Light-induced charge separation in thin tetraphenyl-porphyrin layers deposited on Au

Y. ZIDON; YORAM SHAPIRA; TH. DITTRICH; L. OTERO

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

The American Physical Society

Año: 2007 vol. 75 p. 1 - 6

0163-1829

Charge separation processes in metal-free tetraphenyl-porphyrin H2TPP layers deposited on Au substrate have been studied using surface photovoltage spectroscopy. The results show that dissociation of excitons at the H2TPP/Au interface causes charge separation by holes escaping from the interface region. This interface features a potential barrier due to the ground state of the H2TPP being 0.81 eV below the Fermi level of the Au substrate. Surface photovoltage is built up by internal photoemission at the H2TPP/Au interface, which leads to electron injection into the H2TPP layer with a slow electron backtransfer. The latter is thermally activated with an activation energy of 0.4 eV, which can be attributed to negative polarons in H2TPP.