Influence of one-dimensional TiO2 nanotube on interfacial electron transfer in dye-sensitized solar cells: Insights from theoretical investigation

Abstract

A theoretical study has been carried out on the composed systems of two different kinds of dye molecules (bearing the carboxylate and the hydroxamate anchors, respectively) and TiO2 nanotubes (TiO2 NTs). Our results show that the structure of (12,0) TiO2 NT is similar to that of anatase, while the (0,4) TiO2 NT shows obvious structural deformation along the direction that is vertical to the axis of nanotube. Compared with carboxylate anchor, the highly water-stable hydroxamate anchor exhibits better light-harvesting ability. In addition, the hydroxamate anchor group also exhibits a slightly stronger binding to the TiO2 NT surface than the carboxylate anchor group. The interfacial electron transfer (IET) dynamics reveal that both of the two TiO2 NTs can provide much faster and more complete IET as compared with bulk TiO2. The plots of electronic isosurfaces show different electron transfer mechanisms for (12,0) and (0,4) TiO2 NTs. In (12,0) TiO2 NT, the optical-excited electrons can transfer on the surface of the nanotube with directions both parallel and vertical to the nanotube axis. While for (0,4) TiO2 NT, the electrons can only transfer on the surface along the nanotube axis. Our study is expected to promote the further development of such one dimensional nanotube in enhancing performance of DSSCs and in other optical-excited related applications.