Large photo-induced voltage in a ferroelectric thin film with in-plane polarization
TL;DR: In this article, a large photoinduced voltage of 7 V was obtained with an in-plane poled ferroelectric thin film having a composition of WO3 modified Pb0.97La0.03(Zr0.52Ti0.48)O3 (PLWZT) under ultraviolet (UV) illumination for about 80 s.
Abstract: A large photoinduced voltage of 7 V was obtained with an in-plane poled ferroelectric thin film having a composition of WO3 modified Pb0.97La0.03(Zr0.52Ti0.48)O3 (PLWZT), under ultraviolet (UV) illumination for about 80 s. By poling the ferroelectric film along the surface plane through pairs of interdigital electrodes, the interelectrode distance constraint on the voltage magnitude arising from the small film thickness was broken. Our experimental results showed that both the direction and magnitude of the photovoltaic output could be tuned with the poling electric field. The dependence of the photoinduced voltage on light wavelength, light intensity, and the gap of the interdigital electrode were investigated. The advantages of the photovoltaic configuration on the basis of an in-plane poled ferroelectric thin film were analyzed.
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TL;DR: An insight into the analogies, state-of-the-art technologies, concepts, and prospects under the umbrella of perovskite materials (both inorganic-organic hybrid halideperovskites and ferroelectric perovkites) for future multifunctional energy conversion and storage devices is provided.
Abstract: An insight into the analogies, state-of-the-art technologies, concepts, and prospects under the umbrella of perovskite materials (both inorganic-organic hybrid halide perovskites and ferroelectric perovskites) for future multifunctional energy conversion and storage devices is provided. Often, these are considered entirely different branches of research; however, considering them simultaneously and holistically can provide several new opportunities. Recent advancements have highlighted the potential of hybrid perovskites for high-efficiency solar cells. The intrinsic polar properties of these materials, including the potential for ferroelectricity, provide additional possibilities for simultaneously exploiting several energy conversion mechanisms such as the piezoelectric, pyroelectric, and thermoelectric effect and electrical energy storage. The presence of these phenomena can support the performance of perovskite solar cells. The energy conversion using these effects (piezo-, pyro-, and thermoelectric effect) can also be enhanced by a change in the light intensity. Thus, there lies a range of possibilities for tuning the structural, electronic, optical, and magnetic properties of perovskites to simultaneously harvest energy using more than one mechanism to realize an improved efficiency. This requires a basic understanding of concepts, mechanisms, corresponding material properties, and the underlying physics involved with these effects.
1,015 citations
TL;DR: In this paper, the long range electromigration of methylammonium ions (MA+) in MAPbI3 perovskite was observed directly using the photo-thermal induced resonance technique.
Abstract: In this study, long range electromigration of methylammonium ions (MA+) in methyl ammonium lead tri-iodide (MAPbI3) film is observed directly using the photothermal induced resonance technique. The electromigration of MA+ leads to the formation of a lateral p-i-n structure, which is the origin of the switchable photovoltaic effect in MAPbI3 perovskite devices.
549 citations
TL;DR: The photovoltaic effect in epitaxial BFO thin films is studied and an open-circuit voltage Voc of 0.3 V is obtained, demonstrating that photocurrent direction can be switched by the polarization direction of the BFO film and that the ferroelectric polarization is the main driving force of the observed photov Holtaic effect.
Abstract: Adv. Mater. 2010, 22, 1763–1766 2010 WILEY-VCH Verlag G T IO N While silicon-based diodes have been the dominant solar cell type, novel photovoltaic mechanisms are being explored in pursuit of lower cost or improved efficiency. In a semiconductor photodiode, such as a Si solar cell, photons with energy higher than the band gap are absorbed to produce electron-hole pairs, which are separated by the internal field in the p–n junction and collected with the electrodes. However, a p–n junction is not a prerequisite for the photovoltaic effect. For exitonic solar cells, photon absorption creates excitons, which dissociate at a heterojunction. In materials without a center of symmetry, such as ferroelectric materials, steady-state photocurrent can exist in a homogeneous medium under uniform illumination, a phenomenon called bulk photovoltaic effect (BPVE). BPVE is a fascinating mechanism with many unique features such as extremely large photovoltage, a photocurrent proportional to the polarization magnitude, and charge-carrier separation in homogeneous media. Observed in bulk ferroelectrics in as early as 1950s, BPVE has seen a resurgent interest recently, especially in ferroelectric thin films. It has been proposed that remarkably higher photovoltaic efficiency can be achieved in thin films. On the other hand, open-circuit voltage much larger than the band gap has also been achieved with ferroelectric thin films with in-plane interdigital electrodes, which has led to the development of UV sensors and dosimeters. The ferroelectric thin-film materials under the previous study, such as BaTiO3 and Pb(ZrTi)O3, have wide band gaps (typically larger than 3.3 eV) corresponding to the UV region. BPVE in visible wavelength could lead to the development of new photovoltaic cells or other novel optoelectronic devices. BiFeO3 (BFO), a multiferroic material at room temperature with a band gap near 2.74 eV and a very large remnant ferroelectric polarization, offers a unique opportunity for such an investigation. Appreciable photoconductivity in visible light has been reported in BFO. Optical studies by absorption spectroscopy and spectroscopic ellipsometry have shown that BFO has a direct band gap with high absorption coefficient. Recently, a switchable-diode effect and a visible-light photovoltaic effect has been observed in BFO bulk crystals. However, no value of photovoltage has been reported for BFO single crystals and significant bulk photovoltaic response has not been demonstrated in BFO thin film. It is also unclear if the photovoltaic response in BFO is due to the diode effect. Here, we studied the photovoltaic effect in epitaxial BFO thin films and obtained an open-circuit voltage Voc of 0.3 V. We further demonstrated that photocurrent direction can be switched by the polarization direction of the BFO film and that the ferroelectric polarization is the main driving force of the observed photovoltaic effect. Moreover, the as-deposited BFO films were self-polarized and they could readily function as a photovoltaic cell without any poling. Epitaxial BFO thin films of 170 nm were grown by radiofrequency (RF) magnetron sputter deposition on a (001)c SrTiO3 (STO) substrate, with a 60-nm layer of SrRuO3 (SRO) as the bottom electrode. The resulting films show good epitaxy as determined by high-resolution X-ray diffraction (HRXRD; Supporting Information, Fig. S1). The polarization–electric field (P–E) hysteresis measurement shows a remnant polarization (Pr) of more than 65mCcm 2 with a Au top electrode (Fig. S2). Devices with an indium tin oxide (ITO) top electrode have a slightly smaller Pr. Figure 1a shows the spectral response of the short-circuit current (Jsc) of the BFO film. Highest current density is detected at 460 nm, closely corresponding to the measured BFO band gap of 2.72 eV (Fig. S3). Incident light at 435 nm, slightly above band gap, was used for the current-density–voltage (J–V) measurement (Fig. 1b). The as-deposited samples were electrically poled before measurement. The poling direction is termed positive if a positive bias voltage is applied to the top electrode with the bottom electrode grounded. In the J–Vmeasurement, the applied voltage is positive if a positive bias voltage is applied to the bottom electrode. Fig. 1b shows that for the positively poled samples the photocurrent is positive (i.e., it flows out of the top electrode). In contrast, after the negative poling, the photocurrent direction is reversed. The magnitudes of both the photocurrent and photovoltage are smaller in positively poled samples than in negatively poled ones. Jsc is observed to increase almost linearly with the illumination intensity (Fig. 1c), whileVoc saturates at high illumination intensity (Fig. 1d). At the highest illumination intensitymeasured,Voc in the negatively poled film of 170-nm thickness is 0.286V. The substantialVoc obtainedhere is probably a result of the low conductivity of our samples, which is on the order of 10V 1 cm , six orders of magnitude smaller than that reported by Basu et al. and also much smaller than that reported by Choi. The photovoltaic response for the as-deposited films without any poling was also measured. The results are surprisingly
505 citations
TL;DR: In this paper, the authors reviewed the advance in understanding the mechanisms of the ferroelectric photovoltaic effects and recent progress in improving the photiovoltaic device performance.
Abstract: The ferroelectric-photovoltaic (FE-PV) device, in which a homogeneous ferroelectric material is used as a light absorbing layer, has been investigated during the past several decades with numerous ferroelectric oxides. The FE-PV effect is distinctly different from the typical photovoltaic (PV) effect in semiconductor p–n junctions in that the polarization electric field is the driving force for the photocurrent in FE-PV devices. In addition, the anomalous photovoltaic effect, in which the voltage output along the polarization direction can be significantly larger than the bandgap of the ferroelectric materials, has been frequently observed in FE-PV devices. However, a big challenge faced by the FE-PV devices is the very low photocurrent output. The research interest in FE-PV devices has been re-spurred by the recent discovery of above-bandgap photovoltage in materials with ferroelectric domain walls, electric switchable diodes and photovoltaic effects, tip-enhanced photovoltaic effects at the nanoscale, and new low-bandgap ferroelectric materials and device design. In this feature article, we reviewed the advance in understanding the mechanisms of the ferroelectric photovoltaic effects and recent progress in improving the photovoltaic device performance, including the emerging approaches of integrating the ferroelectric materials into organic heterojunction photovoltaic devices for very high efficiency PV devices.
391 citations
TL;DR: The surge of interest in multiferroic materials over the past 15 years has been driven by their fascinating physical properties and huge potential for technological applications as discussed by the authors, which can deliver a new wave of technological advances and economic impact comparable to the silicon industrial revolution of the 1950s.
Abstract: Materials science is recognized as one of the main factors driving development and economic growth. Since the silicon industrial revolution of the 1950s, research and developments in materials and solid state science have radically impacted and transformed our society by enabling the emergence of the computer technologies, wireless communications, Internet, digital data storage, and widespread consumer electronics. Today's emergent topics in solid state physics, such as nano-materials, graphene and carbon nano-tubes, smart and advanced functional materials, spintronic materials, bio-materials, and multiferroic materials, promise to deliver a new wave of technological advances and economic impact, comparable to the silicon industrial revolution of the 1950s.The surge of interest in multiferroic materials over the past 15 years has been driven by their fascinating physical properties and huge potential for technological applications. This article addresses some of the fundamental aspects of solid-state mult...
387 citations
References
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TL;DR: This method results in a power conversion efficiency 50 per cent higher than the best values reported for comparable bilayer devices, suggesting that this strained annealing process could allow for the formation of low-cost and high-efficiency thin film organic solar cells based on vacuum-deposited small-molecular-weight organic materials.
Abstract: The power conversion efficiency of small-molecular-weight and polymer organic photovoltaic cells has increased steadily over the past decade This progress is chiefly attributable to the introduction of the donor–acceptor heterojunction1,2 that functions as a dissociation site for the strongly bound photogenerated excitons Further progress was realized in polymer devices through use of blends of the donor and acceptor materials3,4,5: phase separation during spin-coating leads to a bulk heterojunction that removes the exciton diffusion bottleneck by creating an interpenetrating network of the donor and acceptor materials The realization of bulk heterojunctions using mixtures of vacuum-deposited small-molecular-weight materials has, on the other hand, posed elusive: phase separation induced by elevating the substrate temperature inevitably leads to a significant roughening of the film surface and to short-circuited devices Here, we demonstrate that the use of a metal cap to confine the organic materials during annealing prevents the formation of a rough surface morphology while allowing for the formation of an interpenetrating donor–acceptor network This method results in a power conversion efficiency 50 per cent higher than the best values reported for comparable bilayer devices, suggesting that this strained annealing process could allow for the formation of low-cost and high-efficiency thin film organic solar cells based on vacuum-deposited small-molecular-weight organic materials
1,306 citations
TL;DR: The advantages and limitations of photovoltaic solar modules for energy generation are reviewed with their operation principles and physical efficiency limits, and recent developments suggest that thin-film crystalline silicon (especially microcrystalline silicon) is becoming a prime candidate for future photov electricity generation.
Abstract: The advantages and limitations of photovoltaic solar modules for energy generation are reviewed with their operation principles and physical efficiency limits. Although the main materials currently used or investigated and the associated fabrication technologies are individually described, emphasis is on silicon-based solar cells. Wafer-based crystalline silicon solar modules dominate in terms of production, but amorphous silicon solar cells have the potential to undercut costs owing, for example, to the roll-to-roll production possibilities for modules. Recent developments suggest that thin-film crystalline silicon (especially microcrystalline silicon) is becoming a prime candidate for future photovoltaics.
1,177 citations
Journal Article•
TL;DR: This is the first volume of a set of three within the Springer Series in Optical Sciences, and is devoted to photorefractive effects, photoreFractive materials, and their applications.
Abstract: This is the first volume of a set of three within the Springer Series in Optical Sciences, and is devoted to photorefractive effects, photorefractive materials, and their applications. Since the publication of our first two Springer books on Photorefractive Materials and Their Applications (Topics in Applied Physics, Vols. 61 and 62) almost 20 years ago, a lot of research has been done in this area. New and often expected effects have been discovered, theoretical models developed, known effects finally explained, and novel applications proposed. We believe that the field has now reached a high level of maturity, even if research continues in all areas mentioned above and with new discoveries arriving quite regularly. We therefore have decided to invite some of the top experts in the field to put together the state of the art in their respective fields. This after we had been encouraged to do so for more than ten years by the publisher, due to the fact that the former volumes were long out of print.
1,154 citations
Book•
20 Dec 1999TL;DR: In this article, the authors present and propose PV cells for stand-alone and utility-interactive PV systems, and discuss the physics of photovoltaic cells and their applications.
Abstract: Background.- The Sun.- Introduction to PV Systems.- PV System Examples.- Cost Considerations.- Mechanical Considerations.- Stand-Alone PV Systems.- Utility Interactive PV Systems.- Externalities and Photovoltaics.- The Physics of Photovoltaic Cells.- Present and Proposed PV Cells.
638 citations