Showing papers by "Michael Grätzel published in 1991"

A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films

Abstract: THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.

The Artificial Leaf, Molecular Photovoltaics Achieve Efficient Generation of Electricity from Sunlight

Abstract: A new molecular photovoltaic system for solar light harvesting and conversion to electricity has been developed. It is based on the spectral sensitization of a thin ceramic membrane by suitable transition metal complexes. The film consists of nanometer-sized colloidal titanium dioxide particles sintered together to allow for charge carrier transport. When derivatized with a suitable chromophore these membranes give extraordinary efficiencies for the conversion of incident photons into electric current, exceeding 90% for certain transition metal complexes within the wavelength range of their absorption band. The present paper discusses the underlying physical principles of these astonishing findings. Exploiting this discovery, we have developed a new type of photovoltaic device whose overall light to electric energy conversion yield is 11% in diffuse daylight and 6% under direct (AM1) solar irradiation.

Ground- and excited-state properties of some ligand-bridged ruthenium(II) polypyridyl complexes with spectator-ligand-based emission

Abstract: From an examination of the absorption, luminescence and redox properties, the lowest excited state of the ligand-bridged polypyridyl complexes [{Ru(biq)2}2(dpp)]4+ and [(bipy)2Ru(dpp)Ru(biq)2]4+[dpp = 2,3-bis(2′-pyridyl)pyrazine, biq = 2,2′-biquinoline and bipy = 2,2′-bipyridine] is assigned to that of the charge-transfer type involving the spectator ligand biq.