Materials Research Society | EPFL Graph Search

The Materials Research Society (MRS) is a non-profit, professional organization for materials researchers, scientists and engineers. Established in 1973, MRS is a member-driven organization of approximately 14,000 materials researchers from academia, industry and government. Headquartered in Warrendale, Pennsylvania, MRS membership spans over 90 countries, with approximately 48% of MRS members residing outside the United States. MRS members work in all areas of materials science and research, including physics, chemistry, biology, mathematics and engineering. MRS provides a collaborative environment for idea exchange across all disciplines of materials science through its meetings, publications and other programs designed to foster networking and cooperation. The Society’s mission is to promote communication for the advancement of interdisciplinary materials research to improve the quality of life. Governance MRS is governed by a board of directors which is composed of

Investigation of Lead-free perovskites for Optoelectronic Application

Alexander Fedorovskiy

The search for new energy sources and materials is at the foundations of scientific and technological progress. These two, often interconnected, fundamental elements open a way to create novel designs and improve existing ones for all types of machines and devices.Perovskite solar cells (PSCs) are a great example of this kind of system. Achievements in halide perovskite materials research made a remarkably rapid growth of energy conversion efficiency in PSC technology possible. In turn, a manufacturing process for the technology is potentially cheaper and more straightforward (relative to Si-based). As a result, the PSCs can be a solid background for producing the next generation of solar cells.However, unfortunately, PSCs are still not ready for a market, primarily because of three problems: large-scale production, stability, and toxicity. The first problem is mainly a result of the rawness of the technology, requires mostly resolving engineering tasks, and is not a fundamental barrier. The second problem â stability has a deeper connection to the properties of the material itself. The nature of degradation processes in PSCs is not completely clear. Still, different studies have found some promising ways to stabilize PSCs for a range of thousands of hours. Thus, a combination of engineering and material research can solve this problem, despite its deeper basis.The third problem, toxicity, is a fundamental property of the high efficient PSCs because of its lead-based compound. Lead is one of the critical components of halide perovskites used in the technology, and at the same time, this metal has confirmed toxicity. The water solubility of lead in halide perovskites (primarily as PbI2 and PbBr2) complicates the situation for the whole lifecycle of the devices - from production to recycling. The toxicity of the materials used in PSCs can affect one of the main goals of solar energy: to be produced safe, clean, and sustainable.Taking into account these facts, I focused this thesis on searching for lead-free alternatives for PSCs.Initially, I focused on searching for a model to predict promising vacancy-ordered double perovskites' formability as part of initial screening. I demonstrated the applicability of the geometrical approach based on Goldschmidt's Tolerance Factor for a simple, easy-to-use formability prediction technique for this class of materials. During this part of the study, I also demonstrated a difference between using the method for classic and vacancy-ordered perovskites.In the next part, I used a novel approach based on deep learning to design a new model of perovskite formability. As a result, I successfully forecast perovskite formability with an accuracy of over 98% for the best case. Moreover, I found that the resulting models were able to find some inaccuracies in the original data.Following, I synthesized and researched the structure and properties of tellurium-based vacancy-ordered perovskites. During the research, I found an unexpected complex situation of the optical gap determination for the materials. To solve this challenge, I demonstrated different approaches of absorption spectra fitting and cross-referenced it with other experimental data.

EPFL2021

Computational development of the nanoporous materials genome

Peter George Boyd, Yongjin Lee, Berend Smit

There is currently a push towards big data and data mining in materials research to accelerate discovery. Zeolites, metal-organic frameworks and other related crystalline porous materials are not immune to this phenomenon, as evidenced by the proliferation of porous structure databases and computational gas-adsorption screening studies over the past decade. The endeavour to identify the best materials for various gas separation and storage applications has led not only to thousands of synthesized structures, but also to the development of algorithms for building hypothetical materials. The materials databases assembled with these algorithms contain a much wider range of complex pore structures than have been synthesized, with the reasoning being that we have discovered only a small fraction of realizable structures and expanding upon these will accelerate rational design. In this Review, we highlight the methods developed to build these databases, and some of the important outcomes from large-scale computational screening studies.

Nature Publishing Group2017

Preserving Porosity of Mesoporous Metal-Organic Frameworks through the Introduction of Polymer Guests

Mehrdad Asgari, Aron Joel Huckaba, Sudabeh Jawahery, Seyedmohamad Moosavi, Mohammad Khaja Nazeeruddin, Emadeddin Oveisi, Li Peng, Wendy Lee Queen, Berend Smit, Shuliang Yang

High internal surface areas, an asset that is highly sought after in material design, has brought metal-organic frameworks (MOFs) to the forefront of materials research. In fact, a major focus in the field is on creating innovative ways to maximize MOF surface areas. Despite this, large-pore MOFs, particularly those with mesopores, continue to face problems with pore collapse upon activation. Herein, we demonstrate an easy method to inhibit this problem via the introduction of small quantities of polymer. For several mesoporous, isostructural MOFs, known as M-2(NDISA) (where M = Ni2+, Co2+, Mg2+, or Zn2+), the accessible surface areas are increased dramatically, from 5 to 50 times, as the polymer effectively pins the MOFs open. Postpolymerization, the high surface areas and crystallinity are now readily maintained after heating the materials to 150 degrees C under vacuum. These activation conditions, which could not previously be attained due to pore collapse, also provide accessibility to high densities of open metal coordination sites. Molecular simulations are used to provide insight into the origin of instability of the M-2(NDISA) series and to propose a potential mechanism for how the polymers immobilize the linkers, improving framework stability. Last, we demonstrate that the resulting MOF-polymer composites, referred to as M-2(NDISA)-PDA, offer a perfect platform for the appendage/immobilization of small nanocrystals inside rendering high-performance catalysts. After decorating one of the composites with Pd (average size: 2 nm) nanocrystals, the material shows outstanding catalytic activity for Suzuki-Miyaura cross-coupling reactions.

2019

Investigation of Lead-free perovskites for Optoelectronic Application

Alexander Fedorovskiy

EPFL2021