Bulk Photovoltaic Effect at Visible Wavelength in Epitaxial Ferroelectric BiFeO<sub>3</sub> Thin Films

Ji, Wei; Yao, Kui; Liang, Yung C.

doi:10.1002/adma.200902985

Cited by 564 publications

(486 citation statements)

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“…Second, as shown in the upper left insets of Figures 1c and d, these features commonly exhibit a photovoltaic effect in the low-E-field region, consistent with the literature. [3][4][5][6][7][8] Figures 2a and d show the in-plane domain images and the corresponding I sc images for single-domain switching. In the intermediate reversal field, as in the domain image of E poling at þ 45 V and the I sc image at À20 V, the domain breaks up into two subdomains, showing signs of I sc to each other.…”

Section: Resultsmentioning

confidence: 99%

“…This phenomenon has been recently revisited with a small band-gap, BiFeO 3 (BFO) ferroelectric, from which a substantially higher photon-to-charge generation efficiency can be achieved in the visible range compared with that of other insulating ferroelectrics. [3][4][5][6][7][8] reported that diodelike rectification follows the polarization-dependent interface bandbending of BFO single-crystal slabs that are electrically switchable, that is, V oc and I sc are defined by the remanent polarization directions. In general, the spatial extent of spontaneous polarization vectors in ferroelectric crystals is typically manifested as domains (typically spanning over a few mm in size) and domain walls (DW, 1-2 nm in…”

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Single ferroelectric-domain photovoltaic switch based on lateral BiFeO3 cells

Sung

Lee

et al. 2013

NPG Asia Mater

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The bistability of ferroelectric polarization states serves as a basis for solid-state memory. This phenomenon can also yield an interesting photovoltaic effect in such a way that the directional photocarrier motion follows the inherent potential gradient imposed by the ferroelectric polarization vectors. Here, we demonstrate a single-domain photovoltaic switch based on lateral BiFeO 3 channels, in which such photovoltaic switching is achieved by a coherent single-domain reversal with a short electrical pulse. We then provide visual evidence for such operations with a series of spatially and spectrally resolved short-circuit photocurrent images. Specifically, we reveal that the sequential photovoltaic current images directly reflect the remanent polarization states of a single-domain channel. We also verify that, in multidomain channels, diffusive switching characteristics are determined not only by the internal polarization vector within the domain but also by oxygen vacancy accumulation at the domain walls. Keywords: ferroelectrics; multiferroics; oxide photonics; photovoltaics INTRODUCTIONHomogeneous light illumination on non-centrosymmetric crystals, such as ferroelectrics, in the intrinsic absorption range can give rise to an interesting photovoltaic effect, dubbed as the bulk photovoltaic effect. 1,2 This effect is distinct from that of typical semiconductor p-n junction photovoltaics and excitonic heterojunction photovoltaics in that the photogenerated carriers can be separated along the inherent polar directions, ensuing the unidirectional photocurrent (I ph ) and photovoltage (V ph ), associated with the spontaneous ferroelectric polarization vector (P s ). Therein, the open-circuit voltage (V oc ) is determined by the magnitude of the remanent polarization of ferroelectrics, and it can be additively as large as a few hundreds of volts, although the short-circuit current (I sc I ph at 0 V) is low due to the insulating character of the system. This phenomenon has been recently revisited with a small band-gap, BiFeO 3 (BFO) ferroelectric, from which a substantially higher photon-to-charge generation efficiency can be achieved in the visible range compared with that of other insulating ferroelectrics. [3][4][5][6][7][8] reported that diodelike rectification follows the polarization-dependent interface bandbending of BFO single-crystal slabs that are electrically switchable, that is, V oc and I sc are defined by the remanent polarization directions. In general, the spatial extent of spontaneous polarization vectors in ferroelectric crystals is typically manifested as domains (typically spanning over a few mm in size) and domain walls (DW, 1-2 nm in

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Single ferroelectric-domain photovoltaic switch based on lateral BiFeO3 cells

Sung

Lee

et al. 2013

NPG Asia Mater

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“…Bulk polarization is not required; only inversion symmetry must be broken. Shift currents have been investigated experimentally [19,[27][28][29][30][31][32][33][34], analytically [20,23,[35][36][37], and computationally, although only for a few nonpolar materials [23][24][25]. Perturbative analysis treating the electromagnetic field classically yields the shift current expression [20,23] J q ¼ rsq E r E s rsq ð!Þ ¼ e e m@!…”

Section: First Principles Calculation Of the Shift Current Photovoltamentioning

confidence: 99%

First Principles Calculation of the Shift Current Photovoltaic Effect in Ferroelectrics

2012

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We calculate the bulk photovoltaic response of the ferroelectrics BaTiO 3 and PbTiO 3 from first principles by applying "shift current" theory to the electronic structure from density functional theory. The first principles results for BaTiO 3 reproduce eperimental photocurrent direction and magnitude as a function of light frequency, as well as the dependence of current on light polarization, demonstrating that shift current is the dominant mechanism of the bulk photovoltaic effect in BaTiO 3 . Additionally, we analyze the relationship between response and material properties in detail. The photocurrent does not depend simply or strongly on the magnitude of material polarization, as has been previously assumed; instead, electronic states with delocalized, covalent bonding that is highly asymmetric along the current direction are required for strong shift current enhancements. The complexity of the response dependence on both external and material parameters suggests applications not only in solar energy conversion, but to photocatalysis and sensor and switch type devices as well.

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“…Shift current materials have been suggested as candidates for light-harvesting energy applications, due to active photocurrent generation in the entire bulk of the material and their above-band gap photovoltages [47]. The BPVE is a ballistic hot carrier effect.…”

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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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Bulk Photovoltaic Effect at Visible Wavelength in Epitaxial Ferroelectric BiFeO₃ Thin Films

Cited by 564 publications

References 32 publications

Single ferroelectric-domain photovoltaic switch based on lateral BiFeO3 cells

Single ferroelectric-domain photovoltaic switch based on lateral BiFeO3 cells

First Principles Calculation of the Shift Current Photovoltaic Effect in Ferroelectrics

Enhancement of the Bulk Photovoltaic Effect in Topological Insulators

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Bulk Photovoltaic Effect at Visible Wavelength in Epitaxial Ferroelectric BiFeO3 Thin Films

Cited by 564 publications

References 32 publications

Single ferroelectric-domain photovoltaic switch based on lateral BiFeO3 cells

Single ferroelectric-domain photovoltaic switch based on lateral BiFeO3 cells

First Principles Calculation of the Shift Current Photovoltaic Effect in Ferroelectrics

Enhancement of the Bulk Photovoltaic Effect in Topological Insulators

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Product

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Bulk Photovoltaic Effect at Visible Wavelength in Epitaxial Ferroelectric BiFeO₃ Thin Films