Photosensitization of novel ruthenium-functionalized photoconductive polymers: Effect of ruthenium complex as photosensitizer

• We synthesized PVK–Ru(phen)2(m-COOH)(PF6)2 complexes to enhance the photoconductivity.
• The photo-charge generation efficiency and photoconductivity was related with their metal-ligand charge transfer and intraligand charge transfer absorption spectra.
• PVK polymer containing 0.194 wt% Ru(phen)2(m-COOH)(PF6)2 shows a charge-generation quantum efficiency and photoconductivity of 1.69 × 10−4 at 100 V/μm and 1.15 pS/cm at 60 V/μm.

Owing to their efficient photo-charge generation, ruthenium derivatives are emerging as an important class of photosensitizers. Despite their promising characteristics, several deficiencies, such as the relatively low quantum yield and short lifetime of the lowest energy metal-ligand charge transfer, have limited their applications. Here, we present new photoconducting polymers that contain ruthenium complexes as a photosensitizer. Ru(phen)2(m-COOH)(PF6)2 complexes, which covalently bind the poly(N-vinyl carbazole) (PVK) side chain, provided a high quantum yield and sufficient lifetime of the lowest energy metal-ligand charge transfer state for photo-charge generation. A series of PVK–Ru(phen)2(m-COOH)(PF6)2 complexes were thus prepared with various concentrations of Ru. We employed a helium-neon (HeNe) laser (633 nm) and a xenon lamp to measure the photo-charge generation efficiency and photoconductivity of the studied complexes. The wavelength dependence of the photo-charge generation efficiency and photoconductivity was found to be similar to their metal-ligand charge transfer absorption spectra. This suggests that the Ru complexes can extend the photosensitivity of the conductive polymers to longer wavelengths due to the lowest metal-ligand charge transfer energy. The photo-charge generation efficiency and photoconductivity of these polymers was found to be greater than those of PVK–Ru-complex composites.