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Dive into the research topics where Rajib Mondal is active.

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Featured researches published by Rajib Mondal.


Nature Communications | 2011

From computational discovery to experimental characterization of a high hole mobility organic crystal

Anatoliy N. Sokolov; Sule Atahan-Evrenk; Rajib Mondal; Hylke B. Akkerman; Roel S. Sánchez-Carrera; Sergio Granados-Focil; Joshua Schrier; Stefan C. B. Mannsfeld; Arjan P. Zoombelt; Zhenan Bao; Alán Aspuru-Guzik

For organic semiconductors to find ubiquitous electronics applications, the development of new materials with high mobility and air stability is critical. Despite the versatility of carbon, exploratory chemical synthesis in the vast chemical space can be hindered by synthetic and characterization difficulties. Here we show that in silico screening of novel derivatives of the dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene semiconductor with high hole mobility and air stability can lead to the discovery of a new high-performance semiconductor. On the basis of estimates from the Marcus theory of charge transfer rates, we identified a novel compound expected to demonstrate a theoretic twofold improvement in mobility over the parent molecule. Synthetic and electrical characterization of the compound is reported with single-crystal field-effect transistors, showing a remarkable saturation and linear mobility of 12.3 and 16 cm2 V−1 s−1, respectively. This is one of the very few organic semiconductors with mobility greater than 10 cm2 V−1 s−1 reported to date.


Journal of the American Chemical Society | 2009

Synthesis, stability, and photochemistry of pentacene, hexacene, and heptacene: a matrix isolation study.

Rajib Mondal; Christina Tönshoff; Dmitriy Khon; Douglas C. Neckers; Holger F. Bettinger

The photochemical bisdecarbonylation of bridged alpha-diketones (Strating-Zwanenburg reaction) to give the oligoacenes pentacene (2), hexacene (3), and heptacene (4) is investigated in solid inert gas matrices at cryogenic temperatures. The photodecomposition using visible light irradiation cleanly produces the corresponding oligoacene without formation of observable intermediates. This synthetic approach to the higher acenes allows a comprehensive comparative study of their electronic absorption and infrared spectral properties under identical conditions for the first time. In addition, the route makes it possible to investigate the thermal and photochemical stability of these higher acenes and addresses the problem of heptacene stability which dates back almost 70 years. This largest known member of the acene series is found to be unstable at room temperature. Furthermore, all oligoacenes 2-4 undergo a photoredox reaction upon 185 nm excitation, resulting in the concurrent formation of radical cations and anions in the noble gas matrix. These polaron states of the oligoacenes are stable under the conditions of their generation but collapse to the uncharged acenes upon visible light irradiation.


Energy and Environmental Science | 2014

Lead candidates for high-performance organic photovoltaics from high-throughput quantum chemistry - the Harvard Clean Energy Project

Johannes Hachmann; Roberto Olivares-Amaya; Adrian Jinich; Anthony L. Appleton; Martin A. Blood-Forsythe; Laszlo Ryan Seress; Carolina Román-Salgado; Kai Trepte; Sule Atahan-Evrenk; Süleyman Er; Supriya Shrestha; Rajib Mondal; Anatoliy N. Sokolov; Zhenan Bao; Alán Aspuru-Guzik

The virtual high-throughput screening framework of the Harvard Clean Energy Project allows for the computational assessment of candidate structures for organic electronic materials – in particular photovoltaics – at an unprecedented scale. We report the most promising compounds that have emerged after studying 2.3 million molecular motifs by means of 150 million density functional theory calculations. Our top candidates are analyzed with respect to their structural makeup in order to identify important building blocks and extract design rules for efficient materials. An online database of the results is made available to the community.


Journal of Materials Chemistry | 2010

Thiophene-Rich Fused-Aromatic Thienopyrazine Acceptor for Donor-Acceptor Low Band-Gap Polymers for Otft and Polymer Solar Cell Applications

Rajib Mondal; Héctor A. Becerril; Eric Verploegen; Dongwook Kim; Joseph E. Norton; Sangwon Ko; Nobuyuki Miyaki; Sangjun Lee; Michael F. Toney; Jean-Luc Brédas; Michael D. McGehee; Zhenan Bao

Thiophene enriched fused-aromatic thieno[3,4-b]pyrazine systems were designed and employed to produce low band gap polymers (Eg = 1.0–1.4 eV) when copolymerized with fluorene and cyclopentadithiophene. The copolymers are mainly investigated for organic thin film transistor and organic photovoltaic applications. Molecular packing in the thin films of these polymers was investigated using Grazing incidence X-ray Scattering. Although both fluorene and cyclopentadithiophene polymers follow similar face to face π–π stacking, the latter polymers show much smaller lamellar d-spacings due to side-chain interdigitation between the lamellae. This lead to the higher charge carrier mobilities in cyclopentadithiophene polymers (up to 0.044 cm2/V.s) compared to fluorene polymers (up to 8.1 × 10−3 cm2/V.s). Power conversion efficiency of 1.4% was achieved using fluorene copolymer in solar cells with a fullerene derivative as an acceptor. Although the cyclopentadithiophene polymers show lower band gaps with higher absorption coefficients compared to fluorene copolymers, but the power conversion efficiencies in solar cells of these polymers are low due to their low ionization potentials.


Journal of the American Chemical Society | 2011

3,4-Disubstituted Polyalkylthiophenes for High-Performance Thin-Film Transistors and Photovoltaics

Sangwon Ko; Eric Verploegen; Sanghyun Hong; Rajib Mondal; Eric T. Hoke; Michael F. Toney; Michael D. McGehee; Zhenan Bao

We demonstrate that poly(3,4-dialkylterthiophenes) (P34ATs) have comparable transistor mobilities (0.17 cm(2) V(-1) s(-1)) and greater environmental stability (less degradation of on/off ratio) than regioregular poly(3-alkylthiophenes) (P3ATs). Unlike poly(3-hexylthiophene) (P3HT), P34ATs do not show a strong and distinct π-π stacking in X-ray diffraction. This suggests that a strong π-π stacking is not always necessary for high charge-carrier mobility and that other potential polymer packing motifs in addition to the edge-on structure (π-π stacking direction parallel to the substrate) can lead to a high carrier mobility. The high charge-carrier mobilities of the hexyl and octyl-substituted P34AT produce power conversion efficiencies of 4.2% in polymer:fullerene bulk heterojunction photovoltaic devices. An enhanced open-circuit voltage (0.716-0.771 eV) in P34AT solar cells relative to P3HT due to increased ionization potentials was observed.


Journal of Materials Chemistry | 2009

Molecular design for improved photovoltaic efficiency: band gap and absorption coefficient engineering

Rajib Mondal; Sangwon Ko; Joseph E. Norton; Nobuyuki Miyaki; Héctor A. Becerril; Eric Verploegen; Michael F. Toney; Jean-Luc Brédas; Michael D. McGehee; Zhenan Bao

Removing the adjacent thiophene groups around the acceptor core in low band gap polymers significantly enhances solar cell efficiency through increasing the optical absorption and raising the ionization potential of the polymer.


Journal of Materials Chemistry | 2009

Transistor and solar cell performance of donor–acceptor low bandgap copolymers bearing an acenaphtho[1,2-b]thieno[3,4-e]pyrazine (ACTP) motif

Héctor A. Becerril; Nobuyuki Miyaki; Ming Lee Tang; Rajib Mondal; Ya-Sen Sun; Alex C. Mayer; Jack E. Parmer; Michael D. McGehee; Zhenan Bao

We report the performance of low-bandgap polymers with a new ACTP acceptor in organic transistors (max. field-effect mobility 0.2 cm2V−1s−1), and solar cells (max. efficiency 1.4%).


Journal of Organic Chemistry | 2008

Photochemical formation of substituted pentacenes.

Yuewei Zhao; Rajib Mondal; Douglas C. Neckers

Substituted pentacenes (8a, 8b, 14a, and 14b) were prepared by Strating-Zwanenburg photodecarbonylation of diones (7a, 7b, 13a, and 13b). The compounds are red and stable in the solid state under inert atmosphere as well as in degassed solutions, but not in air. Each is soluble in common organic solvents where, unless protected, they are oxygen sensitive.


Physical Chemistry Chemical Physics | 2012

The importance of dye chemistry and TiCl4 surface treatment in the behavior of Al2O3 recombination barrier layers deposited by atomic layer deposition in solid-state dye-sensitized solar cells

Thomas P. Brennan; Jonathan R. Bakke; I-Kang Ding; Brian E. Hardin; William H. Nguyen; Rajib Mondal; Colin D. Bailie; George Y. Margulis; Eric T. Hoke; Alan Sellinger; Michael D. McGehee; Stacey F. Bent

Atomic layer deposition (ALD) was used to fabricate Al(2)O(3) recombination barriers in solid-state dye-sensitized solar cells (ss-DSSCs) employing an organic hole transport material (HTM) for the first time. Al(2)O(3) recombination barriers of varying thickness were incorporated into efficient ss-DSSCs utilizing the Z907 dye adsorbed onto a 2 μm-thick nanoporous TiO(2) active layer and the HTM spiro-OMeTAD. The impact of Al(2)O(3) barriers was also studied in devices employing different dyes, with increased active layer thicknesses, and with substrates that did not undergo the TiCl(4) surface treatment. In all instances, electron lifetimes (as determined by transient photovoltage measurements) increased and dark current was suppressed after Al(2)O(3) deposition. However, only when the TiCl(4) treatment was eliminated did device efficiency increase; in all other instances efficiency decreased due to a drop in short-circuit current. These results are attributed in the former case to the similar effects of Al(2)O(3) ALD and the TiCl(4) surface treatment whereas the insulating properties of Al(2)O(3) hinder charge injection and lead to current loss in TiCl(4)-treated devices. The impact of Al(2)O(3) barrier layers was unaffected by doubling the active layer thickness or using an alternative ruthenium dye, but a metal-free donor-π-acceptor dye exhibited a much smaller decrease in current due to its higher excited state energy. We develop a model employing prior research on Al(2)O(3) growth and dye kinetics that successfully predicts the reduction in device current as a function of ALD cycles and is extendable to different dye-barrier systems.


Journal of Materials Chemistry | 2010

Fused aromatic thienopyrazines: structure, properties and function

Rajib Mondal; Sangwon Ko; Zhenan Bao

Recent development of a fused aromatic thieno[3.4-b]pyrazine system and their application in optoelectronic devices are reviewed. Introduction of a fused aromatic unit followed by side chain engineering, dramatically enhanced the charge carrier mobility in thin film transistor devices and mobilities up to 0.2 cm2/Vs were achieved. The optoelectronic properties of these fused aromatic thienopyrazine polymers (Eg = 1.3 to 1.6 eV, HOMO = −4.9 to −5.2 V) were tuned by introduction of various fused aromatic rings within thienopyrazine. By balancing the fundamental properties of these polymers, both high charge carrier mobilities and moderate PCEs in solar cells were achieved. Further, effects of copolymerizing units are discussed. Low band gap semiconducting polymer (Eg ∼ 1 eV) with high field effect mobility (0.044 cm2/Vs) was obtained using cyclopentadithiophene as copolymerizing unit. Finally, a molecular design approach to enhance the absorption coefficients is discussed, which resulted in improved power conversion efficiency in bulk heterojunction solar cells.

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Douglas C. Neckers

Bowling Green State University

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Bipin K. Shah

Bowling Green State University

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Michael F. Toney

SLAC National Accelerator Laboratory

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Jean-Luc Brédas

Georgia Institute of Technology

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