The origin of slow electron recombination processes in dye-sensitized solar cells with alumina barrier coatings
We investigate the effect of a thin alumina coating of nanocrystalline TiO2 films on recombination dynamics of dye-sensitized solar cells. Both coated and uncoated cells were measured by a combination of techniques: transient absorption spectroscopy, electrochemical impedance spectroscopy, and open-circuit voltage decay. It is found that the alumina barrier reduces the recombination of photoinjected electrons to both dye cations and the oxidized redox couple. It is proposed that this observed retardation can be attributed primarily to two effects: almost complete passivation of surface trap states in TiO2 that are able to inject electrons to acceptor species, and slowing down by a factor of…
Determination of electron and hole energy levels in mesoporous nanocrystalline TiO2 solid-state dye solar cell
A study of a hybrid heterojunction solar cell based on nanocrystalline mesoporous TiO2 and the hole conductor spiro-OMeTAD (2,2′7,7′-tetrakis(N,N′-di-p-methoxyphenyl-amine)-9,9′-spiro-bifluorene) has been realized. Impedance and cyclic voltammetry techniques were used to measure the interfacial properties of the hybrid heterojunction and establish the energy levels of the solid-state electrolyte. It was observed that the energy levels of the organic hole transport material are changed when it forms a film deposited onto indium-doped tin oxide (ITO). Moreover, the HOMO level of the mono oxidized spiro-OMeTAD is well coupled with the HOMO level of the dye N719 (Ru(4,4′-dicarboxy-2,2′-bipyridy…