Versatile Biogenic Electrolytes for Highly Performing and Self-Stable Light-Emitting Electrochemical Cells

Light-emitting electrochemical cells (LECs) are the simplest and cheapest solid-state lighting technology for soft and/or single-use purposes. However, a major concern is a transition toward eco-friendly devices (emitters/electrolytes/electrodes) to meet green optoelectronic requirements without jeopardizing device performance. In this context, this study shows the first biogenic electrolyte applied to LECs, realizing self-stable and highly performing devices with cellulose-based electrolytes combined with archetypical emitters (conjugated polymers or CPs and ionic transition-metal complexes or iTMCs). In contrast to reference devices with traditional electrolytes, self-stability tests (ambient storage/thermal-stress) show that devices with this bio-electrolyte hold film roughness and photoluminescence quantum yields over time. In addition, charge injection is enhanced due to the high dielectric constant, leading to high efficacies of 15 cd A⁻¹@3750 cd m⁻² and 2.5 cd A⁻¹@600 cd m⁻² associated with stabilities of 3000/7.5 h and 153/0.7 J for CPs/iTMCs-LECs, respectively. They represent four-/twofold enhancement compared to reference devices. Hence, this novel biogenic electrolyte approach does not reduce device performance as in the prior-art bio-degradable polymer and DNA-hybrid electrolytes, while the easiness of chemical modification provides plenty of room for future developments. All-in-all, this study reinforces the relevance of carbohydrate-based electrolytes not only for energy-related applications, but also for a new field in lighting.