This is the “mobile” era, characterized by a growing demand of flexible substrates for novel products such as curved screens, folding smartphones, and wearable devices. In this framework, plastic electronics represents a suitable technology to replace silicon-based electronics. However, up to now, little attention has been devoted to rendering this technology more environmentally sustainable. It is thus necessary to develop new eco-designed devices that allow recycling of all the components and recovering the valuable materials through sustainable methods. For the first time, we report the fabrication of organic light emitting diodes made on an as-cast biopolymeric flexible substrate. Sodium alginate is a natural biodegradable polymer derived from brown algae; it is water-soluble and easy to manipulate for the realization of flat and transparent foils using an environmentally friendly process. Thus, the active stack …