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Ulf Anders Hagfeldt

Cette personne n’est plus à l’EPFL

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Publications associées (296)

Morphology Engineering: A Route to Highly Reproducible and High Efficiency Perovskite Solar Cells

Michael Graetzel, Arnaud Magrez, Ulf Anders Hagfeldt, Jingshan Luo, Dongqin Bi, Fei Zhang

Despite the rapid increase in the performance of perovskite solar cells (PSC), they still suffer from low lab-to-lab or people-to-people reproducibility. Aiming for a universal condition to high-performance devices, we investigated the morphology evolution ...

Wiley-VCH Verlag Berlin2017

Chemical Distribution of Multiple Cation (Rb+, Cs+, MA(+), and FA(+)) Perovskite Materials by Photoelectron Spectroscopy

Michael Graetzel, Ulf Anders Hagfeldt, Juan-Pablo Correa-Baena, Michael Saliba, Silver Hamill Turren Cruz

Lead-based mixed perovskite materials have emerged in the last couple of years as promising photovoltaic materials. Recently, it was shown that improved material stability can be achieved by incorporating small amounts of inorganic cations (Cs+ and Rb+), p ...

American Chemical Society2017

Identifying and suppressing interfacial recombination to achieve high open-circuit voltage in perovskite solar cells

Michael Graetzel, Ulf Anders Hagfeldt, Konrad Domanski, Wolfgang Richard Tress, Juan-Pablo Correa-Baena, Antonio Abate, Michael Saliba, Elham Halvani Anaraki, Silver Hamill Turren Cruz

With close to 100% internal quantum efficiency over the absorption spectrum, photocurrents in perovskite solar cells (PSCs) are at their practical limits. It is therefore imperative to improve open-circuit voltages (VOC) in order to go beyond the current 1 ...

Royal Society of Chemistry2017

Electrochemical Properties of Cu(II/I)-Based Redox Mediators for Dye-Sensitized Solar Cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ladislav Kavan, Ulf Anders Hagfeldt, Yasemin Saygili, Marina Freitag

Three Cu(II/I)-phenanthroline and Cu(II/I)-bipyridine redox mediators are studied on various electrodes and in variety of electrolyte solutions using cyclic voltammetry and impedance spectroscopy on symmetrical dummy cells. Graphene-based catalysts provide ...

2017

Novel highly active Pt/graphene catalyst for cathodes of Cu(II/I)-mediated dye-sensitized solar cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ladislav Kavan, Ulf Anders Hagfeldt, Yasemin Saygili, Marina Freitag

Novel highly active, optically-transparent electrode catalyst containing Pt, PtOx, graphene oxide and stacked graphene platelet nanofibers is developed for a cathode of Cu(II/I)-mediated dye-sensitized solar cells. The catalyst layer is deposited on a FTO ...

Pergamon-Elsevier Science Ltd2017

Migration of cations induces reversible performance losses over day/night cycling in perovskite solar cells

Michael Graetzel, Mohammad Khaja Nazeeruddin, Ulf Anders Hagfeldt, Konrad Domanski, Wolfgang Richard Tress, Juan-Pablo Correa-Baena, Antonio Abate, Taisuke Matsui, Michael Saliba, Filippo de Angelis, Silver Hamill Turren Cruz

Perovskites have been demonstrated in solar cells with a power conversion efficiency of well above 20%, which makes them one of the strongest contenders for next generation photovoltaics. While there are no concerns about their efficiency, very little is ...

Royal Soc Chemistry2017

11% efficiency solid-state dye-sensitized solar cells with copper(II/I) hole transport materials

Jacques-Edouard Moser, Shaik Mohammed Zakeeruddin, Joël Teuscher, Ulf Anders Hagfeldt, Norman Pellet, Yiming Cao, Amita Ummadisingu, Fabrizio Giordano, Jingshan Luo, Yasemin Saygili, Marina Freitag

Solid-state dye-sensitized solar cells currently suffer from issues such as inadequate nanopore filling, low conductivity and crystallization of hole-transport materials infiltrated in the mesoscopic TiO2 scaffolds, leading to low performances. Here we rep ...

Nature Publishing Group2017

The rapid evolution of highly efficient perovskite solar cells

Michael Graetzel, Ulf Anders Hagfeldt, Wolfgang Richard Tress, Juan-Pablo Correa-Baena, Antonio Abate, Michael Saliba, Tor Jesper Jacobsson

Perovskite solar cells (PSCs) have attracted much attention because of their rapid rise to 22% efficiencies. Here, we review the rapid evolution of PSCs as they enter a new phase that could revolutionize the photovoltaic industry. In particular, we describ ...

Royal Society of Chemistry2017

Elucidating the role of chlorine in perovskite solar cells

Ulf Anders Hagfeldt, Li Fan, Yi Ding, Jingshan Luo, Xiaoyu Zhang, Di Zhang, Gang Wang

It has been proposed that introducing the chlorine anion into a CH3NH3PbI3 perovskite material can substantially improve the materials properties as well as the solar cell performance. To elucidate the role of chlorine in perovskite solar cells (PSCs), her ...

Royal Society of Chemistry2017

Promises and challenges of perovskite solar cells

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

The efficiencies of perovskite solar cells have gone from single digits to a certified 22.1% in a few years' time. At this stage of their development, the key issues concern how to achieve further improvements in efficiency and long-term stability. We revi ...

American Association for the Advancement of Science2017

Intrinsic Origin of Superior Catalytic Properties of Tungsten-based Catalysts in Dye-sensitized Solar Cells

Ulf Anders Hagfeldt, Yao Liu, Sining Yun, Xiao Zhou, Jing Li

To clarify the intrinsic factor of the superior catalytic activity of tungsten (W)-based catalysts in DSSCs, W-based compounds, including W18O49, W2N, WC, and WO3, were prepared as CEs and tested in I-/I-3(-) redox shuttle. A systematic investigation of th ...

Elsevier2017

Tailor-Making Low-Cost Spiro[fluorene-9,9 '-xanthene]-Based 3D Oligomers for Perovskite Solar Cells

Ulf Anders Hagfeldt, Liang Wang, Peng Liu, Jiahuan Zhang

The power-conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have increased rapidly from about 4% to 22% during the past few years. One of the major challenges for further improvement of the efficiency of PSCs is the lack of sufficiently good ...

Cell Press2017

Tandem Heterojunction Photoelectric Cell Based on Organic-Inorganic Hybrid of AlPc-H2Pc and n-Si

Ulf Anders Hagfeldt

The tandem heterojunction photoelectric cell has been fabricated on the basis of organic-inorganic hybrid of AlPc-H2Pc (aluminium phthalocyanine-metal free phthalocyanine) and n-Si using pressing technique along with vapor deposition. Initially, the AlPc-H ...

Esg2017

Organic-inorganic hybrid tandem bulk heterojunction ITO/A1Pc:H2Pc/n-Si/Al photoelectric cell

Ulf Anders Hagfeldt

Organic-inorganic hybrid tandem heterojunction ITO/AIPc:H2Pc/n-Si/Al photoelectric cell was fabricated by a pressing technology using preliminary vapor deposited bulk heterojunction films of mixed aluminum-phthalocyanine (AIPc) and metal free phthalocyanin ...

Natl Inst Optoelectronics2017

Valence Level Character in a Mixed Perovskite Material and Determination of the Valence Band Maximum from Photoelectron Spectroscopy: Variation with Photon Energy

Ulf Anders Hagfeldt, Juan-Pablo Correa-Baena, Tor Jesper Jacobsson

A better understanding of the electronic structure of perovskite materials used in photovoltaic devices is essential for their development and optimization. In this investigation, synchrotron-based photoelectron spectroscopy (PES) was used to experimentall ...

American Chemical Society2017

Perovskite solar cell - electrochemical double layer capacitor interplay

Michael Graetzel, Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Juan-Pablo Correa-Baena, Michael Saliba, Silver Hamill Turren Cruz

We demonstrate that by a proper design of a system comprising a perovskite solar cell (PSC) coupled to an electrochemical double-layer capacitor (EDLC), it is possible to simultaneously improve both the PSC and EDLC performance and outperform each single u ...

Elsevier2017

Characterization techniques for dye-sensitized solar cells

Ulf Anders Hagfeldt

Dye-sensitized solar cells (DSCs) have been widely studied in the last two decades and start to be commercialized in the photovoltaic market. Comprehensive characterization is needed to fully understand and optimize the device performance and stability. In ...

Royal Soc Chemistry2017

Nondestructive Probing of Perovskite Silicon Tandem Solar Cells Using Multiwavelength Photoluminescence Mapping

Michael Graetzel, Ulf Anders Hagfeldt, Juan-Pablo Correa-Baena, Michael Saliba, Elham Halvani Anaraki

In this paper, spatially resolved photoluminescence (PL) spectroscopy with various excitation wavelengths is presented as a nondestructive and versatile technique providing access to the individual subcells of multijunction solar cells. This method is demo ...

Ieee-Inst Electrical Electronics Engineers Inc2017

Additives, Hole Transporting Materials and Spectroscopic Methods to Characterize the Properties of Perovskite Films

Michael Graetzel, Shaik Mohammed Zakeeruddin, Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Marko Stojanovic, Amita Ummadisingu, Jiyoun Seo, Michael Saliba

The achievement of high efficiency and high stability in perovskite solar cells (PSCs) requires optimal selection and evaluation of the various components. After a brief introduction to the perovskite materials and their historical evolution, the first par ...

Schweizerische Chemische Gesellschaft2017

Spontaneous crystal coalescence enables highly efficient perovskite solar cells

Michael Graetzel, Ulf Anders Hagfeldt, Amita Ummadisingu, Juan-Pablo Correa-Baena, Antonio Abate, Michael Saliba

Perovskite solar cells have recently reached staggering efficiencies, through efforts focused on reducing grain boundaries, by enlarging the size of the crystalline domains that constitute the perovskite films. Here, we demonstrate that smaller crystallite ...

Elsevier Science Bv2017

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