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The self-assembled monolayer (SAM)technique was employed to fabricate a two-layer donor–acceptorfilm on the surface of TiO2. The approach is based on usingdonor and acceptor compounds with anchoring groups of different lengths.The acceptor, a fullerene derivative, has a carboxyl anchor attachedto the fullerene moiety via a short linker that places the fullereneclose to the surface. The donor, a porphyrin derivative, is equippedwith a long linker that can penetrate between the fullerenes and keepporphyrin on top of the fullerene layer. The two-layer fullerene–porphyrinstructures were deposited on a mesoporous film of TiO2nanoparticlesby immersing the TiO2film sequentially into fullereneand porphyrin solutions. Transient absorption spectroscopy studiesof the samples revealed that after the selective photoexcitation ofporphyrin a fast (<5 ps) intermolecular electron transfer (ET)takes place from porphyrin to the fullerene layer, which confirmsthe formation of the interlayer donor–acceptor interface. Furthermore,in the second step of ET the fullerene anions donate electrons tothe TiO2nanoparticles. The latter reaction is relativelyslow with an average time constant of 230 ps. It involves roughlyhalf of the primary generated charges, and the second half relaxesby the interlayer charge recombination. The resulting state with aporphyrin cation and electron in TiO2has an extremelylong lifetime and recombines with an average time constant of 23 ms. [ABSTRACT FROM AUTHOR]