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

2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Semiconductor-based Photocatalytic Hydrogen Generation

The iodide/triiodide redox shuttle has limited the efficiencies accessible in dye-sensitized solar cells. Here, we report mesoscopic solar cells that incorporate a Co(II/III)tris(bipyridyl)–based redox electrolyte in conjunction with a custom synthesized donor-π-bridge-acceptor zinc porphyrin dye as sensitizer (designated YD2-o-C8). The specific molecular design of YD2-o-C8 greatly retards the rate of interfacial back electron transfer from the conduction band of the nanocrystalline titanium dioxide film to the oxidized cobalt mediator, which enables attainment of strikingly high photovoltages approaching 1 volt. Because the YD2-o-C8 porphyrin harvests sunlight across the visible spectrum, large photocurrents are generated. Cosensitization of YD2-o-C8 with another organic dye further enhances the performance of the device, leading to a measured power conversion efficiency of 12.3% under simulated air mass 1.5 global sunlight.

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Porphyrin-Sensitized Solar Cells with Cobalt (II/III)–Based Redox Electrolyte Exceed 12 Percent Efficiency

Simultaneous modification of the dye and redox shuttle boosts the efficiency of a dye-sensitized solar cell. The iodide/triiodide redox shuttle has limited the efficiencies accessible in dye-sensitized solar cells. Here, we report mesoscopic solar cells that incorporate a Co(II/III)tris(bipyridyl)–based redox electrolyte in conjunction with a custom synthesized donor-π-bridge-acceptor zinc porphyrin dye as sensitizer (designated YD2-o-C8). The specific molecular design of YD2-o-C8 greatly retards the rate of interfacial back electron transfer from the conduction band of the nanocrystalline titanium dioxide film to the oxidized cobalt mediator, which enables attainment of strikingly high photovoltages approaching 1 volt. Because the YD2-o-C8 porphyrin harvests sunlight across the visible spectrum, large photocurrents are generated. Cosensitization of YD2-o-C8 with another organic dye further enhances the performance of the device, leading to a measured power conversion efficiency of 12.3% under simulated air mass 1.5 global sunlight.

Porphyrin-sensitized solar cells with cobalt (II/III)-based redox electrolyte exceed 12 percent efficiency (vol 334, pg 629, 2011)

Perhaps the largest challenge for our global society is to find ways to replace the slowly but inevitably vanishing fossil fuel supplies by renewable resources and, at the same time, avoid negative effects from the current energy system on climate, environment, and health. The quality of human life to a large degree depends upon the availability of clean energy sources. The worldwide power consumption is expected to double in the next 3 decades because of the increase in world population and the rising demand of energy in the developing countries. This implies enhanced depletion of fossil fuel reserves, leading to further aggravation of the environmental pollution. As a consequence of dwindling resources, a huge power supply gap of 14 terawatts is expected to open up by year 2050 equaling today’s entire consumption, thus threatening to create a planetary emergency of gigantic dimensions. Solar energy is expected to play a crucial role as a future energy source. The sun provides about 120 000 terawatts to ...

Recent advances in sensitized mesoscopic solar cells.

Dye-sensitized solar cells based on nanocrystalline TiO2 have been fabricated with an amphiphilic ruthenium sensitizer [Ru (4,4‘-dicarboxylic acid-2,2‘-bipyridine) (4,4‘-bis(p-hexyloxystyryl)-2,2‘-bipyridine)(NCS)2], coded as K-19, and 4-guanidinobutyric acid (GBA) as coadsorbent. The cells showed a ∼50 mV increase in open-circuit voltage and a similar current in comparison with cells without GBA cografting. The performance of both types of devices was evaluated on the basis of their photocurrent−voltage characteristics, dark current measurements, cyclic voltammetry, electrochemical impedance spectroscopy, and phototransient decay methods. The results indicate that GBA shifted the conduction band of TiO2 toward a more negative potential and reduced the interfacial charge-transfer reaction from conduction band electrons to triiodide in the electrolyte (also known as the back reaction). In addition, the devices with GBA cografting showed an excellent stability with a power conversion efficiency of approxima...

Influence of 4-Guanidinobutyric Acid as Coadsorbent in Reducing Recombination in Dye-Sensitized Solar Cells

Reference LPI-ARTICLE-2008-056doi:101002/adfm200701041View record in Web of Science Record created on 2008-09-29, modified on 2017-05-12

The 2,2,6,6‐Tetramethyl‐1‐piperidinyloxy Radical: An Efficient, Iodine‐ Free Redox Mediator for Dye‐Sensitized Solar Cells

The performance enhancement of dye-sensitized solar cells (DSCs) in lithium-free and lithium-containing electrolytes under visible light-soaking was examined by impedance spectroscopy and photovoltage transient decay measurements. The improvement was found to arise from the formation of electronic transport levels close to the conduction band, resulting most likely from photoinduced proton intercalation in the TiO2 nanoparticles. These shallow trapping states accelerate the charge carrier transport within the nanocrystalline films without deteriorating the open circuit photovoltage. Subjecting the cells to forward bias in the dark produces a similar effect, whereas the introduction of lithium ions in the electrolyte suppresses the phenomena due to prevailing lithium ion intercalation. The redistribution of localized states in the band gap of TiO2 and the resulting conduction band edge movement appears to play a significant role in the performance of the DSC.

Enhancement of the performance of dye-sensitized solar cell by formation of shallow transport levels under visible light illumination

Efficient and stable mesoscopic dye-sensitized solar cells (DSCs) introducing a low-viscosity binary ionic liquid (1-propyl-3-methyl-imidazolium iodide (PMII) and 1-ethyl-3-methyl-imidazolium tetracyanoborate (EMIB(CN)4)) electrolyte in combination with a new high-molar-extinction-coefficient ruthenium complex, Ru(2,2′-bipyridine-4,4′-dicarboxylic acid)(4,4′-bis(2-(4-tert-butyloxy -phenyl)ethenyl) −2,2′-bipyridine) (NCS)2, are demonstrated. The dependence of photovoltaic performance, charge transport and electron lifetime on the composition of the binary ionic-liquid electrolyte with different ratios of PMII/EMIB(CN)4 were investigated by electrochemical impedance and photovoltage transient techniques. A photovoltaic conversion efficiency of 7.6 % was obtained under simulated full sunlight illumination, which is a record for solvent-free DSCs. These devices exhibit excellent stability at 80 °C in the dark or under visible-light soaking at 60 °C during 1000 h of accelerated tests.

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Stable, High‐Efficiency Ionic‐Liquid‐Based Mesoscopic Dye‐Sensitized Solar Cells

Dye-sensitized solar cells (DSCs) based on nanocrystalline TiO2 have been fabricated with an amphiphilic ruthenium sensitizer NaRu(2,2‘-bipyridine-4-carboxylic acid-4‘-carboxylate)(4,4‘-dinonyl-2,2‘-bipyridine)(NCS)2, coded as Z-907, and a series of ω-guanidinoalkyl acids as coadsorbents. The addition of guanidinoalkyl acids as coadsorbents increased the open-circuit voltage of the DSCs and had no adverse effect on the photocurrent if an appropriate amount was used. Phototransient measurements showed that the addition of these guanidino coadsorbents slowed down the charge recombination and that the increase in the open-circuit voltage was due to suppression of the recombination or an upward shift of the TiO2 band-edge to negative potentials. Thus, for the first time, a class of coadsorbents has been demonstrated to not only shield the surface electrons against recombination but also to shift the band edge to negative potentials, which is essential for future improvements in the performance of DSCs.

Zhipan Zhang

Papers

Influence of 4-Guanidinobutyric Acid as Coadsorbent in Reducing Recombination in Dye-Sensitized Solar Cells

The 2,2,6,6‐Tetramethyl‐1‐piperidinyloxy Radical: An Efficient, Iodine‐ Free Redox Mediator for Dye‐Sensitized Solar Cells

Enhancement of the performance of dye-sensitized solar cell by formation of shallow transport levels under visible light illumination

Stable, High‐Efficiency Ionic‐Liquid‐Based Mesoscopic Dye‐Sensitized Solar Cells

Effects of ω-Guanidinoalkyl Acids as Coadsorbents in Dye-Sensitized Solar Cells