically stacked structures are developed using photolithography processes, which allow for high-resolution displays of over 2,000 pixels per inch. Color-tunable OLEDs, created using vertically stacked R, G, and B OLEDs, have been reported[16,17,18,19,20,21,22,23,24,25,26,27] These devices can express various colors by controlling each color element, and can be a pixel in OLED displays without using FMMs for R, G, and B patterning, complex alignment, or color-filter processes. We are able to make the OLEDs show full-color in a single-pixel, by controlling the driving voltage in each of the R, G, and B units

Methods

Results

Conclusion