Khaya gum – a natural and eco-friendly biopolymer dielectric for low-cost organic field-effect transistors (OFETs)

Nature provides a wide range of dielectric biopolymers that can be used in electronic devices. In this work, organic field-effect transistors (OFETs) using khaya gum (KG), a natural, biodegradable biopolymer that can be directly collected from khaya senegalensis trees, as the gate dielectric are demonstrated. The fabricated bottom gate/top contact poly (3,6-di (2-thien-5-yl)-2,5-di (2-octyldodecyl)-pyrrolo [3,4-c] pyrrole-1,4-dione) thieno [3,2-b] thiophene) (DPPTTT) –(polymethylmethacrylate) (PMMA) OFETs operate at 3 V with a saturation field-effect mobility (μ_sat) 0.3 cm²V⁻¹ s⁻¹, threshold voltage (V_th) -1.3 V, subthreshold swing (SS) 450 mV/dec, and current on/off ratios (I_ON/OFF) larger than 3 × 10³. Significantly, the gate leakage current (I_G) does not exceed 10^–8 A for the gate-source voltage (V_GS) ≤ -3 V. UV–Vis spectra analysis shows that the prepared khaya gum films exhibit low absorbance and high transparency (up to 90%) with a calculated optical band gap of about 4.3 eV. Thermal characterization shows two stages of decomposition and a glass transition at around 60 °C. Characterization of metal–insulator-metal (MIM) capacitors using khaya gum reveals that the KG-based MIM capacitors possess a relatively high capacitance per unit area (C_i) of 130 ± 3 nF/cm² at 1 kHz. As a result, khaya gum emerges as the dielectric of choice for low voltage, transparent OFETs where environmentally friendly device manufacturing is required.