Assessment of elemental distributions at line and planar defects in Cu(In,Ga)Se2 thin films by atom probe tomography

Cojocaru‐Mirédin, Oana; Schwarz, Torsten; Abou‐Ras, Daniel

doi:10.1016/j.scriptamat.2017.03.034

Cited by 39 publications

(62 citation statements)

References 32 publications

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“…APT has the capability of chemically characterizing materials in 3D on an atom‐by‐atom basis, which helps to understand the formation of nanostructures in metals and semiconductors. The technique has been applied to detect off‐stoichiometry around the grain boundaries in various semiconductors such as silicon, chalcogenides, filled skutterdites, zintls, oxides, and other systems . The results suggest that the resistance of the grain boundaries in Mg 3 Sb 2 ‐based materials can be attributed to a Mg deficiency that greatly reduces the local free charge carrier concentration.…”

Section: Introductionsupporting

confidence: 89%

Mg Deficiency in Grain Boundaries of n‐Type Mg₃Sb₂ Identified by Atom Probe Tomography

Kuo

Kang

et al. 2019

Adv Materials Inter

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Highly resistive grain boundaries significantly reduce the electrical conductivity that compromises the thermoelectric figure‐of‐merit zT in n‐type polycrystalline Mg3Sb2. In this work, discovered is a Mg deficiency near grain boundaries using atom‐probe tomography. Approximately 5 at% of Mg deficiency is observed uniformly in a 10 nm region along the grain boundary without any evidence of a stable secondary or impurity phase. The off‐stoichiometry can prevent n‐type dopants from providing electrons, lowering the local carrier concentration near the grain boundary and thus the local conductivity. This observation explains how nanometer scale compositional variations can dramatically determine thermoelectric zT, and provides concrete strategies to reduce grain‐boundary resistance and increase zT in Mg3Sb2‐based materials.

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Section: Introductionsupporting

confidence: 89%

Mg Deficiency in Grain Boundaries of n‐Type Mg₃Sb₂ Identified by Atom Probe Tomography

Kuo

Kang

et al. 2019

Adv Materials Inter

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“…This technique is frequently employed to characterize the elemental distribution in solids on the nanoscale. [ 25,26 ] In atom probe tomography, a voltage is applied to a sharp tip of a specimen creating a high field strength at the apex of the tip (see Figure ). In samples which are nonconducting, in addition, a short laser pulse is applied to dislodge atomic or molecular fragments from the surface.…”

Section: Introducing a New Bonding Mechanism: Metavalent Bondingmentioning

confidence: 99%

Chalcogenides by Design: Functionality through Metavalent Bonding and Confinement

2020

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unprecedented progress of the semiconductor industry and information technology. Yet, we have reached a stage where a simple evolution along established research lines might no longer bear much fruit. Advanced functional materials require increasingly complex and demanding property combinations. Their optimization would thus benefit from novel concepts. In thermoelectrics, which convert waste heat into electricity, for example, materials must show the unusual combination of high electrical and small thermal conductivity. This is demanding since a high electrical conductivity is usually accompanied by a high thermal conductivity. In phase change materials (PCMs) employed for data storage and processing, materials are required which possess a pronounced contrast in optical and/or electrical properties between two different states. Usually one of these states is a metastable one, which is typically amorphous, while the second state is then stable crystalline. The metastable state has to be stable at room temperature and slightly above for 10 years; but it should crystallize, i.e., return to the stable crystalline state in a few nanoseconds if heated to temperatures of typically around 500 °C. The combination of pronounced property contrast and hence presumably different atomic arrangements in the two different phases, yet rapid crystallization is indicative for an unusual correlation of chemical bonding, atomic arrangement, and resulting properties, including crystallization kinetics. Topological insulators, expected to help realize novel electronic functionalities, possess topologically protected spin-polarized surface states with high mobility. These states should govern the sample conductivity, if the bulk is insulating.This raises the question how these demanding requirements can be met and how superior materials can be identified. A number of different approaches have been developed in the past two decades to meet these needs. Combinatorial material synthesis, i.e., the fast preparation of stoichiometric libraries and their efficient analysis to identify superior compounds, has already been promoted over two decades ago. [1,2] While this scheme has indeed been successful in improving certain materials such as metal hydrides for hydrogen storage [3] and benchmarking electrocatalysts for solar water splitting, [4] for many material classes still empirical optimization schemes are employed. Machine learning is an emerging strategy to identify materials with a unique property portfolio. [5][6][7] This novel A unified picture of different application areas for incipient metals is presented. This unconventional material class includes several main-group chalcogenides, such as GeTe, PbTe, Sb 2 Te 3 , Bi 2 Se 3 , AgSbTe 2 and Ge 2 Sb 2 Te 5 . These compounds and related materials show a unique portfolio of physical properties. A novel map is discussed, which helps to explain these properties and separates the different fundamental bonding mechanisms (e.g., ionic, metallic, and covalent). The map also provides evidence ...

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“…The last hypothesis possibly at the origin of the dominant recombination mechanism could be the absence of oxygen near the CIGSe/C24 interface. Indeed, in most of the best devices reported in the literature, oxygen is detected at the absorber/buffer physical junction, but also at grain boundaries (GBs) . The optoelectronic role played by the oxygen is nonetheless rather difficult to evaluate since it can either be substituted to Se, bonded to alkali, or as − OH; however, it has been shown that annealing the cells in ambient atmosphere frequently improves and never degrades the V oc and FF of the solar cells.…”

Section: Discussionmentioning

confidence: 99%

“…The optoelectronic role played by the oxygen is nonetheless rather difficult to evaluate since it can either be substituted to Se, bonded to alkali, or as − OH; however, it has been shown that annealing the cells in ambient atmosphere frequently improves and never degrades the V oc and FF of the solar cells. The model proposed is that O passivates some detrimental point defects . So far, this hypothesis is probably the most realistic because it also implies the specificities of the S‐based co‐evaporation process, and would be an explanation for the absorber bulk modification through O‐free GBs.…”

Section: Discussionmentioning

confidence: 99%

High Efficiency Solar Cell Based on Full PVD Processed Cu(In,Ga)Se₂/CdIn₂S₄ Heterojunction

et al. 2017

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The original goal of our study is to synthesize by co-evaporation the phase that could be formed at the interface between polycrystalline p-Cu(In,Ga)Se 2 treated with KF and n-CdS. Hence, a new buffer layer, CdIn 2 S 4 (C24), deposited by co-evaporation is presented for the use in thin film solar cells, exhibiting device efficiencies as high as 16.2%, comparable to that obtained on a reference standard CdS-buffered device. The physico-chemical and optical properties of close to stoichiometry 400 nm-thick films of C24 show similar properties to what has been reported in the literature for single crystals. The layer stack used for solar cells is investigated by transmission electron microscopy, showing the formation of an ultrathin Cd-deficient C24 layer at the CIGSe/C24 interface, while a clear lattice match is observed at the C24/ZnO interface. Advanced electrical characterizations of the devices suggest that the output voltage and fill factor of the solar cells based on Cu(In,Ga)Se 2 /(PVD)C24 are limited by tunneling-enhanced recombination through extended band tail states. These results open new routes to explain the superiority of wet processes used for the junction formation compared to vacuum-based approaches.

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Assessment of elemental distributions at line and planar defects in Cu(In,Ga)Se2 thin films by atom probe tomography

Cited by 39 publications

References 32 publications

Mg Deficiency in Grain Boundaries of n‐Type Mg₃Sb₂ Identified by Atom Probe Tomography

Mg Deficiency in Grain Boundaries of n‐Type Mg₃Sb₂ Identified by Atom Probe Tomography

Chalcogenides by Design: Functionality through Metavalent Bonding and Confinement

High Efficiency Solar Cell Based on Full PVD Processed Cu(In,Ga)Se₂/CdIn₂S₄ Heterojunction

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Assessment of elemental distributions at line and planar defects in Cu(In,Ga)Se2 thin films by atom probe tomography

Cited by 39 publications

References 32 publications

Mg Deficiency in Grain Boundaries of n‐Type Mg3Sb2 Identified by Atom Probe Tomography

Mg Deficiency in Grain Boundaries of n‐Type Mg3Sb2 Identified by Atom Probe Tomography

Chalcogenides by Design: Functionality through Metavalent Bonding and Confinement

High Efficiency Solar Cell Based on Full PVD Processed Cu(In,Ga)Se2/CdIn2S4 Heterojunction

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Product

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About

Mg Deficiency in Grain Boundaries of n‐Type Mg₃Sb₂ Identified by Atom Probe Tomography

Mg Deficiency in Grain Boundaries of n‐Type Mg₃Sb₂ Identified by Atom Probe Tomography

High Efficiency Solar Cell Based on Full PVD Processed Cu(In,Ga)Se₂/CdIn₂S₄ Heterojunction