Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

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Dye-Sensitized Solar Cells

Excitonic solar cells1—including organic, hybrid organic–inorganic and dye-sensitized cells (DSCs)—are promising devices for inexpensive, large-scale solar energy conversion. The DSC is currently the most efficient2 and stable3 excitonic photocell. Central to this device is a thick nanoparticle film that provides a large surface area for the adsorption of light-harvesting molecules. However, nanoparticle DSCs rely on trap-limited diffusion for electron transport, a slow mechanism that can limit device efficiency, especially at longer wavelengths. Here we introduce a version of the dye-sensitized cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires. The nanowire anode is synthesized by mild aqueous chemistry and features a surface area up to one-fifth as large as a nanoparticle cell. The direct electrical pathways provided by the nanowires ensure the rapid collection of carriers generated throughout the device, and a full Sun efficiency of 1.5% is demonstrated, limited primarily by the surface area of the nanowire array.

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Nanowire dye-sensitized solar cells

Jenny Schneider,*,† Masaya Matsuoka,‡ Masato Takeuchi,‡ Jinlong Zhang, Yu Horiuchi,‡ Masakazu Anpo,‡ and Detlef W. Bahnemann*,† †Institut fur Technische Chemie, Leibniz Universitaẗ Hannover, Callinstrasse 3, D-30167 Hannover, Germany ‡Faculty of Engineering, Osaka Prefecture University, 1 Gakuen-cho, Sakai Osaka 599-8531, Japan Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China

Understanding TiO2 photocatalysis: mechanisms and materials.

The dye-sensitized solar cells (DSC) provides a technically and economically credible alternative concept to present day p–n junction photovoltaic devices. In contrast to the conventional systems where the semiconductor assume both the task of light absorption and charge carrier transport the two functions are separated here. Light is absorbed by a sensitizer, which is anchored to the surface of a wide band semiconductor. Charge separation takes place at the interface via photo-induced electron injection from the dye into the conduction band of the solid. Carriers are transported in the conduction band of the semiconductor to the charge collector. The use of sensitizers having a broad absorption band in conjunction with oxide films of nanocrstalline morphology permits to harvest a large fraction of sunlight. Nearly quantitative conversion of incident photon into electric current is achieved over a large spectral range extending from the UV to the near IR region. Overall solar (standard AM 1.5) to current conversion efficiencies (IPCE) over 10% have been reached. There are good prospects to produce these cells at lower cost than conventional devices. Here we present the current state of the field, discuss new concepts of the dye-sensitized nanocrystalline solar cell (DSC) including heterojunction variants and analyze the perspectives for the future development of the technology.

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Dye-sensitized Solar Cells

A new series of panchromatic ruthenium(II) sensitizers derived from carboxylated terpyridyl complexes of tris-thiocyanato Ru(II) have been developed. Black dye containing different degrees of protonation {(C2H5)3NH}[Ru(H3tcterpy)(NCS)3] 1, {(C4H9)4N}2[Ru(H2tcterpy)(NCS)3] 2, {(C4H9)4N}3[Ru(Htcterpy)(NCS)3] 3, and {(C4H9)4N}4[Ru(tcterpy)(NCS)3] 4 (tcterpy = 4,4‘,4‘ ‘-tricarboxy-2,2‘:6‘,2‘ ‘-terpyridine) have been synthesized and fully characterized by UV−vis, emission, IR, Raman, NMR, cyclic voltammetry, and X-ray diffraction studies. The crystal structure of complex 2 confirms the presence of a RuIIN6 central core derived from the terpyridine ligand and three N-bonded thiocyanates. Intermolecular H-bonding between carboxylates on neighboring terpyridines gives rise to 2-D H-bonded arrays. The absorption and emission maxima of the black dye show a bathochromic shift with decreasing pH and exhibit pH-dependent excited-state lifetimes. The red-shift of the emission maxima is due to better π-acceptor properti...

Engineering of Efficient Panchromatic Sensitizers for Nanocrystalline TiO2-Based Solar Cells

A new polynucleating ligand, 1,2,4,5-tetrakis(1,4,7-triazacyclonon-1-ylmethyl)benzene (Ldur), has been prepared and characterized as its dodecahydrobromide salt. Addition of base to an aqueous solution of this salt and 4 molar equivalents (m.e.) of a Ni(II) salt produces a mixture of bi- and trinuclear complexes, which can be separated by cation-exchange chromatography (CEC) and crystallized as [Ni2Ldur](ClO4)4·2H2O (1) and [Ni3Ldur(H2O)6](ClO4)6·9H2O (2). The “full capacity” tetranuclear complex, [Ni4Ldur(H2O)12](ClO4)8·8H2O (3), is obtained by slow addition of Ldur to a refluxing aqueous solution of excess Ni2+ ions, followed by CEC purification. Treatment of Ldur with 4 m.e. of a copper(II) salt produces exclusively the tetranuclear complex, [Cu4Ldur(H2O)8](ClO4)8·9H2O (4), while reaction with only 2 m.e. of Cu2+ ions yields the binuclear complex, [Cu2Ldur](ClO4)4·4H2O (5). The X-ray structures of complexes 1, 2, 4, and [Cu2Ldur](ClO4)4·3H2O (5‘) have been determined; all are monoclinic, P21/c:  for 1,...

Coordination chemistry of a novel tetramacrocyclic ligand derived from 1,4,7-triazacyclononane: synthesis, structure, and properties of nickel(II) and copper(II) complexes.

The reactions of bidentate diimine ligands (L2) with binuclear [Ru(L1)(CO)Cl2]2 complexes [L1 ≠ L2 = 2,2‘-bipyridine (bpy), 4,4‘-dimethyl-2,2‘-bipyridine (4,4‘-Me2bpy), 5,5‘-dimethyl-2,2‘-bipyridine (5,5‘-Me2bpy), 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (4,7-Me2phen), 5,6-dimethyl-1,10-phenanthroline (5,6-Me2phen), di(2-pyridyl)ketone (dpk), di(2-pyridyl)amine (dpa)] result in cleavage of the dichloride bridge and the formation of cationic [Ru(L1)(L2)(CO)Cl]+ complexes. In addition to spectroscopic characterization, the structures of the [Ru(bpy)(phen)(CO)Cl]+, [Ru(4,4‘-Me2bpy)(5,6-Me2phen)(CO)Cl]+ (as two polymorphs), [Ru(4,4‘-Me2bpy)(4,7-Me2phen)(CO)Cl]+, [Ru(bpy)(dpa)(CO)Cl]+, [Ru(5,5‘-Me2bpy)(dpa)(CO)Cl]+, [Ru(bpy)(dpk)(CO)Cl]+, and [Ru(4,4‘-Me2bpy)(dpk)(CO)Cl]+ cations were confirmed by single crystal X-ray diffraction studies. In each case, the structurally characterized complex had the carbonyl ligand trans to a nitrogen from the incoming diimine ligand, these complexes corresp...

Synthesis of Heteroleptic Bis(diimine)carbonylchlororuthenium(II) Complexes from Photodecarbonylated Precursors

We report two new synthetic routes to the dinuclear Ru(I) complexes, [RuI2(RCO2)(CO)4(N∧N)2]+ (N∧N = 2,2‘-bipyridine or 1,10-phenanthroline derivatives) that use RuCl3·3H2O as a starting material. Direct addition of the bidentate diimine ligand to a methanolic solution of [Ru(CO)2Cl2]n and sodium acetate yielded a mixture of [RuI2(MeCO2)(CO)4(N∧N)2]+ (N∧N = 4,4‘-dmbpy, and 5,6-dmphen), and [RuII(MeCO2)2(CO)2(N∧N)] (N∧N = 4,4‘-dmbpy and 5,5‘-dmbpy). Single-crystal X-ray studies confirmed that the Ru(II) complexes had a trans-acetate−cis-carbonyl arrangement of the ligands. In contrast, the use of sodium benzoate resulted in the unexpected formation of a Ru−C bond producing ortho-cyclometalated complexes, [RuII(O2CC6H4)(CO)2(N∧N)], where N∧N = bpy or phen. A second approach used ligand exchange between a bidentate ligand (N∧N) and the pyridine ligands of [RuI(RCO2)(CO)2(py)]2 to convert these neutral complexes into [RuI2(RCO2)(CO)4(N∧N)2]+. This method, although it involved more steps, was applicable for a ...

Leone Spiccia

Papers

Engineering of Efficient Panchromatic Sensitizers for Nanocrystalline TiO2-Based Solar Cells

Coordination chemistry of a novel tetramacrocyclic ligand derived from 1,4,7-triazacyclononane: synthesis, structure, and properties of nickel(II) and copper(II) complexes.

Synthesis of Heteroleptic Bis(diimine)carbonylchlororuthenium(II) Complexes from Photodecarbonylated Precursors

Carbonyl-Carboxylato-Ruthenium Complexes Incorporating Diimine Ligands and Unexpected Cyclometalation of Carboxylate Ligands

Reinigung von peptiden unter verwendung von metall-ion-affinitätschromatographie