Sumit Chaurasia

Bio: Sumit Chaurasia is an academic researcher from Academia Sinica. The author has contributed to research in topics: Acceptor & Electron acceptor. The author has an hindex of 13, co-authored 25 publications receiving 677 citations. Previous affiliations of Sumit Chaurasia include Indian Institute of Technology Kanpur & Central Drug Research Institute.

Sensitizers with rigidified-aromatics as the conjugated spacers for dye-sensitized solar cells

Abstract: Metal-free dye sensitized solar cells emerged as an important source of a renewable energy resource because of low production, a simple fabrication process and a wide availablility of organic dyes. This review mainly focuses on metal-free sensitizers having rigidifed-aromatics as the conjugated spacers for application in DSSCs. Based on their structures dyes have been divided into three major subsegments: (i) ladder type polyphenylenes with or without heteroatoms; (ii) rigidified-aromatics as donor segments; (iii) fused polyaromatics. Planarization of organic molecules through rigidification of aromatics allows effective communication and their smaller reorganization energy is beneficial to photoinduced charge transfer. Dyes having rigidified aromatics as conjugated spacers emerged as promising candidates and a maximum efficiency of 12.5% has been achieved with DSSCs without a coadsorbate or co-sensitizer.

Methoxylated isoflavones, cajanin and isoformononetin, have non-estrogenic bone forming effect via differential mitogen activated protein kinase (MAPK) signaling.

Abstract: Following a lead obtained from stem-bark extract of Butea monosperma, two structurally related methoxyisoflavones; cajanin and isoformononetin were studied for their effects in osteoblasts. Cajanin had strong mitogenic as well as differentiation-promoting effects on osteoblasts that involved subsequent activation of MEK-Erk and Akt pathways. On the other hand, isoformononetin exhibited potent anti-apoptotic effect in addition to promoting osteoblast differentiation that involved parallel activation of MEK-Erk and Akt pathways. Unlike genistein or daidzein, none of these two compounds appear to act via estrogen receptors in osteoblast. Once daily oral (by gavage) treatment for 30 consecutive days was given to recently weaned female Sprague-Dawley rats with each of these compounds at 10.0 mg kg(-1) day(-1) dose. Cajanin increased bone mineral density (BMD) at all skeletal sites studied, bone biomechanical strength, mineral apposition rate (MAR) and bone formation rate (BFR), compared with control. BMD levels at various anatomic positions were also increased with isoformononetin compared with control however, its effect was less potent than cajanin. Isoformononetin had no effect on the parameters of bone biomechanical strength although it enhanced MAR and BFR compared with control. Isoformononetin had very mild uterotrophic effect, whereas cajanin was devoid of any such effect. Our data suggest that cajanin is more potent than isoformononetin in accelerating peak bone mass achievement. To the best of our knowledge, this work represents the first attempt to elucidate structure-activity relationship between the two methoxylated isoflavones regarding their effects in osteoblasts and bone formation.

Pyrazine-incorporating panchromatic sensitizers for dye sensitized solar cells under one sun and dim light

Abstract: New D–A′–π–A type (D = electron donor, A′ = auxiliary acceptor, π = π-conjugated bridge, and A = electron acceptor/anchor) sensitizers with two bis(alkoxy)phenyl substituents incorporating thieno[3,4-b]pyrazines (TP) or a benzo[3,4-b]pyrazine (BP) entity as the auxiliary acceptor have been synthesized for application in dye-sensitized solar cells (DSSCs). Under 1 sun illumination, the DSSCs fabricated from the two BP dyes with a co-adsorbent have efficiencies of 8.39% and 9.03%, respectively. The latter surpasses that of the standard N719 dye (8.87%). Under dim light conditions MD7 exhibited a power conversion efficiency of 18.95% and 27.17% under 300 lux and 6000 lux irradiance, respectively.

Metal-Free Sensitizers for dye-Sensitized Solar Cells

Abstract: This review focuses on our work on metal-free sensitizers for dye-sensitized solar cells (DSSCs). Sensitizers based on D-A'-π-A architecture (D is a donor, A is an acceptor, A' is an electron-deficient entity) exhibit better light harvesting than D-π-A-type sensitizers. However, appropriate molecular design is needed to avoid excessive aggregation of negative charge at the electron-deficient entity upon photoexcitation. Rigidified aromatics, including aromatic segments comprising fused electron-excessive and -deficient units in the spacer, allow effective electronic communication, and good photoinduced charge transfer leads to excellent cell performance. Sensitizers with two anchors/acceptors, D(-π-A)2 , can more efficiently harvest light, inject electrons, and suppress dark current compared with congeners with a single anchor. Appropriate incorporation of heteroaromatic units in the spacer is beneficial to DSSC performance. High-performance, aqueous-based DSSCs can be achieved with a dual redox couple comprising imidazolium iodide and 2,2,6,6-tetramethylpiperidin-N-oxyl, and/or using dyes of improved wettability through the incorporation of a triethylene oxide methyl ether chain.

Arylamine organic dyes for dye-sensitized solar cells

Abstract: Arylamine organic dyes with donor (D), π-bridge (π) and acceptor (A) moieties for dye-sensitized solar cells (DSCs) have received great attention in the last decade because of their high molar absorption coefficient, low cost and structural variety. In the early stages, the efficiency of DSCs with arylamine organic dyes with D–π–A character was far behind that of DSCs with ruthenium(II) complexes partly due to the lack of information about the relationship between the chemical structures and the photovoltaic performance. However, exciting progress has been recently made, and power conversion efficiencies over 10% were obtained for DSCs with arylamine organic dyes. It is thus that the recent research and development in the field of arylamine organic dyes employing an iodide/triiodide redox couple or polypyridyl cobalt redox shuttles as the electrolytes for either DSCs or solid-state DSCs has been summarized. The cell performance of the arylamine organic dyes are compared, providing a comprehensive overview of arylamine organic dyes, demonstrating the advantages/disadvantages of each class, and pointing out the field that needs to reinforce the research direction in the further application of DSCs.

Triarylamine: Versatile Platform for Organic, Dye-Sensitized, and Perovskite Solar Cells.

Abstract: Triarylamine (TAA) and related materials have dramatically promoted the development of organic and hybrid photovoltaics during the past decade. The power conversion efficiencies of TAA-based organic solar cells (OSCs), dye-sensitized solar cells (DSSCs), and perovskite solar cells (PSCs) have exceeded 11%, 14%, and 20%, which are among the best results for these three kinds of devices, respectively. In this review, we summarize the recent advances of the high-performance TAA-based materials in OSCs, DSSCs, and PSCs. We focus our discussion on the structure–property relationship of the TAA-based materials in order to shed light on the solutions to the challenges in the field of organic and hybrid photovoltaics. Some design strategies for improving the materials and device performance and possible research directions in the near future are also proposed.

Recent progress in flexible–wearable solar cells for self-powered electronic devices

Abstract: Photovoltaic devices have become ideal alternatives to common energy sources due to their excellent mechanical robustness and high power conversion efficiency, which can meet the human requirements for green, inexpensive and portable electricity sources. Moreover, due to the rapid development of wearable devices, telecommunication, transportation, advanced sensors, etc., the need for green and accessible power sources for these state-of-the-art devices accompanied with appropriate mechanical stability has become a new challenge. In this regard, flexible–wearable photovoltaic platforms can be easily adapted to any device/substrate and can supply diverse electronic devices with their required energy via harvesting energy from sunlight. Similarly, photovoltaic platforms can be integrated into hybrid platforms and can be used in diverse applications. Herein, we summarize the recent approaches to developing flexible–wearable solar cells as energy sources for supplying self-powered wearable devices. In this regard, first, recent advances in transparent flexible electrodes and their diversities are reported; then, recently developed flexible solar cells and important factors for designing these platforms are summarized. Further, flexible solar cells are categorized into five different sections (i.e., perovskite, dye-sensitized, organic, fiber-shaped and textile solar cells) and their mechanisms, working principles and design criteria along with their recent advances have been discussed. Finally, novel applications of wearable sensors/devices are summarized and reported to highlight the functionality of these practical platforms.

Insight into D-A-π-A Structured Sensitizers: A Promising Route to Highly Efficient and Stable Dye-Sensitized Solar Cells.

Abstract: The dye-sensitized solar cell (DSSC) is one of the most promising photovoltaic technologies with potential of low cost, light weight, and good flexibility. The practical application of DSSCs requires further improvement in power conversion efficiency and long-term stability. Recently, significant progress has been witnessed in DSSC research owing to the novel concept of the D–A−π–A motif for the molecular engineering of organic photosensitizers. New organic and porphyrin dyes based on the D–A−π–A motif can not only enhance photovoltaic performance, but also improve durability in DSSC applications. This Spotlight on Applications highlights recent advances in the D–A−π–A-based photosensitizers, specifically focusing on the mechanism of efficiency and stability enhancements. Also, we find insight into the additional acceptor as well as the trade-off of long wavelength response. The basic principles are involved in molecular engineering of efficient D–A−π–A sensitizers, providing a clear road map showing how ...

Ultrafast Electron Dynamics in Solar Energy Conversion

Abstract: Electrons are the workhorses of solar energy conversion. Conversion of the energy of light to electricity in photovoltaics, or to energy-rich molecules (solar fuel) through photocatalytic processes, invariably starts with photoinduced generation of energy-rich electrons. The harvesting of these electrons in practical devices rests on a series of electron transfer processes whose dynamics and efficiencies determine the function of materials and devices. To capture the energy of a photogenerated electron–hole pair in a solar cell material, charges of opposite sign have to be separated against electrostatic attractions, prevented from recombining and being transported through the active material to electrodes where they can be extracted. In photocatalytic solar fuel production, these electron processes are coupled to chemical reactions leading to storage of the energy of light in chemical bonds. With the focus on the ultrafast time scale, we here discuss the light-induced electron processes underlying the fu...