Increasing bulk photovoltaic current by strain tuning

Nadupalli, Shankari; Kreisel, J.; Granzow, Torsten

doi:10.1126/sciadv.aau9199

Cited by 66 publications

(55 citation statements)

References 31 publications

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“…Similar to the case of the electronic band structure, the SCs of GeS and SnS show dependence on the localization magnitude of the initial and final states, which has been found to depend on atomic displacements. The increase of nonthermalized polaron hopping leads to increased SCs in bulk LiNbO 3 since the energy of phonons involved in the formation of polarons decreases under strain, 56 and this is the same case in the 2D materials. The compressive strain causes the p-orbital-dominated conduction state to sharply shift downward in energy and overlap with the valence state.…”

Section: Resultsmentioning

confidence: 93%

Enhanced Shift Currents in Monolayer 2D GeS and SnS by Strain-Induced Band Gap Engineering

et al. 2020

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Group IV monochalcogenides exhibit spontaneous polarization and ferroelectricity, which are important in photovoltaic materials. Since strain engineering plays an important role in ferroelectricity, in the present work, the effect of equibiaxial strain on the band structure and shift currents in monolayer two-dimensional (2D) GeS and SnS has systematically been investigated using the first-principles calculations. The conduction bands of those materials are more responsive to strain than the valence bands. Increased equibiaxial compressive strain leads to a drastic reduction in the band gap and finally the occurrence of phase transition from semiconductor to metal at strains of −15 and −14% for GeS and SnS, respectively. On the other hand, tensile equibiaxial strain increases the band gap slightly. Similarly, increased equibiaxial compressive strain leads to a steady almost four times increase in the shift currents at a strain of −12% with direction change occurring at −8% strain. However, at phase transition from semiconductor to metal, the shift currents of the two materials completely vanish. Equibiaxial tensile strain also leads to increased shift currents. For SnS, shift currents do not change direction, just as the case of GeS at low strain; however, at a strain of +8% and beyond, direction reversal of shift currents beyond the band gap in GeS occur.

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Section: Resultsmentioning

confidence: 93%

Enhanced Shift Currents in Monolayer 2D GeS and SnS by Strain-Induced Band Gap Engineering

et al. 2020

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“…Although recent studies suggest that larger BPVE may exist in low-dimensional materials, experimental demonstrations are still rare 5 , 9 . One alternative approach could be the flexo-photovoltaic effect, in which strain gradients are applied to introduce broken inversion symmetry in the materials even without intrinsic BPVE 6 , 14 . However, it remains challenging for this approach to fabricate large-scale devices.…”

Section: Introductionmentioning

confidence: 99%

Zero-bias mid-infrared graphene photodetectors with bulk photoresponse and calibration-free polarization detection

et al. 2020

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Bulk photovoltaic effect (BPVE), featuring polarization-dependent uniform photoresponse at zero external bias, holds potential for exceeding the Shockley-Queisser limit in the efficiency of existing opto-electronic devices. However, the implementation of BPVE has been limited to the naturally existing materials with broken inversion symmetry, such as ferroelectrics, which suffer low efficiencies. Here, we propose metasurface-mediated graphene photodetectors with cascaded polarization-sensitive photoresponse under uniform illumination, mimicking an artificial BPVE. With the assistance of non-centrosymmetric metallic nanoantennas, the hot photocarriers in graphene gain a momentum upon their excitation and form a shift current which is nonlocal and directional. Thereafter, we demonstrate zero-bias uncooled mid-infrared photodetectors with three orders higher responsivity than conventional BPVE and a noise equivalent power of 0.12 nW Hz−1/2. Besides, we observe a vectorial photoresponse which allows us to detect the polarization angle of incident light with a single device. Our strategy opens up alternative possibilities for scalable, low-cost, multifunctional infrared photodetectors.

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“…The remarkable communality between the different transition regions described above and their evolution with driving fields (temperature, stress) is that they lead to exceptional properties and coupling phenomena. Also, it is highly likely that they can be triggered by light and will react to mechanical strain, and thus provide interesting piezo-photovoltaic properties 180 . The existence of such regions relates to different origins or driving forces, ranging from chemistry, phase coexistence, frustrations, fluctuations, and chiral textures, all of which can be in principle encountered in or around domain walls.…”

Section: Transition Regionsmentioning

confidence: 99%

Domain-wall engineering and topological defects in ferroelectric and ferroelastic materials

et al. 2020

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Ferroelectric and ferroelastic domain walls are two-dimensional (2D) topological defects with thicknesses approaching the unit cell level. When this spatial confinement is combined with observations of emergent functional properties, such as polarity in non-polar systems or electrical conductivity in otherwise insulating materials, it becomes clear that domain walls represent a new and exciting state of matter. In this review, we discuss the exotic polarisation profiles that can arise at domain walls with multiple order parameters and the different mechanisms that lead to domain wall polarity in non-polar ferroelastic materials. The emergence of energetically degenerate variants of the domain walls themselves suggests the existence of interesting quasi-1D topological defects within such walls. We also provide an overview of the general notions which have been postulated as fundamental mechanisms responsible for domain wall conduction in ferroelectrics. We then discuss the prospect of combining domain walls with transition regions observed at phase boundaries, homo-and heterointerfaces, and other quasi-2D objects, enabling emergent properties beyond those available in today's topological systems. Key points• In ferroelectrics, the emergence of a second polarisation component leads to analogues of Bloch and Néel walls. The stabilization of these walls opens the possibility for quasi-1D topological defects separating wall regions of opposite polarities.• Polar domain walls in ferroelastics rely on two mechanisms: a polarity imposed by the natural symmetry of strain-compatible domain walls, which can often be described by flexoelectric gradient coupling, and the emergence of a potentially switchable polarity when their natural symmetry is broken.• Several mechanisms are responsible for domain wall conduction in ferroelectrics: extrinsic intra-bandgap defect states, intrinsic suppression of the conduction band and intrinsic shift of the band structure induced by local electric fields.• Transition regions occurring at phase boundaries, homo-and heterointerfaces, and other quasi-2D objects probably exist at a smaller length scale, in the vicinity of domain walls, and could lead to exceptional properties and coupling phenomena.

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Increasing bulk photovoltaic current by strain tuning

Cited by 66 publications

References 31 publications

Enhanced Shift Currents in Monolayer 2D GeS and SnS by Strain-Induced Band Gap Engineering

Enhanced Shift Currents in Monolayer 2D GeS and SnS by Strain-Induced Band Gap Engineering

Zero-bias mid-infrared graphene photodetectors with bulk photoresponse and calibration-free polarization detection

Domain-wall engineering and topological defects in ferroelectric and ferroelastic materials

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