First-principles calculation of the bulk photovoltaic effect in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi mathvariant="normal">KNbO</mml:mi></mml:mrow><mml:mn>3</mml:mn></mml:msub></mml:math>and (K,Ba)(Ni,Nb)<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>−</mml:mo><mml:mi>δ</mml:mi></mml:mrow></mml:msub></mml:math>

Wang, Fenggong; Rappe, Andrew M.

doi:10.1103/physrevb.91.165124

Cited by 60 publications

(41 citation statements)

References 51 publications

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“…The plot for bandgap determination has two slopes, where at low photon energy the slope leads to finding the low gap of 1.85 eV, whereas at higher photon energy there is another slope that gives a gap 2.51 eV. We can speculate the reason for this phenomenon based on many previous studies [9,[16][17][18] and the schematic diagram of the intraband transition were shown in Fig. 4(b).…”

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confidence: 90%

Investigation of microstructural and optical properties of (K,Ba)(Ni,Nb)O3−δ thin films fabricated by pulsed laser deposition

et al. 2016

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Section: Resultsmentioning

confidence: 90%

Investigation of microstructural and optical properties of (K,Ba)(Ni,Nb)O3−δ thin films fabricated by pulsed laser deposition

et al. 2016

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“…The ab initio calculation of the shift current and subsequent analysis yielded several chemical and structural criteria for optimizing the response. These criteria have been used previously to modify or identify existing materials with enhanced response [14,[32][33][34]. In this work, we use these insights to propose several candidate bulk photovoltaics with calculated response as much as an order of magnitude higher than well-known ferroelectrics, while having band gaps in or slightly below the visible spectrum.…”

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First-Principles Materials Design of High-Performing Bulk Photovoltaics with theLiNbO3Structure

2015

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The bulk photovoltaic effect is a long-known but poorly understood phenomenon. Recently, however, the multiferroic bismuth ferrite has been observed to produce strong photovoltaic response to visible light, suggesting that the effect has been underexploited as well. Here we present three polar oxides in the LiNbO3 structure that we predict to have band gaps in the 1-2 eV range and very high bulk photovoltaic response: PbNiO3, Mg 1/2 Zn 1/2 PbO3, and LiBiO3. All three have band gaps determined by cations with d 10 s 0 electronic configurations, leading to conduction bands composed of cation s-orbitals and O p-orbitals. This both dramatically lowers the band gap and increases the bulk photovoltaic response by as much as an order of magnitude over previous materials, demonstrating the potential for high-performing bulk photovoltaics.Photovoltaic effects have long been observed in bulk polar materials, especially ferroelectrics [1][2][3][4]. Known as the bulk photovoltaic effect (BPVE), it appeared to derive from inversion symmetry breaking. Despite intense initial interest, early explorations revealed low energy conversion efficiency, in part due to the high band gaps of most known ferroelectrics. Additionally, despite several proposed mechanisms, the physical origin of the BPVE was unclear [2,[5][6][7][8].However, recent emphasis on alternative energy technologies and the observation of the effect in novel semiconducting ferroelectrics (with band-gaps in the visible range) has renewed interest [9][10][11][12][13][14]. Several studies have attempted to elucidate the various contributions to the photovoltaic response -bulk or otherwise -in ferroelectrics [15][16][17][18][19][20][21][22][23]. In particular, bismuth ferrite (BFO) has been found to generate significant bulk photocurrents; combined with its unusually low band gap of 2.7 eV, it has attracted a great deal of attention for its potential in photovoltaic applications [21,[23][24][25][26][27][28][29][30][31]. The understanding of the fundamental physics behind the effect has advanced as well; recently we demonstrated that the BPVE can be attributed to "shift currents", and that the bulk photocurrents may be calculated from first-principles. The ab initio calculation of the shift current and subsequent analysis yielded several chemical and structural criteria for optimizing the response. These criteria have been used previously to modify or identify existing materials with enhanced response [14,[32][33][34]. In this work, we use these insights to propose several candidate bulk photovoltaics with calculated response as much as an order of magnitude higher than well-known ferroelectrics, while having band gaps in or slightly below the visible spectrum. Our results demonstrate that bulk photovoltaic response can be much stronger than previously observed, supporting the possibility of materials suitable for application.There are two figures of merit for evaluating the BPVE in a material: the current density response to a spatially uniform electric field, and the G...

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“…The shift vector R can be understood as a generalized gauge invariant k-space derivative of the p operator [32,33], and it is odd under the interchange of c and v bands. We apply this formalism to perform first-principles DFT calculations [34][35][36][37] of the shift current BPVE of the polar layered material BiTeI. This material is a normal insulator under ambient pressure, and DFT predicts that it becomes a topological insulator at pressures higher than 1.7 GPa [38].…”

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“…As such, a material with a small band gap can still have carriers emerge with more than the band gap worth of energy, as they do not thermalize before leaving the photovoltaic material. Recent works [37,[48][49][50] have studied how to achieve a large shift current magnitude in real materials, by considering structural modifications such as domain walls and chemical alloying. Our result suggests a new way to design shift current materials based on their electronic topology: to look for materials close to a band inversion transition.…”

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Enhancement of the Bulk Photovoltaic Effect in Topological Insulators

Tan

Rappe

2016

Phys. Rev. Lett.

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We investigate the shift current bulk photovoltaic response of materials close to a band inversion topological phase transition. We find that the bulk photocurrent reverses direction across the band inversion transition, and that its magnitude is enhanced in the vicinity of the phase transition. These results are demonstrated with first principles DFT calculations of BiTeI and CsPbI3 under hydrostatic pressure, and explained with an analytical model, suggesting that this phenomenon remains robust across disparate material systems.The field of topological insulators [1,2] has proven to be a fruitful avenue of research in condensed matter physics in recent years. The symmetry protected surface states of topological insulators [3][4][5] give rise to novel and useful phenomena such as dissipationless transport [6,7]. Even though band topology is a ground state property, defined on the occupied valence bands of an insulator [8], the excited state properties should be affected by topological considerations as well. There is a growing body of research investigating the optical properties of topological insulators[9] using photoemission spectroscopy [3,4], Raman spectroscopy [10][11][12][13], nonlinear optics [14][15][16][17][18][19], and photocurrent generation [20][21][22].While the presence or absence of topological surface states has thus far being the main experimental route for detecting topological phase transitions, in this work we propose an optical, non-surface approach for detecting topological phase transitions in the bulk. This is a direct approach which does not rely on the quality or ease of detection of surface states. We consider the influence of band topology on the bulk photovoltaic effect (BPVE, also known as the photogalvanic effect) [23,24], which is the generation of photocurrents in the bulk of a singlephase material.The bulk photovoltaic effect is a second-order optical effect which gives current densities, J r = σ rst E s E t , as a quadratic function of the applied electric fields. This dictates that the BPVE can only be observed in materials with broken inversion symmetry. Measurements of appreciable BPVE have been reported for many ferroelectric materials [25][26][27][28]. In the prototypical ferroelectric BaTiO 3 , experiments [29,30] and first-principles calculations [31] show that the primary mechanism for BPVE is the shift current [32]. In this mechanism, carriers are excited into a current-carrying superposition of excited states. Due to its dominant effect in the bulk photovoltaic response, we will focus on the shift current in this paper.Because optical excitations probe both the valence and conduction band wavefunctions, we expect the band inversion process, which is the interchange of the conduction and valence band characters, to result in dramatic changes in the finite-frequency response functions of the system. We show that band inversion reverses the direction of the shift current. The magnitude of the shift cur- rent is enhanced in the vicinity of the band inversion transition....

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First-principles calculation of the bulk photovoltaic effect inKNbO3and (K,Ba)(Ni,Nb)O3−δ

Cited by 60 publications

References 51 publications

Investigation of microstructural and optical properties of (K,Ba)(Ni,Nb)O3−δ thin films fabricated by pulsed laser deposition

Investigation of microstructural and optical properties of (K,Ba)(Ni,Nb)O3−δ thin films fabricated by pulsed laser deposition

First-Principles Materials Design of High-Performing Bulk Photovoltaics with theLiNbO3Structure

Enhancement of the Bulk Photovoltaic Effect in Topological Insulators

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