Organic Field-Effect Transistor-Based Ultrafast, Flexible, Physiological-Temperature Sensors with Hexagonal Barium Titanate Nanocrystals in Amorphous Matrix as Sensing Material

Abstract

Organic field-effect transistors (OFETs) with hexagonal barium titanate nanocrystals (h-BTNCs) in amorphous matrix as one of the bilayer dielectric systems have been fabricated on a highly flexible 10 μm thick poly(ethylene terephthalate) substrate. The device current and mobility remain constant up to a bending radius of 4 mm, which makes the substrate suitable for wearable e-skin applications. h-BTNC films are found to be highly temperature-sensitive, and the OFETs designed based on this material showed ultraprecision measurement (∼4.3 mK), low power (∼1 μW at 1.2 V operating voltage), and ultrafast response (∼24 ms) in sensing temperature over a range of 20−45 °C continuously. The sensors are highly stable around body temperature and work at various extreme conditions, such as under water and in solutions of different pH values and various salt concentrations. These properties make this sensor unique and highly suitable for various healthcare and other applications, wherein a small variation of temperature around this temperature range is required to be measured at an ultrahigh speed.

Low Operating Voltage Organic Field-Effect Transistors with Gelatin as a Moisture-Induced Ionic Dielectric Layer: The Issues of High Carrier Mobility

“…The surface roughness of each of the layers has been characterized using AFM after the subsequent growth of the layer. The measured roughness of Al and Al 2 O 3 layers were 2.6 and 3.9 nm, as reported in our previous work, respectively . The roughness of the spin-coated gelatin film on top of the anodized Al gate electrode is about 0.8 nm.…”

“…The measured roughness of Al and Al 2 O 3 layers were 2.6 and 3.9 nm, as reported in our previous work, respectively. 7 The roughness of the spin-coated gelatin film on top of the anodized Al gate electrode is about 0.8 nm. The pentacene film of 20 (±5) nm thickness was grown as a semiconducting layer on top of the dielectric system.…”

“…In recent years, organic field-effect transistors (OFETs) have shown considerable attention due to their suitability in various fields of flexible electronics such as display, , electronic skin, , radio frequency identification tag (RFID), , and a broad range of various wearable sensors. − However, the performance of such devices is limited to their lower field-effect carrier mobility and high operating voltage. The carrier mobility of OFETs crucially depends on the crystallinity of the semiconductor film and the charge trapping at the gate dielectric/semiconductor interface. , The crystallinity of organic thin films is fundamentally poor due to the weak π–π interaction between the molecules leading to inefficient charge transport through the film.…”

When Flexible Organic Field‐Effect Transistors Meet Biomimetics: A Prospective View of the Internet of Things

“…In 1994, Garnier et al fabricated the first all-polymer FET (including the electrodes) realized by printing techniques, where polyester was chosen as the dielectric layer and an adhesive tape worked as the substrate. [36] Tremendous exploration in flexible OFETs has been conducted ever since then, including modification of the molecular structure and design of new molecules, [37][38][39][40][41][42] devising of new device geometry like the hybrid system, [43][44][45][46][47] and development of new fabrication processes exemplified by ultrathin film fabrication. [48][49][50][51] Here, in terms of flexibility, we mainly focus on polymer molecules which are naturally flexible property and we also explore some typical organic small molecules.…”

Temperature Sensors Based on Organic Field-Effect Transistors

“…Mandal et al incorporated hexagonal barium titanate nanocrystals (h-BTNCs) as a dielectric film and pentacene as the channel layer to fabricate ultrafast, flexible OFET temperature sensor devices [70]. The perovskite BaTiO 3 is a ferroelectric material with its ferroelectric property originated from the crystal structure distortion upon temperature change.…”