Organic Electronics: Sensors with a flexible future
In the “Internet of things” era, electronics are embedded in objects and transfer data without human intervention. BP monitoring bands, non-contact cardiac sensors, glucose monitoring medical sensors, driverless cars and electronic wallpaper and gadgets are slowly refining and evolving our lifestyle. Well, these are probably just a few of the possible future applications that are being enabled by solution processible/printable electronic and opto-electronic materials.
The availability of softer materials such as organics and polymers which respond to light and emit light, accompanied by reasonable electrical transport properties provide us with options in the world dominated silicon electronics. There has been growing need for niche applications where there are requirements for flexible-stretchable-bendable smart sensors and display elements.
With the aim to provide an alternative to the conventional silicon based silicon photo-detector approach, researchers at Jawaharlal Nehru Center for Advanced Scientific Research (JNCASR) have used a light-sensitive organic compound while the read-out electronics have been fabricated on a polymer organic thin-film transistor backplane. By developing an integrated organic electronic component similar to a CMOS pixel fabricated by printing methods for image sensing applications, Prof. K S Narayan’s lab at the Chemistry and Physics of Material Unit (CPMU) department of JNCASR have made strides in combining organic thin-cell transistor backplane with a organic photodiode layer which is printed on polymer substrate. Since the components of the organic circuit are deposited from solution phase, they can be sprayed or coated on flexible or stretchable substrates. In a recent article that was published in Applied Physics Letters, the researchers have shown that the optoelectronic response of the photodiode (with polymer based semiconductors) was large and sufficient to control the field effect transistor consisting of the polymer semiconductor. The highlight of the results is the demonstration of an organic electronics circuit with an efficient light sensing photodiode and a low turn-ON field effect transistor (FET). It was shown that the output characteristics of the FET were dependent on the light-level incident on the photodiode.
Prof. Narayan says “the possibility of fabricating circuits by simple dispensing methods with response equivalent to elaborate Si based structures which require complex manufacturing requirements is interesting, and the added features of such devices over large-area on non-rigid and flexible substrates provides some exciting applications in life sciences and ambient electronics sensors. We have some novel strategies to further increase the spatial resolution and the sensitivity of the organic pixel element.”
We have developed a method of spraying or coating of the polymer based substrates, and we believe the method will enable distributed sensor arrays over larger areas than that achievable for silicon-based processes. We will be interested in fabricating a large-area prototype and explore the feasibility in real world applications noted Ms. Swati, PhD scholar in Prof. Narayan’s lab. who spearheads this activity.
This article is authored by Kripa V. Jalapathy, Technical Research Center (TRC), JNCASR.
- Swathi, and K. S. Narayan Image pixel device using integrated organic electronic components Appl. Phys. Lett. 109, 193302 (2016)
- Swathi, K.S. Narayan, Solution processed integrated pixel element for an imaging device, Proc. SPIE 9944, Organic Sensors and Bioelectronics IX, 99440T (September 27, 2016)