Publications de Negar Ashari Astani

A theoretical perspective of the ultrafast transient absorption dynamics of CsPbBr3

Ursula Röthlisberger, Negar Ashari Astani, Elisa Liberatore, Ariadni Boziki, Pablo Jonas Baudin

Transient absorption spectra (TAS) of lead halide perovskites can provide important insights into the nature of the photoexcited state dynamics of this prototypical class of materials. Here, we perform ground and excited state molecular dynamics (MD) simul ...

WILEY2022

Ruddlesden–Popper Phases of Methylammonium-Based Two-Dimensional Perovskites with 5-Ammonium Valeric Acid AVA2MAn–1PbnI3n+1 with n = 1, 2, and 3

Michael Graetzel, Ursula Röthlisberger, Negar Ashari Astani, Mohammad Ibrahim Dar, Marko Mladenovic, Farzaneh Jahanbakhshi, Anwar Qasem M Alanazi

2019

Effect of graphene oxide nanosheets on visible light-assisted antibacterial activity of vertically-aligned copper oxide nanowire arrays

Ursula Röthlisberger, Negar Ashari Astani, Ehsan Hashemi, Fateme Kiani Shahvandi

2018

Computational Characterization of the Dependence of Halide Perovskite Effective Masses on Chemical Composition and Structure

Michael Graetzel, Ursula Röthlisberger, Amir Hesam Salavati, Negar Ashari Astani, Giulia Palermo, Simone Meloni

Effective masses are calculated for a large variety of perovskites of the form ABX(3) differing in chemical composition (A= Na, Li, Cs; B = Pb, Sn; X= Cl, Br, I) and crystal structure. In addition, the effects of some defects and dopants are assessed. We s ...

2017

Entropic stabilization of mixed A-cation ABX3 metal halide perovskites for high performance perovskite solar cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ursula Röthlisberger, Negar Ashari Astani, Chenyi Yi, Simone Meloni, Jingshan Luo, Ariadni Boziki

ABX(3)-type organic lead halide perovskites currently attract broad attention as light harvesters for solar cells due to their high power conversion efficiency (PCE). Mixtures of formamidinium (FA) with methylammonium (MA) as A-cations show currently the b ...

2016

Valence and conduction band tuning in halide perovskites for solar cell applications

Ursula Röthlisberger, Negar Ashari Astani, Giulia Palermo, Simone Meloni

We performed density functional calculations aimed at identifying the atomistic and electronic structure origin of the valence and conduction band, and band gap tunability of halide perovskites ABX(3) upon variations of the monovalent and bivalent cations ...

Royal Society of Chemistry2016

Extended Intermolecular Interactions Governing Photocurrent-Voltage Relations in Ternary Organic Solar Cells

Ursula Röthlisberger, Beatrice Beyer, Negar Ashari Astani, Simone Meloni, Wolfgang Richard Tress, Feng Gao

Efficient organic solar cells are based on (electron) donor-acceptor heterojunctions. An optically generated excited molecular state (exciton) is dissociated at this junction, forming a charge-transfer (CT) state in an intermediate step before the electron ...

2016

Synthesis, characterization and ab initio investigation of a panchromatic ullazine–porphyrin photosensitizer for dye-sensitized solar cells

Michael Graetzel, Mohammad Khaja Nazeeruddin, Ursula Röthlisberger, Basile Curchod, Magdalena Anna Marszalek, Negar Ashari Astani, Julien Edouard Frey, Simon Mathew

An ullazine unit was employed as a donor moiety in a donor-pi-acceptor (D-p-A) motif, employing the porphyrin macrocycle as a pi-system. Synthesis of this ullazine-porphyrin dyad containing sensitizer (SM63) was achieved and an investigation of the electro ...

Royal Society of Chemistry2016

Computational studies for the characterization and design of dye sensitized solar cells (DSSCs) with improved efficiencies

Negar Ashari Astani

During millions of years of evolution, all creatures have found their ways of harvesting, storing and utilizing the energy coming from the sun. Plants use photosynthesis to convert carbon dioxide to glucose. With a low efficiency of only 3%, plants still c ...

EPFL2015

In-situ mapping of the molecular arrangement of amphiphilic dye molecules at the TiO2 surface of dye sensitized solar cells

Michael Graetzel, Ursula Röthlisberger, Ivano Tavernelli, Nicolas Tétreault, Negar Ashari Astani, Francesco Stellacci, Kislon Voitchovsky, Hauke Arne Harms

Amphiphilic sensitizers are central to the function of dye-sensitized solar cells. It is known that the cells performance depends on the molecular arrangement and the density of the dye on the semiconductor surface, but a molecular-level picture of the cel ...

2015

Dye-sensitized solar cells with 13% efficiency achieved through the molecular engineering of porphyrin sensitizers

Michael Graetzel, Mohammad Khaja Nazeeruddin, Robin Humphry-Baker, Ursula Röthlisberger, Ivano Tavernelli, Basile Curchod, Negar Ashari Astani, Aswani Yella, Peng Gao, Simon Mathew

Dye-sensitized solar cells have gained widespread attention in recent years because of their low production costs, ease of fabrication and tunable optical properties, such as colour and transparency. Here, we report a molecularly engineered porphyrin dye, ...

2014

Lessons from Nature: Computational Design of Biomimetic Compounds and Processes

Ursula Röthlisberger, Pablo Campomanes Ramos, Elizabeth Claire Brunk, Negar Ashari Astani, Esra Bozkurt, Marta Andreia Da Silva Perez, Nicholas John Browning

Through millions of years of evolution, Nature has accomplished the development of highly efficient and sustainable processes and the idea to understand and copy natural strategies is therefore very appealing. However, in spite of intense experimental and ...

2014

Towards Compatibility between Ruthenium Sensitizers and Cobalt Electrolytes in Dye-Sensitized Solar Cells

Michael Graetzel, Jacques-Edouard Moser, Mohammad Khaja Nazeeruddin, Joël Teuscher, Rosario Scopelliti, Ursula Röthlisberger, Ivano Tavernelli, Basile Curchod, Negar Ashari Astani, Aswani Yella, Julien Edouard Frey, Peng Gao, Simon Mathew, Lauren Elizabeth Polander

Wiley-Blackwell2013

Molecular Engineering of a Fluorene Donor for Dye-Sensitized Solar Cells

Michael Graetzel, Jacques-Edouard Moser, Mohammad Khaja Nazeeruddin, Robin Humphry-Baker, Joël Teuscher, Ursula Röthlisberger, Ivano Tavernelli, Basile Curchod, Negar Ashari Astani, Aswani Yella, Julien Edouard Frey, Simon Mathew, Lauren Elizabeth Polander

To improve their efficiency beyond the state-of-the-art, D-pi-A dyes must display increased spectral breadth and account for the physical limitations observed in the dye. sensitized solar cells. In particular, they should be designed to control the electro ...

Amer Chemical Soc2013

Unravelling the Potential for Dithienopyrrole Sensitizers in Dye-Sensitized Solar Cells

Michael Graetzel, Jacques-Edouard Moser, Mohammad Khaja Nazeeruddin, Robin Humphry-Baker, Joël Teuscher, Ursula Röthlisberger, Ivano Tavernelli, Basile Curchod, Negar Ashari Astani, Aswani Yella, Julien Edouard Frey, Peng Gao, Lauren Elizabeth Polander

Two D−π−A dyes based on the dithieno[3,2-b:2′,3′-d]pyrrole π-bridge (DTP) were synthesized, characterized using UV−vis absorption spectroscopy and electrochemistry, modeled using quantum chemical calculations, and used as sensitizers in dye-sensitized sola ...

Amer Chemical Soc2013

Pushing the Frontiers of First-Principles Based Computer Simulations of Chemical and Biological Systems

Ursula Röthlisberger, Ivano Tavernelli, Basile Curchod, Marilisa Neri, Pablo Campomanes Ramos, Stefano Vanni, Elizabeth Claire Brunk, Manuel Dömer, Andrey Laktionov, Negar Ashari Astani, Polydefkis Diamantis, Thomas James Penfold, Giulia Palermo

The Laboratory of Computational Chemistry and Biochemistry is active in the development and application of first-principles based simulations of complex chemical and biochemical phenomena. Here, we review some of our recent efforts in extending these metho ...

2011