Indium-Gallium-Zinc-Oxide Based Semitransparent Electrodes on Flexible Substrates for Biodegradable Electronics

Indium gallium zinc oxide (IGZO)/silver/IGZO (IAgI) electrodes were sputtered on films of tattoo-paper (TP), cellulose nanocrystals (CNCs), silk fibroin (SF), and on a 75:25 v/v % SF :CNCs blend with a view to developing biocompatible, sustainable materials for printed electronics. Drop-cast films of CNCs, SF and their blends show an average visible transmittance of 90.9%, 81.5%, and 49.5% respectively. Mechanical measurements reveal average strain at break values of 26% for CNCs, 13% for SF, and 5.4% for the blend, with respective Young's moduli of 1200 MPa, 270 MPa, and 1000 MPa. IAgI electrodes on glass (as controls) display an average visible transparency ~71.6%, a sheet resistance of 5 Ohm/sq, and a work function of ~ 4.4 eV. We transferred electrodes on CNCs, blend, and TP flexible substrates to a Kalanchoe blossfeldiana plant leaf and monitored their resistance over a full day/night cycle in a controlled environment as a proof-of-concept demonstration for sensing applications.