In a recent publication in the journal Advanced Materialsa team of physicists and chemists from the TU Dresden presents an organic thin-film sensor that describes a completely new way of determining the wavelength of light and achieves a spectral resolution of less than one nanometer. As integrated components, the thin-film sensors could make external spectrometers superfluous in the future. The new technology has already been patented.
Spectroscopy comprises a group of experimental methods that break down radiation according to a specific property, such as wavelength or mass. It is considered one of the most important analysis methods in research and industry. Spectrometers can determine colors (wavelengths) of light sources and are used as sensors in various applications such as medicine, mechanical engineering, the food industry and many more. Commercially available instruments are usually relatively large and very expensive. They are usually based on the principle of the prism or grating: light is refracted and assigned to the wavelength based on the angle of refraction.
At the Institute for Applied Physics (IAP) and the Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) of the TU Dresden, such sensor components based on organic semiconductors have been researched for years. With the spin-offs Senorics and PRUUVE, two technologies have already been developed to market maturity. Researchers at the IAP and IAPP, in cooperation with the Institute of Physical Chemistry, have now developed a thin-film sensor that describes a completely new way of determining the wavelength of light and, due to its small size and cost, has significant advantages over standard spectrometers.
The functional principle of the new sensors is as follows: Light of an unknown wavelength excites phosphors in a wafer-thin film. The film consists of a mixture of long-glow (phosphorescent) and short-glow (fluorescent) units that absorb the light of interest in different ways. The wavelength of the unknown input light can be deduced from the intensity of the afterglow.
“We use the fundamental physics of excited states in phosphors,” explains Anton Kirch, a doctoral student at the IAP. “In such a system, light of different wavelengths excites certain proportions of long-lived triplet and short-lived singlet spin states if the composition is correct. And we reverse that dependency. By identifying the spin fractions with a photodetector, we can identify wavelengths of light.” .”
“The great strength of our research network here in Dresden is our partners,” says Prof. Sebastian Reineke, who coordinated the project. “Together with the groups of Prof. Alexander Eychmüller from Physical Chemistry and Karl Leo, Professor of Optoelectronics, we can carry out all manufacturing and analysis steps ourselves, starting with the material synthesis and film processing through to the production of the organic detector. “
dr Johannes Benduhn is group leader for organic sensors and solar cells at the IAP: “To be honest, I was very impressed that a simple photoactive foil in combination with a photodetector can form such a high-resolution device.”
Using this strategy, scientists have achieved spectral resolution in the subnanometer range and have successfully tracked subtle changes in the wavelength of light sources. In addition to characterizing light sources, the new sensors can also be used to protect against counterfeiting. “With the small and inexpensive sensors, for example, banknotes or documents can be checked quickly and reliably for certain security features and thus their authenticity can be determined without expensive laboratory technology,” explains Anton Kirch.
Optical OPD sensors that reproduce any color
Anton Kirch et al, Accurate Wavelength Tracking by Exciton Spin Mixing, Advanced Materials (2022). DOI: 10.1002/adma.202205015
Provided by the Technical University of Dresden
Citation: Organic thin-film sensors for light-source analysis and anti-counterfeiting applications (2022, September 5), retrieved September 5, 2022 from https://phys.org/news/2022-09-thin-film-sensors -light-source-analysis-anti-counterfeiting.html
This document is protected by copyright. Except for fair trade for the purpose of private study or research, no part may be reproduced without written permission. The content is for informational purposes only.