Interface engineering for solid-state dye-sensitized nanocrystalline solar cells: The use of ion-solvating hole-transporting polymers

The control of interfacial charge transfer is central to the design of photovoltaic devices. This charge transfer is strongly dependent upon the local chemical environment at each interface. In this paper we report a methodology for the fabrication of a novel nanostructured multicomponent film, employing a dual-function supramolecular organic semiconductor to allow molecular-level control of the local chemical composition at a nanostructured inorganic/organic semiconductor heterojunction. The multicomponent film comprises a lithium ion doped dual-functional hole-transporting material (Li+-DFHTM), sandwiched between a dye-sensitized nanocrystalline TiO2 film and a mono-functional organic hole-transporting material (MFHTM). The DFHTM consists of a conjugated organic semiconductor with ion supporting side chains, designed to allow both electronic and ionic charge transport properties. The Li+-DFHTM layers provide a new and versatile way to control the interface electrostatics, and consequently the charge transfer, at a nanostructured dye-sensitized inorganic/organic semiconductor heterojunction.