At DESY´s brilliant X-ray source PETRA III, An international team of researchers can see alive at the PETRA III X-ray light source the strong effect of ambient light on the production of organic semiconductors. This group, by researchers from the Technical University of Denmark, combined different research methods (Organic semiconductors love brightness) and found that semiconductors behave differently during the plating process under red light or in the dark, certain wavelengths, as in the latest issue of Advanced Functional Materials. The experiments show the possibility of controlling the morphology of organic semiconductor components during their production using visible light.
Organic semiconductors have the potential to replace their silicon predecessors in many applications. Organic LEDs (OLEDs) are already (Organic semiconductors love brightness) built into monitors as a standard, and solar cells already have similar functions in their siblings. However, the production process for solar cells, for example, which works like that is not useful. Therefore, their ongoing research and development is high on the scholars’ agenda.
A Danish-German research team has taken a closer look at the manufacturing process of a common organic semiconductor (poly(3-hexylthiophene) or P3HT), which is used for flexible solar cells and organic electronics. , for instance. Here, the photographic material is printed directly on the polymer film, which can be moved under the printing surface as on the press.
This process, called roll printing, can be used in the production process and increases production and reduces costs. When creating the active layer, scientists stimulated the semiconducting polymer using visible light of different wavelengths. The team was able to see live how colored light changes the structure of the polymer’s semiconducting units: while the polymer chains are ordered without light or under red light, they are give the system a small command while it is flashing. blue light. The latter hinders a high flow of electrons and thus creates a rather poor semiconductor material.
Using the PETRA III beamline P03, the researchers were able to observe how the polymer chains in a solution very quickly begin to “sort” and form ordered domains when they are in the dark or illuminated with red light. In contrast, when illuminated under green or blue light, the polymer chains stiffen, stimulated by the light. This hinders the emergence of domains or even breaks existing orders. Observations during roll-to-roll printing have confirmed this: the result is less ordered and differently structured films when the active layer is deposited under green or blue light. This affects the conductive properties of the material, which results in changes in charge mobility in different directions in the sheet.
The researchers explain the results by saying that green or even short-wavelength light stimulates the polymer in such a way that it interacts with the material. dissolved during production and therefore cannot move freely and organize within the sector during the drying process. This hypothesis is supported by theoretical simulations and measurements in neutron and terahertz spectroscopy. “Our results show a complete picture of the production of organic semiconductors, by showing the application of our method to the basic understanding of the change of morphology and physical properties of P3HT during coating,” said the director Researcher Jens Wenzel Andreasen said. Technical University of Denmark.
“We were able to show that organic semiconductors in the excited state select different configurations of particles by visible light and thus change the morphology,” says Matthias Schwartzkopf of the PETRA III P03 beamline. in addition, is an expert in monitoring live electronic systems. . “This may work in the design of solar cells and organic electronics in the future. For example, processing using red light similar to traditional photo development may be useful, depending on the behavior of the materials used.”
