IISc. scientists develop composite semiconductor for next-gen foldable phones and wearable devices

The composite semiconductor is made up of two materials – a water-insoluble polymer, such as ethyl cellulose that provides flexibility, and indium oxide, a semiconductor which brings in excellent electronic transport properties.

Scientists in the Department of Materials Engineering at the Indian Institute of Science (IISc.) have developed a super flexible, composite semiconductor material that can have possible applications in next-generation flexible or curved display and foldable phones, and in wearable electronics.

Traditional semiconductor devices – such as transistors, the building blocks of most electronic circuits – used in display units are either made of amorphous silicon or amorphous oxides, both of which are not flexible and strain tolerant.

According to IISc, adding polymers to the oxide semiconductors may increase their flexibility, but there is a limit to how much can be added without compromising the semiconductor’s performance.

In the current study, published in Advanced Materials Technologies, researchers have found a way to fabricate a composite containing a significant amount of polymer – up to 40% of the material weight – using a solution-process technique, specifically inkjet printing.

In contrast, previous studies have reported only up to 1-2% polymer addition. Interestingly, the approach enabled the semiconducting properties of the oxide semiconductor to remain unaltered with the polymer addition. The large quantity of polymer made the composite semiconductor highly flexible and foldable without deteriorating its performance.

The composite semiconductor is made up of two materials – a water-insoluble polymer, such as ethyl cellulose that provides flexibility, and indium oxide, a semiconductor which brings in excellent electronic transport properties.

To design the material, researchers mixed the polymer with the oxide precursor in such a way that interconnected oxide nanoparticle channels are formed (around phase-separated polymer islands) through which electrons can move from one end of a transistor (source) to the other (drain), ensuring a steady flow of current. The key to form these connected pathways, the researchers found, was the choice of the right kind of water-insoluble polymer that does not mix with the oxide lattice when the oxide semiconductor is being fabricated.