Towards predictive band gaps for halide perovskites: Lessons from one-shot and eigenvalue self-consistent 
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Leppert, Linn; Rangel, Tonatiuh; Neaton, Jeffrey B.

doi:10.1103/physrevmaterials.3.103803

Cited by 53 publications

(52 citation statements)

References 74 publications

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“…This underestimation is consistent with prior studies of the QP band gaps in both halide double perovskites and lead-based perovskites and can be understood as originating with limitations associated with the DFT starting point. 22 , 35 Nonetheless, the experimental and theoretical lineshapes are very similar and exhibit a well-defined peak before the onset of a broader continuum; our GW +BSE calculations allow us to assign this peak to a resonant excitonic feature.…”

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confidence: 66%

“…The screened range-separated hybrid functional HSE06 predicts the band gap of Cs 2 AgBiBr 6 to be 1.8 eV, 1 but it underestimates the band gaps of other double perovskites. 22 More accurate QP band gaps and band structures can be obtained using Green’s function-based ab initio many-body perturbation theory with the GW approximation. The QP band gap of Cs 2 AgBiBr 6 has been computed with GW approaches to lie between 1.8 eV 21 and 2.2 eV, 22 in good agreement with the range of experimental values.…”

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confidence: 99%

“…This is slightly less than the range of experimentally reported band gaps of 1.8–2.2 eV 1 , 2 , 16 but consistent with previous GW calculations. 21 , 22 The smallest direct band gap is computed to be 2.41 eV at X ( Table 1 ).…”

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confidence: 99%

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Chemically Localized Resonant Excitons in Silver–Pnictogen Halide Double Perovskites

Biega

Filip

Leppert

et al. 2021

J. Phys. Chem. Lett.

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Halide double perovskites with alternating silver and pnictogen cations are an emerging family of photoabsorber materials with robust stability and band gaps in the visible range. However, the nature of optical excitations in these systems is not yet well understood, limiting their utility. Here, we use ab initio many-body perturbation theory within the GW approximation and the Bethe–Salpeter equation approach to calculate the electronic structure and optical excitations of the double perovskite series Cs 2 AgBX 6 , with B = Bi 3+ , Sb 3+ and X = Br – , Cl – . We find that these materials exhibit strongly localized resonant excitons with energies from 170 to 434 meV below the direct band gap. In contrast to lead-based perovskites, the Cs 2 AgBX 6 excitons are computed to be non-hydrogenic with anisotropic effective masses and sensitive to local field effects, a consequence of their chemical heterogeneity. Our calculations demonstrate the limitations of the Wannier–Mott and Elliott models for this class of double perovskites and contribute to a detailed atomistic understanding of their light–matter interactions.

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Chemically Localized Resonant Excitons in Silver–Pnictogen Halide Double Perovskites

Biega

Filip

Leppert

et al. 2021

J. Phys. Chem. Lett.

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“…Such Pb‐6p‐derived bands are found at energies much higher than the dmpz‐derived conduction band in 1 Br. The HSE06 + SOC band gap of 1 Br is 1.1 eV, which underestimates the experimental gap as commonly seen for Pb‐based halide perovskites . Therefore, we also calculated the band gap using the GW approach, finding a value of 1.7 eV in very good agreement with experiment (see Supporting Information for computational details).…”

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confidence: 51%

Expanded Analogs of Three‐Dimensional Lead‐Halide Hybrid Perovskites

et al. 2020

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Replacing the PbÀXo ctahedral building unit of A I PbX 3 perovskites (X = halide) with ap air of edge-sharing PbÀXo ctahedra affords the expanded perovskite analogs: A II Pb 2 X 6 .W er eport seven members of this new family of materials.I n3 Dh ybrid perovskites,o rbitals from the organic molecules do not participate in the band edges.Incontrast, the more spacious inorganic sublattice of the expanded analogs accommodates larger pyrazinium-based cations with low-lying p*o rbitals that form the conduction band, substantially decreasing the band gap of the expanded lattice.The molecular nature of the conduction band allows us to electronically dope the materials by reducing the organic molecules.Bysynthesizing derivatives with A II = pyridinium and ammonium, we can isolate the contributions of the pyrazinium-based orbitals in the band gap transition of A II Pb 2 X 6 .T he organic-molecule-based conduction band and the inorganic-ion-based valence band provideanunusual electronic platform with localized states for electrons and more disperse bands for holes upon optical or thermal excitation.

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“…However, hybrid functionals predict a range of band gaps, depending on the amount of exact exchange included, thereby affecting subsequent "oneshot" GW results. [12,23,24] Specifically, the Heyd-Scuseria-Ernzerhof (HSE) [25] short-range hybrid functional yields accurate results for narrow band gap semiconductors, but GW using it as a starting point produces results of similar quality only if self-consistency is employed. [26,27] A method to a priori select the right parameters of hybrid functionals for band gap prediction and for generating GW starting points remains an active area of research.…”

Section: Doi: 101002/adts202000220mentioning

confidence: 99%

Time‐Dependent Density Functional Theory of Narrow Band Gap Semiconductors Using a Screened Range‐Separated Hybrid Functional

Wing

Neaton

Kronik

2020

Advcd Theory and Sims

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Predicting the band structure and optical absorption spectra of narrow band gap semiconductors is challenging for electronic structure methods. Here, it is shown shown that density functional theory can yield accurate band structures and time-dependent density functional theory (TDDFT) can yield accurate optical absorption spectra for these systems. This is achieved by using a screened range-separated hybrid (SRSH) functional with a single empirical parameter, fit to reproduce the experimental band gap. By comparing TDDFT results based on the SRSH approach with those obtained based on the Heyd-Scuseria-Ernzerhof functional it is shown that screened long-range exact exchange improves the accuracy of the TDDFT spectra for these systems. The optical absorption spectra of narrow band gap semiconductors (i.e., those with a band gap smaller than ≈ 0.8 eV) are often challenging to predict. A standard technique to calculate optical absorption spectra is to use many-body perturbation theory with the GW approximation [1-6] and the Bethe-Salpeter equation (BSE) [7-10] approach. While the GW-BSE approach is known for its accuracy, it can exhibit sensitivity to the density functional theory (DFT) starting point. For narrow band gap semiconductors, a challenge is that semilocal functionals, often used to generate a starting point for GW calculations, spuriously predict a metallic ground state [11-14] and even use of a self-consistent scheme does not result in sufficiently accurate band gaps. [15-18]

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Towards predictive band gaps for halide perovskites: Lessons from one-shot and eigenvalue self-consistent GW

Cited by 53 publications

References 74 publications

Chemically Localized Resonant Excitons in Silver–Pnictogen Halide Double Perovskites

Chemically Localized Resonant Excitons in Silver–Pnictogen Halide Double Perovskites

Expanded Analogs of Three‐Dimensional Lead‐Halide Hybrid Perovskites

Time‐Dependent Density Functional Theory of Narrow Band Gap Semiconductors Using a Screened Range‐Separated Hybrid Functional

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