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Optimizing molecule-like gold clusters for light energy conversion

Though metal nanoparticles support plasmon absorptions, gold and silver clusters less than 1 nm in diameter have long lived molecule-like excited states.  The optical properties of gold clusters are primarily dependent on the number of gold atoms, and the choice of thiol used to stabilize of the cluster.  When measuring the efficiency of a light harvesting cell, the ability of a cell to absorb a large fraction of the solar spectrum and the ability of the excited state to transfer an excited electron to the TiO2 metal oxide support should be considered.  The efficiencies and photovoltaic performance of variously sized glutathione (GSH) protected gold clusters (Au25GSH18, Au18GSH14, Au15GSH13 and Au11GSH11) are investigated with respect to their abilities to absorb a broad spectrum of sunlight as well as their relative ability to convert absorbed photons into photocurrent.  From investigation, Au18GSH14 provides the highest solar cell efficiency as it combines good light absorption across the visible spectrum with a long excited-state lifetime, allowing for an increased circuit voltage. (Read More)