Researchers at Linköping University have demonstrated that the material employed in organic solar cells can also serve as light sensors in electronic devices. Their innovative sensor is capable of detecting circularly polarized red light.
Rui Zhang, a postdoc fellow at IFM is one of the principal authors of the article published in Nature Photonics. Image Credit: Olov Planthaber
Their study, published in Nature Photonics, sets the stage for more dependable self-driving vehicles and other uses where night vision is significant.
Certain beetles, firefly larvae, and vibrant mantis shrimps exhibit the ability to reflect a unique form of light called circularly polarized light. This optical phenomenon arises from minuscule structures within their shells that interact with electromagnetic light waves in a distinctive manner.
Circularly polarized light finds numerous practical applications in fields such as satellite communication, bioimaging, and various sensing technologies. Its significance lies in the fact that circularly polarized light encodes a wealth of information as the electromagnetic field surrounding the light beam spirals either in a rightward or leftward direction.
The Entire Visible Light Spectrum
Detecting circularly polarized light requires a material capable of discerning the direction of the spiral twist.
Presently, materials exist that can perceive and decipher circularly polarized light across nearly the entire visible light spectrum, with the exception of the near-infrared region. However, researchers at Linköping University have recently harnessed a material typically utilized in organic solar cells to capture these specific light wavelengths.
Constructing high-quality sensors that can detect circularly polarising light in the near-infrared spectrum has long been a challenge. But thanks to further development of a material normally used in solar cells, we can now detect circularly polarised light across the entire visible light spectrum.
Feng Gao, Professor, Department of Physics, Chemistry and Biology, Linköping University
This breakthrough opens doors to technical innovations in situations where night vision is crucial, notably in applications like self-driving cars. The lightweight nature of the material and the straightforward manufacturing process render it ideal for incorporation into compact and cost-effective sensor systems.
Examine Different Materials
The solar cell material is composed of polymers, which are long chains of carbohydrates. It can possess a molecular structure, either spherical, known as fullerene, or a different structure, leading to it being referred to as non-fullerene.
In the current study performed, the material used is of the non-fullerene variety, and this choice has proven advantageous not only in solar cells but also in other applications like light sensors.
The material’s capacity to detect circularly polarized light stems from its chirality, which determines how the molecules interact with light.
Chirality in molecules can be likened to a pair of hands: one’s right hand and one’s left hand share the same basic structure but are mirror images of each other, exhibiting slightly different properties. Thanks to chirality, diverse molecules can differentiate whether electromagnetic radiation spirals to the right or to the left.
The next step is to expand these trials to include several different materials and examine how molecules and light interact in them. This way, we hope to be able to increase effectivity.
Li Wan, Postdoc Fellow, Department of Physics, Chemistry and Biology, Linköping University
Rui Zhang, also a postdoc fellow at IFM added, “The packing control between molecules could be very important.”
The study was financially supported by the Knut and Alice Wallenberg Foundation, through the Swedish Government Research Area in Materials Science on Functional Materials, AFM, at Linköping University, and from the Swedish Foundation for Strategic Research.
Journal Reference
Wan, L., et al. (2023) Sensitive near-infrared circularly polarized light detection via non-fullerene acceptor blends. Nature Photonics. doi.org/10.1038/s41566-023-01230-z.