Suchergebnisse

Lead-based halide perovskites have emerged as a most prominent candidate for emerging opto-electronic applications. In this talk we will briefly showcase recent efforts towards designing new Pb-free semiconductors that are alternatives to traditional halide perovskites, for which computational approaches from first-principles have been extensively successful and revealed a series of new compounds within the so-called halide double perovskites family and vacancy ordered perovskites. Among these, Cs2BiAgBr6 has the narrower indirect band gap of 1.9 eV, [1] and Cs2InAgCl6 is the only direct band gap semiconductor, yet with a large gap of 3.3 eV. [2] All of them exhibit low carrier effective masses and consequently, are prominent candidates for a range of opto-electronic applications such as photovoltaics, light-emitting devices, sensors, and photo-catalysts. [3] We will specifically outline the computational ab initio design strategy that led to the synthesis of these compounds, and particularly focus on the insights we can get from first-principles calculations in order to facilitate the synthesis, improve their opto-electronic properties and the in-silico identification of compounds with properties that are similar to the lead-halide perovskites. The newly developed concept of analogs will lead us to identify a new oxide double perovskite semiconductor, Ba2AgIO6, which exhibits an electronic band structure remarkably similar to that of our recently discovered halide double perovskite Cs2AgInCl6, but with a band gap in the visible range at 1.9 eV. [4] In the final part of our talk, we will employ this strategy to explore the phase space of vacancy-ordered double perovskite and discuss the case of Zr-based compounds as stable alternates to Cs2TiX4 with X=Br,I, which exhibit lighter charge carrier effective masses.[5] This DROP-IT project has received funding from the European Union's Horizon 2020 research and innovation Program under the grant agreement No 862656. The information and views set out in the abstracts ...

DROP-IT is a 3years H2020 European project starting in November 2019. DROP-IT "DRop-on demand flexible Optoelectronics & Photovoltaics by means of Lead-Free halide perovskITes". FOTON Institute - INSA Rennes and ISCR are part of the DROP-IT consortium (8 European partners). DROP-IT will combine optoelectronics and photonics in a single flexible drop-on demand inkjet technology platform by means of exploiting the enormous potential of lead-free perovskite materials. FOTON Institute – INSA Rennes will be in charge of the simulation task of the project. The first year has been mainly focusing on 2 tasks i) the state-of-art bibliography and analysis of the lead-free materials for solar cells, leds,photocatalysts, and then ii) the exploration of new lead-free materials by Density Functional Theory. DROP IT consortium : UNIVERSITAT DE VALENCIA (Spain), UNIVERSITAT DE BARCELONA (Spain), UNIVERSITAT JAUME I DE CASTELLON (Spain), EIDGENOESSISCHE TECHNISCHE HOCHSCHULE ZUERICH (Switzerland), FUNDACJA SAULE RESEARCH INSTITUTE (Poland), SAULE SP ZOO (Poland), AVANTAMA AG (Switzerland), INSTITUT NATIONAL DES SCIENCES APPLIQUEES DE RENNES (France) Disclaimer excluding Agency responsibility: This project has received funding from the European Union's Horizon 2020 research and innovation Programme under the grant agreement No 862656. The information and views set out in the abstracts and presentations are those of the authors and do not necessarily reflect the official opinion of the European Union. Neither the European Union institutions and bodies nor any person acting on their behalf may be held responsible for the use which may be made of the information contained herein.

Poster on Electronic properties of vacancy ordered double perovskites. This project has received funding from the European Union's Horizon 2020 research and in- novation Programme under the grant agreement No 862656. The information and views set out in the abstracts and presentations are those of the authors and do not necessarily reflect the official opinion of the European Union. Neither the European Union institutions and bodies nor any person acting on their behalf may be held responsible for the use which may be made of the information contained herein.

Vacancy ordered halide perovskites have been extensively investigated as promising lead-free alternatives to halide perovskites for various opto-electronic applications. Among these, Cs2TiBr6 has been reported as a stable absorber with interesting electronic and optical properties, such as a bandgap in the visible, and long carrier diffusion lengths. Yet, a thorough theoretical analysis of the exhibited properties is still missing in order to further assess its application potential from a material's design point of view. In this Letter, we perform a detailed analysis for the established Ti-based compounds and investigate the less-known materials based on Zr. We discuss in detail their electronic properties and band symmetries, highlight the similarity between the materials in terms of properties, and reveal limits for tuning electronic and optical properties within this family of vacancy ordered double perovskites that share the same electron configuration. We also show the challenges to compute accurate and meaningful quasi-particle corrections at the GW level. Furthermore, we address their chemical stability against different decomposition reaction pathways, identifying stable regions for the formation of all materials, while probing their mechanical stability employing phonon calculations. We predict that Cs2ZrI6, a material practically unexplored to date, shall exhibit a quasi-direct electronic bandgap well within the visible range, the smallest charge carrier effective masses within the Cs2BX6 (B = Ti, Zr; X = Br, I) compounds, and a good chemical stability. The research leading to these results has received funding from the Chaire de Recherche Rennes Metropole project and from the European Union's Horizon 2020 program through a FET Open research and innovation action under Grant Agreement No. 862656 (DROP-IT). This work was granted access to the HPC resources of TGCC under Allocation Nos. 2020-A0100911434 and 2020-A0090907682 made by GENCI. We acknowledge PRACE for awarding us access to the ARCHER2, ...

Following the emergence of lead halide perovskites as record-breaking materials for emerging photovoltaic applications, lead-free perovskites are gaining interest as novel materials which are compatible with inkjet-printing based technologies1,2,3. Bulk properties are of the prime importance, but charge transport can be rapidly altered across the interface of perovskite/ (hole or electron) transport layer (HTL or ETL). Yet, due to the size and complexity of the interface systems, a thorough ab initio modeling of the interfaces remains elusive to-date. Within this work, to explore the atomic-scale details of the structural and electronic properties of these materials, we employ state-of-the-art density functional theory (DFT) based calculations of model tin-based heterostructures. We investigate in particular three-dimensional corner-sharing Sn-based perovskites, their surface and interface properties and calculate the interaction of the materials with charge transport layers (CTLs). Our approach reveals the electronic band alignments and dielectric mismatches between perovskite layers and the most important hole and electron transport layers that have been used in prototype thin film device architectures4,5. In an effort to understand the fundamental physico-chemical mechanisms that govern the interactions between the photo-active absorber material and CTLs, we also probe the influence of surface termination on structural and electronic properties at FASnI3/C60 (as ETL) interfaces and FASnI3/NiOx (as ETL) interfaces. Our findings give a detailed insight into the interface engineering necessary for optimizing the next generation of environmental-friendly high-performing opto-electronic devices. This DROP-IT project1 has received funding from the European Union's Horizon 2020 research and innovation Program under the grant agreement No 862656. The information and views set out in the abstracts and presentations are those of the authors and do not necessarily reflect the official opinion of the European Union. ...

Ever since organic-inorganic halide perovskites have been employed in electronics and optoelectronics, their unique and excellent photophysical and electrical properties[1–3] have guaranteed their versatile applications in solar cells, LEDs, lasers, photodetectors and beyond[4,5]. Sn-based perovskites along with their surface and interface functionalization after assembling with charge transport layers (CTLs) are considered promising ways to achieve a win-win between environmental friendliness and cell performance [6–10]. In view of the sophisticated chemical and physical properties of Sn-based perovskites, the theoretical calculation based on density functional theory (DFT) has been employed to feasibly and flexibly model the interplay between absorbers and CTLs. In order to understand the fundamental physico-chemical mechanisms of that interplay, the influence of surface termination on structural and electronic properties at FASnI3/C60 (as ETL) interfaces, in particular, the dependence of vacuum level (and by that work function) within surface alone and interface integrated frameworks, thereupon constructing the heterostructure energy level alignment, has been investigated thoroughly. The resulting type-II heterostructures coupled with the increased surface dipole moments and charge carrier mobilities tell an effective charge transport from FASnI3 to C60. Our findings contribute to discovering other promising alternatives as ETLs for lead-free perovskites in the light of surface and interface engineering. This DROP-IT project1 has received funding from the European Union's Horizon 2020 research and innovation Program under the grant agreement No 862656. The information and views set out in the abstracts and presentations are those of the authors and do not necessarily reflect the official opinion of the European Union. Neither the European Union institutions and bodies nor any person acting on their behalf may be held responsible for the use which may be made of the information contained herein. References: 1. ...

We demonstrate four-and two-terminal perovskite-perovskite tandem solar cells with ideally matched band gaps. We develop an infrared-absorbing 1.2-electron volt band-gap perovskite, FA(0.75)Cs(0.25)Sn(0.5)Pb(0.5)I(3), that can deliver 14.8% efficiency. By combining this material with a wider-band gap FA(0.83)Cs(0.17)Pb(I0.5Br0.5)(3) material, we achieve monolithic two-terminal tandem efficiencies of 17.0% with > 1.65-volt open-circuit voltage. We also make mechanically stacked four-terminal tandem cells and obtain 20.3% efficiency. Notably, we find that our infrared-absorbing perovskite cells exhibit excellent thermal and atmospheric stability, not previously achieved for Sn-based perovskites. This device architecture and materials set will enable "all-perovskite" thin-film solar cells to reach the highest efficiencies in the long term at the lowest costs. ; We thank M. T. Horantner for performing the Shockley-Queisser calculation. The research leading to these results has received funding from the Graphene Flagship (Horizon 2020 grant no. 696656 - GrapheneCore1), the Leverhulme Trust (grant RL-2012-001), the UK Engineering and Physical Sciences Research Council (grant EP/J009857/1 and EP/M020517/1), and the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement nos. 239578 (ALIGN) and 604032 (MESO). T.L. is funded by a Marie Sklodowska Curie International Fellowship under grant agreement H2O2IF-GA-2015-659225. A.B. is financed by IMEC (Leuven) in the framework of a joint Ph.D. program with Hasselt University. B.C. is a postdoctoral research fellow of the Research Fund Flanders (FWO). We also acknowledge the U.S. Office of Naval Research for support. We acknowledge the use of the University of Oxford Advanced Research Computing (ARC) facility (http://dx.doi.org/10.5281/zenodo.22558) and the ARCHER UK National Super-computing Service under the "AMSEC" Leadership project. We thank the Global Climate and Energy Project (GCEP) at Stanford University. All data pertaining to the conclusions of this work can be found in the main paper and the supplementary materials.