Box 19-1 Converting Light into Electricity

Earth s deserts receive 250-300 W/m2 of solar irradiance. If solar eneigy could be used with 10% efficiency, 4% of the sunlight falling on the deserts would provide all the energy used in the world in 2000. The solar cell17 described here has a conversion efficiency close to 7%. 

When Ru(II) sensitizer absorbs light, it is promoted to an excited state from which an electron is injected into the conduction band of the semiconductor Ti02 within —50 fs. This is one of the 

Sensitizer Ig/Pin bonded to low-vapor-pressure particles organic electrolyte F-doped I 

Essential features of a photocell based on sensitizer-coated nanometer-size Ti02 particles. 

Ru(II) — Ru(III) + e (injected into Ti02) e flows through circuit from tin oxide electrode to Pt at Pt electrode If + 2e — 31  

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