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Ulf Anders Hagfeldt

Cette personne n’est plus à l’EPFL

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Publications associées (296)

Transparent Cuprous Oxide Photocathode Enabling a Stacked Tandem Cell for Unbiased Water Splitting

Michael Graetzel, Ulf Anders Hagfeldt, Marcel Roland Schreier, Stanley David Tilley, Matthew Thomas Mayer, Jingshan Luo, Dongqin Bi

Photoelectrochemical water splitting represents an attractive method of capturing and storing the immense energy of sunlight in the form of hydrogen, a clean chemical fuel. Given the large energetic demand of water electrolysis, and the defined spectrum of ...

Wiley-VCH Verlag Berlin2015

Silolothiophene-linked triphenylamines as stable hole transporting materials for high efficiency perovskite solar cells

Michael Graetzel, Mohammad Khaja Nazeeruddin, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Peng Gao, Fabrizio Giordano, Sanghyun Paek, Juan-Pablo Correa-Baena, Antonio Abate, Taisuke Matsui, Michael Saliba

In this work, we synthesized novel hole transporting materials (HTMs) and studied their impact on the stability of perovskite-based solar cells (PSCs). The steady-state maximum power output of devices in working condition was monitored to assess the stabil ...

Royal Society of Chemistry2015

Highly efficient planar perovskite solar cells through band alignment engineering

Michael Graetzel, Mohammad Khaja Nazeeruddin, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Ludmilla Steier, Fabrizio Giordano, Wolfgang Richard Tress, Antonio Abate, Taisuke Matsui, Michael Saliba, Tor Jesper Jacobsson

The simplification of perovskite solar cells (PSCs), by replacing the mesoporous electron selective layer (ESL) with a planar one, is advantageous for large-scale manufacturing. PSCs with a planar TiO2 ESL have been demonstrated, but these exhibit unstabil ...

Royal Society of Chemistry2015

Efficient dye regeneration at low driving force achieved in triphenylamine dye LEG4 and TEMPO redox mediator based dye-sensitized solar cells

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Yan Hao

Minimizing the driving force required for the regeneration of oxidized dyes using redox mediators in an electrolyte is essential to further improve the open-circuit voltage and efficiency of dye-sensitized solar cells (DSSCs). Appropriate combinations of r ...

Royal Society of Chemistry2015

Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric Analysis of Poly(3,4-ethylenedioxythiophene) in Solid-State Dye-Sensitized Solar Cells: Comparison of In Situ Photoelectrochemical Polymerization in Aqueous Micellar and Organic Media

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Lin Yang, Jiahuan Zhang

Solid-state dye-sensitized solar cells (sDSCs) are devoid of such issues as electrolyte evaporation or leakage and electrode corrosion, which are typical for traditional liquid electrolyte-based DSCs. Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the ...

American Chemical Society2015

High efficiency stable inverted perovskite solar cells without current hysteresis

Michael Graetzel, Mohammad Khaja Nazeeruddin, Ulf Anders Hagfeldt

The inverted perovskite solar cell fabricated using a two-step method exhibited the highest FF of 0.85 and good efficiency of 18% based on CH3NH3PbI3. A small amount of H2O was added into PbI2/DMF to make a homogenous precursor solution. A high quality PbI ...

Royal Soc Chemistry2015

Carbon nanotube film replacing silver in high-efficiency solid-state dye solar cells employing polymer hole conductor

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Jiahuan Zhang

A semitransparent, flexible single-walled carbon nanotube (SWCNT) film was efficiently used in place of evaporated silver as the counter electrode of a poly(3,4-ethylenedioxythiophene) polymer-based solid-state dye solar cell (SSDSC): the solar-to-electric ...

Springer Verlag2015

Spectral splitting photovoltaics using perovskite and wideband dye-sensitized solar cells

Michael Graetzel, Mohammad Khaja Nazeeruddin, Ulf Anders Hagfeldt, Fabrizio Giordano, Kazuteru Nonomura, Antonio Abate

The extension of the light absorption of photovoltaics into the near-infrared region is important to increase the energy conversion efficiency. Although the progress of the lead halide perovskite solar cells is remarkable, and high conversion efficiency of ...

Nature Publishing Group2015

Determination of Thermal Expansion Coefficients and Locating the Temperature-Induced Phase Transition in Methylammonium Lead Perovskites Using X-ray Diffraction

Ulf Anders Hagfeldt, Tor Jesper Jacobsson

Lead halogen perovskites, and particularly methylammonium lead iodine, CH3NH3PbI3, have recently attracted considerable interest as alternative solar cell materials, and record solar cell efficiencies have now surpassed 20%. Concerns have, however, been ra ...

American Chemical Society2015

Laser desorption/ionization mass spectrometry of dye-sensitized solar cells: identification of the dye-electrolyte interaction

Ulf Anders Hagfeldt

Dye-sensitized solar cells (DSCs) have great potential to provide sustainable electricity from sunlight. The photoanode in DSCs consists of a dye-sensitized metal oxide film deposited on a conductive substrate. This configuration makes the photoanode a per ...

Wiley-Blackwell2015

Influence of Dye Architecture of Triphenylamine Based Organic Dyes on the Kinetics in Dye-Sensitized Solar Cells

Ulf Anders Hagfeldt, Gunther Wittstock

The impact of the dye architecture on the kinetics in the dyesensitized solar cell (DSC) was investigated for two structurally similar organic dyes, adsorbed adsorbed to a mesoporous TiO2 film. Differences in the HOMO and LUMO levels of the triphenylamine ...

American Chemical Society2015

Chemistry and Light: The International Year of Light

Ulf Anders Hagfeldt

Schweizerische Chemische Gesellschaft2015

Resonance Raman and Excitation Energy Dependent Charge Transfer Mechanism in Halide-Substituted Hybrid Perovskite Solar Cells

Ulf Anders Hagfeldt

Organo-metal halide perovskites (OMHPs) are materials with attractive properties for optoelectronics. They made a recent introduction in the photovoltaics world by methylammonium (MA) lead triiodide and show remarkably improved charge separation capabiliti ...

American Chemical Society2015

Facile route to freestanding CH3NH3PbI3 crystals using inverse solubility

Michael Graetzel, Ulf Anders Hagfeldt, Jeannette Medina Kadro, Kazuteru Nonomura

CH3NH3PbI3 was found to exhibit inverse solubility at high temperatures in gamma-butyrolactone. Making use of this unusual, so far unreported phenomenon, we present a facile method for the growth of freestanding crystals of CH3NH3PbI3 from solution without ...

Nature Publishing Group2015

Synthesis of highly effective Pt/carbon fiber composite counter electrode catalyst for dye-sensitized solar cells

Ulf Anders Hagfeldt, Wenyan Li

Pt/carbon fiber composite (Pt/Cf) with a low Pt loading of 1.0 wt% is introduced into dye-sensitized solar cells as counter electrode (CE) catalyst. The cobalt-electrolyte based device using this composite CE achieves power conversion efficiency of 8.97%, ...

Elsevier2015

Goldschmidt's Rules and Strontium Replacement in Lead Halogen Perovskite Solar Cells: Theory and Preliminary Experiments on CH3NH3SrI3

Ulf Anders Hagfeldt, Tor Jesper Jacobsson

During the past few years, organic lead halogen perovskites have emerged as a class of highly promising solar cell materials, with certified solar cell efficiencies now surpassing 20%. Concerns have, however, been raised about the possible environmental an ...

American Chemical Society2015

Solvent-dependent structure of the I3 - ion derived from photoelectron spectroscopy and Ab initio molecular dynamics simulations

Ulf Anders Hagfeldt

Ab initio molecular dynamics (MD) simulations of the solvation of LiI3 in four different solvents (water, methanol, ethanol, and acetonitrile) are employed to investigate the molecular and electronic structure of the I-3(-) ion in relation to X-ray photoel ...

Wiley-Blackwell2015

Synthesis and characterization of an immobilizable photochemical molecular device for H-2-generation

Ulf Anders Hagfeldt

With Ru-II(bpyMeP)(2)tpphzPtCl(2) (4) a molecular photocatalyst has been synthesized for visible-light-driven H-2-evolution. It contains the ligand bpyMeP (4,4'-bis(diethyl-(methylene)-phosphonate)-2,2'-bipyridine) with phosphate ester groups as prec ...

Royal Society of Chemistry2015

Dye-sensitized Solar Cells: New Approaches with Organic Solid-state Hole Conductors

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Jiahuan Zhang

Solid-state dye-sensitized solar cells (sDSCs) in which a solid organic charge-transfer medium, or hole conductor (HC), is interposed between a dye-coated mesoporous oxide electrode and a conductive counter electrode, have attracted considerable interest a ...

Schweizerische Chemische Gesellschaft2015

Probing Photocurrent Generation, Charge Transport, and Recombination Mechanisms in Mesostructured Hybrid Perovskite through Photoconductivity Measurements

Ulf Anders Hagfeldt

Conductivity of methylammonium lead triiodide (MAPbI(3)) perovskite was measured on different mesoporous metal oxide scaffolds: TiO2, Al2O3, and ZrO2, as a function of incident light irradiation and temperature. It was found that MAPbI(3) exhibits intrinsi ...

Amer Chemical Soc2015

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