Mango and cactus saps as natural, biodegradable dielectric materials for sustainable production of low-voltage OFETs

Eco-friendly solutions using natural, biocompatible, biodegradable materials with low-cost fabrication techniques, such as solution processes, have been utilised in organic field-effect transistors (OFETs). This paper evaluated the integration of mango and cactus saps as natural high-k dielectric materials in OFETs. It was observed that the thinner (170 nm) mango sap dielectric layers showed a 30% higher areal capacitance (C_i) value (42.56 ± 5.29 nF/cm² at 1 kHz). The dielectric constant (k) values of thinner mango sap and cactus sap: PMMA bilayer were calculated as k ~ 8 and k ~ 16, respectively. Leakage current densities were < 10^–7 A/cm² at 3 V for single layers of mango sap. Cactus sap was used as a dielectric layer with an ultrathin (30 nm) PMMA passivating layer. The cactus bilayer yielded 93.53 ± 8.23 nF/cm² average areal capacitance at 1 kHz with ~ 10^–8 A/cm² leakage current density. DPP-DTT: PMMA blend OFET devices using cactus sap: PMMA dielectric layer exhibited one of the highest reported (1 ± 0.2 cm²V^{− 1} s^{− 1}) field-effect mobility and lowest subthreshold swing (105 ± 7 mV/dec), threshold voltage (–0.2 V) and interfacial trap density (1.86 × 10¹² cm^–2eV^–1) at − 3 V for natural dielectrics. Transistors with a thicker single-layer mango sap dielectric showed superior figures-of-merit compared to those using a thinner mango sap dielectric layer, including higher mobility and I_on/off current and smaller SS. Such natural, biodegradable plant saps are promising future dielectric materials for the sustainable fabrication of low-voltage electronic devices.