Home

Person

Ulf Anders Hagfeldt

This person is no longer with EPFL

About
Privacy
Disclaimer

Graph Chatbot

Related publications (296)

PbZrTiO3 ferroelectric oxide as an electron extraction material for stable halide perovskite solar cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Michael Saliba, Silver Hamill Turren Cruz, Hui-Seon Kim, Zaiwei Wang, Monica Marcela Lira Cantu, Anna Morales Melgares, Haibing Xie

State-of-the-art halide perovskite solar cells employ semiconductor oxides as electron transportmaterials. Defects in these oxides, such as oxygen vacancies (Ovac), act as recombination centres and, in air and UV light, reduce the stability of the solar ce ...

2019

Origin of apparent light-enhanced and negative capacitance in perovskite solar cells

Ulf Anders Hagfeldt, Wolfgang Richard Tress, Firouzeh Ebadi Garjan

So-called negative capacitance seems to remain an obscure feature in the analysis of the frequency-dependent impedance of perovskite solar cells. It belongs to one of the puzzling peculiarities arising from the mixed ionic-electronic conductivity of this c ...

Springer2019

13.6% Efficient Organic Dye-Sensitized Solar Cells by Minimizing Energy Losses of the Excited State

Ulf Anders Hagfeldt, Li Zhang

The electron-injection energy losses of dye-sensitized solar cells (DSSCs) are among the fundamental problems hindering their successful breakthrough application. Two triazatruxene (TAT)-based sensitizers, with one containing a flexible Z-type double bond ...

AMER CHEMICAL SOC2019

A comprehensive experimental study of five fundamental phenothiazine geometries increasing the diversity of the phenothiazine dye class for dye-sensitized solar cells

Ulf Anders Hagfeldt

Phenothiazine is a versatile scaffold frequently used in both pharmaceutical and photovoltaic applications. Still, the structural diversity within the class of phenothiazine sensitizers for dye-sensitized solar cells is minute. Substituents are found in 3, ...

2019

Directly Photoexcited Oxides for Photoelectrochemical Water Splitting

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Linfeng Pan

Artificial photosynthesis promises to become a sustainable way to harvest solar energy and store it in chemical fuels by means of photoelectrochemical (PEC) cells. Although it is intriguing to shift the fossil-fuel-based economy to a renewable carbon-neutr ...

WILEY-V C H VERLAG GMBH2019

Power output stabilizing feature in perovskite solar cells at operating condition: Selective contact-dependent charge recombination dynamics

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

Stabilized power output at maximum power point (mpp) has been considered as one of the most reliable parameters as it provides a key performance indicator for perovskite solar cells (PSCs) revealing the operational stability of the photovoltaic device. Her ...

Elsevier Science Bv2019

Electron-Withdrawing Anchor Group of Sensitizer for Dye-Sensitized Solar Cells, Cyanoacrylic Acid, or Benzoic Acid?

Ulf Anders Hagfeldt, Li Zhang

High electron-injection efficiency is important for further development of dye-sensitized solar cells (DSSCs). Different electron acceptors have different electron-injection capabilities, which affect device performance. Herein, the effects of two organic ...

WILEY-V C H VERLAG GMBH2019

Photoinduced Lattice Symmetry Enhancement in Mixed Hybrid Perovskites and Its Beneficial Effect on the Recombination Behavior

Ulf Anders Hagfeldt, Hui-Seon Kim

The strategy of mixing cations and halides in hybrid organic lead halide perovskites has recently been shown to be very successful in achieving high efficiency with long-term perovskite solar cell stability. In this study, the effect of photoexcitation on ...

WILEY-V C H VERLAG GMBH2019

Towards Oxide Electronics: a Roadmap

Brahim Dkhil, Francisco Sanchez, Ulf Anders Hagfeldt, Mauro Fanciulli, Monica Marcela Lira Cantu

At the end of a rush lasting over half a century, in which CMOS technology has been experiencing a constant and breathtaking increase of device speed and density, Moore's law is approaching the insurmountable barrier given by the ultimate atomic nature of ...

2019

Phosphonic Acid Modification of the Electron Selective Contact: Interfacial Effects in Perovskite Solar Cells

Ulf Anders Hagfeldt, Rebecca Hill, Wolfgang Richard Tress, Juan-Pablo Correa-Baena, Silver Hamill Turren Cruz

The role electron-transport layers (ETLs) play in perovskite solar cells (PSCs) is still widely debated. Conduction band alignment at the perovskite/ETL interface has been suggested to be an important role for the performance of the solar cells. However, l ...

AMER CHEMICAL SOC2019

Nanoscale mapping of chemical composition in organic-inorganic hybrid perovskite films

Ulf Anders Hagfeldt, Jorge Miguel Dias Almeida Rodrigues Soares, Silver Hamill Turren Cruz, Rodrigo Szostak

Lead-based organic-inorganic hybrid perovskite (OIHP) solar cells can attain efficiencies over 20%. However, the impact of ion mobility and/or organic depletion, structural changes, and segregation under operating conditions urge for decisive and more accu ...

American Association for the Advancement of Science (AAAS)2019

Morphological and compositional progress in halide perovskite solar cells

Ulf Anders Hagfeldt, Hui-Seon Kim

Perovskite solar cells (PSCs) reached a certified 23.7% efficiency in 2018 by boosting their surprisingly high open-circuit voltage (V-OC) and photocurrent. The suppressed recombination in PSCs significantly cut down the voltage loss between the bandgap en ...

Royal Society of Chemistry2019

Molecular Engineering of Copper Phthalocyanines: A Strategy in Developing Dopant-Free Hole-Transporting Materials for Efficient and Ambient-Stable Perovskite Solar Cells

Ulf Anders Hagfeldt, Feng Liu, Xiaoqing Jiang

Copper (II) phthalocyanines (CuPcs) have attracted growing interest as promising hole-transporting materials (HTMs) in perovskite solar cells (PSCs) due to their low-cost and excellent stability. However, the most efficient PSCs using CuPc-based HTMs repor ...

WILEY-V C H VERLAG GMBH2019

Performance of perovskite solar cells under simulated temperature-illumination real-world operating conditions

Michael Graetzel, Ulf Anders Hagfeldt, Konrad Domanski, Wolfgang Richard Tress, Essa Awadh R Alharbi, Anand Agarwalla, Brian Irving Carlsen

Since reaching 20% efficiency, research in perovskite photovoltaics has shifted from a race for efficiency to a race for stability. For efficiency, the standard test conditions set the rules for the race. However, the term 'stability' is used very broadly ...

NATURE PUBLISHING GROUP2019

Toward an alternative approach for the preparation of low-temperature titanium dioxide blocking underlayers for perovskite solar cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Kazuteru Nonomura, Lichen Zhao, Su Htike Aung

The anodic electrodeposition method is investigated as an alternative technique for the preparation of a titanium oxide (TiO2) blocking underlayer (UL) for perovskite solar cells (PSCs). Extremely thin Ti-IV-based films are grown from aqueous acidic titani ...

Royal Society of Chemistry2019

Design, synthesis and characterization of 1,8-naphthalimide based fullerene derivative as electron transport material for inverted perovskite solar cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Hui-Seon Kim

A new fullerene derivative, PC61BNI, was designed and synthesized in which [6,6]-phenyl C-61-butyric acid methyl ester (PC61BM) was modified by replacing the methyl group with 1,8-naphthalimide (NI) to investigate the molecular structure modification effec ...

ELSEVIER SCIENCE SA2019

Metal Coordination Complexes as Redox Mediators in Regenerative Dye-Sensitized Solar Cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Marko Stojanovic, Yasemin Saygili, Natalie Flores Diaz

Dye-sensitized solar cells (DSSCs) have attracted a substantial interest in the last 30 years for the conversion of solar power to electricity. An important component is the redox mediator effecting the transport of charge between the photoelectrode and th ...

2019

Atomic Layer Deposition of ZnO on CuO Enables Selective and Efficient Electroreduction of Carbon Dioxide to Liquid Fuels

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Jingshan Luo, Linfeng Pan, Zaiwei Wang, Dan Ren, Jing Gao

Electrochemical reduction of carbon dioxide, if powered by renewable electricity, could serve as a sustainable technology for carbon recycling and energy storage. Among all the products, ethanol is an attractive liquid fuel. However, the maximum faradaic e ...

Wiley-VCH Verlag GmbH2019

Europium-Doped CsPbI2Br for Stable and Highly Efficient Inorganic Perovskite Solar Cells

Michael Graetzel, Giovanni Dietler, Ulf Anders Hagfeldt, Dominik Józef Kubicki, Wolfgang Richard Tress, Jingshan Luo, David Lyndon Emsley, Jiangtao Zhou, Daniel Prochowicz, Zaiwei Wang, Wanchun Xiang, Seckin Akin

All-inorganic perovskite films hold promise for improving the stability of perovskite solar cells (PSCs). However, the 3D alpha phase of narrow-bandgap inorganic perovskites is thermodynamically unstable at room temperature, limiting the development of hig ...

CELL PRESS2019

Auxiliary donors for phenothiazine sensitizers for dye-sensitized solar cells - how important are they really?

Ulf Anders Hagfeldt

Auxiliary donors are common design motifs for phenothiazine sensitizers for dye-sensitized solar cells. Despite this, there are only a few reports on their overall contribution to the photon-to-electron conversion efficiency. Twelve sensitizers have been p ...

Royal Society of Chemistry2019

Page 8 of 15