Photoconductivity of Self-Assembled Hexabenzocoronene Nanotube: Insight into the Charge Carrier Mobilities on Local and Long-Range Scales

We performed kinetic study on the photoconductivity of coassembled nanotubes consisting of an amphiphilic hexa-peri-benzocoronene (HBC) and a HBC derivative appended with an electron-accepting trinitrofluorenone (TNF) moiety. The transient signals measured by flash-photolysis time-resolved microwave conductivity (FP-TRMC) were analyzed with a modified analytical solution of a first- and second-order differential equation. On the basis of charge-carrier generation efficiency independently determined by transient absorption spectroscopy (TAS), we simultaneously assessed the local and long-range charge carrier mobilities of the coassembled nanotubes. The former was found to be 3 cm(2) V-1 s(-1) for the coassemblies but dropped to 0.7 cm(2) V-1 s(-1) at HBC-TNF = 100% due to lowering of a structural integrity of pi-stacked HBC arrays. In contrast, the latter was <1.5 x 10(-4) cm(2) V-1 s(-1) and monotonically decreased when the HBC-TNF content was increased. Discussion would be of help in the better understanding of the electrical property of self-assembled organic nanoelectronics.