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Ulf Anders Hagfeldt

Cette personne n’est plus à l’EPFL

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Publications associées (296)

Effect of Coordination Sphere Geometry of Copper Redox Mediators on Regeneration and Recombination Behavior in Dye-Sensitized Solar Cell Applications

Jacques-Edouard Moser, Shaik Mohammed Zakeeruddin, Joël Teuscher, Ulf Anders Hagfeldt, Marko Stojanovic, Fabrizio Giordano, Yasemin Saygili, Marina Freitag, Jan Tiepelt

The recombination of injected electrons with oxidized redox species and regeneration behavior of copper redox mediators are investigated for four copper complexes, [Cu(dmby)2]2+/1+ (dmby = 6,6′-dimethyl-2,2′- bipyridine), [Cu(tmby)2]2+/1+ (tmby = 4,4′,6,6′ ...

2018

Lateral Intermolecular Electronic Interactions of Diketopyrrolopyrrole D−π–A Solar Dye Sensitizers Adsorbed on Mesoporous Alumina

Jacques-Edouard Moser, Ulf Anders Hagfeldt, Heewon Bahng

The development of push−pull organic dyes utilizing the donor−(π-conjugated bridge)−acceptor (D−π−A) motif has induced a paradigm shift in the design of efficient nanocrystalline dye-sensitized solar cells (DSSCs), offering control over the aesthetic prope ...

2018

Boosting the performance of Cu2O photocathodes for unassisted solar water splitting devices

Ulf Anders Hagfeldt, Amita Ummadisingu, Matthew Thomas Mayer, Jingshan Luo, Minkyu Son, Linfeng Pan, Jinhyun Kim

Although large research efforts have been devoted to photoelectrochemical (PEC) water splitting in the past several decades, the lack of efficient, stable and Earth-abundant photoelectrodes remains a bottleneck for practical application. Here, we report a ...

2018

Donor Effect on the Photoinduced Interfacial Charge Transfer Dynamics of D−π–A Diketopyrrolopyrrole Dye Sensitizers Adsorbed on Titanium Dioxide

Jacques-Edouard Moser, Ulf Anders Hagfeldt, Heewon Bahng

In this report, we investigate the effects of a strong electron-donating group on the electron injection and recombination processes of diketopyrrolopyrrole (DPP)-sensitized TiO2 films by comparing the dynamics of triphenylamine donor-installed DPP_A and d ...

2018

Comprehensive control of voltage loss enables 11.7% efficient solid-state dye-sensitized solar cells

Jacques-Edouard Moser, Shaik Mohammed Zakeeruddin, Ladislav Kavan, Ulf Anders Hagfeldt, Chenyi Yi, Yiming Cao, Jingshan Luo, Yasemin Saygili, Heewon Bahng, Weiwei Zhang, Yuhang Liu, Yinghui Wu

The relatively large voltage loss (Vloss) in excitonic type solar cells severely limits their power conversion efficiencies (PCEs). Here, we report a comprehensive control of Vloss through efficacious engineering of the sensitizer and redox mediator, makin ...

2018

Redox melts formed by copper (i)/(ii) complexes as charge transfer and charge storage materials

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Yiming Cao, Marko Stojanovic, Marina Freitag

The present invention relates to a redox copper complex melt comprising a metalorganic complex of formula (I) [Cu (La) n ] (I), wherein n is an integer 2; and La is a bidentate ligand selected from a ligand according to any one of formulae (1) and (2): ...

2018

How the formation of interfacial charge causes hysteresis in perovskite solar cells

Michael Graetzel, Ulf Anders Hagfeldt, Wolfgang Richard Tress, Silver Hamill Turren Cruz

In this study, we discuss the underlying mechanism of the current-voltage hysteresis in a hybrid lead-halide perovskite solar cell. We have developed a method based on Kelvin probe force microscopy that enables mapping charge redistribution in an operating ...

ROYAL SOC CHEMISTRY2018

Efficient and Stable Dye-Sensitized Solar Cells Based on a Tetradentate Copper(II/I) Redox Mediator

Ulf Anders Hagfeldt, Zerrin Yumak, Mei Wang

The identification of an efficient and stable redox mediator is of paramount importance for commercialization of dye-sensitized solar cells (DSCs). Herein, we report a new class of copper complexes containing diamine-dipyridine tetradentate ligands (L1 = N ...

AMER CHEMICAL SOC2018

Novel p-dopant toward highly efficient and stable perovskite solar cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Marko Stojanovic, Jiyoun Seo, Hui-Seon Kim, Seckin Akin

Li-TFSI is the most common p-dopant for the hole conductor spiro-MeOTAD in the normal structure (n-i-p) of perovskite solar cells (PSCs), which consistently yield the highest power conversion efficiency (PCE) albeit at the risk of lower long-term operation ...

ROYAL SOC CHEMISTRY2018

Cu Complex Redox Couples Open Up New Possibilities for Dye-Sensitized Solar Cells

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt

Dye-sensitized solar cells (DSSCs) are based on molecular and nanometer-scale components. Record cell efficiencies of 12%, promising stability data, and means of energy efficient production methods have been accomplished. As selling points for the DSSC tec ...

Wiley2018

Phase stabilization of all-inorganic perovskite materials for photovoltaics

Ulf Anders Hagfeldt, Wanchun Xiang

Cubic phase stabilization is extremely important for the application of cesium lead halide inorganic perovskite materials into fabrication of perovskite solar cells. Methods on how to stabilize inorganic perovskite phase have been discussed in this review. ...

ELSEVIER SCIENCE BV2018

One plus one greater than two: high-performance inverted planar perovskite solar cells based on a composite CuI/CuSCN hole-transporting layer

Ulf Anders Hagfeldt, Zerrin Yumak

The low-cost and stable inorganic p-type semiconductor copper(i) iodide (CuI) is a promising hole-transporting layer (HTL) material for inverted planar perovskite solar cells (PSCs). However, the power conversion efficiencies (PCEs) of inverted planar PSCs ...

Royal Society of Chemistry2018

Greener, Nonhalogenated Solvent Systems for Highly Efficient Perovskite Solar Cells

Michael Graetzel, Ulf Anders Hagfeldt, Michael Saliba, Silver Hamill Turren Cruz, Mozhgan Yavari, Mohammad Mahdi Tavakoli

All current highest efficiency perovskite solar cells (PSCs) use highly toxic, halogenated solvents, such as chlorobenzene (CB) or toluene (TLN), in an antisolvent step or as solvent for the hole transporter material (HTM). A more environmentally friendly ...

WILEY-V C H VERLAG GMBH2018

Interfacial Engineering of Metal Oxides for Highly Stable Halide Perovskite Solar Cells

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Wolfgang Richard Tress, Kazuteru Nonomura, Hui-Seon Kim, Zaiwei Wang, Monica Marcela Lira Cantu, Anna Morales Melgares, Haibing Xie

Oxides employed in halide perovskite solar cells (PSCs) have already demonstrated to deliver enhanced stability, low cost, and the ease of fabrication required for the commercialization of the technology. The most stable PSCs configuration, the carbon-base ...

WILEY2018

Methylammonium-free, high-performance, and stable perovskite solar cells on a planar architecture

Ulf Anders Hagfeldt, Michael Saliba, Silver Hamill Turren Cruz

Currently, perovskite solar cells (PSCs) with high performances greater than 20% contain bromine (Br), causing a suboptimal bandgap, and the thermally unstable methylammonium (MA) molecule. Avoiding Br and especially MA can therefore result in more optimal ...

American Association for the Advancement of Science2018

Resurgence of DSCs with copper electrolyte: a detailed investigation of interfacial charge dynamics with cobalt and iodine based electrolytes

Ulf Anders Hagfeldt

Deploying earth abundant copper as a redox mediator in dye-sensitized solar cells (DSCs) has been found to be a very promising strategy to achieve higher photovoltage and power conversion efficiencies in full sun (100 mW cm(-2)) and in low/diffuse light co ...

Royal Society of Chemistry2018

Electron-Affinity-Triggered Variations on the Optical and Electrical Properties of Dye Molecules Enabling Highly Efficient Dye-Sensitized Solar Cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Péter Kalman Péchy, Ulf Anders Hagfeldt, Yiming Cao, Marko Stojanovic, Mohammad Ibrahim Dar, Yasemin Saygili, Weiwei Zhang, Yuhang Liu

The synthesis, characterization, and photovoltaic performance of a series of indacenodithiophene (IDT)-based D--A organic dyes with varying electron-accepting units is presented. By control of the electron affinity, perfectly matching energy levels were ac ...

Wiley-VCH Verlag GmbH2018

High Temperature-Stable Perovskite Solar Cell Based on Low-Cost Carbon Nanotube Hole Contact

Michael Graetzel, Ulf Anders Hagfeldt, Konrad Domanski, Wolfgang Richard Tress, Juan-Pablo Correa-Baena, Antonio Abate, Michael Saliba

Mixed ion perovskite solar cells (PSC) are manufactured with a metal-free hole contact based on press-transferred single-walled carbon nanotube (SWCNT) film infiltrated with 2,2,7,-7-tetrakis(N, N-di-p-methoxyphenylamine)-9,90-spirobifluorene (Spiro-OMeTAD ...

Wiley-Blackwell2017

Dye-sensitized solar cells for efficient power generation under ambient lighting

Paul Liska, Jacques-Edouard Moser, Shaik Mohammed Zakeeruddin, Joël Teuscher, Ulf Anders Hagfeldt, Fabrizio Giordano, Yasemin Saygili, Xiaoyu Zhang, Marina Freitag

Solar cells that operate efficiently under indoor lighting are of great practical interest as they can serve as electric power sources for portable electronics and devices for wireless sensor networks or the Internet of Things. Here, we demonstrate a dye-s ...

Nature Publishing Group2017

Globularity-Selected Large Molecules for a New Generation of Multication Perovskites

Michael Graetzel, Ulf Anders Hagfeldt, Wolfgang Richard Tress, Juan-Pablo Correa-Baena, Antonio Abate, Michael Saliba, Filippo de Angelis, Silver Hamill Turren Cruz

Perovskite solar cells (PSCs) use perovskites with an APbX(3) structure, where A is a monovalent cation and X is a halide such as Cl, Br, and/or I. Currently, the cations for high-efficiency PSCs are Rb, Cs, methylammonium (MA), and/or formamidinium (FA). ...

Wiley-Blackwell2017

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