Publications de Amita Ummadisingu

Speciation of Lanthanide Metal Ion Dopants in Microcrystalline All-Inorganic Halide Perovskite CsPbCl3

Amita Ummadisingu, Dominik Józef Kubicki, David Lyndon Emsley, Albert Hofstetter, Daniel Prochowicz

Lanthanides are versatile modulators of optoelectronic properties owing to their narrow optical emission spectra across the visible and near-infrared range. Their use in metal halide perovskites (MHPs) has recently gained prominence, although their fate in ...

Amer Chemical Soc2024

Crystal-Size-Induced Band Gap Tuning in Perovskite Films

Michael Graetzel, Amita Ummadisingu, Simone Meloni, Wolfgang Richard Tress

A comprehensive picture explaining the effect of the crystal size in metal halide perovskite films on their opto-electronic characteristics is currently lacking. We report that perovskite nanocrystallites exhibit a wider band gap due to concurrent quantum ...

Wiley-VCH Verlag GmbH2021

Multi-Length Scale Structure of 2D/3D Dion-Jacobson Hybrid Perovskites Based on an Aromatic Diammonium Spacer

Michael Graetzel, Thomas La Grange, Amita Ummadisingu, Dominik Józef Kubicki, David Lyndon Emsley, Jovana Milic, Algirdas Ducinskas, Aditya Mishra

Dion-Jacobson (DJ) iodoplumbates based on 1,4-phenylenedimethanammonium (PDMA) have recently emerged as promising light absorbers for perovskite solar cells. While PDMA is one of the simplest aromatic spacers potentially capable of forming a DJ structure b ...

2021

Guanine‐Stabilized Formamidinium Lead Iodide Perovskites

Shaik Mohammed Zakeeruddin, Ursula Röthlisberger, Ulf Anders Hagfeldt, Amita Ummadisingu, Marko Mladenovic, Dominik Józef Kubicki, David Lyndon Emsley, Linfeng Pan, Paramvir Ahlawat, Yuhang Liu, Jovana Milic, Dan Ren, Li Hong, Marco Alejandro Ruiz Preciado

Formamidinium (FA) lead iodide perovskite materials feature promising photovoltaic performances and superior thermal stabilities. However, conversion of the perovskite α‐FAPbI3 phase to the thermodynamically stable yet photovoltaically inactive δ‐FAPbI3 ph ...

2020

Supramolecular Modulation of Hybrid Perovskite Solar Cells via Bifunctional Halogen Bonding Revealed by Two-Dimensional 19F Solid-State NMR Spectroscopy

Shaik Mohammed Zakeeruddin, Amita Ummadisingu, Dominik Józef Kubicki, David Lyndon Emsley, Albert Hofstetter, Jovana Milic, Marco Alejandro Ruiz Preciado

There has been an ongoing effort to overcome the limitations associated with the stability of hybrid organic–inorganic perovskite solar cells by using different organic agents as additives to the perovskite formulations. The functionality of organic additi ...

2020

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

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

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 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

A chain is as strong as its weakest link - Stability study of MAPbI(3) under light and temperature

Michael Graetzel, Ulf Anders Hagfeldt, Amita Ummadisingu, Michael Saliba, Philippe Jürgen Holzhey, Pankaj Kumar Yadav, Silver Hamill Turren Cruz

The stability of perovskite solar cells is a key issue for industrial development. One reason for this is the volatile organic methylammonium (MA) cation, which is prone to degas under elevated temperatures from the perovskite. At the same time, small amou ...

2019

Bifunctional Organic Spacers for Formamidinium-Based Hybrid Dion-Jacobson Two-Dimensional Perovskite Solar Cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Amita Ummadisingu, Mohammad Ibrahim Dar, Jeong-Hyeok Im, Jiyoun Seo, Peng Wang, Hui-Seon Kim, Yuhang Liu, Yang Li, Jovana Milic, Yang Li

Three-dimensional (3D) perovskite materials display remarkable potential in photovoltaics owing to their superior solar-to-electric power conversion efficiency, with current efforts focused on improving stability. Two-dimensional (2D) perovskite analogues ...

AMER CHEMICAL SOC2019

Supramolecular Engineering for Formamidinium-Based Layered 2D Perovskite Solar Cells: Structural Complexity and Dynamics Revealed by Solid-State NMR Spectroscopy

Michael Graetzel, Shaik Mohammed Zakeeruddin, Amita Ummadisingu, Mohammad Ibrahim Dar, Dominik Józef Kubicki, Jeong-Hyeok Im, David Lyndon Emsley, Jiyoun Seo, Yang Li, Jovana Milic, Yang Li, Marco Alejandro Ruiz Preciado

Perovskite solar cells are one of the most promising photovoltaic technologies, although their molecular level design and stability toward environmental factors remain a challenge. Layered 2D Ruddlesden-Popper perovskite phases feature an organic spacer bi ...

WILEY-V C H VERLAG GMBH2019

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

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

Poly(ethylene glycol)-[60]Fullerene-Based Materials for Perovskite Solar Cells with Improved Moisture Resistance and Reduced Hysteresis

Shaik Mohammed Zakeeruddin, Amita Ummadisingu, Konrad Domanski, Wolfgang Richard Tress, Michael Saliba, Philippe Jürgen Holzhey, Silver Hamill Turren Cruz

2018

Revealing the detailed path of sequential deposition for metal halide perovskite formation

Amita Ummadisingu

2018

Fundamentals of perovskite formation for photovoltaics

Amita Ummadisingu

Perovskite solar cells have become strong contenders in the arena of photovoltaics due to the stunning rise in their efficiency from 3 % to over 20 % in just seven years. In this time, numerous device architectures and thin film deposition methods have bee ...

EPFL2018

11% efficiency solid-state dye-sensitized solar cells with copper(II/I) hole transport materials

Jacques-Edouard Moser, Shaik Mohammed Zakeeruddin, Joël Teuscher, Ulf Anders Hagfeldt, Norman Pellet, Yiming Cao, Amita Ummadisingu, Fabrizio Giordano, Jingshan Luo, Yasemin Saygili, Marina Freitag

Solid-state dye-sensitized solar cells currently suffer from issues such as inadequate nanopore filling, low conductivity and crystallization of hole-transport materials infiltrated in the mesoscopic TiO2 scaffolds, leading to low performances. Here we rep ...

Nature Publishing Group2017

The effect of illumination on the formation of metal halide perovskite films

Michael Graetzel, Ludmilla Steier, Amita Ummadisingu, Wolfgang Richard Tress, Antonio Abate, Jiyoun Seo, Taisuke Matsui

Optimizing the morphology of metal halide perovskite films is an important way to improve the performance of solar cells(1) when these materials are used as light harvesters(2), because film homogeneity is correlated with photovoltaic performance(3). Many ...

Nature Publishing Group2017

Additives, Hole Transporting Materials and Spectroscopic Methods to Characterize the Properties of Perovskite Films

Michael Graetzel, Shaik Mohammed Zakeeruddin, Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Marko Stojanovic, Amita Ummadisingu, Jiyoun Seo, Michael Saliba

The achievement of high efficiency and high stability in perovskite solar cells (PSCs) requires optimal selection and evaluation of the various components. After a brief introduction to the perovskite materials and their historical evolution, the first par ...

Schweizerische Chemische Gesellschaft2017

Spontaneous crystal coalescence enables highly efficient perovskite solar cells

Michael Graetzel, Ulf Anders Hagfeldt, Amita Ummadisingu, Juan-Pablo Correa-Baena, Antonio Abate, Michael Saliba

Perovskite solar cells have recently reached staggering efficiencies, through efforts focused on reducing grain boundaries, by enlarging the size of the crystalline domains that constitute the perovskite films. Here, we demonstrate that smaller crystallite ...

Elsevier Science Bv2017

Ionic Liquid Control Crystal Growth to Enhance Planar Perovskite Solar Cells Efficiency

Michael Graetzel, Shaik Mohammed Zakeeruddin, Kurt Schenk, Ulf Anders Hagfeldt, Amita Ummadisingu, Konrad Domanski, Fabrizio Giordano, Jingshan Luo, Juan-Pablo Correa-Baena, Antonio Abate, Jiyoun Seo, Taisuke Matsui, Michael Saliba, Mahboobeh Hadadian

Ionic liquids can retard the perovskite crystallization with the aim to form compact films with larger and more uniformly distributed grain size. The ionic liquid driven crystallization is exploited to prepared a record planar perovskite solar cell with st ...

Wiley-VCH Verlag Berlin2016

Incorporation of rubidium cations into perovskite solar cells improves photovoltaic performance

Michael Graetzel, Shaik Mohammed Zakeeruddin, Ulf Anders Hagfeldt, Amita Ummadisingu, Konrad Domanski, Wolfgang Richard Tress, Juan-Pablo Correa-Baena, Antonio Abate, Jiyoun Seo, Taisuke Matsui, Michael Saliba

All of the cations currently used in perovskite solar cells abide by the tolerance factor for incorporation into the lattice. We show that the small and oxidation-stable rubidium cation (Rb+) can be embedded into a "cation cascade" to create perovskite mat ...

American Association for the Advancement of Science2016