Green-light switching of Schottky-gated transistors made from phosphorylated cellulose nanofibers

In this study, we investigate the green-light switching effect of Schottky-gated metal–semiconductor field-effect transistors (MESFETs) fabricated using amorphous n-type phosphorylated cellulose nanofibers (PCNFs) with an electric conductivity of 0.61 mS/m, a carrier mobility of 16.33 cm2/V s, a work function of 5.31 eV, and optical transparency 91.7% at 640 nm. When the transparent PCNF-MESFET is irradiated with green light of wavelength = 490–550 nm, the Id–Vg amplification effect induced by gate modulation is suppressed to ∼1/32 of the maximum drain current. Electron spin resonance analysis, photoluminescence analysis, and first-principles density functional calculations show that this phenomenon is attributed to a reduction in mobile charge-transfer electrons and an effective increase in the depletion region associated with the loss of free electrons from oxygen atoms of hydroxyl radical (O9·H) in the phosphate group OPO3H2 under green-light irradiation. Broadband impedance analysis further suggests that interfacial capacitance associated with pseudo-solid water and electric double layer formation may also contribute to gate modulation. This green light switching phenomenon offers new possibilities for photoelectric electronics that are not possible with conventional opaque and poor mobility semiconductors and promises low-cost, abundant, and environmentally benign electronics.