The Transport and Kinetics of Photogenerated Carriers in Colloidal Semiconductor Electrode Particles

The transport and kinetics of photogenerated majority and minority carriers in a spherical semiconductor particle of colloidal size are considered. The Poisson‐Boltzmann equation is solved for the sphere, and the potential distribution in the particle is obtained. The recombination of the carriers according to Hall‐Shockley‐Read kinetics gives rise to a number of different cases, for which equations describing the flux of photogenerated species in the external solution are obtained. Kinetic case diagrams show how the different cases are related to each other and how they depend upon such variables as the irradiance, the Fermi level in the electrolyte, the surface rate constants, and the radius of the particle. Three different strategies which could lead to devices for efficient solar energy conversion are found and discussed.