The transparent and low-cost nature of dye-sensitised solar cells (DSCs) affords them niche prospects for electricity-generating windows in buildings for energy-sustainable future cities. Despite their vast industrial potential, innovation is being held up by a lack of suitable dyes. Better dyes can only be realised if we can better understand how the dye...TiO2 interface of a working electrode in a DSC functions at the molecular level. To this end, we propose to study this interfacial structure (dye adsorption modes, interdye separation and dye/TiO2 tilt angles) of three high-performance DSC dyes on TiO2 surfaces in solar cell conditions, and relate this structure to the photovoltaic properties of the associated device. The structure-function relationships established will act as molecular design rules to guide the molecular engineering of new dyes that offer superior DSC performance.