Quantum yields for triplet formation have been determined for seven common π-conjugated polymers in benzene solution using time-resolved photoacoustic calorimetry (PAC) in conjunction with fluorescence quantum yields, singlet and triplet energies. The polymers studied include three poly(thiophenes), poly(2-methoxy,5-(2^′-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV), a cyano derivative of MEH-PPV, a ladder type poly(p-phenylene) (MeLPPP), and a poly(fluorene). Yields of singlet oxygen formation have also been determined for these polymers in benzene by time-resolved phosphorimetry, and are in reasonable agreement with triplet yields obtained by PAC. Polythiophenes show the highest intersystem crossing yields, which are suggested to result from extensive spin-orbit coupling. Where singlet oxygen yields are less than triplet yields, it is suggested that interaction of molecular oxygen with the ground state of the polymers may be involved.

This paper describes the synthesis of a new, yellow triphenylamine dye, 4-[2-(4-diphenylaminophenyl)vinyl]benzoic acid] (6), with a sorption maximum at 380 nm in solution for which EQE data show shifts to 420 nm on sorption to TiO₂. The performance of this dye has been measured in dye-sensitized solar cell (DSC) devices, showing η = 2.6% for 1 cm² devices. Light soaking of (6) shows excellent long-term stability with <10% variation in device performance over 1800 h. Full characterization data are reported for (6) and the intermediates used in its synthesis including single-crystal X-ray structural analysis of all compounds. The paper also describes the ultra-fast dye sensitization and co-sensitization of TiO₂ photo-electrodes in 5 minutes using one or two dyes and the first example of ultra-fast tri-sensitization. The dyes tested include the ruthenium dye N719, the squaraine dye SQ1, the red triphenylamine dye 2-cyano-3-{4-[2-(4-diphenylaminophenyl)vinyl]phenyl}acrylic acid (5) and (6). DSC efficiencies of 7.5% have been achieved for 1 cm² devices co-sensitized using (6) and N719. These efficiencies exceed those recorded for single dye devices and EQE measurements confirm efficient photon capture from two or more dyes in a single photo-electrode. Photo-acoustic calorimetry (PAC) has also been used to measure the energy of the charge separation states formed for (6) and N719, showing a larger value (1.47 eV) for (6) compared to N719 (1.08 eV), whilst a TiO₂ film co-sensitized with both (6) and N719 gave an intermediate value (1.28 eV). These data have been used to calculate dye HOMO, LUMO and λ_max levels for (6) and N719 leading to important insights for future successful co-sensitization.

5,10,15,20-Tetrakis(2,6-dichloro-3-chlorosulfophenyl)porphyrin and its tin and zinc complexes were synthesized with high yields and fully characterized. The corresponding water-soluble 5,10,15,20-tetrakis(2,6-dichloro-3-sulfophenyl)porphyrins were obtained by hydrolysis with water. An extensive photophysical study of the new water soluble porphyrinic compounds was carried out including absorption and fluorescence spectra, fluorescence quantum yields, triplet absorption spectra, triplet lifetimes, triplet and singlet oxygen quantum yields. These sensitizers were successfully used in the photodegradation of 4-chlorophenol and 2,6-dimethylphenol. A comparison is made of their efficiencies, and some mechanistic considerations are highlighted.