Home

Person

Ulf Anders Hagfeldt

This person has left EPFL

About
Privacy
Disclaimer

Graph Chatbot

Related publications (296)

Page 4 of 15

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

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

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

Thermodynamic stability screening of IR-photonic processed multication halide perovskite thin films

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Pascal Alexander Schouwink, Brian Irving Carlsen, Sandy Sanchez Alonso, Natalie Flores Diaz

We report a material screening study for phase transitions of multication hybrid halide perovskite films. Two hundred sixty-six films processed with flash infrared annealing were optically and structurally characterized. This data was compiled into a datab ...

Royal Society of Chemistry2021

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

Low-Cost Dopant Additive-Free Hole-Transporting Material for a Robust Perovskite Solar Cell with Efficiency Exceeding 21%

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Felix Thomas Eickemeyer, Yuhang Liu, Linfeng Pan, Hongwei Zhu, Yameng Ren, Zhongjin Shen

Developing hole-transporting materials (HTMs) with appropriate molecular configuration and charge mobility is important to improve perovskite solar cell (PSC) photovoltaic performance and their feasibility for commercialization. In this work, a novel pyram ...

2021

Efficient solid-state dye sensitized solar cells: The influence of dye molecular structures for the in-situ photoelectrochemically polymerized PEDOT as hole transporting material

Mohammad Khaja Nazeeruddin, Ulf Anders Hagfeldt, Nikolaos Vlachopoulos

Solid-state dye sensitized solar cells (sDSCs) with organic small molecule hole transporting materials (HTMs) have limited efficiencies due to the incomplete pore filling of the HTMs in the thick mesoporous electrodes and the low hole conductivity of HTMs. ...

Elsevier Science Bv2016

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

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

Ulf Anders Hagfeldt, Nikolaos Vlachopoulos

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

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

Ulf Anders Hagfeldt, Nikolaos Vlachopoulos, 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

An experimental and theoretical exploration of the role of tri-element metal-nonmetal nanohybrids in photovoltaics

Ulf Anders Hagfeldt

Inexpensive electrocatalysts with excellent catalytic activity as the counter electrodes (CEs) are crucial for the commercialization of solar cells. Herein, we report a unique rhombic dodecahedron framework of N-doped porous carbon loaded with 0.66 wt% Fe ...

ELSEVIER SCIENCE SA2021

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

Ulf Anders Hagfeldt, Nikolaos Vlachopoulos, Lin Yang

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

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

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

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

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

Regeneration and recombination kinetics in cobalt polypyridine based dye-sensitized solar cells, explained using Marcus theory

Michael Graetzel, Mohammad Khaja Nazeeruddin, Ulf Anders Hagfeldt

Regeneration and recombination kinetics was investigated for dye-sensitized solar cells (DSCs) using a series of different cobalt polypyridine redox couples, with redox potentials ranging between 0.34 and 1.20 V vs. NHE. Marcus theory was applied to explai ...

Royal Society of Chemistry2013

A combined molecular dynamics and experimental study of two-step process enabling low-temperature formation of phase-pure α-FAPbI3

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ursula Röthlisberger, Ulf Anders Hagfeldt, Paramvir Ahlawat, Essa Awadh R Alharbi, Haizhou Lu

It is well established that the lack of understanding the crystallization process in a two-step sequential deposition has a direct impact on efficiency, stability, and reproducibility of perovskite solar cells. Here, we try to understand the solid-solid ph ...

2021

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

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

Photoelectrochemical Water-Splitting Using CuO-Based Electrodes for Hydrogen Production: A Review

Ulf Anders Hagfeldt

The cost-effective, robust, and efficient electrocatalysts for photoelectrochemical (PEC) water-splitting has been extensively studied over the past decade to address a solution for the energy crisis. The interesting physicochemical properties of CuO have ...

Wiley-V C H Verlag Gmbh2021

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

Ulf Anders Hagfeldt, Lin Yang

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

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

Ulf Anders Hagfeldt, Nikolaos Vlachopoulos

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

Cu2O photocathodes with band-tail states assisted hole transport for standalone solar water splitting

Michael Graetzel, Ulf Anders Hagfeldt, Kevin Sivula, Liang Yao, Yuhang Liu, Dan Ren, Linfeng Pan

Photoelectrochemical water splitting provides a promising solution for harvesting and storing solar energy. As the best-performing oxide photocathode, the Cu2O photocathode holds the performance rivaling that of many photovoltaic semiconductor-based photoc ...

Nature Research2020