A new biopolymer obtained from onion pulp (Allium cepa L.) was employed to produce a sustainable substrate for flexible organic light-emitting diodes (FOLEDs). Indium tin oxide (ITO) and SiO2 thin films were deposited by rf-magnetron sputtering onto these biosubstrates to obtain flexible, transparent, and conductive anodes, on top of which FOLEDs were produced. This new biomaterial exhibits an optical transparency of 63% at 550 nm. ITO films were optimized by varying rf power during deposition onto the biopolymers, and their electrical properties are comparable to the those of ITO grown on top of rigid substrates: a carrier concentration of −3.63 × 1021 cm–3 and carrier mobility of 7.72 cm2 V–1 s–1 for the optimized film. Consequently, the sheet resistance and resistivity of this ITO film were 8.92 Ω sq–1 and 2.23 × 10–4 Ω cm, respectively, hence allowing the production of FOLEDs. The A. cepa L. based FOLED was fabricated using CuPc, β-NPB, and Alq3 as organic layers, and it exhibited a maximum luminance of about 2062 cd m–2 at 16.6 V. The current efficiency reached a maximum value of 2.1 cd A–1 at 85.3 mA cm–2. The obtained results suggest the possibility to use these substrates for innovative biocompatible applications in optoelectronics, such as photodynamic therapy.

Nowadays, flexible organic electronics are under intense investigation for environmentally friendly and biocompatible applications. One of the main components of electronic devices is the substrate, which gives support for building devices. There is great interest in the scientific community for the development of biocompatible and biodegradable substrates for the manufacture of these kinds of devices, aiming at technological and medical applications. In this work, we produced a flexible and transparent biosubstrate based on a gellan gum polymer by a solvent casting method to manufacture flexible organic light-emitting diodes (FOLEDs). The gellan substrate exhibited optical transparency of about 78% at 550 nm and 80% at 900 nm. In addition, the optimized indium tin oxide (ITO)/SiO2-coated gellan substrate exhibited a resistivity of 2.8 × 10–4 Ω·cm and a sheet resistance of 11.2 Ω/sq. These values are better or equal to those found in the literature for similar biosubstrates. Finally, the fabricated FOLEDs exhibited a maximum luminance of about 2327 cd/m2 and the current efficiency reached a maximum value of 2.9 cd/A. These characteristics reveal that this biosubstrate has interesting potential for applications in flexible green electronics, mainly due to its biocompatible properties and the results obtained by the developed FOLEDs.