Electronic and protonic transport in bio-sourced materials: a new perspective on semiconductivity

Over the last few decades, the terrific development in the field of consumer electronics, paralleled by wider access to technology, short device lifetime and replacement cycles, has generated an unsustainable amount of waste of electrical and electronic equipment. Accumulation of e-waste is posing serious environmental and health concerns for the present and future generations. Abundant, bio-sourced, biocompatible, solution-processable organic materials are promising for promoting the development of low eco- and human-toxic electronic technologies. Therefore, unraveling the structure-to-property relationships in bio-sourced materials is paramount. The study of the charge carrier transport properties of bio-sourced materials is challenging. The presence of ions, and among them protons, in these systems profoundly affects the local molecular environment and, in turn, their charge carrier transport properties. In this context, the question whether the classical concept of semiconductivity developed for inorganic materials applies to protonic as well as mixed protonic-electronic counterparts is a matter of debate. In this review, we shed light on the elusive concept of semiconductivity for nature-inspired materials and provide new perspectives on protonic transport on the definition of bio-sourced semiconductors.