Author
Ritu Gupta
Other affiliations: Purdue University, Jawaharlal Nehru Centre for Advanced Scientific Research
Bio: Ritu Gupta is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Coating & Grating. The author has an hindex of 20, co-authored 60 publications receiving 1409 citations. Previous affiliations of Ritu Gupta include Purdue University & Jawaharlal Nehru Centre for Advanced Scientific Research.
Topics: Coating, Grating, Joule heating, Diffraction efficiency, Diffraction
Papers
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TL;DR: This review provides topical coverage of next generation transparent conducting electrodes (TCE) based on a wide range of materials such as oxide nanoparticles, CNTs, graphene, metal nanowires, metal meshes and their hybrids.
Abstract: Heater plates or sheets that are visibly transparent have many interesting applications in optoelectronic devices such as displays, as well as in defrosting, defogging, gas sensing and point-of-care disposable devices. In recent years, there have been many advances in this area with the advent of next generation transparent conducting electrodes (TCE) based on a wide range of materials such as oxide nanoparticles, CNTs, graphene, metal nanowires, metal meshes and their hybrids. The challenge has been to obtain uniform and stable temperature distribution over large areas, fast heating and cooling rates at low enough input power yet not sacrificing the visible transmittance. This review provides topical coverage of this important research field paying due attention to all the issues mentioned above.
183 citations
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TL;DR: In this paper, the performance of polyethylene terephthalate foil (P3HT:PCBM)-based polysilicon solar cell modules was evaluated on thin flexible barrier polycarbonate foil.
139 citations
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TL;DR: Spray coating in the context of crack template is a powerful method for producing transparent heaters, which is shown for the first time in this work.
Abstract: Transparent conducting electrodes (TCEs) have been made on flat, flexible, and curved surfaces, following a crack template method in which a desired surface was uniformly spray-coated with a crackle precursor (CP) and metal (Ag) was deposited by vacuum evaporation. An acrylic resin (CP1) and a SiO2 nanoparticle-based dispersion (CP2) derived from commercial products served as CPs to produce U-shaped cracks in highly interconnected networks. The crack width and the density could be controlled by varying the spray conditions, resulting in varying template thicknesses. By depositing Ag in the crack regions of the templates, we have successfully produced Ag wire network TCEs on flat-flexible PET sheets, cylindrical glass tube, flask and lens surface with transmittance up to 86%, sheet resistance below 11 Ω/□ for electrothermal application. When used as a transparent heater by joule heating of the Ag network, AgCP1 and AgCP2 on PET showed high thermal resistance values of 515 and 409 °C cm2/W, respectively, wi...
125 citations
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TL;DR: In this article, a single micro/nanowire network of a metal deposited over a large area on a transparent substrate serves as a transparent conducting electrode with optoelectronic properties that are enhanced in many ways relative to the conventional indium tin oxide films.
Abstract: A single micro/nanowire network of a metal deposited over a large area on a transparent substrate serves as a transparent conducting electrode with optoelectronic properties that are enhanced in many ways relative to the conventional indium tin oxide films. The wire surface is extremely smooth and the junctions are seamless, thanks to the crackle lithography process. The method is applicable to various metals and hybrid materials as well as to flexible and curved substrates.
92 citations
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TL;DR: In this article, the authors used a four-step process involving deposition of commercially available colloidal dispersions onto polyethylene terephthalate (PET), drying to induce crackle network formation, nucleating Au or Pd seed nanoparticles inside the crackle regions, washing away the sacrificial layer and finally, depositing Cu electrolessly or by electroplating.
Abstract: Virtually unlimited and highly interconnected Cu wire networks have been fabricated on polyethylene terephthalate (PET) substrates with sheet resistance of <5 Ω □−1 and transmittance of ∼75%, as alternatives to the commonly used tin doped indium oxide (ITO) based electrodes. This is a four step process involving deposition of commercially available colloidal dispersions onto PET, drying to induce crackle network formation, nucleating Au or Pd seed nanoparticles inside the crackle regions, washing away the sacrificial layer and finally, depositing Cu electrolessly or by electroplating. The formed Cu wire network is continuous and seamless, and devoid of crossbar junctions, a property which brings high stability to the electrode towards oxidation in air even at 130 °C. The flexible property of the PET substrate is easily carried over to the TCE. The sheet resistance remained unaltered even after a thousand bending cycles. The as-prepared Cu wire network TCE is hydrophobic (contact angle, 80°) which, upon UV–ozone treatment, turned to hydrophilic (∼40°).
82 citations
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2,219 citations
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TL;DR: This work demonstrates highly efficient and stable solar cells using a ternary approach, wherein two non-fullerene acceptors are combined with both a scalable and affordable donor polymer, poly(3-hexylthiophene) (P3HT), and a high-efficiency, low-bandgap polymer in a single-layer bulk-heterojunction device.
Abstract: Technological deployment of organic photovoltaic modules requires improvements in device light-conversion efficiency and stability while keeping material costs low. Here we demonstrate highly efficient and stable solar cells using a ternary approach, wherein two non-fullerene acceptors are combined with both a scalable and affordable donor polymer, poly(3-hexylthiophene) (P3HT), and a high-efficiency, low-bandgap polymer in a single-layer bulk-heterojunction device. The addition of a strongly absorbing small molecule acceptor into a P3HT-based non-fullerene blend increases the device efficiency up to 7.7 ± 0.1% without any solvent additives. The improvement is assigned to changes in microstructure that reduce charge recombination and increase the photovoltage, and to improved light harvesting across the visible region. The stability of P3HT-based devices in ambient conditions is also significantly improved relative to polymer:fullerene devices. Combined with a low-bandgap donor polymer (PBDTTT-EFT, also known as PCE10), the two mixed acceptors also lead to solar cells with 11.0 ± 0.4% efficiency and a high open-circuit voltage of 1.03 ± 0.01 V. Ternary organic blends using two non-fullerene acceptors are shown to improve the efficiency and stability of low-cost solar cells based on P3HT and of high-performance photovoltaic devices based on low-bandgap donor polymers.
887 citations
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TL;DR: The factors limiting the stability of OSCs are summarized, such as metastable morphology, diffusion of electrodes and buffer layers, oxygen and water, irradiation, heating and mechanical stress, and recent progress in strategies to increase the stability are surveyed.
Abstract: Organic solar cells (OSCs) present some advantages, such as simple preparation, light weight, low cost and large-area flexible fabrication, and have attracted much attention in recent years. Although the power conversion efficiencies have exceeded 10%, the inferior device stability still remains a great challenge. In this review, we summarize the factors limiting the stability of OSCs, such as metastable morphology, diffusion of electrodes and buffer layers, oxygen and water, irradiation, heating and mechanical stress, and survey recent progress in strategies to increase the stability of OSCs, such as material design, device engineering of active layers, employing inverted geometry, optimizing buffer layers, using stable electrodes and encapsulation. Some research areas of device stability that may deserve further attention are also discussed to help readers understand the challenges and opportunities in achieving high efficiency and high stability of OSCs towards future industrial manufacture.
743 citations
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Helmholtz-Zentrum Berlin1, Ben-Gurion University of the Negev2, National Renewable Energy Laboratory3, Forschungszentrum Jülich4, University of Erlangen-Nuremberg5, University of Rome Tor Vergata6, Massachusetts Institute of Technology7, Princeton University8, Chulalongkorn University9, Wuhan University of Technology10, Karlsruhe Institute of Technology11, University of Grenoble12, Commonwealth Scientific and Industrial Research Organisation13, University of Michigan14, Sapienza University of Rome15, École Polytechnique Fédérale de Lausanne16, VU University Amsterdam17, University of Jena18, Bangor University19, University of Maryland, College Park20, University of California, Davis21, Shaanxi Normal University22, Dalian Institute of Chemical Physics23, Chinese Academy of Sciences24, University of Southern Denmark25, University of Colorado Boulder26, State University of Campinas27, Boğaziçi University28, Sungkyunkwan University29, Swansea University30, Technische Universität Darmstadt31, University of Oxford32, University of Cambridge33, Skolkovo Institute of Science and Technology34, Imperial College London35, Yonsei University36
TL;DR: A consensus between researchers in the field is reported on procedures for testing perovskite solar cell stability, which are based on the International Summit on Organic Photovoltaic Stability (ISOS) protocols, and additional procedures to account for properties specific to PSCs are proposed.
Abstract: Improving the long-term stability of perovskite solar cells is critical to the deployment of this technology. Despite the great emphasis laid on stability-related investigations, publications lack consistency in experimental procedures and parameters reported. It is therefore challenging to reproduce and compare results and thereby develop a deep understanding of degradation mechanisms. Here, we report a consensus between researchers in the field on procedures for testing perovskite solar cell stability, which are based on the International Summit on Organic Photovoltaic Stability (ISOS) protocols. We propose additional procedures to account for properties specific to PSCs such as ion redistribution under electric fields, reversible degradation and to distinguish ambient-induced degradation from other stress factors. These protocols are not intended as a replacement of the existing qualification standards, but rather they aim to unify the stability assessment and to understand failure modes. Finally, we identify key procedural information which we suggest reporting in publications to improve reproducibility and enable large data set analysis. Reliability of stability data for perovskite solar cells is undermined by a lack of consistency in the test conditions and reporting. This Consensus Statement outlines practices for testing and reporting stability tailoring ISOS protocols for perovskite devices.
621 citations
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TL;DR: This Review highlights the large number of methods to exploit colloidal assembly of comparably simple particles with nano- to micrometer dimensions in order to access complex structural hierarchies from nanoscopic over microscopic to macroscopic dimensions.
Abstract: This Review highlights the large number of methods to exploit colloidal assembly of comparably simple particles with nano- to micrometer dimensions in order to access complex structural hierarchies from nanoscopic over microscopic to macroscopic dimensions
609 citations