IIT-B develops ultra-thin optical sensor for wearable electronics

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Published on Jul 19, 2020 11:21 PM IST
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ByPriyanka Sahoo, Mumbai

A team of researchers from Indian Institute of Technology-Bombay (IIT-B) developed an ultra-thin next-generation optical sensor prototype that can be used for applications such as bioimaging, wearable electronics, environmental monitoring, defence and telecommunications.

Optical sensors, such as photodetectors, can convert rays of light into electronic signals. These sensors are used as optical switches in telecommunication, for capturing images in defence and biomedical equipment, as toxic gas monitors for pollution control, as well as photovoltaic cells for renewable power generation.

However, conventional optical sensors currently in use are made from thick silicon or III-V compound semiconductors which make them power hungry. Hence, they are difficult to use in emerging applications such as wearable devices, flexible electronics, and multi-sensor networks for the internet-of-things (IoT).

The researchers at IIT-B, led by Saurabh Lodha, professor, department of electrical engineering, designed a prototype of ultra-thin optical sensors using graphene-like two-dimensional (2D) materials that has high optical sensitivity and can also generate power. The prototype overcomes the limitations of conventional optical sensors owing to the exceptional electronic, mechanical, and optical properties of these 2D materials.

Their study was published in the American Chemical Society’s monthly peer-reviewed journal Nano Letters in February.

“We conductedseveral rounds of theoretical calculations before we started work on the prototype. The thickness of the materials was critical. We found that two specific materials from the graphene family, when stacked on top of each other with the right thicknesses, form a heterojunction that results in excellent optoelectronic performance and enables broadband light detection from visible to infra-red, which is not possible with the individual materials,” said Lodha, the principal investigator of the project.

“The recent work from IIT-B is of great interest to the device community; it is expected to give a new direction to this field because it exploits the light sensing and energy harvesting potential at the junction of two dissimilar 2D materials which are just a few atomic layers thin. We call it “interlayer band gap” and, to my knowledge, no one has investigated or reported it earlier to show promising solar cell behaviour and ultrafast photodetectors,” said Digbijoy Nath, assistant professor, Centre for Nano Science and Engineering (CeNSE) at the Indian Institute of Science (IISc), Bangalore, who was not a part of the research.

The theoretical calculations were conducted at IIT-B with inputs from Monash University, Australia, and the prototype was fabricated at IIT-B’s Nanofabrication Facility. Key theoretical predictions of the sensors were experimentally verified in collaboration with the Tata Institute of Fundamental Research, Mumbai, said Abin Varghese, PhD student and first author of the study.

“Most of the research on photodetection using low-dimensional materials focusses on enhancing one or two performance parameters, typically at the expense of other metrics. However, it is the multi-functional excellence of this heterostructure platform that makes it promising and brings us a step closer to the real-world technologies”, said Lodha.

“In the future, we plan to take this work forward from lab-to-fab using wafer-scale material growth techniques. Then, we plan to integrate optical, gas and thermal sensors to build an energy-efficient IoT sensor network,” he added.

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