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We designed and developed a new class of thiocyanate-free cyclometalated ruthenium sensitizers for sensitizing nanocrystalline TiO2 solar cells. This complex shows appreciably broad absorption range. Anchoring to nanocrystalline TiO2 films for light to electrical energy conversion in regenerative photoelectrochemical cells achieves efficient sensitization to TiO2 electrode. With this new sensitizer, there were a power conversion efficiency of 4.76%, a short-circuit photocurrent density of 11.21 mA/cm², an open-circuit voltage of 0.62 V, and a fill factor of 0.68 obtained under standard AM 1.5 sunlight. [ABSTRACT FROM AUTHOR]

Nanocrystalline rutile-anatase mixing phase TiO2 film was synthesized for dye-sensitized solar cells (DSCs). The mixing-phase nanocrystals, composed of 52 wt% rutile and 48 wt% anatase, contained nanorods with diameter of 20 nm and the length of more than 200 nm ascribed to rutile phase. The short circuit photocurrent of DSCs based on the rutile-anatase TiO2 nanocrystals was enhanced in comparison with that of DSCs based on anatase TiO2 because the light was effectively scattered by rutile nanorods in the mixing-phase TiO2 films. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline TiO2 colloids were prepared by hydrothermalization. The porosity and the size distribution of the particles increase with a longer hydrothermalization reaction period. The particle size decreases with lower reaction temperature. Electron transport in nanocrystalline TiO2 film electrodes sensitized with [NBu4]2[Ru(Htcterpy)(NCS)3] ([NBu4]+ =tetrabutylammonium cation; H3tcterpy=4,4′,4″-tricarboxy-2,4:2′,4′:2″-terpyridine) (black dye) was investigated from the standpoint of TiO2 particle properties such as particle size, size distribution, and porosity. When the size distribution and the porosity were comparable, the electron lifetime (τ rec) increased and the electron diffusion coefficient (D) decreased at smaller particle sizes. The value of D decreased when the porosity increased. Large differences in the diffusion length () among the TiO2 films were observed. However, J sc did not depend on L. Thus, we conclude that the J sc values were more effectively influenced by the absorption coefficient (α) than by L. [Copyright &y& Elsevier]

Compares the spectral, electrochemical and photoelectrochemical properties of nanocrystalline titanium dioxide with cis-bis(4-carboxy-2-[2'-(4'-carboxypyridyl)]quinoline)bis(thiocyanato-N) ruthenium(II). Absorbed photon-to-current conversion efficiency; Reverse electron transfer; Quantum yields of charge injection from ruthenium complexes to titanium dioxide.

cis-[Ru(Hmcpq)2(NCS)2] (1; Hmcpq=4-carboxy-2-(2′-pyridyl)quinoline) was newly synthesized, and its spectral (absorption, luminescence) and electrochemical properties were compared with those of cis-[Ru(H2dcpq)2(NCS)2] (2; H2dcpq=4-carboxy-2-[2′-(4′-carboxypyridyl)]quinoline). Solar cells based on nanocrystalline TiO2 film sensitized with 1 showed efficient photosensitization over a large portion of the visible and near-IR spectral region. These solar cells generated a large short-circuit photocurrent (12 mA cm−2), produced an open-circuit voltage of 0.53 V, and exhibited a solar energy conversion efficiency of 4.6% under simulated AM 1.5 solar irradiation (100 mW cm−2). The effects of the number of carboxyl groups in 1 and 2 on the binding to nanocrystalline TiO2 and on the photovoltaic performance of the solar cells were investigated. [Copyright &y& Elsevier]

We compared electron transport in nanocrystalline TiO2 films sensitized with [NBu4]2[cis-Ru(Hdcbpy)2(NCS)2] (N719; [NBu4]+ = tetrabutylammonium cation; H2dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and with [NBu4]2[Ru(Htcterpy)-(NCS)3] (B-dye; H3tcterpy = 4,4',4"-tricarboxy-2.2':6'.2"-terpyridine). The electron diffusion coefficient (D) and the electron lifetime (τ) of the N719-sensitized TiO2 were comparable to those of B-dye-sensitized TiO2, although the open circuit photovoltage (Voc) of the solar cells based on N719-sensitized TiO2 was ca. 60 mV larger than that of the solar cells based on B-dye-sensitized TiO2. We concluded that the energy of the conduction band edge (Ecb) of TiO2 sensitized with N719 was ca. 50mV more negative than that of TiO2 sensitized with B-dye. [ABSTRACT FROM AUTHOR]

We compared electron transport in nanocrystalline TiO2 films sensitized with [NBu4]2[cis-Ru(Hdcbpy)2(NCS)2] (N719; [NBu4]+ = tetrabutylammonium cation; H2dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and with [NBu4]2[Ru(Htcterpy)-(NCS)3] (B-dye; H3tcterpy = 4,4',4"-tricarboxy-2.2':6'.2"-terpyridine). The electron diffusion coefficient (D) and the electron lifetime (τ) of the N719-sensitized TiO2 were comparable to those of B-dye-sensitized TiO2, although the open circuit photovoltage (Voc) of the solar cells based on N719-sensitized TiO2 was ca. 60 mV larger than that of the solar cells based on B-dye-sensitized TiO2. We concluded that the energy of the conduction band edge (Ecb) of TiO2 sensitized with N719 was ca. 50mV more negative than that of TiO2 sensitized with B-dye. [ABSTRACT FROM AUTHOR]

The ethylenediamine Ru(II) tricarboxyterpyridine complex [Ru(tctpy)(en)(NCS)]Cl (1) was newly synthesized, and its photophysical and photovoltaic properties were characterized. Solar cells based on nanocrystalline TiO2 films sensitized with 1 exhibited efficient sensitization over the visible and near-infrared region. These solar cells generated a large short-circuit photocurrent of 17.7 mA cm-2 and an open-circuit potential of 0.68 V under simulated AM 1.5 solar irradiation (100 mW cm-2) with a solar energy conversion efficiency of 8.5%. [ABSTRACT FROM AUTHOR]

Abstract: To improve the performance of tris(isothiocyanato)-ruthenium(II)-2,2′:6′,2′′-terpyridine-4,4′,4″-tricarboxylic acid, tris-tetrabutylammonium salt (Black-dye) sensitized TiO2 solar cells, nanocrystalline TiO2 particles, which were used as film photoelectrodes, were synthesized from TiCl4 and ammonium carbonate. The resulting nanocrystalline TiO2 particles, which had a pure anatase crystal structure, had smaller surfaces areas, larger size distribution and mean size compared to nanoparticles prepared by the traditional method using titanium(IV) tetraisopropoxide (Ti(OCH(CH3)2)4) and HNO3. The dye-adsorbed TiO2 photoelectrode synthesized from TiCl4 and ammonium carbonate had a more thorough surface coverage of the Black-dye. The short circuit photocurrent density (J sc) and the incident monochromatic photon-to-electron conversion efficiency (IPCE) value of the cell using TiO2 prepared from TiCl4 were higher than that prepared from Ti(OCH(CH3)2)4. Consequently, the solar energy conversion efficiency (η) is 16% larger under AM 1.5 (1sun, 100mW/cm2). The characterizations of the TiO2 photoelectrode suggested that pure anatase crystallites, the less surface area and the more thorough surface coverage of the sensitizing dye enhance the absorbed photon to current efficiency (APCE) and the light harvesting efficiency (LHE), respectively, which improves the IPCE, J sc, and the η values. [Copyright &y& Elsevier]

Examines the dye sensitization of nanocrystalline titanium dioxide with square planar platinum(II) diimine dithiolate complexes. Assessment of charge-transfer absorption bands; Variation of molecular orbitals; Protonation of the carboxylate group.