Polaritons combine the best of two worlds. These hybrid particles combine light with organic material molecules, making them excellent energy transfer vessels for organic semiconductors. Because of their photonic origins, they are compatible with modern electronics and can move quickly.

Andrew Musser, Cornell University College of Arts and Sciences assistant professor of chemical biology and chemistry, discovered a way to control the speed of this energy flow. This “throttle” can move the polaritons from near standstill to something similar to the speed of light, increasing their range, and could lead to more efficient solar cells and sensors as well as LEDs.

The paper by the team, “Tuning Coherent Propagation Of Organic Exciton-Polaritons Through Dark State Delocalization,” appeared in the journal Advanced Science on April 27, 2022. Raj Pandya, University of Cambridge, is the lead author.

Musser and his colleagues from the University of Sheffield explored how to create polaritons using tiny sandwich structures of mirrors. These are called microcavities. They trap light and force it into interaction with excitons, which are mobile bundles of energy consisting of an electron-hole pair.

They have previously shown how microcavities are able to rescue organic semiconductors in “dark states”, where they don’t emit any light. This has implications for organic LEDs.

The team used laser pulses to monitor the energy moving within the microcavity structures. The team ran into a speed bump of their own. The complex nature of polaritons makes it difficult to interpret them.

“What we discovered was totally unexpected. Musser, senior author of the paper, said that they spent two years looking at the data and trying to figure out what it meant.

The researchers eventually realized that they could turbocharge the polaritons by adding more mirrors to the system and increasing the reflectivity of the microcavity resonance resonator.

He said, “The speed at which we were changing the motion of these particles was still basically unheard of in the literature.” We now have the ability to control how fast states can move by putting materials in these structures. We now have a clear plan for improving them.

Musser says that elementary excitations in organic materials move at a speed of about 10 nanometers per second, which is approximately equal to Usain Bolt’s world-champion sprinting speed.

He noted that while it may seem fast for humans, it is quite slow at the nanoscale.

Microcavity launches polaritons 100-thousand-times faster, a speed that is 1% slower than the speed of light. Although the transport takes a short time, the polaritons travel 50 times faster.

Musser stated that the absolute speed of a vehicle is not important. The distance is more important. If they can travel hundreds or thousands of nanometers, then when you reduce the device, say with terminals 10’s of Nanometers apart, that means they will get from A to B without any losses. That’s what it all boils down to.

Scientists, chemists, and material scientists are now closer to their goal of developing new, efficient devices and next-generation electronics that don’t suffer from overheating. You can achieve some interesting and exciting functionality at room temperatures with organic semiconductors. These same phenomena can be used to create new types of lasers, quantum simulators, and computers. If we understand these polariton particles better, there are many applications.