Multifunctional Flexible Organic Transistors with a High-k/Natural Protein Bilayer Gate Dielectric for Circuit and Sensing Applications

Abstract

Organic field-effect transistors (OFETs) have opened up new possibilities as key elements for skinlike intelligent systems, due to the capability of possessing multiple functionalities. Here, multifunctional OFET devices based on gelatin, a natural biopolymer gate dielectric, and TIPS-pentacene as an organic semiconductor are extensively explored. Gelatin is combined with a thin high-k HfO2 dielectric layer deposited by atomic layer deposition (ALD) to achieve a low leakage current and low-voltage operation. The natural biopolymer offers a better semiconductor:dielectric interface, leading to better charge conduction in the devices, along with an enhancement of sensing capabilities giving additional functionality. These fabricated flexible OFET devices exhibit excellent electrical characteristics with a high field-effect mobility reaching over 2 cm2/(V s) (extracted with C i at 1 kHz), a low subthreshold swing (SS) of ∼200 mV/dec, and a high current on–off (I on/I off) ratio at a low operating voltage of −5 V with excellent electrical and mechanical stability. Moreover, circuit and multiparameter sensing capabilities for visible and UV light, as well as for humidity and breath rate, have been successfully demonstrated for these devices. Our results indicate that these multifunctional OFET devices can open up a plethora of opportunities for practical applications such as real-time health and environmental monitoring.

Edible Dielectric Composite for the Enhancement of Performance and Electromechanical Stability of Eco-Friendly Flexible Organic Transistors

“…For the same, a 2 wt % chitosan solution in aqueous acetic acid was prepared by stirring at 50 °C for 6 h. Similarly, 10 wt % gelatin solution in DI water was prepared by stirring at 60 °C for 2.5 h. Both the prepared solutions were mixed with different gelatin/chitosan ratios, that is, with 10:0, 10:1, 10:5, and 10:10, and stirred for 1 h. These composite solutions were spin-coated at 2000 rpm for 60 s and annealed at room temperature for 24 h to form thin films of gelatin/chitosan edible dielectrics. TIPS-pentacene/PS blend was prepared and deposited over the dielectric film through drop-casting as explained earlier. , Finally, gold (Au) source/drain top contacts were deposited through shadow mask. Surface morphology for all dielectric composite films was investigated with the help of AFM images.…”

“…In addition, these dielectrics are not suitable for biodegradability. Significant contributions have been made by researchers through the development of entirely or partially biodegradable transistors using numerous edible or biopolymer dielectrics such as gelatin, cellulose, guanine, silk, adenine, chitosan, starch, dextran, and so forth. − However, considerable challenges still exist in the accomplishment of low voltage operated organic transistors with excellent electrical and operational endurance with these natural dielectric materials. ,, The use of pristine biopolymers generally results in low electromechanical stability in devices due to inherent polar hydrophilic functional groups in these biopolymers which cause the device to degrade rapidly . These hydrophilic groups can trap mobile charge carriers, constraining the performance with reduced drain current and induction of hysteresis .…”

“…The effect of enhanced properties of this composite is comprehensively investigated on various performance parameters for flexible organic transistors. For the same, different gelatin/chitosan ratios of 10:0, 10:1, 10:5, and 10:10 were explored in a combination of air-stable solution-processed semiconductor polymer blend TIPS-pentacene/polystyrene (PS) , for p-channel transistor performance. All types of fabricated devices exhibited excellent p-channel performance for −5 V operation.…”

A Sub‐20 nm Organic/Inorganic Hybrid Dielectric for Ultralow‐Power Organic Thin‐Film Transistor (OTFT) With Enhanced Operational Stability

“…As an alternative, organic/inorganic hybrid dielectric layers where polymer films were utilized as organic layers have also been suggested (Table S1, Supporting Information). [27][28][29][30][31][32][33][34][35][36][37][38] Polymeric layers with reliable insulating properties can provide a favorable interface with organic semiconductors, and thus, high-performance OTFTs have been demonstrated therewith. [41] Moreover, one of the most important advantages obtained from the polymer/inorganic hybrid layers is the improved operational stability of OTFTs.…”

“…[ 16,17 ] Along this line, various types of organic and inorganic hybrid dielectric materials have been investigated extensively to exploit the advantages from both organic and inorganic dielectric materials. [ 6,18–38 ] For example, inorganic dielectric materials such as aluminum oxide (AlO x ) and hafnium oxide (HfO x ) generally exhibited high dielectric constant as well as outstanding dielectric strength. [ 39 ] However, the abundant amount of hydroxyl groups on the surface of the oxide layer often generates unwanted trap sites, which thus impair the OTFT performance.…”