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. The introduction of a new family of green electrolytes in light‐emitting electrochemical cells (LECs) is presented. Self‐stable and highly performing LECs are achieved by combining novel biogenic cellulose‐based electrolytes and archetypical emitters (i.e., conjugated polymers (CPs) and ionic transition metal complexes). For the first time in the field, green electrolytes do not jeopardize device performance.