scholarly journals Composition and Dimension Dependent Static and Dynamic Stabilities of Inorganic Mixed Halide Antimony Perovskites

2021 ◽  
Author(s):  
Jack Yang
Keyword(s):  
Density Functional ◽  
Configurational Entropy ◽  
Density Functional Theory Calculations ◽  
Optoelectronic Properties ◽  
Lead Free ◽  
Photovoltaic Devices ◽  
Functional Theory ◽  
Inorganic Lead ◽  
Electronic Dynamics ◽  
Important Approach

Halide intermixing is an important approach to stabilise halide perovskite in the phase that gives the best optoelectronic properties, whereas replacing Pb is critical for eliminating the material toxicity to meet the requirements for domestic applications. Recently, all-inorganic lead-free Cs3Sb2I9 emerges as a promising lead-free absorber, with its optoelectronic properties being further controllable by manipulating its structural dimensionality (0D or 2D) via composition engineering. In particular, superior photoconversion efficiency (up to 5 %) under indoor illumination with high photostabilities have been demonstrated experimentally in 2D Cs3Sb2ClyI9-y}. To gain a more thorough understanding on how the properties of this family of materials are controlled by their chemistry and dimensionality, here, we employ density functional theory calculations to explore the phase stability, structural and electronic dynamics of Cs3Sb2X9 (X=Br and Cl) across 74 different combinations of composition/dimensionality. The results show that Cs3Sb2X9 solid solutions are predominantly stabilised by configurational entropy rather than enthalpy. In stark contrast to cubic inorganic lead/tin halides perovskites, Cs3Sb2X9 are dynamically more stable at 300 K, as reflected by their low vibrational anharmonicities, the values of which also exhibit weak compositional dependency. This consequentially reduces the strength of electron-phonon couplings, thus enhancing the photoexcited carrier lifetime in these materials, which further demonstrates their promising potential to be integrated into indoor photovoltaic devices.

scholarly journals Composition and Dimension Dependent Static and Dynamic Stabilities of Inorganic Mixed Halide Antimony Perovskites

2021 ◽  
Author(s):  
Jack Yang
Keyword(s):  
Density Functional ◽  
Configurational Entropy ◽  
Density Functional Theory Calculations ◽  
Optoelectronic Properties ◽  
Lead Free ◽  
Photovoltaic Devices ◽  
Functional Theory ◽  
Inorganic Lead ◽  
Electronic Dynamics ◽  
Important Approach

Halide intermixing is an important approach to stabilise halide perovskite in the phase that gives the best optoelectronic properties, whereas replacing Pb is critical for eliminating the material toxicity to meet the requirements for domestic applications. Recently, all-inorganic lead-free Cs3Sb2I9 emerges as a promising lead-free absorber, with its optoelectronic properties being further controllable by manipulating its structural dimensionality (0D or 2D) via composition engineering. In particular, superior photoconversion efficiency (up to 5 %) under indoor illumination with high photostabilities have been demonstrated experimentally in 2D Cs3Sb2ClyI9-y}. To gain a more thorough understanding on how the properties of this family of materials are controlled by their chemistry and dimensionality, here, we employ density functional theory calculations to explore the phase stability, structural and electronic dynamics of Cs3Sb2X9 (X=Br and Cl) across 74 different combinations of composition/dimensionality. The results show that Cs3Sb2X9 solid solutions are predominantly stabilised by configurational entropy rather than enthalpy. In stark contrast to cubic inorganic lead/tin halides perovskites, Cs3Sb2X9 are dynamically more stable at 300 K, as reflected by their low vibrational anharmonicities, the values of which also exhibit weak compositional dependency. This consequentially reduces the strength of electron-phonon couplings, thus enhancing the photoexcited carrier lifetime in these materials, which further demonstrates their promising potential to be integrated into indoor photovoltaic devices.

scholarly journals How to Extract Adsorption Energies, Adsorbateadsorbate Interaction Parameters, and Saturation Coverages from Temperature Programmed Desorption Experiments

2021 ◽  
Author(s):  
Sudarshan Vijay ◽  
Henrik Høgh Kristoffersen ◽  
Yu Katayama ◽  
Yang Shao-Horn ◽  
Ib Chorkendorff ◽  
...  
Keyword(s):  
Adsorption Energy ◽  
Density Functional ◽  
Configurational Entropy ◽  
Density Functional Theory Calculations ◽  
Temperature Programmed Desorption ◽  
Functional Theory ◽  
Interaction Terms ◽  
Saturation Coverage ◽  
Adsorption Energies ◽  
Temperature Programmed

<p>We present a simple scheme to extract the adsorption energy, adsorbate interaction parameter and the saturation coverage from temperature programmed desorption (TPD) experiments. We propose that the coverage dependent adsorption energy can be fit using a functional form including the configurational entropy and linear adsorbate-adsorbate interaction terms. As one example of this scheme, we analyze TPD spectra of desorption on Au(211) and Au(310) surfaces. We determine that under atmospheric pressure, the <i>steps</i> of both facets adsorb between 0.4-0.9 ML coverage of CO*. We show this result to be consistent with density functional theory calculations of adsorption energies with the BEEF-vdW functional. <b></b></p>

scholarly journals Hybrid Density Functional Study of Au2Cs2I6, Ag2GeBaS4, Ag2ZnSnS4, and AgCuPO4 for the Intermediate Band Solar Cells

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3457 ◽  
Author(s):  
Murugesan Rasukkannu ◽  
Dhayalan Velauthapillai ◽  
Ponniah Vajeeston
Keyword(s):  
Density Functional ◽  
Mechanical Stability ◽  
Density Functional Theory Calculations ◽  
Functional Study ◽  
Photovoltaic Devices ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Intermediate Band ◽  
Intermediate Band Solar Cells ◽  
Hybrid Density Functional

We present a comprehensive investigation of the structural, electronic, mechanical, and optical properties of four promising candidates, namely Au2Cs2I6, Ag2GeBaS4, Ag2ZnSnS4, and AgCuPO4, for application in photovoltaic devices based on intermediate band (IB) cells. We perform accurate density functional theory calculations by employing the hybrid functional of Heyd, Scuseria, and Erhzerhof (HSE06). Calculations reveal that IBs are present in all proposed compounds at unoccupied states in the range of 0.34–2.19 eV from the Fermi level. The structural and mechanical stability of these four materials are also systematically investigated. Additional peaks are present in the optical spectra of these compounds, as characterised by a broadened energy range and high intensity for light absorption. Our findings, as reported in this work, may provide a substantial breakthrough on the understanding of these materials, and thus help the design of more efficient IB solar devices.

scholarly journals A band-gap database for semiconducting inorganic materials calculated with hybrid functional

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Sangtae Kim ◽  
Miso Lee ◽  
Changho Hong ◽  
Youngchae Yoon ◽  
Hyungmin An ◽  
...  
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Magnetic Ordering ◽  
Density Functional Theory Calculations ◽  
Inorganic Materials ◽  
Band Gaps ◽  
Device Performance ◽  
Photovoltaic Devices ◽  
Hybrid Functional ◽  
Functional Theory

Abstract Semiconducting inorganic materials with band gaps ranging between 0 and 5 eV constitute major components in electronic, optoelectronic and photovoltaic devices. Since the band gap is a primary material property that affects the device performance, large band-gap databases are useful in selecting optimal materials in each application. While there exist several band-gap databases that are theoretically compiled by density-functional-theory calculations, they suffer from computational limitations such as band-gap underestimation and metastable magnetism. In this data descriptor, we present a computational database of band gaps for 10,481 materials compiled by applying a hybrid functional and considering the stable magnetic ordering. For benchmark materials, the root-mean-square error in reference to experimental data is 0.36 eV, significantly smaller than 0.75–1.05 eV in the existing databases. Furthermore, we identify many small-gap materials that are misclassified as metals in other databases. By providing accurate band gaps, the present database will be useful in screening materials in diverse applications.

scholarly journals Strain Effects on the Electronic and Optical Properties of Kesterite Cu2ZnGeX4 (X = S, Se): First-Principles Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2692
Author(s):  
Jawad El Hamdaou ◽  
Mohamed El-Yadri ◽  
Mohamed Farkous ◽  
Mohamed Kria ◽  
Maykel Courel ◽  
...  
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Band Gap Energy ◽  
Applied Strain ◽  
Photovoltaic Devices ◽  
Functional Theory ◽  
Electronic And Optical Properties ◽  
Low Energies ◽  
Semiconductor Compounds

Following the chronological stages of calculations imposed by the WIEN2K code, we have performed a series of density functional theory calculations, from which we were able to study the effect of strain on the kesterite structures for two quaternary semiconductor compounds Cu2ZnGeS4 and Cu2ZnGeSe4. Remarkable changes were found in the electronic and optical properties of these two materials during the application of biaxial strain. Indeed, the band gap energy of both materials decreases from the equilibrium state, and the applied strain is more pronounced. The main optical features are also related to the applied strain. Notably, we found that the energies of the peaks present in the dielectric function spectra are slightly shifted towards low energies with strain, leading to significant refraction and extinction index responses. The obtained results can be used to reinforce the candidature of Cu2ZnGeX4(X = S, Se) in the field of photovoltaic devices.

scholarly journals How to Extract Adsorption Energies, Adsorbateadsorbate Interaction Parameters, and Saturation Coverages from Temperature Programmed Desorption Experiments

2021 ◽  
Author(s):  
Sudarshan Vijay ◽  
Henrik Høgh Kristoffersen ◽  
Yu Katayama ◽  
Yang Shao-Horn ◽  
Ib Chorkendorff ◽  
...  
Keyword(s):  
Adsorption Energy ◽  
Density Functional ◽  
Configurational Entropy ◽  
Density Functional Theory Calculations ◽  
Temperature Programmed Desorption ◽  
Functional Theory ◽  
Interaction Terms ◽  
Saturation Coverage ◽  
Adsorption Energies ◽  
Temperature Programmed

<p>We present a simple scheme to extract the adsorption energy, adsorbate interaction parameter and the saturation coverage from temperature programmed desorption (TPD) experiments. We propose that the coverage dependent adsorption energy can be fit using a functional form including the configurational entropy and linear adsorbate-adsorbate interaction terms. As one example of this scheme, we analyze TPD spectra of desorption on Au(211) and Au(310) surfaces. We determine that under atmospheric pressure, the <i>steps</i> of both facets adsorb between 0.4-0.9 ML coverage of CO*. We show this result to be consistent with density functional theory calculations of adsorption energies with the BEEF-vdW functional. <b></b></p>

First principles investigation on how site preference and entropy affect the stability of (EuxM1–x)2Ge2Pb (M = Ca, Sr, Ba) polar intermetallics

2016 ◽  
Vol 94 (4) ◽  
pp. 312-320 ◽  
Author(s):  
Tyson Terpstra ◽  
James Hooper ◽  
Eva Zurek
Keyword(s):  
Density Functional ◽  
Composition Range ◽  
Configurational Entropy ◽  
Density Functional Theory Calculations ◽  
Site Preference ◽  
Free Energies ◽  
Functional Theory ◽  
Wide Composition Range ◽  
The Stability ◽  
Realistic Structure

Density functional theory calculations have been carried out to analyze the factors contributing to the stabilities of a set of recently synthesized quaternary polar intermetallic compounds, (EuxM1–x)2Ge2Pb with M = Ca, Sr, and Ba. Experiments showed that these preferentially crystallized with Pbam (M = Ca) or Cmmm (M = Sr, Ba) symmetry. We systematically explored how the electronic energies of these structures depended on how they were “colored” by the europium/M ions for a wide composition range. It was found that whereas there was very little site preference in the Cmmm structure, the “B” site in the Pbam structure strongly preferred smaller cations. The configurational entropy was also found to play a role in determining which structures might be preferred. However, the experimentally obtained product ratios could only be fully rationalized by the Gibbs free energies of structures containing M:Eu ratios resembling those that were synthesized experimentally. Our results highlight the importance of calculating vibrational contributions to the entropy for realistic structure models (in terms of coloring and composition) to explain product ratios for syntheses carried out at high temperatures.

On the Linear Geometry of Lanthanide Hydroxide (Ln—OH, Ln=La-Lu)

2019 ◽  
Author(s):  
Hassan Harb ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Triple Bond ◽  
Density Functional ◽  
Valence Electron ◽  
Density Functional Theory Calculations ◽  
Electron Configuration ◽  
Functional Theory ◽  
Key Species ◽  
Pi Orbitals ◽  
Lanthanide Hydroxide ◽  
Linear Geometry

Lanthanide hydroxides are key species in a variety of catalytic processes and in the preparation of corresponding oxides. This work explores the fundamental structure and bonding of the simplest lanthanide hydroxide, LnOH (Ln=La-Lu), using density functional theory calculations. Interestingly, the calculations predict that all structures of this series will be linear. Furthermore, these results indicate a valence electron configuration featuring an occupied sigma orbital and two occupied pi orbitals for all LnOH compounds, suggesting that the lanthanide-hydroxide bond is best characterized as a covalent triple bond.

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