Degradation of methylammonium lead iodide perovskite structures through light and electron beam driven ion migration

[Image: see text] Organometal halide perovskites show promising features for cost-effective application in photovoltaics. The material instability remains a major obstacle to broad application because of the poorly understood degradation pathways. Here, we apply simultaneous luminescence and electron microscopy on perovskites for the first time, allowing us to monitor in situ morphology evolution and optical properties upon perovskite degradation. Interestingly, morphology, photoluminescence (PL), and cathodoluminescence of perovskite samples evolve differently upon degradation driven by electron beam (e-beam) or by light. A transversal electric current generated by a scanning electron beam leads to dramatic changes in PL and tunes the energy band gaps continuously alongside film thinning. In contrast, light-induced degradation results in material decomposition to scattered particles and shows little PL spectral shifts. The differences in degradation can be ascribed to different electric currents that drive ion migration. Moreover, solution-processed perovskite cuboids show heterogeneity in stability which is likely related to crystallinity and morphology. Our results reveal the essential role of ion migration in perovskite degradation and provide potential avenues to rationally enhance the stability of perovskite materials by reducing ion migration while improving morphology and crystallinity. It is worth noting that even moderate e-beam currents (86 pA) and acceleration voltages (10 kV) readily induce significant perovskite degradation and alter their optical properties. Therefore, attention has to be paid while characterizing such materials using scanning electron microscopy or transmission electron microscopy techniques

Разработка системы измерения производительности реализаций blockchain

Долголев Филипп Петрович Разработка системы измерения производительности реализаций blockchain Старший преподаватель кафедры системного программирования Кириленко Яков Александрович При разработке приложений на основе технологии blockchain, из-за наличия множества различных реализаций, разработчики сталкиваются с проблемой выбора. Один из важных критериев при выборе - производительность. В процессе поиска системы, позволяющей измерить производительность различных реализаций blockchain, не обнаружены ни проприетарные системы, ни с открытым исходным кодом. В рамках этой работы рассматривается разработка модульной системы, решающей эту проблему. Использованных источников: 18 Долголев, Ф. П. Разработка системы измерения производительности реализаций blockchain: выпускная квалификационная работа: защищена 01.06.2017 / Долголев Филипп Петрович. – СПб., 2017. – 21 с. – Библиография: с. 20–21.Filipp Dolgolev Blockchain Implementations Benchmarking Tool senior lecturer, dept. of software engineering Iakov Kirilenko Mathematics & mechanics, software engineering department Since there are many different types of blockchain technologies, developers are faced with a dilemma of which technology to choose when developing applications for a particular use case. One of the most important criteria effecting the selection is performance. During our research, we were unable to source either proprietary, or open source solutions allowing to benchmark various blockchain technologies performances. In this context, we are considering the development of such a solution. Sources cited: 18 Dolgolev, F. Blockchain Implementations Benchmarking Tool: Graduation thesis: Defended 01.06.2017 / Filipp Dolgolev. – St. Petersburg., 2017. – 21 pp. – Bibliography: pp. 20–21

Lead-Free Halide Perovskite Materials and Optoelectronic Devices: Progress and Prospective

Halide perovskites, in the form of thin films and colloidal nanocrystals, have recently taken semiconductor optoelectronics research by storm, and have emerged as promising candidates for high-performance solar cells, light-emitting diodes (LEDs), lasers, photodetectors, and radiation detectors. The impressive optical and optoelectronic properties, along with the rapid increase in efficiencies of solar cells and LEDs, have greatly attracted researchers across many disciplines. However, most advances made so far in terms of preparation (colloidal nanocrystals and thin films), and the devices with highest efficiencies are based on Pb-based halide perovskites, which have raised concerns over their commercialization due to the toxicity of Pb. This has triggered the search for lower-toxicity Pb-free halide perovskites and has led to significant progress in the last few years. In this roadmap review, researchers of different expertise have joined together to summarize the latest progress, outstanding challenges, and future directions of Pb-free halide perovskite thin films and nanocrystals, regarding their synthesis, optical spectroscopy, and optoelectronic devices, to guide the researchers currently working in this area as well as those that will join the field in the future.I.L.-F., D.V., C.-Y.W., S.S., T.O., Y.-T.H., K.S., Y.L., V.S.C., J.Z., L.D.T., and D.G. contributed equally to this work. L.P. acknowledges the support from the Spanish Ministerio de Ciencia e Innovación through the Ramón y Cajal grant (RYC2018-026103-I) and the Spanish State Research Agency (Grant No. PID2020-117371RA-I00; TED2021-131628A-100), as well as the grant from the Xunta de Galicia (ED431F2021/05). C.-Y.W. acknowledges the financial support from Alexander von Humboldt Foundation. K.S. acknowledges the financial support from China Scholarship Council (CSC), and P.M.-B. acknowledges support from Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy – EXC 2089/1–390776260 (e-conversion). V.B. and T.O. acknowledge the MEXT JSPS Grants 20J00974, 21K14580, and 23H01781. H.Z acknowledges the financial supported by NSFC (62222405, 52131304), the Natural Science Foundation of Jiangsu Province (BK20220142), the Fundamental Research Funds for the Central Universities (30922010713), and NSFC-RGC (62261160392). H.-T.S. acknowledges the financial support from JSPS KAKENHI (21H01743). Y.-T.H and R.L.Z.H. would like to thank the Engineering and Physical Sciences Research Council (EPSRC) for funding (no. EP/V014498/2). R.L.Z.H. also thanks the Royal Academy of Engineering through the Research Fellowships scheme (no. RF∖201718∖17101). D.V. and E.D. acknowledge financial support from the Research Foundation – Flanders through an FWO doctoral fellowship to D.V. (FWO Grant Number 1S45223N) and the KU Leuven Internal Funds (Grant Numbers STG/21/010, C14/23/090, and CELSA/23/018). T.D. acknowledges the Department of Science and Technology (DST) and the Science and Engineering Research Board (SERB) for the Ramanujan Fellowship Award (RJF/2021/000125). I.M.-S. acknowledges Ministry of Science and Innovation of Spain under Step-Up (TED2021-131600B-C31) project and by Generalitat Valenciana under Print-P (MFA/2022/020) project. V.S.C., I.M.-S. and J.P.M.-P acknowledges the support of the Horizon 2020 research and innovation program through the DROP-IT project (grant agreement no. 862656)

Development of a metallostar MRI contrast agent based on a DTPA derivative of 8-hydroxyquinoline

poster presentation by Elke Debroyestatus: publishe

Self-assembled heteropolymetallic complexes as MRI contrast agents

Oral presentation by Geert Dehaenstatus: publishe

Self-assembled heteropolymetallic complexes as MRI contrast agents

poster presentation by Geert Dehaenstatus: publishe

Development of a metallostar MRI contrast agent based on a DTPA derivative of 8-hydroxy-quinoline

Poster presented by Elke Debroyestatus: publishe

Efficient Photocatalytic CO2 Reduction with MIL-100(Fe)-CsPbBr3 Composites

Bromide-based metal halide perovskites (MHPs) are promising photocatalysts with strong blue-green light absorption. Composite photocatalysts of MHPs with MIL-100(Fe), as a powerful photocatalyst itself, have been investigated to extend the responsiveness towards red light. The composites, with a high specific surface area, display an enhanced solar light response, and the improved charge carrier separation in the heterojunctions is employed to maximize the photocatalytic performance. Optimization of the relative composition, with the formation of a dual-phase CsPbBr3 to CsPb2Br5 perovskite composite, shows an excellent photocatalytic performance with 20.4 μmol CO produced per gram of photocatalyst during one hour of visible light irradiation

Incorporation of Cesium Lead Halide Perovskites into g-C3N4 for Photocatalytic CO2 Reduction

CsPbBr3 perovskite-based composites so far have been synthesized by postdeposition of CsPbBr3 on a parent material. However, in situ construction offers enhanced surface contact, better activity, and improved stability. Instead of applying a typical thermal condensation at highly elevated temperatures, we report for the first time CsPb(Br x Cl1-x )3/graphitic-C3N4 (CsPbX3/g-C3N4) composites synthesized by a simple and mild solvothermal route, with enhanced efficacy in visible-light-driven photocatalytic CO2 reduction. The composite exhibited a CO production rate of 28.5 μmol g-1 h-1 at an optimized loading amount of g-C3N4. This rate is about five times those of pure g-C3N4 and CsPbBr3. This work reports a new in situ approach for constructing perovskite-based heterostructure photocatalysts with enhanced light-harvesting ability and improved solar energy conversion efficiency.status: publishe

Luminescence and Relaxometric Properties of Heteropolymetallic Metallostar Complexes with Selectively Incorporated Lanthanide(III) Ions

The synthesis and characterization of two diethylenetriaminepentaacetic acid (DTPA) based heteropolymetallic metallostar lanthanide complexes with the general formulas (GdL1)3Ln and (GdL2)3Ln are described. The synthesis uses a synthetic approach recently developed in our group for the selective complexation of gadolinium(III) and luminescent lanthanide ions with a ditopic ligand to form highly paramagnetic and luminescent metallostar complexes. The luminescence data and relaxometric studies suggest the potential applicability of the complexes as bimodal contrast agents for magnetic resonance and optical imaging. Owing to the higher excited state of L1, better sensitization was observed for all (GdL1)3Ln complexes than for (GdL2)3Ln. A large increase of the quantum yield from 1.5 to 9.8 % was observed for the (GdL1)3Eu complex compared with (GdL2)3Eu, whereas the (GdL1)3Tb complex exhibited a quantum yield (QY) of 30.9 % compared with 15.3 % for (GdL2)3Tb. A slight increase of the QY from 0.8 to 1.2 % was observed for the Dy(III) complex when switching from ligand L2 to L1. The nuclear magnetic relaxation dispersion (NMRD) measurements of the (GdL2)3Ln complexes (Ln = EuIII, DyIII, TbIII) showed respective longitudinal relaxivity (r1) values of 24.27, 22.80 and 21.72 s–1 mmol–1 per metallostar complex at 310 K and 20 MHz.status: publishe