Small Molecules in Light-Emitting Electrochemical Cells: Promising Light-Emitting Materials

Light-emitting electrochemical cells (LECs) are solid-state lighting devices that convert electric current to light within electroluminescent organic semiconductors, and these devices have recently attracted significant attention. Introduced in 1995, LECs are considered a great breakthrough in the field of light-emitting devices for their applications in scalable and adaptable fabrication processes aimed at producing cost-efficient devices. Since then, LECs have evolved through the discovery of new suitable emitters, understanding the working mechanism of devices, and the development of various fabrication methods. LECs are best known for their simple architecture and easy, low-cost fabrication techniques. The key feature of their fabrication is the use of air stable electrodes and a single active layer consisting of mobile ions that enable efficient charge injection and transport processes within LEC devices. More importantly, LEC devices can be operated at low voltages with high efficiencies, contributing to their widespread interest. This review provides a general overview of the development of LECs and discusses how small molecules can be utilized in LEC applications by overcoming the use of traditional lighting materials like polymers and ionic transition metal complexes. The achievements of each study concerning small molecule LECs are discussed.