Publications de Negar Ashari Astani

A theoretical perspective of the ultrafast transient absorption dynamics of CsPbBr3

Ursula Röthlisberger, Ariadni Boziki, Negar Ashari Astani, Elisa Liberatore, 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, Marko Mladenovic, Mohammad Ibrahim Dar, Negar Ashari Astani, Anwar Qasem M Alanazi, Farzaneh Jahanbakhshi

2019

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

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

2018

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

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

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, Ariadni Boziki, Simone Meloni, Jingshan Luo, Chenyi Yi, Negar Ashari Astani

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, Simone Meloni, Giulia Palermo, Negar Ashari Astani

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

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, Francesco Stellacci, Ivano Tavernelli, Nicolas Tétreault, Negar Ashari Astani, 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