Journal article

Energy alignment and surface dipoles of rylene dyes adsorbed to TiO2 nanoparticles

The energy loss in dye-sensitized solar cells calcd. from the energy difference between the lowest electronic transition of the dye and the obtained open-circuit voltage is often 1 eV or even more. To minimize this loss, it is important to accurately det. the energy alignment at the TiO2/dye/redox-mediator interface. The authors compared the results from electrochem. and photoelectron spectroscopy for detg. the energy alignment of three rylene dyes, two of which absorb relatively far in the red. The trends obsd. with the methods were different, as in the former, the energy alignment is measured relative to an external ref. and includes contributions from solvent reorganization energies, while in the latter, it is measured relative to the energetics of the TiO2 and is lacking such contributions. The influence of the dyes' dipole moments on the energetics of the TiO2 was also measured and explained some of the differences in trends. Finally, the authors compared the injection efficiencies of the two red-absorbing dyes and found that the differences in injection efficiencies can be better explained using the energy alignment detd. from photoelectron spectroscopy. The method for measuring the energetics of a DSC should be chosen according to what process one intends to study.


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