Muon spin relaxation study of spin dynamics in poly(triarylamine)

Organic semiconductors (OSCs) have been of great interest over the last couple of decades owing to their mechanic flexibility, ease of processing, high tuneability and availability. One area of OSCs that is of growing interest is polymers as they possess many of the desirable properties, in particular print processing and tunability of electronic properties, necessary for application in devices such as organic solar cells and the spin valves being engineered for hard disks and logic devices. Much focus has been given in recent years to the areas of research including the electron and hole dynamics, transport mechanisms and spin relaxation in OSCs in order to utilise them in novel organic devices. In this paper the µSR technique is applied to carry out an in depth study of the electron dynamics and spin relaxation in the commonly used Poly(triarylamine) polymer (PTAA). It is shown that the electron wavefunction can be considered localised to the aromatic rings providing a strong hyperfine coupling interaction with the muon. In addition the presence of an electron spin relaxation (eSR) is demonstratated that resembles that previously reported in the small organic molecule series