Showing papers on "Anomalous photovoltaic effect published in 2023"
TL;DR: In this article , a 2D lead-free double perovskite (BBA)2 CsAgBiBr7 (1, BBA = 4-bromobenzylammonium), tailored by mixing aromatic and alkali cations in the confined architecture to form electric polarization is obtained.
Abstract: The bulk anomalous photovoltaic (BAPV) effect of acentric materials refers to a distinct concept from traditional semiconductor-based devices, of which the above-bandgap photovoltage hints at a promise for solar-energy conversion. However, it is still a challenge to exploit new BAPV-active systems due to the lacking of knowledge on the structural origin of this concept. BAPV effects in single crystals of a 2D lead-free double perovskite, (BBA)2 CsAgBiBr7 (1, BBA = 4-bromobenzylammonium), tailored by mixing aromatic and alkali cations in the confined architecture to form electric polarization are acquired here. Strikingly, BAPV effects manifested by above-bandgap photovoltage (VOC ) show unique attributes of directional anisotropy and positive dependence on electrode spacing. The driving source stems from orientations of the polar aromatic spacer and Cs+ ion drift, being different from the known built-in asymmetry photovoltaic heterojunctions. As the first demonstration of the BAPV effect in the double perovskites, the results will enrich the family of environmentally green BAPV-active candidates and further facilitate their new optoelectronic application.
1 citations
TL;DR: In this article , the bulk photovoltaic effect of polycrystalline solution-deposited bismuth ferrite thin films is studied under different stress conditions induced by different substrates and quantified using a direct strain assessment via x-ray diffraction.
Abstract: Bulk or anomalous photovoltaic effect in ferroelectrics has recently sparked interest due to the generation of switchable photovoltages that are not limited by the bandgap of the material. The development of strategies to tune its magnitude is a key for the development of light-driven devices, e.g., photostrictive actuators, photostrictive sensors, or reconfigurable waveguides. In this paper, the bulk photovoltaic effect of polycrystalline solution-deposited bismuth ferrite thin films is studied under different stress conditions induced by different substrates and quantified using a direct strain assessment via x-ray diffraction. An increase in the short-circuit bulk photovoltaic current of 150% is observed with a change from a compressive stress of 0.54 GPa to a tensile stress of 0.93 GPa. This change is attributed to intrinsic piezophotovoltaic effect, demonstrating the potential to strain engineer the bulk photovoltaic effect in thin films.
1 citations
TL;DR: In this paper , a simple proof of principle method was proposed to demonstrate the value of photo generated current being the sum of ballistic current and shift current, which are combined to form the so-called bulk photovoltaic current, and can be related to the prototype intrinsic properties such as magneto-optical coupling and ferroelectric polarization.
Abstract: After the discovery of bulk photovoltaic effect more than half a century ago, ferro-electrical and magneto-optical experiments have provided insights into various related topics, revealing above bandgap open voltages and non-central symmetrical current mechanisms. However, the nature of the photon-generated carriers responses and their microscopic mechanisms remain unclear. Here, all-inorganic perovskite Bi0.85Gd0.15Fe1−xMnxO3 thin films were prepared by a sol-gel process and the effects of Gd and Mn co-doped bismuth ferrites on their microtopography, grain boundries, multiferroic, and optical properties were studied. We discovered a simple “proof of principle” type new method that by one-step measuring the leakage current, one can demonstrate the value of photo generated current being the sum of ballistic current and shift current, which are combined to form the so-called bulk photovoltaic current, and can be related to the prototype intrinsic properties such as magneto-optical coupling and ferroelectric polarization. This result has significant potential influence on design principles for engineering multiferroic optoelectronic devices and future photovoltaic industry development.
1 citations
TL;DR: In this paper , the photovoltaic response of BiFeO3-based vertical heterostructures was investigated under white light illumination, and it was shown that polarization-modulated Schottky barrier at the interface is the dominating mechanism.
Abstract: The ferroelectric photovoltaic effect has been extensively studied for possible applications in energy conversion and photo-electrics. The reversible spontaneous polarization gives rise to a switchable photovoltaic behavior. However, despite its long history, the origin of the ferroelectric photovoltaic effect still lacks a full understanding since multiple mechanisms such as bulk and Schottky-barrier-related interface effects are involved. Herein, we report a comprehensive study on the photovoltaic response of BiFeO3-based vertical heterostructures, using multiple strategies to clarify its origin. We found that, under white light illumination, polarization-modulated Schottky barrier at the interface is the dominating mechanism. By varying the top metal contacts, only the photovoltaic effect of the polarization downward state is strongly modulated, suggesting selective interface contribution in different polarization states. A Schottky-barrier-free device shows negligible photovoltaic effect, suggesting the lack of bulk photovoltaic effect in vertical heterostructures under white light illumination.
1 citations
27 Apr 2023
TL;DR: In this article , the authors proposed a concept of bulk electro-photovoltaic effect, that is, an out-of-plane external electric-field can continuously tune in-plane shift current along with its sign flip in a hetero-nodal-line (HNL) system.
Abstract: Realization of giant and continuously tunable second-order photocurrent is desired for many nonlinear optical (NLO) and optoelectronic applications, which remains to be a great challenge. Here, based on a simple two-band model, we propose a concept of bulk electro-photovoltaic effect, that is, an out-of-plane external electric-field ($E_{ext}$) can continuously tune in-plane shift current along with its sign flip in a hetero-nodal-line (HNL) system. While strong linear optical transition around the nodal-loop may potentially generate giant shift current, an $E_{ext}$ can effectively control the radius of nodal-loop, which can continuously modulate the shift-vector components inside and outside nodal-loop holding opposite signs. This concept has been demonstrated in the HNL HSnN/MoS$_2$ system using first-principles calculations. The HSnN/MoS$_2$ hetero-bilayer not only can produce giant shift current with 1~2 magnitude order larger than other reported systems, but also can realize a giant bulk electro-photovoltaic effect. Our finding opens new routes to create and manipulate giant NLO responses in 2D materials.
19 Feb 2023
TL;DR: In this paper , the authors presented a comprehensive study on the BPVE response of different magnetic structures through symmetry analysis and first-principles calculation, and demonstrated that the interlayer antiferromagnetic (AFM) $EuSn_2As_2$ of even-layer breaks the inversion symmetry and has the second-order optical responses.
Abstract: The bulk photovoltaic effect (BPVE) is a second-order optical process in noncentrosymmetric materials that converts the light into DC currents. BPVE is classified into shift current and injection current according to the generation mechanisms, whose dependence on the polarization of light is sensitive to the spatial and time-reversal symmetry of materials. In this work, we present a comprehensive study on the BPVE response of $EuSn_2As_2$ with different magnetic structures through symmetry analysis and first-principles calculation. We demonstrate that the interlayer antiferromagnetic (AFM) $EuSn_2As_2$ of even-layer breaks the inversion symmetry and has the second-order optical responses. Moreover, the bilayer AFM $EuSn_2As_2$ not only displays distinct BPVE responses when magnetic moments align in different directions, but also shows symmetry-related responses in two phases which have mutually perpendicular in-plane magnetic moments. Due to the dependence of BPVE responses on the polarization of light and magnetic symmetry, these magnetic structures can be distinguished by the circular polarized light with well-designed experiments. Our work demonstrates the feasibility of the BPVE response as a tool to probe the magnetic structure.
TL;DR: In this paper , the authors demonstrate self-driven NIR photodetectors based on SnTe/Si and SnTe:Si/Si heterostructures with a high detectivity of 3.3 × 1012 Jones.
Abstract: The upsurge of new materials that can be used for near-infrared (NIR) photodetectors operated without cooling is crucial. As a novel material with a small bandgap of ≈0.28 eV, the topological crystalline insulator SnTe has attracted considerable attention. Herein, this work demonstrates self-driven NIR photodetectors based on SnTe/Si and SnTe:Si/Si heterostructures. The SnTe/Si heterostructure has a high detectivity D* of 3.3 × 1012 Jones. By Si doping, the SnTe:Si/Si heterostructure reduces the dark current density and increases the photocurrent by ≈1 order of magnitude simultaneously, which improves the detectivity D* by ≈2 orders of magnitude up to 1.59 × 1014 Jones. Further theoretical analysis indicates that the improved device performance may be ascribed to the bulk photovoltaic effect (BPVE), in which doped Si atoms break the inversion symmetry and thus enable the generation of additional photocurrents beyond the heterostructure. In addition, the external quantum efficiency (EQE) measured at room temperature at 850 nm increases by a factor of 7.5 times, from 38.5% to 289%. A high responsivity of 1979 mA W-1 without bias and fast rising time of 8 µs are also observed. The significantly improved photodetection achieved by the Si doping is of great interest and may provide a novel strategy for superior photodetectors.
TL;DR: In this article , the photovoltaic effect can be produced in metals, semimetals, and semiconductor 3D topological insulators with crystalline and nanostructured states.
Abstract: We report that the photovoltaic effect can be produced in metals, semimetals, and semiconductor 3D topological insulators with crystalline and nanostructured states. The behavior of charge carriers in topological insulator...
TL;DR: In this article , the defect-induced bandgap intermediate state is derived from the 3D split state of Ni and plays a dominant role in lowering the bandgap of Semiconducting (1−x) KNbO3−xBaNi 0.5Hf0.5O3 −δ (KNBNH, x = 2, 4, 6, 8%) ferroelectric ceramics with enhanced photovoltaic performance.
Abstract: The inversion asymmetry of polar crystals enables ferroelectric ceramics to possess unique physical properties, among which the anomalous photovoltaic effect drives their potential application in photovoltaic conversion. Semiconducting (1−x) KNbO3−xBaNi0.5Hf0.5O3−δ (KNBNH, x = 2, 4, 6, 8%) ferroelectric ceramics with enhanced photovoltaic performance were prepared by utilizing conventional solid-state sintering strategies. In these ceramics, the defect-induced bandgap intermediate state is derived from the 3d split state of Ni and plays a dominant role in lowering the bandgap of KN. The defective bandgap state induced by Ni in KNBNH promotes its absorption of light and the separation of photogenerated carriers, thus enhancing its photovoltaic response. The KNBNH6 shows a maximum value of 138.7 nA/cm2 for short-circuit photocurrent density (Jsc) among these ceramics, which is further enhanced to 702.9 nA/cm2 after 30 kV/cm polarization. Structural investigations after polarization indicate that polarization induced lattice distortion in KNBNH6, leading to an increase in the polarity of its cells. This work provides an understanding of defect-induced bandgap states and high-field polarization to enhance ferroelectric photovoltaic properties. This article is protected by copyright. All rights reserved
TL;DR: In this article , the spontaneous electric field (Es) in polar structures is shown to be crucial for understanding the physical and chemical properties of compound semiconductors and improving their performanes.
Abstract: The concept of spontaneous electric field (Es) in polar structures is crucial for understanding the physical and chemical properties of compound semiconductors and improving their performanes. However, this concept has not been widely accepted so far. Here, we show the first observation of rectification and photovoltaic effects in the polar [0001] direction on the nonpolar ZnO (1010) crystal plane. However, no rectification and photovoltaic effects are observed in the nonpolar [1210] direction perpendicular to the [0001]. When a stress was applied in the [0001] direction of the ZnO single crystal, the rectification and photovoltaic effects are abated and disappeared. The disappearance of the two effects results from the pressure-induced disappearance of the polar structure. The results fully demonstrated that the rectification and photovoltaic effects arise from the existence of Es in the polar [0001] direction. The Es motivates the directional transfer of the electrons and photocreated charges along the [0001] direction, and the rectification and photovoltaic effects are thus observed. These results provide direct evidence for the polar structure theory and suggest that the polar structures can be employed to develop new types of photovoltaic and other electronic and photoelectronic devices.
30 May 2023
TL;DR: In this article , the authors present experiments in electromigrated planar MIM structures, designed with asymmetric plasmonic properties using Au and Pt electrodes, showing that hot electron photocurrent on the Au side of the junction preferentially creates hot electrons on the Pt side, leading to a clear preferred directionality of the hot electrons and hence a preferred polarity of the resulting OCPV.
Abstract: Tunneling metal-insulator-metal (MIM) junctions can exhibit an open-circuit photovoltage (OCPV) response under illumination that may be useful for photodetection. One mechanism for photovoltage generation is hot carrier tunneling, in which photoexcited carriers generate a net photocurrent that must be balanced by a drift current in the open-circuit configuration. We present experiments in electromigrated planar MIM structures, designed with asymmetric plasmonic properties using Au and Pt electrodes. Decay of optically excited local plasmonic modes preferentially creates hot carriers on the Au side of the junction, leading to a clear preferred directionality of the hot electron photocurrent and hence a preferred polarity of the resulting OCPV. In contrast, in an ensemble of symmetric devices constructed from only one Au, polarity of the OCPV has no preferred direction.