Diacetylene bridged triphenylamines as hole transport materials for solid state dye sensitized solar cells†
We have synthesized and characterized a series of triphenylamine-based hole-transport materials (HTMs), and studied their function in solid-state dye sensitized solar cells (ss-DSSCs). By increasing the electron-donating strength of functional groups (–H < –Me < –SMe < –OMe) we have systematically shifted the oxidation potential and ensuing photocurrent generation and open-circuit voltage of the solar cells. Correlating the electronic properties of the HTM to the device operation highlights a significant energy offset required between the Dye – HTM highest occupied molecular orbital (HOMO) energy levels. From this study, it is apparent that precise control and tuning of the oxidation potential is a necessity, and usually not achieved with most HTMs developed to date for ss-DSSCs. To significantly increase the efficiency of solid-state DSSCs understanding these properties, and implementing dye-HTM combinations to minimize the required HOMO offset is of central importance.