High-performance flexible organic field-effect transistors with natural protein gelatin as a dielectric layer and solution-processed TIPS-pentacene as an active layer were fabricated on a flexible poly(ethyleneterephthalate) substrate. The fabricated devices exhibited high performance and electromechanical stability, demonstrating high field-effect mobility with near-zero threshold voltage and the I on to I off ratio approaching 10 5 with a low operating voltage of −5 V. Devices exhibited highly stable electrical characteristics under multiple transfer scan measurements. The flexible nature of these devices was tested through the tensile strain test by subjecting them to a 5 mm bending radius. High electromechanical stability was observed with minuscule variation in the electrical parameters under strain application. These flexible devices were demonstrated for circuit and sensing applications. Under the humidity exposure test, the devices responded quickly with rapid response and recovery time and acted as a humidity sensor. This property was utilized for real time health monitoring applications by testing these devices as a breath rate analyzer. In addition, to test the credibility of these flexible devices in circuit applications, the external load invertor circuits were demonstrated before and after applying strain to these devices.
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.
The use of natural material components in organic devices increases nature friendliness and biodegradability. In this paper, water-soluble natural protein gelatin is explored as a gate dielectric for demonstration of high performance and low voltage (-3V) operation in flexible organic field-effect transistors (OFETs). The fabricated p-channel devices showed excellent electrical characteristics of maximum field-effect mobility upto 3.0 cm2 V-1 s-1, high current on/off ratios, low subthreshold swing, and nearly zero threshold voltage due to the high-quality dielectric semiconductor interface achieved through optimized processes of fabricating flexible OFET devices. These devices exhibited very high operational stability as confirmed by various stability tests including bias-stress, repeatability, electromechanical stability, cyclic stability, and long-term ambient stability. For electromechanical stability, no significant changes in the performance were observed upon application of compressive and tensile strain due to bending. A very high environmental stability with almost unchanged electrical characteristics over 24 weeks was demonstrated. Further, circuit applicability was analyzed by switching characteristics from resistive load inverters. These results indicate gelatin as a promising biodegradable dielectric candidate for low voltage flexible OFETs.
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