Photocurrent generation by benzoporphyrin films prepared by a solution process

Abstract

Tetrabenzoporphyrin films on indium-tin-oxide electrodes were prepared by continuous spin-coating of indium-tin-oxide electrodes with a soluble precursor, tetrabicyclo[2.2.2]octadiene-fused porphyrin, and subsequent thermal conversion of the precursor to tetrabenzoporphyrin by annealing the modified electrodes. When the tetrabenzoporhyrin-modified indium-tin-oxide working electrode was irradiated in a three-electrode system, using Pt as a counter electrode and Ag / Ag + as a reference electrode in the presence of hexyl viologen as an electron acceptor, a cathodic photocurrent was observed. A double layer structure consisting of tetrabenzoporphyrin and [6,6]-phenyl- C 61 butyric acid methyl ester (PCBM) films and a triple layer structure consisting of tetrabenzoporphyrin; a mixture of tetrabenzoporphyrin and PCBM; and PCBM films were also prepared on indium-tin-oxide electrodes by repeated spin-coating. The incident photon to photocurrent efficiency values of up to 6.8% were obtained for the triple layer structure, in which the mixed layer contained tetrabenzoporphyrin and PCBM molecules in a 7:3 ratio. Action spectra of the triple layer structure showed that visible light from 380 to 700 nm sensitized the system for photocurrent generation.