Making organic light-emitting diodes sustainable-from metal-free emitters to less energy-intensive processing

Abstract

Organic light-emitting diodes (OLEDs) are arguably the most commercially successful devices that have been developed from organic semiconductors due to their use in advancing display technologies and solid-state lighting. These devices can be lightweight, flexible, and stretchable, suggesting that they can be adapted more easily into future developments, such as wearable devices, compared to inorganic LEDs. This chapter summarizes the development of emitters for OLEDs, from fluorescent materials to phosphorescent complexes and compounds showing thermally activated delayed fluorescence (TADF). The promising properties of TADF systems indicate that these can replace the heavy metal-containing phosphorescent complexes presently used in commercial OLEDs. There will also be discussion on how emissive materials for OLEDs can be adapted for solution deposition to move away from energy-intensive vacuum deposition methods. The challenge of modifying the structure of emissive materials to become solution-processable, while maintaining high device performance is highlighted. Solution deposition methods will be examined, with discussion on the merits of electrochemistry as a sustainable deposition method. Finally, the future of OLEDs will be considered, particularly how device lifetime can be extended and how OLEDs can be adopted into new applications, with reflection on how this might impact on the sustainability of the technology. © 2022 Elsevier B.V., All rights reserved.