Lignin: a potential renewable material candidate for organic devices

Lignin is one of the main constituents of lignocellulosic biomass. Lignin is recovered as a waste product of the cellulose industry, and it is an attractive feedstock for renewable chemicals and materials production. Nowadays, attention to lignin valorization into new chemicals and materials has increased.1 However, lignin possesses a complex chemical structure and variable properties depending on its natural origin and isolation procedure.2 Furthermore, lignin’s poor solubility in common solvents and broad distribution of molecular weight limit the use of lignin in devices. Indeed, devices fabrication requires materials with a highly regular and definite molecular structure.3 In this communication, we describe the structural and chemical-physical characterization of two kraft lignins, L1 and L2, and their thin film deposition to apply them as dielectric layers in organic field-effect transistor (OFETs) devices. Thanks to deposition from hydroalcoholic ammonia, we could achieve successfully smooth and semi-transparent lignin thin films. This enabled the use of L1 and L2 in pentacene or C60-based bottom gate top contacts OFET devices.4 In addition, we present the solvent fractionation of L1 and L2 by Soxhlet or Kumagawa methods, supporting a deeper characterization of their chemical structures.