Rising atmospheric levels of carbon dioxide and the depletion of fossil fuel reserves raise serious concerns about the ensuing effects on the global climate and future energy supply. Utilizing the ...abundant solar energy to convert CO2 into fuels such as methane or methanol could address both problems simultaneously as well as provide a convenient means of energy storage. In this Review, current approaches for the heterogeneous photocatalytic reduction of CO2 on TiO2 and other metal oxide, oxynitride, sulfide, and phosphide semiconductors are presented. Research in this field is focused primarily on the development of novel nanostructured photocatalytic materials and on the investigation of the mechanism of the process, from light absorption through charge separation and transport to CO2 reduction pathways. The measures used to quantify the efficiency of the process are also discussed in detail.
It cuts both ways: The photocatalytic conversion of CO2 into valuable solar fuels such as methane or methanol has the potential to address the future energy supply demand and mitigate CO2 emissions. This Review presents the current state of the art of the heterogeneous photocatalytic reduction of CO2 on TiO2 and other metal oxides, oxynitrides, sulfides, and phosphides. The mechanisms and the measures of the efficiency of the process are discussed in detail.
Interfaces in Perovskite Solar Cells Fakharuddin, Azhar; Schmidt‐Mende, Lukas; Garcia‐Belmonte, Germà ...
Advanced energy materials,
November 22, 2017, Letnik:
7, Številka:
22
Journal Article
Recenzirano
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Rapid improvement in photoconversion efficiency (PCE) of solution processable organometallic hybrid halide based perovskite solar cells (PSCs) have taken the photovoltaic (PV) community with a ...surprise and has extended their application in other electronic devices such as light emitting diodes, photo detectors and batteries. Together with efforts to push the PCE of PSCs to record values >22% – now at par with that of crystalline silicon solar cells – origin of their PV action and underlying physical processes are also deeply investigated worldwide in diverse device configurations. A typical PSC consists of a perovskite film sandwiched between an electron and a hole selective contact thereby creating ESC/perovskite and perovskite/HSC interfaces, respectively. The selective contacts and their interfaces determine properties of perovskite layer and also control the performance, origin of PV action, open circuit voltage, device stability, and hysteresis in PSCs. Herein, we define ideal charge selective contacts, and provide an overview on how the choice of interfacing materials impacts charge accumulation, transport, transfer/recombination, band‐alignment, and electrical stability in PSCs. We then discuss device related considerations such as morphology of the selective contacts (planar or mesoporous), energetics and electrical properties (insulating and conducting), and its chemical properties (organic vs inorganic). Finally, the outlook highlights key challenges and future directions for a commercially viable perovskite based PV technology.
The past few years marked a new era of organometallic halide hybrid perovskite efficient solar cell technology. To capitalize the potential of this new class of materials in solar cells, in particular, and in any electronic devices in general, an understanding of interfacial physical processes is crucial. Herein, a comprehensive analysis of the role of interfaces in determining the PV performance and long term operational stability of this PV technology is provided.
Organic–inorganic halide perovskites are making breakthroughs in a range of optoelectronic devices. Reports of >23% certified power conversion efficiency in photovoltaic devices, external quantum ...efficiency >21% in light‐emitting diodes (LEDs), continuous‐wave lasing and ultralow lasing thresholds in optically pumped lasers, and detectivity in photodetectors on a par with commercial GaAs rivals are being witnessed, making them the fastest ever emerging material technology. Still, questions on their toxicity and long‐term stability raise concerns toward their market entry. The intrinsic instability in these materials arises due to the organic cation, typically the volatile methylamine (MA), which contributes to hysteresis in the current–voltage characteristics and ion migration. Alternative inorganic substitutes to MA, such as cesium, and large organic cations that lead to a layered structure, enhance structural as well as device operational stability. These perovskites also provide a high exciton binding energy that is a prerequisite to enhance radiative emission yield in LEDs. The incorporation of inorganic and layered perovskites, in the form of polycrystalline films or as single‐crystalline nanostructure morphologies, is now leading to the demonstration of stable devices with excellent performance parameters. Herein, key developments made in various optoelectronic devices using these perovskites are summarized and an outlook toward stable yet efficient devices is presented.
Inorganic and layered perovskites have broadened research paradigm for a range of optoelectronic devices. Their unique electronic and photophysical properties show that they are an excellent material, leading forefronts of solar cells, light‐emitting diodes, photodetectors, lasers, and beyond. An overview of key research activities for these devices is provided and challenges for their future research are identified.
Lithography is one of the most widely used methods for cutting‐edge research and industrial applications, mainly owing to its ability to draw patterns in the micro and even nanoscale. However, the ...fabrication of semiconductor micro/nanostructures via conventional electron or optical lithography technologies often requires a time‐consuming multistep process and the use of expensive facilities. Herein, a low‐cost, high‐resolution, facile, and versatile direct patterning method based on metal–organic molecular precursors is reported. The ink‐based metal–organic precursors are found to operate as negative resists, with the material exposed by different methods (electron‐beam/laser/heat/ultraviolet (UV)) to render them insoluble in the development process. This technical process can deliver metal chalcogenide semiconductors with arbitrary 2D/3D patterns with sub‐50 nm resolution. Electron beam lithography, two‐photon absorption lithography, thermal scanning probe lithography, and UV photolithography are demonstrated for the direct patterning process. Different metal chalcogenide semiconductor nanodevices, such as photoconductive selenium‐doped Sb2S3 nanoribbons, p‐type PbS single‐nanowire field‐effect transistors, and p‐n junction CdS/Cu2S nanowire solar cells, are fabricated by this method. This direct patterning technique is a versatile and simple micro/nanolithography technology with considerable potential for “lab‐on‐a‐chip” preparation of semiconductor devices.
Direct patterning is a method ideal for the fabrication of micro‐ and nanostructures. In this study, metal‐butyldithiocarbamic acid is found to operate as negative resists, with the chemical reaction triggered by different methods (electron‐beam/laser/heat/UV). As a result, high‐resolution 2D/3D metal chalcogenide nanostructures can be obtained by direct patterning. Semiconductor nanodevices are fabricated to demonstrate associated optoelectronic applications.
Fiber‐Shaped Electronic Devices Fakharuddin, Azhar; Li, Haizeng; Di Giacomo, Francesco ...
Advanced energy materials,
09/2021, Letnik:
11, Številka:
34
Journal Article
Recenzirano
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Textile electronics embedded in clothing represent an exciting new frontier for modern healthcare and communication systems. Fundamental to the development of these textile electronics is the ...development of the fibers forming the cloths into electronic devices. An electronic fiber must undergo diverse scrutiny for its selection for a multifunctional textile, viz., from the material selection to the device architecture, from the wearability to mechanical stresses, and from the environmental compatibility to the end‐use management. Herein, the performance requirements of fiber‐shaped electronics are reviewed considering the characteristics of single electronic fibers and their assemblies in smart clothing. Broadly, this article includes i) processing strategies of electronic fibers with required properties from precursor to material, ii) the state‐of‐art of current fiber‐shaped electronics emphasizing light‐emitting devices, solar cells, sensors, nanogenerators, supercapacitors storage, and chromatic devices, iii) mechanisms involved in the operation of the above devices, iv) limitations of the current materials and device manufacturing techniques to achieve the target performance, and v) the knowledge gap that must be minimized prior to their deployment. Lessons learned from this review with regard to the challenges and prospects for developing fiber‐shaped electronic components are presented as directions for future research on wearable electronics.
The next generation of electronic devices such as modern communication and healthcare systems and wearable electronics require omnidirectional flexibility, and must be super lightweight, and bendable. Fiber‐ and wire‐shaped devices with a typical thickness of several tens of micrometers offer incredible opportunities and have been widely investigated for a range of energy harvesting, storage, and functional devices.
Nanostructured Organic and Hybrid Solar Cells Weickert, Jonas; Dunbar, Ricky B.; Hesse, Holger C. ...
Advanced materials (Weinheim),
April 26, 2011, Letnik:
23, Številka:
16
Journal Article
Recenzirano
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This Progress Report highlights recent developments in nanostructured organic and hybrid solar cells. The authors discuss novel approaches to control the film morphology in fully organic solar cells ...and the design of nanostructured hybrid solar cells. The motivation and recent results concerning fabrication and effects on device physics are emphasized. The aim of this review is not to give a summary of all recent results in organic and hybrid solar cells, but rather to focus on the fabrication, device physics, and light trapping properties of nanostructured organic and hybrid devices.
Recent progress in nanostructured organic and hybrid solar cells is discussed in this report. Ordered nanostructures allow systematic analysis of physical working principles such as charge carrier separation, transport and recombination in excitonic solar cells. Besides, light trapping is possible. In this progress report we describe new concepts, fabrication techniques and device physics of this new generation solar cells.
The synthesis of dinuclear ruthenium alkenyl complexes with {Ru(CO)(PiPr3)2(L)} entities (L=Cl− in complexes Ru2‐3 and Ru2‐7; L=acetylacetonate (acac−) in complexes Ru2‐4 and Ru2‐8) and with ...π‐conjugated 2,7‐divinylphenanthrenediyl (Ru2‐3, Ru2‐4) or 5,8‐divinylquinoxalinediyl (Ru2‐7, Ru2‐8) as bridging ligands are reported. The bridging ligands are laterally π‐extended by anellating a pyrene (Ru2‐7, Ru2‐8) or a 6,7‐benzoquinoxaline (Ru2‐3, Ru2‐4) π‐perimeter. This was done with the hope that the open π‐faces of the electron‐rich complexes will foster association with planar electron acceptors via π‐stacking. The dinuclear complexes were subjected to cyclic and square‐wave voltammetry and were characterized in all accessible redox states by IR, UV/Vis/NIR and, where applicable, by EPR spectroscopy. These studies signified the one‐electron oxidized forms of divinylphenylene‐bridged complexes Ru2‐7, Ru2‐8 as intrinsically delocalized mixed‐valent species, and those of complexes Ru2‐3 and Ru2‐4 with the longer divinylphenanthrenediyl linker as partially localized on the IR, yet delocalized on the EPR timescale. The more electron‐rich acac− congeners formed non‐conductive 1 : 1 charge‐transfer (CT) salts on treatment with the F4TCNQ electron acceptor. All spectroscopic techniques confirmed the presence of pairs of complex radical cations and F4TCNQ.− radical anions in these CT salts, but produced no firm evidence for the relevance of π‐stacking to their formation and properties.
The synthesis of charge‐transfer salts from diruthenium complexes with two differently extended π‐conjugated ligands and the strong electron‐acceptor F4TCNQ is presented. These salts have been characterized by EPR, UV/Vis/NIR (in solution and solid states) and IR spectroscopy.
Perovskite solar cells (PSCs) have achieved certified power conversion efficiency (PCE) over 25%. Though their high PCE can be achieved by optimizing absorber layer and device interfaces, the ...intrinsic instability of perovskite materials is still a key issue to be resolved. Mixed‐halide perovskites using multiple halogen constituents have been proved to improve robustness; however, the anion at the X site in the ABX3 formula is not limited to halogens. Other negative monovalent ions with similar properties to halogens, such as pseudo‐halogens, have the opportunity to form perovskites with ABX3 stoichiometry. Recently, thiocyanates and formates have been utilized to synthesize stable perovskite materials. This review presents the evolution of pseudo‐halide perovskite solar cells in the past few years. The intrinsic properties, their effects on crystal structure, and bandgap engineering of the pseudo‐halide perovskites are summarized. Various thiocyanate compounds applied in the fabrication of perovskite solar cells are discussed. The fabrication process, film formation mechanism, and crystallinity of pseudo‐halide perovskites are elucidated to understand their effects on the photovoltaic performance and device stability. Other applications of pseudo‐halide perovskites are summarized in the final section. Lastly, this review concludes with suggestions and outlooks for further research directions.
Monovalent pseudo‐halide anions share similar properties to halide anions. This review presents the evolution of pseudo‐halide perovskite solar cells in the past few years. The role of pseudo‐halides and their position and occupation in perovskite crystal, its impact on perovskite film quality, solar cell stability and photovoltaic performance, and pseudo‐halide optoelectronic devices beyond solar cells are compared comprehensively.
Electrodeposited Cu2O‐ZnO heterojunctions are promising low‐cost solar cells. While nanostructured architectures improve charge collection in these devices, low open‐circuit voltages result. Bilayer ...and nanowire Cu2O‐ZnO heterojunction architectures are systematically studied as a function of the Cu2O layer thickness, ZnO nanowire length, and nanowire seed layer. It is shown that a thick depletion layer exists in the Cu2O layer of bilayer devices, owing to the low carrier density of electrodeposited Cu2O, such that the predominant charge transport mechanisms in the Cu2O and ZnO are drift and diffusion, respectively. This suggests that the low open‐circuit voltage of the nanowire cells is due to an incompatibility between the nanostructure spacing required for good charge collection (<1 μm) and the heterojunction thickness necessary to form the full built‐in potential that inhibits recombination (>2 μm). The work shows the way to improve low‐cost Cu2O cells: increasing the carrier concentration or mobility in Cu2O synthesized at low temperatures.
Electrodeposited bilayer and nanowire Cu2O‐ZnO photovoltaics are studied as a function of the Cu2O absorber thickness, ZnO nanowire length, and nanowire seed layer. The low open‐circuit voltage of nanostructured Cu2O‐ZnO cells is shown to result from an incompatibility between the desired nanostructure spacing and the Cu2O thickness required to form the full built‐in bias that inhibits recombination.
This study introduces a new chemical method for controlling the strain in methylammonium lead iodide (MAPbI3) perovskite crystals by varying the ratio of Pb(Ac)2 and PbCl2 in the precursor solution. ...To observe the effect on crystal strain, a combination of piezoresponse force microscopy (PFM) and X‐ray diffraction (XRD) is used. The PFM images show an increase in the average size of ferroelastic twin domains upon increasing the PbCl2 content, indicating an increase in crystal strain. The XRD spectra support this observation with strong crystal twinning features that appear in the spectra. This behavior is caused by a strain gradient during the crystallization due to different evaporation rates of methylammonium acetate and methylammonium chloride as revealed by time‐of‐flight secondary ion mass spectroscopy and grazing incidince X‐ray diffraction measurements. Additional time‐resolved photoluminescence shows an increased carrier lifetime in the MAPbI3 films prepared with higher PbCl2 content, suggesting a decreased trap density in films with larger twin domain structures. The results demonstrate the potential of chemical strain engineering as a simple method for controlling strain‐related effects in lead halide perovskites.
This study introduces a chemical route to control the crystal strain within methylammonium lead iodide (MAPbI3) perovskite films. The effects of the changing strain are observed by tracing ferroelastic twin domains in MAPbI3 perovskites via piezoresponse force microscopy, as well as by X‐ray diffraction and time‐of‐flight secondary ion mass spectroscopy.
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