- The study, published in Advanced Materials, reports organic photodetectors that detect light below its absorption band and with a high efficiency
- The presented devices demonstrate a wide spectroscopic photodetection and compactness of the device, making them much more portable and suitable for integrated electronics applications
- The study was carried out by ICMAB researchers in collaboration with researchers from Dresden (Germany) and from Beijing (China).
The active layer of the photodetectors is formed by two types of organic molecules that act simultaneously, exchanging the electrical charge between them. The absorption of light by these molecules, although very weak, can occur in a wide range of the electromagnetic spectrum, from the UV to the infrared.
The wavelength absorbed is adjusted by changing the thickness of the optical cavity. If the absorption of the molecules was very intense or occupied a wide range, the desired absorbed frequency could not be changed so accurately.
Current inorganic commercial detectors absorb light between the energy bands, and organic ones use the absorption of a single molecule, which is why they are more difficult to synthesize, occupy much more volume, and cannot adjust to different wavelengths. In this study, a photodetector that does not depend on the chemical structure of the molecules, but on the interaction between the two species is obtained, which can be modified based on the geometry of the device.
A possible application of these photodetectors, featured in the article, is a mini-UV-Vis spectrophotometer, used as a portable detector. The device of a few centimeters in length is used as a current UV-Vis spectrophotometer. Other potential uses are in the field of integrated electronics, in lab-on-a-chip applications, in colorimetry, or in thermal sensors, which require devices much smaller and portable than the current ones.
The study, funded by the European Research Council (ERC) and the Severo Ochoa project of the ICMAB, was carried out by ICMAB researchers in collaboration with the Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and the Institute for Applied Physics of the Technische Universität Dresden (Germany) and the Beijing National Laboratory for Molecular Sciences (China).
Polymer:Fullerene Bimolecular Crystals for Near-Infrared Spectroscopic Photodetectors. Zheng Tang, Zaifei Ma, Antonio Sánchez-Díaz, Sascha Ullbrich, Yuan Liu, Bernhard Siegmund, Andreas Mischok, Karl Leo, Mariano Campoy-Quiles, Weiwei Li, and Koen Vandewal. Advanced Materials, 2017, 1702184
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