Large area inkjet-printed OLED fabrication with solution-processed TADF ink

Chandra Kant; Atul Shukla; Sarah K M McGregor; Shih-Chun Lo; Ebinazar B Namdas; Monica Katiyar

doi:10.1038/s41467-023-43014-7

Large area inkjet-printed OLED fabrication with solution-processed TADF ink

Nat Commun. 2023 Nov 9;14(1):7220. doi: 10.1038/s41467-023-43014-7.

Authors

Chandra Kant^{1

2}, Atul Shukla^{3

4}, Sarah K M McGregor^{3

5}, Shih-Chun Lo^{6

7}, Ebinazar B Namdas^{8

9}, Monica Katiyar^{10

11}

Affiliations

¹ Materials Science and Engineering Department, Indian Institute of Technology Kanpur, Kanpur, India.
² National Centre for Flexible Electronics, Indian Institute of Technology Kanpur, Kanpur, India.
³ Centre for Organic Photonics & Electronics, The University of Queensland, Brisbane, Australia.
⁴ School of Mathematics and Physics, The University of Queensland, Brisbane, Australia.
⁵ School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia.
⁶ Centre for Organic Photonics & Electronics, The University of Queensland, Brisbane, Australia. s.lo@uq.edu.au.
⁷ School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia. s.lo@uq.edu.au.
⁸ Centre for Organic Photonics & Electronics, The University of Queensland, Brisbane, Australia. e.namdas@uq.edu.au.
⁹ School of Mathematics and Physics, The University of Queensland, Brisbane, Australia. e.namdas@uq.edu.au.
¹⁰ Materials Science and Engineering Department, Indian Institute of Technology Kanpur, Kanpur, India. mk@iitk.ac.in.
¹¹ National Centre for Flexible Electronics, Indian Institute of Technology Kanpur, Kanpur, India. mk@iitk.ac.in.

Abstract

This work demonstrates successful large area inkjet printing of a thermally activated delayed fluorescence (TADF) material as the emitting layer of organic light-emitting diodes (OLEDs). TADF materials enable efficient light emission without relying on heavy metals such as platinum or iridium. However, low-cost manufacturing of large-scale TADF OLEDs has been restricted due to their incompatibility with solution processing techniques. In this study, we develop ink formulation for a TADF material and show successful ink jet printing of intricate patterns over a large area (6400 mm²) without the use of any lithography. The stable ink is successfully achieved using a non-chlorinated binary solvent mixture for a solution processable TADF material, 3-(9,9-dimethylacridin-10(9H)-yl)-9H-xanthen-9-one dispersed in 4,4'-bis-(N-carbazolyl)-1,1'-biphenyl host. Using this ink, large area ink jet printed OLEDs with performance comparable to the control spin coated OLEDs are successfully achieved. In this work, we also show the impact of ink viscosity, density, and surface tension on the droplet formation and film quality as well as its potential for large-area roll-to-roll printing on a flexible substrate. The results represent a major step towards the use of TADF materials for large-area OLEDs without employing any lithography.