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Ulf Anders Hagfeldt

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Related publications (296)

Unravelling the structural complexity and photophysical properties of adamantyl-based layered hybrid perovskites

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ursula Röthlisberger, Ulf Anders Hagfeldt, Amita Ummadisingu, Mohammad Ibrahim Dar, Marko Mladenovic, Wolfgang Richard Tress, Farzaneh Jahanbakhshi, Paramvir Ahlawat, Brian Irving Carlsen, Yang Li, Jovana Milic, Yang Li, Algirdas Ducinskas

Layered hybrid perovskites comprising adamantyl spacer (A) cations based on the A(2)FA(n-1)Pb(n)I(3n+1)(n= 1-3, FA = formamidinium) compositions have recently been shown to act as promising materials for photovoltaic applications. While the corresponding p ...

Royal Society of Chemistry2020

Outstanding Passivation Effect by a Mixed-Salt Interlayer with Internal Interactions in Perovskite Solar Cells

Ulf Anders Hagfeldt, Wolfgang Richard Tress, Filippo de Angelis, Hui-Seon Kim, Bowen Yang, Jiajia Suo

Nonradiative recombination is a major limiting factor in obtaining efficient metal-halide perovskite photovoltaics. Here, a passivation treatment is developed by applying a mixture of a new ammonium salt, CF3(CF2)(2)CH2NH3I (HBAI), and a conventional forma ...

AMER CHEMICAL SOC2020

Revealing the Mechanism of Doping of spiro-MeOTAD via Zn Complexation in the Absence of Oxygen and Light

Ulf Anders Hagfeldt, Yasemin Saygili, Hui-Seon Kim, Bowen Yang, Jiajia Suo

In this study, a new mechanism for doping of spiro-MeOTAD by Zn(TFSI)(2) is revealed, which is completely different from the mechanism induced by LiTFSI. The oxidation of spiro-MeOTAD is facilitated by complexation between the zinc cation and tert-butylpyr ...

AMER CHEMICAL SOC2020

Passivation Mechanism Exploiting Surface Dipoles Affords High-Performance Perovskite Solar Cells

Michael Graetzel, Mohammad Khaja Nazeeruddin, Shaik Mohammed Zakeeruddin, Thomas La Grange, Paul Joseph Dyson, Ulf Anders Hagfeldt, Jun Ho Yum, Kevin Sivula, Kazuteru Nonomura, Erfan Shirzadi, Fatemeh Ansari

The employment of 2D perovskites is a promising approach to tackling the stability and voltage issues inherent in perovskite solar cells. It remains unclear, however, whether other perovskites with different dimensionalities have the same effect on efficie ...

AMER CHEMICAL SOC2020

Unveiling the light soaking effects of the CsPbI3 perovskite solar cells

Ulf Anders Hagfeldt

Pure inorganic perovskite of CsPbI3 attracts great attentions due to its excellent thermal stability and more suitable bandgap for tandem solar cells. The power conversion efficiency (PCE) of CsPbI3 perovskite solar cells has swiftly increased to 19.03%. H ...

ELSEVIER2020

Stabilization of Highly Efficient and Stable Phase-Pure FAPbI(3)Perovskite Solar Cells by Molecularly Tailored 2D-Overlayers

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Mohammad Ibrahim Dar, Jiyoun Seo, Yuhang Liu, Seckin Akin, Jiahuan Zhang, Felix Thomas Eickemeyer, Hong Zhang, Hongwei Zhu

As a result of their attractive optoelectronic properties, metal halide APbI(3)perovskites employing formamidinium (FA(+)) as the A cation are the focus of research. The superior chemical and thermal stability of FA(+)cations makes alpha-FAPbI(3)more suita ...

Wiley-VCH Verlag GmbH2020

Side-chain engineering of PEDOT derivatives as dopant-free hole-transporting materials for efficient and stable n-i-p structured perovskite solar cells

Ulf Anders Hagfeldt, Xiaoqing Jiang

Low-cost poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives have been widely used as hole-transporting materials (HTMs) in p-i-n perovskite solar cells (PSCs). However, reports on the use of PEDOT-based HTMs in regular PSCs have been rather limit ...

Royal Society of Chemistry2020

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

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

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

Polymeric room-temperature molten salt as a multifunctional additive toward highly efficient and stable inverted planar perovskite solar cells

Ulf Anders Hagfeldt, Jiabao Yang, Ziwei He, Bowen Yang, Jiajia Suo, Chao Tang, Shilong Wang

The inferior power conversion efficiency (PCE) compared to their regular counterparts (n-i-p) and undesirable stability issues of inverted (p-i-n) perovskite solar cells (PSCs) are the foremost issues hindering their commercialization. Here, for the first ...

ROYAL SOC CHEMISTRY2020

Reduced Graphene Oxide Improves Moisture and Thermal Stability of Perovskite Solar Cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Bowen Yang

Reduced graphene oxide (rGO) is a very stable material with tunable electronic properties dependent on its reduction level. Nevertheless, the incorporation of rGO into perovskite solar cells (PSCs) frequently demonstrates inconsistent results, and it plays ...

2020

Dual Passivation of CsPbI3 Perovskite Nanocrystals with Amino Acid Ligands for Efficient Quantum Dot Solar Cells

Ulf Anders Hagfeldt, Jianhua Liu

Inorganic CsPbI3 perovskite quantum dot (PQD) receives increasing attention for the application in the new generation solar cells, but the defects on the surface of PQDs significantly affect the photovoltaic performance and stability of solar cells. Herein ...

2020

Fine-Tuning by Triple Bond of Carbazole Derivative Dyes to Obtain High Efficiency for Dye-Sensitized Solar Cells with Copper Electrolyte

Ulf Anders Hagfeldt, Li Zhang

Three novel dyes consisting of a 5,8,15-tris(2-ethylhexyl)-8,15-dihydro-SH-benzo[1,2-b:3,4-b':6,5-b '']tricarbazole (BTC) electron-donating group and a 4,7-bis(4-hexylthiophen-2-yl)benzo[c][1,2,5]thiadiazole (BTBT) pi-bridge with an anchoring group of phen ...

AMER CHEMICAL SOC2020

Efficient and stable planar all-inorganic perovskite solar cells based on high-quality CsPbBr3 films with controllable morphology

Ulf Anders Hagfeldt

All-inorganic cesium lead bromide (CsPbBr3) perovskite is attracting growing interest as functional materials in photovoltaics and other optoelectronic devices due to its superb stability. However, the fabrication of high-quality CsPbBr3 films still remain ...

2020

Formamidinium-Based Dion-Jacobson Layered Hybrid Perovskites: Structural Complexity and Optoelectronic Properties

Layered hybrid perovskites have emerged as a promising alternative to stabilizing hybrid organic-inorganic perovskite materials, which are predominantly based on Ruddlesden-Popper structures. Formamidinium (FA)-based Dion-Jacobson perovskite analogs are de ...

2020

Ligand-Modulated Excess PbI2 Nanosheets for Highly Efficient and Stable Perovskite Solar Cells

Ulf Anders Hagfeldt, Chenyi Yi, Yi Ding, Jingshan Luo, Xiaoyu Zhang, Zaiwei Wang, Zhen Yang

Excess lead iodide (PbI2), as a defect passivation material in perovskite films, contributes to the longer carrier lifetime and reduced halide vacancies for high-efficiency perovskite solar cells. However, the random distribution of excess PbI2 also leads ...

Wiley-V C H Verlag Gmbh2020

Blocking the Charge Recombination with Diiodide Radicals by TiO2 Compact Layer in Dye-Sensitized Solar Cells

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Kazuteru Nonomura

The addition of a compact titanium dioxide (TiO2) layer between the fluorine-doped tin oxide (FTO) coated glass substrate and the mesoporous TiO2 layer in the dye-sensitized solar cell (DSC) based on the iodide/triiodide redox couple (I-/I-3(-)) is known t ...

ELECTROCHEMICAL SOC INC2019

Dye sensitized photoelectrolysis cells

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Sining Yun

To advance the progress of photoelectrolysis, various promising devices integrated with p- and n-type photocatalysts and dye sensitized photoelectrodes have been systematically studied. This review discusses, from theory to practice, an integration strateg ...

Royal Society of Chemistry2019

Electronic Structures and Catalytic Activities of Niobium Oxides as Electrocatalysts in Liquid-Junction Photovoltaic Devices

Ulf Anders Hagfeldt, Sheng Meng, Sining Yun, Hang Liu

Two types of nanosized niobium oxides and their composites, pseudohexagonal Nb2O5 (TT-Nb2O5), monoclinic NbO2 (M-NbO2), and the coexistence of TT-Nb2O5 and M-NbO2 (TT-Nb2O5/M-NbO2), are successfully synthesized through the urea-metal chloride route, and th ...

WILEY-V C H VERLAG GMBH2019

A tandem redox system with a cobalt complex and 2-azaadamantane-N-oxyl for fast dye regeneration and open circuit voltages exceeding 1 V

Michael Graetzel, Jacques-Edouard Moser, Shaik Mohammed Zakeeruddin, Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Heewon Bahng, Natalie Flores Diaz

A new tandem electrolyte composed of two redox pairs, the organic radical 2-azaadamantane-N-oxyl (AZ) and the well-known redox pair Co(bpy)(3) was investigated in dye sensitized solar cells. Importantly, an increase in V-OC was achieved using the ...

Royal Society of Chemistry2019

Ultrahydrophobic 3D/2D fluoroarene bilayer-based water-resistant perovskite solar cells with efficiencies exceeding 22%

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Mohammad Ibrahim Dar, Neha Arora, Linfeng Pan, Ryusuke Uchida, Yuhang Liu, Jovana Milic, Alexander Roland Uhl, Seckin Akin

Preventing the degradation of metal perovskite solar cells (PSCs) by humid air poses a substantial challenge for their future deployment. We introduce here a two-dimensional (2D) A(2)PbI(4) perovskite layer using pentafluoro-phenylethylammonium (FEA) as a ...

2019

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