Electron-phonon coupling in binary organic semiconducting crystals*

Semiconducting materials made from small organic molecules show great promise for applications in energy conversion, display technologies, and flexible electronics among many others. However, the electronic mobilities of these materials are much lower than traditional inorganic materials, which limits their application, and despite extensive research in this field, the fundamental processes that govern the generation and motion of charge in these materials is not completely understood. It is known that vibrational motions (phonons) in the material have a strong impact on the electronic, optical and transport properties. We explore a range of binary semiconducting single crystals made from two different small organic molecules, a donor and an acceptor, arranged in mixed stacks. We have completed resonance Raman measurements to quantify the electron-phonon coupling constants in these materials, which will give us information on the types of vibrational modes have a strong impact on charge transfer, and help in selecting and designing materials more suitable characteristics.