The role of water in the device performance of n-type PTCDI-C8 organic field-effect transistors with solution-based gelatin dielectric

• Gelatin is a very good bio-dielectric for n-type PTCDI-C8 OFETs.
• The μFE,sat value increases from 0.22 cm2 V−1 s−1 in vacuum to 0.74 cm2 V−1 s−1 in air.
• The VT value reduces from 55 V in vacuum to 2.6 V in air.
• H3O+ and OH− mobile ions and immobile charged side chains may form in gelatin in air.
• Generation of charged ions in gelatin well explain the device performance in air.

Gelatin is a natural protein, which works well as the gate dielectric for N,N-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8) organic field-effect transistors (OFETs). An aqueous solution process was applied to form the gelatin gate dielectric on poly(ethylene terephthalate) (PET) by spin-coating and subsequent casting. The field-effect mobility in the saturation regime (μFE,sat) and the threshold voltage (VT) values of a typical 40 nm PTCDI-C8 OFET are (0.22 cm2 V−1 s−1, 55 V) in vacuum and (0.74 cm2 V−1 s−1, 2.6 V) in air ambient. The maximum voltage shift in hysteresis is also reduced from 10 V to 2 V when the operation environment for PTCDI-C8 OFETs is changed from vacuum to air ambient. Nevertheless, a slight reduction of electron mobility was found when the device was stressed in the air ambient. The change in the device performance has been attributed to the charged ions generation owing to water absorption in gelatin in air ambient.

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