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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