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Michael Allan Hope

Cette personne a quitté l’EPFL

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Publications associées (26)

Page 1 sur 2

Dynamic Nuclear Polarization Enables NMR of Surface Passivating Agents on Hybrid Perovskite Thin Films

Michael Graetzel, Shaik Mohammed Zakeeruddin, David Lyndon Emsley, Masaud Hassan S Almalki, Aditya Mishra, Michael Allan Hope, Lukas Pfeifer

Surface and bulk molecular modulators are the key to improving the efficiency and stability of hybrid perovskite solar cells. However, due to their low concentration, heterogeneous environments, and low sample mass, it remains challenging to characterize t ...

2022

A Complete Picture of Cation Dynamics in Hybrid Perovskite Materials from Solid-State NMR Spectroscopy

Michael Graetzel, David Lyndon Emsley, Aditya Mishra, Michael Allan Hope

The organic cations in hybrid organic-inorganic perovskites rotate rapidly inside the cuboctahedral cavities formed by the inorganic lattice, influencing optoelectronic properties. Here, we provide a complete quantitative picture of cation dynamics for for ...

AMER CHEMICAL SOC2023

Colloidal-ALD Grown Hybrid Shells Nucleate via a Ligand–Precursor Complex

David Lyndon Emsley, Raffaella Buonsanti, Anna Loiudice, Snaedis Björgvinsdóttir, Kevin Rossi, Michael Allan Hope, Ona Segura Lecina, Amrit Venkatesh

Colloidal atomic layer deposition (c-ALD) enables the growth of hybrid organic/inorganic oxide shells with tunable thickness at the nanometer scale around ligand-functionalized inorganic nanoparticles (NPs). This recently developed method has demonstrated ...

2022

Dynamic nuclear polarisation of 1H in Gd-doped In(OH)3

David Lyndon Emsley, Michael Allan Hope, Amrit Venkatesh, Yuxuan Zhang

Dynamic nuclear polarisation (DNP) of solids doped with high-spin metal ions, such as Gd3+, is a useful strategy to enhance the nuclear magnetic resonance (NMR) sensitivity for these samples. Spin diffusion can relay polarisation throughout a sample, which ...

Academic Press Inc - Elsevier Science2023

Probing structural and dynamic properties of MAPbCl3 hybrid perovskite using Mn2+ EPR

Michael Allan Hope, Yuxuan Zhang

Hybrid methylammonium (MA) lead halide perovskites have emerged as materials exhibiting excellent photovoltaic performance related to their rich structural and dynamic properties. Here, we use multifrequency (X-, Q-, and W-band) electron paramagnetic reson ...

Royal Soc Chemistry2024

Optically Enhanced Solid-State H-1 NMR Spectroscopy

Jean-Philippe Ansermet, Jonas Milani, Dominik Józef Kubicki, David Lyndon Emsley, Aaron James Rossini, Claudia Esther Avalos, Gabriele Stevanato, Aditya Mishra, Michael Allan Hope, Federico De Biasi, Saumya Badoni

Low sensitivity is the primary limitation to extendingnuclearmagnetic resonance (NMR) techniques to more advanced chemical andstructural studies. Photochemically induced dynamic nuclear polarization(photo-CIDNP) is an NMR hyperpolarization technique where ...

AMER CHEMICAL SOC2023

Crown Ether Modulation Enables over 23% Efficient Formamidinium-Based Perovskite Solar Cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Mounir Driss Mensi, Ursula Röthlisberger, Ulf Anders Hagfeldt, Jun Ho Yum, Kevin Sivula, Marko Mladenovic, David Lyndon Emsley, Farzaneh Jahanbakhshi, Jovana Milic, Dan Ren, Aditya Mishra, Felix Thomas Eickemeyer, Hong Zhang, Michael Allan Hope, Jun Li, Anurag Krishna, Olivier Ouellette, Zhiwen Zhou

The use of molecular modulators to reduce the defect density at the surface and grain boundaries of perovskite materials has been demonstrated to be an effective approach to enhance the photovoltaic performance and device stability of perovskite solar cell ...

2020

Formamidinium Incorporates into Rb-based Non-Perovskite Phases in Solar Cell Formulations

Michael Graetzel, David Lyndon Emsley, Michael Allan Hope, Lukas Pfeifer, Ümmügülsüm Günes, Yuxuan Zhang, Likai Zheng

Organic-inorganic hybrid perovskite materials, such as formamidinium lead iodide (FAPbI3), are among the most promising emerging photovoltaic materials. However, the spontaneous phase transition from the photoactive perovskite phase to an inactive non-pero ...

Wiley-VCH Verlag GmbH2024

Strain-induced rubidium incorporation into wide-bandgap perovskites reduces photovoltage loss

Michael Graetzel, Shaik Mohammed Zakeeruddin, Mounir Driss Mensi, Ursula Röthlisberger, David Lyndon Emsley, Pascal Alexander Schouwink, Jing Gao, Felix Thomas Eickemeyer, Michael Allan Hope, Lukas Pfeifer, Nikolaos Lempesis, Virginia Carnevali, Ümmügülsüm Günes, Lorenzo Agosta, Yuxuan Zhang, Likai Zheng, Vladislav Slama, Francesco Biasoni

A-site cation mixing can enhance the photovoltaic performance of a wide-bandgap (WBG) perovskite, but rubidium (Rb) cation mixing generally forms a nonperovskite phase. We report that lattice strain locks Rb ions into the α-phase of the lattice of a triple ...

American Association for the Advancement of Science (AAAS)2025

Endogenous O-17 Dynamic Nuclear Polarization of Gd-Doped CeO2 from 100 to 370 K

David Lyndon Emsley, Snaedis Björgvinsdóttir, Michael Allan Hope

O-17 NMR is an invaluable tool to study the structure and dynamics of oxide materials but remains challenging to apply in many systems. Even with isotopic enrichment, studies of samples with low masses and/or concentrations of the active species, such as t ...

2021

Efficient and Stable Large Bandgap MAPbBr(3) Perovskite Solar Cell Attaining an Open Circuit Voltage of 1.65 V

Michael Graetzel, Shaik Mohammed Zakeeruddin, Thomas Paul Baumeler, David Lyndon Emsley, Linfeng Pan, Anwar Qasem M Alanazi, Yuhang Liu, Jing Gao, Felix Thomas Eickemeyer, Hongwei Zhu, Michael Allan Hope, Olivier Ouellette

We report on the preparation of MAPbBr(3) perovskite films of high electronic quality by applying a methylamine (MA) vapor treatment and mitigating surface defects using the amphiphilic molecular passivator, neopentylammonium chloride (NPACl). We find that ...

2022

Light-Induced Metallic and Paramagnetic Defects in Halide Perovskites from Magnetic Resonance

David Lyndon Emsley, Aditya Mishra, Michael Allan Hope

Halide perovskites are promising next-generation solar cell materials, but their commercialization is hampered by their propensity to degrade under operating conditions, particularly under heat, humidity, and light. Identifying degradation products and lin ...

2024

The Role of Alkyl Chain Length and Halide Counter Ion in Layered Dion−Jacobson Perovskites with Aromatic Spacers

Michael Graetzel, Jacques-Edouard Moser, Joachim Maier, Jovana Milic, George Cameron Fish, Algirdas Ducinskas, Michael Allan Hope

Layered hybrid perovskites based on Dion−Jacobson phases are of interest to various optoelectronic applications. However, the understanding of their structure−property relationships remains limited. Here, we present a systematic study of Dion−Jacobson pero ...

2021

Axial-Equatorial Halide Ordering in Layered Hybrid Perovskites from Isotropic-Anisotropic 207Pb NMR

Manuel Cordova, David Lyndon Emsley, Aditya Mishra, Michael Allan Hope, Ümmügülsüm Günes

Bandgap-tuneable mixed-halide 3D perovskites are of interest for multi-junction solar cells, but suffer from photoinduced spatial halide segregation. Mixed-halide 2D perovskites are more resistant to halide segregation and are promising coatings for 3D per ...

Wiley-VCH Verlag GmbH2024

Magic Angle Spinning Solid-State 13C Photochemically Induced Dynamic Nuclear Polarization by a Synthetic Donor-Chromophore-Acceptor System at 9.4 T

David Lyndon Emsley, Michael Allan Hope, Máté Visegrádi, Federico De Biasi

Solid-state photochemically induced dynamic nuclear polarization (photo-CIDNP) is a nuclear magnetic resonance spectroscopy technique in which nuclear spin hyperpolarization is generated upon optical irradiation of an appropriate donor-acceptor system. Unt ...

Amer Chemical Soc2024

Dynamic Nuclear Polarization of Inorganic Halide Perovskites

Dominik Józef Kubicki, David Lyndon Emsley, Gabriele Stevanato, Aditya Mishra, Michael Allan Hope

The intrinsic low sensitivity of nuclear magnetic resonance (NMR) experiments limits their utility for structure determination of materials. Dynamic nuclear polarization (DNP) under magic angle spinning (MAS) has shown tremendous potential to overcome this ...

2023

Light-Induced 1H NMR Hyperpolarization in Solids at 9.4 and 21.1 T

David Lyndon Emsley, Michael Allan Hope, Máté Visegrádi, Federico De Biasi, Marcel Levien

The inherently low sensitivity of nuclear magnetic resonance (NMR) spectroscopy is the major limiting factor for its application to elucidate structure and dynamics in solids. In the solid state, nuclear spin hyperpolarization methods based on microwave-in ...

2024

Light-Induced Halide Segregation in 2D and Quasi-2D Mixed-Halide Perovskites

Manuel Cordova, David Lyndon Emsley, Aditya Mishra, Michael Allan Hope

Photoinduced halide segregation hinders widespread application of three-dimensional (3D) mixed-halide perovskites. Much less is known about this phenomenon in lower-dimensional systems. Here, we study photoinduced halide segregation in lower-dimensional mi ...

AMER CHEMICAL SOC2023

Sensitivity Enhancements in Lithium Titanates by Incipient Wetness Impregnation DNP NMR

David Lyndon Emsley, Snaedis Björgvinsdóttir, Pierrick Berruyer, Pinelopi Moutzouri, Michael Allan Hope

Solid-state NMR spectroscopy is a widely used method for investigating structural and electronic properties of inorganic materials, but its use is often limited by low sensitivity. Here, we show how solvent-generated dynamic nuclear polarization can be use ...

2020

Multimodal host–guest complexation for efficient and stable perovskite photovoltaics

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ursula Röthlisberger, Ulf Anders Hagfeldt, Marko Mladenovic, David Lyndon Emsley, Farzaneh Jahanbakhshi, Paramvir Ahlawat, Zaiwei Wang, Jovana Milic, Dan Ren, Aditya Mishra, Felix Thomas Eickemeyer, Hong Zhang, Zhaowen Dong, Jinming Guo, Michael Allan Hope, Anurag Krishna, Olivier Ouellette, Zhiwen Zhou

Formamidinium lead iodide perovskites are promising light-harvesting materials, yet stabilizing them under operating conditions without compromising optimal optoelectronic properties remains challenging. We report a multimodal host–guest complexation strat ...

Nature Research2021