Fabrication of solution-processed light-emitting devices from a single deposition step

Abstract

Simple, scale-up, and low-cost processing is required for emerging electronic/optoelectronic applications, such as smart packaging, devices for instant information access, large-area billboards, and many others. Over the past decades, different types of new electronic materials and devices have been developed, aiming at the fabrication of thin-film light-emitting devices with flexible and lightweight capabilities. Light-emitting device structures that avoid using indium–tin oxide (ITO) as transparent electrodes are highly desirable, representing a considerable reduction in fabrication costs and an alternative to future material (indium) shortage. Despite the use (or not) of ITO, even the simplest device structure needs to undergo at least three deposition steps, comprising a transparent electrode (also used in many cases as the substrate), the electroluminescent active layer, and a back electrode. Here, we present a proof of concept for the fabrication of electroluminescent devices, with the primary innovation being the significant reduction in processing steps. We demonstrate herein a single-step process where the electroluminescent active layer and the transparent electrode are formed simultaneously by drop casting a multiphasic suspension onto a metallic foil, which acts simultaneously as the device back electrode and substrate. The resulting device exhibited a turn-on voltage of 23 V, a luminance on the order of 10 cd/m2, and a luminous efficacy on the order of 10−3 cd/A. Although these performance parameters are lower compared to more mature technologies, such as polymer light-emitting diodes (PLEDs) and polymer light-emitting electrochemical cells (PLECs), our findings introduce a novel fabrication concept for electroluminescent devices, broadening the potential for the development of emerging technologies.