Using transient absorption spectroscopy, we investigated the effects of 4-tert-butylpyridine (tBP) and Li ions on photoinduced electron injection efficiency in nanocrystalline TiO 2 films sensitized by black dye. The efficiency increased with the addition of Li ions but decreased with the addition of tBP molecules. These results indicate that a conduction band shift was induced by the solvation effect of the additives. Using recombination kinetic measurements, we examined that such a solvation effect was induced by the intercalation of Li ions into TiO 2 particles and by the adsorption of tBP on the TiO 2 surface. When both additives were used simultaneously, the efficiency was suppressed more than when only tBP was added. This difference in efficiency suggests that the local concentration of tBP near the TiO 2 surface increased with the addition of Li ions. This cooperative effect may have been caused by the formation of a complex between tBP and Li in solution. IntroductionSince highly efficient dye-sensitized solar cells (DSSCs) were first reported, 1 much research has been carried out to improve their performance. Solar cells consisting of N719 dye, in which two protons of N3 dye [cis-di(thiocyanato)-bis(2,2′-bipyridiyl-4,4′-dicarboxylate)ruthenium(II); Ru(dcbpy) 2 (NCS) 2 ] are replaced by tetrabutylammonium (TBA) cations, adsorbed on nanocrystalline TiO 2 films (N719/TiO 2 ) show high solar-energyto-electricity-conversion efficiency (η > 11%). 2 Black dye (BD; trithiocyanato(4,4′,4′′-tricarboxy-2,2′:6′,2′′-terpyridine)ruthenium(II); Ru(tcterpy)(NCS) 3 ) is also a promising sensitizer dye for DSSCs because its lowest unoccupied molecular orbital (LUMO) is located just above the conduction band of TiO 2 , and because its absorption edge is in the near-infrared range. [3][4][5] With further optimizations, such as the reduction of internal resistance and the preparation of a high-haze electrode, 6-8 η values greater than 11% can be achieved with BD-sensitized nanocrystalline TiO 2 (BD/TiO 2 ) DSSCs. 9 However, to further improve these DSSCs, more detailed knowledge of the mechanisms of DSSC processes, especially with regard to the electron injection mechanism, is required.To understand the primary processes that occur in DSSCs, the photophysical processes of dye-sensitized TiO 2 electrodes have been studied extensively by means of various experimental techniques. Electron injection, which is the most important primary process, has been studied mainly by means of transient absorption (TA) spectroscopy. 10-12 Electron injection dynamics can be studied by means of femtosecond TA measurements. For dye-sensitized films based on N3 and N719 complex dyes, nonexponential ultrafast electron injection has been observed in the 100-fs to 100-ps time range. 13-18 Furthermore, microsecond TA measurements are used to study the recombination

We tried the assignment of the origin of phosphorescent bands in Ir complexes. It is important to elucidate the luminescent mechanism in order to design organic light-emitting devices (OLEDs) besed on new materials. The Stokes shift between the phosphorescence and phosphorescence excitation spectra of Ir complexes such as fac-tris(2-phenylpyridine) iridium(III) [Ir(ppy) 3 ], fac-tris(2-(2-thienyl)pyridine) iridium(III) [Ir(thpy) 3 ], bis(2-phenylpyridine [Ir(bzq) 3 ] and bis [(4,6-difluorophenyl)pyridinato](picolinato) iridium(III) [FIrpic] was measured in a solution and (phenyl) 4 Sn at 6 K. The amount of Stokes shift corresponds to the nature of the lowest triplet state. We discovered that the amount of Stokes shift clearly differs depending on whether the lowest triplet state of each Ir complex is triplet metal-to-ligand charge transfer ( 3 MLCT) or 3 -Ã . Namely, the case of 3 MLCT shows a large shift, while the case of 3 -Ã shows a small shift. We also present the resolved phosphorescence and phosphorescence excitation spectra of Ir complexes in (phenyl) 4 Sn. The sharp bands were assigned to the 3 -Ã transition, and the broad bands were assigned to the 3 MLCT state. The nature of the lowest triplet state is also discussed on the basis of resolved spectra.

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A novel FRET based strategy for DNA sequence analysis utilising base-discriminating fluorescence (BDF) nucleoside, (Py)U/(2-Ant)U, as donor in the dual-labelled oligonucleotide probe is reported; a selective/specific emission from acceptor, was observed upon excitation at the donor, only when the opposite base of the "smart" fluorescently labeled BDF nucleoside, (Py)U/(2-Ant)U, is adenine on the complementary target sequence.