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Assessing the potential of new organic semiconductors via THz mobility spectroscopy

Organic semiconductors are rapidly becoming an established materials class in optoelectronic devices owing to their ready processing from liquid phase methods, which makes device fabrication straightforward and cheaper than traditional inorganic semiconductors. Their performance in a wide range of devices, such as light emitting diodes, sensors, memories and solar cells, is highly dependent on their electrical performance, for which a key figure of merit is their mobility (or speed divided by the applied electric field).


In the search for new and improved organic semiconductor materials, it is often challenging to measure the electrical mobility of candidate compounds, as this can require the time-consuming fabrication of test devices. Extracting the mobility from electrical measurements on devices is also complicated by numerous effects, including imperfect charge injection across the interfaces to metal contacts. Hence, non-contact measurements of the mobility via spectroscopic methods are an attractive means to rapidly assess the mobility without the need for device fabrication. The vibrational modes of the molecules and their crystals also significantly impact upon the electrical mobility. The THz and mid-infrared vibrational modes will therefore be studied and identified in order to full constrain how molecular and crystalline structure may alter the electrical functionality.


In this project you will become familiar with the experimental techniques and data analysis methods required to determine the mobility of organic semiconductors. You will be trained in the use of ultrafast lasers and terahertz (far infrared) radiation to probe the motion of electrons in semiconductors. Finally, you will explore the mobility of a state-of-the-art organic semiconductor from our industrial collaborator, Smartkem, in order to gain invaluable experience leading into PhD research in this area.