Optimizing molecule-like gold clusters for light energy conversion

Atomically precise gold clusters that are less than similar to 1 nm in diameter are emerging as a new class of light absorbing material for harvesting solar energy. Herein, we explore the size dependent properties of glutathione-protected clusters, (Au(25)GSH(18), Au(18)GSH(14), Au(15)GSH(13) and Au(11)GSH(11)) in sensitizing mesoscopic TiO2 films. The excited state properties of gold clusters are correlated with the photovoltaic performance of metal cluster sensitized solar cell. Au18GSH14 exhibit the highest photoconversion efficiency. The size dependent photovoltaic results are rationalized based on optimizing both the light absorption of the clusters as well as the size dependent excited state behavior.