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Ulf Anders Hagfeldt

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Publications associées (296)

Low-cost high-efficiency system for solar-driven conversion of CO2 to hydrocarbons

Ulf Anders Hagfeldt, Silver Hamill Turren Cruz

Conversion of carbon dioxide into hydrocarbons using solar energy is an attractive strategy for storing such a renewable source of energy into the form of chemical energy (a fuel). This can be achieved in a system coupling a photovoltaic (PV) cell to an el ...

National Academy of Sciences2019

Synergistic Crystal and Interface Engineering for Efficient and Stable Perovskite Photovoltaics

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Michael Saliba, Philippe Jürgen Holzhey, Pankaj Kumar Yadav, Mohammad Mahdi Tavakoli

The presence of bulk and surface defects in perovskite light harvesting materials limits the overall efficiency of perovskite solar cells (PSCs). The formation of such defects is suppressed by adding methylammonium chloride (MACl) as a crystallization aid ...

WILEY-V C H VERLAG GMBH2019

A Scalable Methylamine Gas Healing Strategy for High-Efficiency Inorganic Perovskite Solar Cells

Ulf Anders Hagfeldt, Zaiwei Wang, Zhipeng Li

An easy and scalable methylamine (MA) gas healing method was realized for inorganic cesium-based perovskite (CsPbX3) layers by incorporating a certain amount of MAX (X=I or Br) initiators into the raw film. It was found that the excess MAX accelerated the ...

Wiley-VCH Verlag GmbH2019

D35-TiO2 nano-crystalline film as a high performance visible-light photocatalyst towards the degradation of bis-phenol A

Ulf Anders Hagfeldt, Lin Yang, Xue Bai

Dye-sensitized photocatalytic suspension system for wastewater treatment is still limited in practice due to particle aggregation, fast charge carrier recombination, poor stability and recycling issue. In this study, we combine TiO2 nano-crystalline film w ...

ELSEVIER SCIENCE SA2019

Triarylamine-based hydrido-carboxylate rhenium(i) complexes as photosensitizers for dye-sensitized solar cells

Ulf Anders Hagfeldt, Thomas Moehl, Kazuteru Nonomura, Lorenzo Veronese

Two new dyes based on a dinuclear rhenium complex and (E)-3-(5-(4-(bis(2,4-dibutoxy-[1,1-biphenyl]-4-yl)amino)phenyl)thiophen-2-yl)-2-cyanoacrylic acid (namely D35) have been investigated as sensitizers for dye sensitized solar cells (DSSCs). Two different ...

ROYAL SOC CHEMISTRY2019

Crystal Orientation and Grain Size: Do They Determine Optoelectronic Properties of MAPbI(3) Perovskite?

Ulf Anders Hagfeldt, Sandy Sanchez Alonso, Michael Saliba

Growing large, oriented grains of perovskite often leads to efficient devices, but it is unclear if properties of the grains are responsible for the efficiency. Domains observed in SEM are commonly misidentified with crystallographic grains, but SEM images ...

2019

Diverging surface reactions at TiO2- or ZnO-based photoanodes in dye-sensitized solar cells

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Gunther Wittstock, Kazuteru Nonomura

Fast recombination of electrons from semiconductors with the oxidized redox species in the electrolyte represents a major bottleneck in the improvement of ZnO-based dye-sensitized solar cells (DSSCs). While processes at the semiconductor-electrolyte interf ...

ROYAL SOC CHEMISTRY2019

Electrochemically polymerized poly (3, 4-phenylenedioxythiophene) as efficient and transparent counter electrode for dye sensitized solar cells

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

A new conducting polymer poly (3, 4-phenylenedioxythiophene) is synthesized by the electrochemical polymerization technique with different solvents. We find that solvents used in electrochemical polymerization play important roles for the catalytic activit ...

PERGAMON-ELSEVIER SCIENCE LTD2019

Perovskite Solar Cells Based on Oligotriarylamine Hexaarylbenzene as Hole-Transporting Materials

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Mona Shasti

A cobalt-catalyzed cyclotrimerization of bis(aryl)alkyne is used as an innovative tool to obtain hole-transport materials (HTMs). The novel HTM containing six units of oligotriarylamine (HAB1), characterized by UV-vis, cyclic voltammetry, DFT, and thermogr ...

AMER CHEMICAL SOC2019

Indeno[1,2-b]carbazole as Methoxy-Free Donor Group: Constructing Efficient and Stable Hole-Transporting Materials for Perovskite Solar Cells

Ulf Anders Hagfeldt, Zhe Sun, Yinghui Wu, Zhiye Wang, Jialin Wang, Han Zhang

With perovskite-based solar cells (PSCs) now reaching efficiencies of greater than 20 %, the stability of PSC devices has become a critical challenge for commercialization. However, most efficient hole-transporting materials (HTMs) thus far still rely on t ...

Wiley-VCH Verlag GmbH2019

Fine-tuning the coordination atoms of copper redox mediators: an effective strategy for boosting the photovoltage of dye-sensitized solar cells

Ulf Anders Hagfeldt, Mei Wang, Chong Liu

Natural systems have marvelously utilized copper complexes featuring sulfur-coordinating ligands, known as blue copper proteins, as efficient electron-transfer mediators in biological processes. Copper complexes with sulfur-coordinating ligands have been a ...

Royal Society of Chemistry2019

Improving energy transfer efficiency of dye-sensitized solar cell by fine tuning of dye planarity

Ulf Anders Hagfeldt

Two push-pull metal-free sensitizers with 5,11-dihydroindolo[3,2-b]carbazole derivatives as electron-donating groups and 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid (BTZ) as electron-withdrawing unit, denoted by SK201 and SK202, were synthesized ...

PERGAMON-ELSEVIER SCIENCE LTD2019

A chain is as strong as its weakest link - Stability study of MAPbI(3) under light and temperature

Michael Graetzel, Ulf Anders Hagfeldt, Amita Ummadisingu, Michael Saliba, Philippe Jürgen Holzhey, Pankaj Kumar Yadav, Silver Hamill Turren Cruz

The stability of perovskite solar cells is a key issue for industrial development. One reason for this is the volatile organic methylammonium (MA) cation, which is prone to degas under elevated temperatures from the perovskite. At the same time, small amou ...

2019

Boosting the power conversion efficiency of perovskite solar cells to 17.7% with an indolo[3,2-b]carbazole dopant-free hole transporting material by improving its spatial configuration

Ulf Anders Hagfeldt, Xiaoqing Jiang

The development of facilely synthesized, dopant-free hole-transporting materials (HTMs) with high efficiency is of great significance for the potential application of perovskite solar cells (PSCs). Herein, we report two novel indolo[3,2-b]carbazole (ICZ) b ...

Royal Society of Chemistry2019

A hybrid niobium-based oxide with bio-based porous carbon as an efficient electrocatalyst in photovoltaics: a general strategy for understanding the catalytic mechanism

Ulf Anders Hagfeldt, Cheng Wang, Sining Yun

Developing a high-performance catalyst and establishing a catalytic mechanism for understanding the catalytic activity are crucial to new generation photovoltaic technology. In this work, we present a feasible and general route to synthesize a bio-based po ...

Royal Society of Chemistry2019

Bifunctional Organic Spacers for Formamidinium-Based Hybrid Dion-Jacobson Two-Dimensional Perovskite Solar Cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Amita Ummadisingu, Mohammad Ibrahim Dar, Jeong-Hyeok Im, Jiyoun Seo, Peng Wang, Hui-Seon Kim, Yuhang Liu, Yang Li, Jovana Milic, Yang Li

Three-dimensional (3D) perovskite materials display remarkable potential in photovoltaics owing to their superior solar-to-electric power conversion efficiency, with current efforts focused on improving stability. Two-dimensional (2D) perovskite analogues ...

AMER CHEMICAL SOC2019

SnS Quantum Dots as Hole Transporter of Perovskite Solar Cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Xiaofei Dong, Peng Wang, Zaiwei Wang, Yuhang Liu, Yang Li, Dan Ren, Yang Li

Perovskite solar cells have achieved comparable power conversion efficiencies as commercial silicon cells, making the issue of long-term operation stability as the most critical scientific factor toward industrial realization. In this work, we introduce Sn ...

AMER CHEMICAL SOC2019

Photoelectrochemical Cells Based on Dye Sensitization for Electricity and Fuel Production

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt

Dye-sensitized semiconductor oxide photoelectrodes in which light is absorbed by a monomolecular layer of dye chemisorbed on a porous oxide substrate have attracted considerable interest in the last 35 years, mainly for the conversion of sunlight to electr ...

SWISS CHEMICAL SOC2019

Ba-induced phase segregation and band gap reduction in mixed-halide inorganic perovskite solar cells

Michael Graetzel, Ulf Anders Hagfeldt, Dominik Józef Kubicki, Wolfgang Richard Tress, Jingshan Luo, David Lyndon Emsley, Albert Hofstetter, Xiaoyan Wang, Zaiwei Wang, Wanchun Xiang, Jiahuan Zhang, Xiaoyu Wang

All-inorganic metal halide perovskites are showing promising development towards efficient long-term stable materials and solar cells. Element doping, especially on the lead site, has been proved to be a useful strategy to obtain the desired film quality a ...

Nature Research2019

Effect of furan pi-spacer and triethylene oxide methyl ether substituents on performance of phenothiazine sensitizers in dye-sensitized solar cells

Ulf Anders Hagfeldt

Conjugated pi-spacers are used to improve the light harvesting properties of sensitizers for dye-sensitized solar cells. In several recent works, furan has outperformed other popular pi-spacers such as thiophene and phenyl. One of the best performing pheno ...

ROYAL SOC CHEMISTRY2019

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