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The electronic structure and band interface of cesium bismuth iodide on a titania heterostructure using hard X-ray spectroscopy
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Swansea Univ, Coll Engn, SPECIFIC, Bay Campus,Fabian Way, Swansea SA1 8EN, W Glam, Wales.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.ORCID-id: 0000-0003-2412-8503
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.ORCID-id: 0000-0003-2046-1229
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2018 (Engelska)Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, nr 20, s. 9498-9505Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Bismuth halide compounds as a non-toxic alternative are increasingly investigated because of their potential in optoelectronic devices and their rich structural chemistry. Hard X-ray spectroscopy was applied to the ternary bismuth halide Cs3Bi2I9 and its related precursors BiI3 and CsI to understand its electronic structure at an atomic level. We specifically investigated the core levels and valence band using X-ray photoemission spectroscopy (PES), high-resolution X-ray absorption (HERFD-XAS), and resonant inelastic X-ray scattering (RIXS) to get insight into the chemistry and the band edge properties of the two bismuth compounds. Using these element specific X-ray techniques, our experimental electronic structures show that the primary differences between the two bismuth samples are the position of the iodine states in the valence and conduction bands and the degree of hybridization with bismuth lone pair (6s(2)) states. The crystal structure of the two layered quasi-perovskite compounds plays a minor role in modifying the overall electronic structure, with variations in bismuth lone pair states and iodine band edge states. Density Functional Theory (DFT) calculations are used to compare with experimental data. The results demonstrate the effectiveness of hard X-ray spectroscopies to identify element specific bulk electronic structures and their use in optoelectronic devices.

Ort, förlag, år, upplaga, sidor
2018. Vol. 6, nr 20, s. 9498-9505
Nationell ämneskategori
Materialkemi Fysikalisk kemi
Identifikatorer
URN: urn:nbn:se:uu:diva-357561DOI: 10.1039/c8ta00947cISI: 000433427300020OAI: oai:DiVA.org:uu-357561DiVA, id: diva2:1239969
Forskningsfinansiär
Vetenskapsrådet, 2014-6019Vetenskapsrådet, 2016-4524Energimyndigheten, P43549-1Stiftelsen för strategisk forskning (SSF), 15-0130Wallenbergstiftelserna, 2012.0031StandUpTillgänglig från: 2018-08-20 Skapad: 2018-08-20 Senast uppdaterad: 2019-02-19Bibliografiskt granskad
Ingår i avhandling
1. An X-ray Spectroscopic Study of Perovskites Oxides and Halides for Emerging Devices
Öppna denna publikation i ny flik eller fönster >>An X-ray Spectroscopic Study of Perovskites Oxides and Halides for Emerging Devices
2018 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

This thesis investigates the electronic structures on several perovskite oxide and halide materials with a focus on light harvesting applications. The systematic study of the electronic properties of the transition metal oxides and post-transition metal halides is a key point if one is to understand their properties. The element and site selective nature of several x-ray based spectroscopic techniques are given special emphasis in order to obtain a complete picture of the electronic properties of the compounds in question. Much of the experimental studies are accompanied by ab initio calculations that corroborate with our experimental results.

In the oxide portion of this work, a new class of metallic oxides based on doping of an antiferromagnetic LaFeO3 was synthesized and systematically studied with x-ray absorption, x-ray emission, and photoemission spectroscopies. The compound’s electronic structure is complex, having itinerant as well as localized components that give rise to a unique physical state where antiferromagnetism, metallicity and charge-disproportionation coexist. Our resonant photoemission results establish that the Fe states in both magnetically ordered oxides show insulting properties, while the Mo states provide an itinerant band crossing the Fermi level. An excitation energy-dependent RIXS investigation on LaFe1-xMoxO3 and the double perovskite Sr2FeMoO6 revealed a double peak structure located in proximity to the elastic peak that is identified to purely d-d excitations, attributed to the strongly correlated nature of these transition metal compounds.

The growth of high-quality thin film ferroelectric based on BaTiO3 grown epitaxially by means of pulsed laser deposition were investigated. We systematically reduce the band gap of the ferroelectric thin film while retaining its polarization at ambient conditions in spite of the aliovalent doping. The electronic structure is studied by several x-ray techniques that show how the ferroelectricity persists as well as the effective reduction of the band gap through hybridized states.

In the post-transition metal halides, the valence and conduction bands were mapped using x-ray absorption, emission, and photoemission spectroscopies. The spectroscopic results identify the constituent states that form the valence band as well as the band energy positions, which is an imperative parameter in optoelectronic devices. In addition, x-ray based spectroscopy was used to demonstrate the stereochemical activity of lone-pair states (5s2 and 6s2) for several different halide compounds and their influence on the chemical, structural, and electronic properties of the material. Nanostructured halide perovskites are also explored. The position of iodine p states and valence band states in reduced dimensional lead-based compounds were examined, as their states are found to be confined in one crystallographic direction in contrast to their three-dimensional counterpart. This information highlights the interesting material properties and their use in current third generation solar cell research.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2018. s. 84
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1740
Nyckelord
perovskite oxides, halide perovskites, x-ray spectroscopy, electronic structure
Nationell ämneskategori
Den kondenserade materiens fysik
Forskningsämne
Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik
Identifikatorer
urn:nbn:se:uu:diva-364407 (URN)978-91-513-0493-9 (ISBN)
Disputation
2018-12-14, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2018-11-21 Skapad: 2018-10-26 Senast uppdaterad: 2018-11-30

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Phuyal, DibyaJain, Sagar MotilalPhilippe, BertrandJohansson, Malin BPazoki, MeysamKullgren, JollaKlintenberg, MattiasJohansson, ErikButorin, SergeiKaris, OlofRensmo, Håkan
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