Intra-molecular mobility of holes along rod-like helical Si backbones in optically active polysilanes

Intra-molecular mobility of positive charge carriers in poly(n-hexyl-[S]-2-methylbutylsilane) (PHMBS) films doped with N,N′-bis(2,5-di-tert-buthylphenyl)-3,4,9,10-perylenedicarboximide (PDI) is studied by time-resolved microwave conductivity (TRMC) measurements. PHMBS with optically active side chains has a rod-like tightly locked Si catenation with unlikely long persistence length compared with conventional dialkyl-substituted polysilanes. It was found that PDI is a suitable electron acceptor for PHMBS as it provides the high product of photo carrier generation yield ϕ as ∼0.08% under an excitation at 355 nm. The efficient electron transfer reaction from PHMBS to PDI gives clear conductivity transients ascribed to the positive charges on the Si catenation of PHMBS by TRMC measurements. The estimated value of isotropic mobility along the tightly locked Si catenation is 0.36 cm2 V−1 s−1, suggesting the presence of mobile holes on the backbones of PHMBS.