Organic transistor technologies are emerging as a cornerstone for next-generation flexible, lightweight, and biocompatible electronics, offering pathways to reduce environmental impact. Over the past decades, silicon-based electronics have driven global digitalization, but their growing ubiquity has contributed to mounting e-waste challenges. Sustainable organic transistors (OTs) leverage green materials and processes to address this issue, aiming for devices that are recyclable, biodegradable, or safely bioresorbable.
The substrate, comprising over 99.5% of an OT’s mass, plays a decisive role in environmental footprint. Glass remains a widely used non-flexible option, valued for its recyclability and low surface roughness, enabling high-performance semiconductor deposition. Soda-lime glass, the dominant type, can save up to 300 kg of CO₂ emissions per ton recycled. Paper substrates, derived from cellulose fibers, offer flexibility and compatibility with roll-to-roll manufacturing. Nanocellulose, produced by fibril disintegration, provides smoother surfaces and higher tensile strength than conventional paper, making it a leading candidate for OT-grade substrates. Other natural substrates include polysaccharides such as chitin, chitosan, and galactomannan, and proteins like silk fibroin and keratin, each offering biodegradability and, in some cases, recyclability.
Gate dielectrics have seen innovation with biomaterials such as shellac, albumen, and polymethacrylated tannic acid (PMTA). Shellac’s hydroxyl groups suppress electron trapping, making it suitable for n-type or ambipolar OFETs. Albumen, thermally cross-linked via disulfide bonds, yields smooth films with high specific capacitance and stability under varied humidity. PMTA, derived from tannic acid, combines robust dielectric properties with degradability in saltwater within weeks, producing non-toxic byproducts.
Semiconductors and conductors are transitioning toward green alternatives. Natural dyes like beta-carotene and indigo have been tested, alongside bioinspired anthraquinone derivatives and oligo-furans processed with non-halogenated solvents. Synthetic biodegradable semiconductors such as diketopyrrolopyrrole-phenylenediamine (PDPP-PD) exploit pH-sensitive imine bonds for controlled degradation. Conductors pose a greater challenge; while noble metals like gold are biocompatible, they are not degradable. Earth-abundant metals such as iron, zinc, and magnesium dissolve under mild conditions, offering greener electrode options. Conductive polymers like PEDOT:PSS can be blended with biodegradable matrices to enhance compostability.
Solvent choice is critical. Traditional halogenated solvents are being replaced by greener options such as isobutyl acetate, dimethyl carbonate, and anisole, which have enabled mobilities comparable to chlorinated solvents in TIPS-pentacene devices. Orthogonal solvents like limonene allow selective layer deposition without damaging underlying materials.
Architecturally, bottom-gate top-contact (BG-TC) configurations dominate green OT fabrication, reducing semiconductor sensitivity to substrate roughness. Ion-gated designs, including electrolyte-gated OFETs (EGOFETs) and organic electrochemical transistors (OECTs), use biocompatible hydrogels or solid-state electrolytes to achieve sub-volt operation. Notably, Bao’s group demonstrated fully disintegrable cellulose-based BG-TC OFETs with iron electrodes, operating at −10 V and degrading completely in acidic buffer within 30 days.
Manufacturing approaches favor low-temperature, additive techniques. Vacuum deposition through shadow masks avoids solvent compatibility issues but has energy costs. Transfer printing enables fabrication on conventional substrates before moving devices to biodegradable targets, expanding material compatibility. Printing methods—screen, inkjet, spray—are increasingly applied to natural-based substrates. Caironi’s team integrated OFETs onto edible gelatin capsules using tattoo-paper transfer of ethylcellulose layers, with inkjet-printed silver nanoparticle electrodes and semiconductors.
Applications span flexible circuits, biosensors, and neuromorphic devices. Inkjet-printed complementary inverters on paper have achieved static gains near −14 at 5 V, with noise margins suitable for robust digital logic. Biodegradable OECTs with levan-based solid-state electrolytes have recorded ECG signals from human skin and rat hearts, dissolving harmlessly post-use. Ultra-flexible dextran-based synaptic transistors emulate excitatory postsynaptic currents and degrade in soil within seconds, pointing toward sustainable neuromorphic computing.
Advancing green OT technology requires expanding material databases, optimizing solubility in benign solvents, accurately calculating embodied energy and carbon footprints, and refining ultra-low temperature, solvent-free manufacturing. The progress to date signals a promising trajectory toward ubiquitous, sustainable electronics and bioelectronics.