Venkataraman, Dhandapani

Job Title

Professor, Department of Chemistry

Last Name

Venkataraman

First Name

Dhandapani

Discipline

Chemistry

Expertise

Organic, Inorganic, Polymer and Materials Chemistry

Introduction

Principal Research Interests:
Interdisciplinary approach is taken to address some of the topical research problems in Chemistry. The research areas of current focus include catalysis, nanoscale segregated semiconductor morphologies in organic and hybrid photovoltaic cells, chiroptical properties of helical electroactive molecules, proton transport in rigid scaffolds, hydrogen production through photoelectrocatalysis. Visit our group’s website for further description of these projects.

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Now showing 1 - 8 of 8

Open Access
Tuning charge transport dynamics via clustering of doping in organic semiconductor thin films
(2019-01) Boyle, Connor J.; Upadhyaya, Meenakshi; Wang, Peijan; Renna, Lawrence A.; Lu-Díaz, Michael; Jeong, Seung Pyo; Hight-Huf, Nicholas; Korugic-Karasz, Ljiljana; Barnes, Michael D.; Aksamija, Zlatan; Venkataraman, Dhandapani
A significant challenge in the rational design of organic thermoelectric materials is to realize simultaneously high electrical conductivity and high induced-voltage in response to a thermal gradient, which is represented by the Seebeck coefficient. Conventional wisdom posits that the polymer alone dictates thermoelectric efficiency. Herein, we show that doping — in particular, clustering of dopants within conjugated polymer films — has a profound and predictable influence on their thermoelectric properties. We correlate Seebeck coefficient and electrical conductivity of iodine-doped poly(3-hexylthiophene) and poly[2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-3,6-diyl)-alt-(2,2′;5′,2′′;5′′,2′′′-quaterthiophen-5,5′′′-diyl)] films with Kelvin probe force microscopy to highlight the role of the spatial distribution of dopants in determining overall charge transport. We fit the experimental data to a phonon-assisted hopping model and found that the distribution of dopants alters the distribution of the density of states and the Kang–Snyder transport parameter. These results highlight the importance of controlling dopant distribution within conjugated polymer films for thermoelectric and other electronic applications.
Open Access
Persistent radical anion polymers based on naphthalenediimide and a vinylene spacer
(2018-01) Debnath, Sashi; Boyle, Connor J.; Zhou, Dongming; Wong, Bryan M.; Kittilstved, Kevin R.; Venkataraman, Dhandapani
Persistent n-doped conjugated polymers were achieved by doping the electron accepting PDNDIV and PFNDIVpolymers with ionic (TBACN) or neutral (TDAE) dopants. The great electron affinities, as indicated by the low LUMO levels of PDNDIV (−4.09 eV) and PFNDIV (−4.27 eV), facilitated the chemical reduction from either TBACN or TDAE. The low-lying LUMOs of the neutral polymers PDNDIV and PFNDIV were achieved by incorporation of vinylene spacers between the electron poor NDI units to increase the conjugation length without the use of an electron donor, and this was lowered further by an electron-withdrawing fluorinated N-substituent on the NDI moiety. The polymer radical anions were found to persist for several days under ambient conditions by EPR spectroscopy. A distinguishing and noteworthy feature of these polymers is that they can be consecutively reduced by up to four electrons in acetonitrile. Conductivity measurements demonstrate the prospective impact of PDNDIV and PFNDIV for organic electronics.
Open Access
Making Solar Cells
(2013-01-01) Venkataraman, D.
Overview of solar energy and photovoltaic cells. Making a cuprous oxide cell activity.
Open Access
High Energy Density in Azobenzene-based Materials for Photo-Thermal Batteries via Controlled Polymer Architecture and Polymer-Solvent Interactions
(2017-01) Jeong, Seung Pyo; Renna, Lawrence A.; Boyle, Connor J.; Kwak, Hyunwook S.; Harder, Edward; Damm, Wolfgang; Venkataraman, Dhandapani
Energy densities of ~510 J/g (max: 698 J/g) have been achieved in azobenzene-based syndiotactic-rich poly(methacrylate) polymers. The processing solvent and polymer-solvent interactions are important to achieve morphologically optimal structures for high-energy density materials. This work shows that morphological changes of solid-state syndiotactic polymers, driven by different solvent processings play an important role in controlling the activation energy of Z-E isomerization as well as the shape of the DSC exotherm. Thus, this study shows the crucial role of processing solvents and thin film structure in achieving higher energy densities.
Open Access
Enabling an Equitable Energy Transition Through Inclusive Research
(2023-01-01) Ash, Michael; Baker, Erin; Tuominen, Mark; Venkataraman, Dhandapani; Burke, Matthew; Castellanos, S.; Cha, M.; Chan, Gabe; Djokic, D.; Ford, J.C.; Goldstein, Anna P.; Hsu, David; Lacker, Matt; Miller, C.; Nock, D.; Ravikumar, A.P.; Bates, Allison; Stefanopoulou, Anna; Grubert, E; Kammen, D.M; Pastor, M.; Attari, S.Z,; Carley, S.; Clark, D.L; Dean-Ryan, D.; Kosar, U.; Bowie, Kerry; Johnson, Tina
Comprehensive and meaningful inclusion of marginalized communities within the research enterprise will be critical to ensuring an equitable, technology-informed, clean energy transition. We provide five key action items for government agencies and philanthropic institutions to operationalize the commitment to an equitable energy transition.
Open Access
Data for Dopant-induced Energetic Disorder in Conjugated Polymers: Determinant Roles of Polymer-Dopant Distance and Composite Electronic Structures
(2024-01-01) Lu Diaz, Michael; Duhandzic, Muhamed; Harrity, Simon; Samanta, Subhayan; Aksamija, Zlatan; Venkataraman, Dhandapani; Venkataraman, Dhandapani; Venkataraman, Dhandapani
The data here is the raw data for Figures in the publication "Dopant-Induced Energetic Disorder in Conjugated Polymers: Determinant Roles of Polymer−Dopant Distance and Composite Electronic Structures" In the Journal of Physical Chemistry C. (https://doi.org/10.1021/acs.jpcc.3c07197)
Open Access
Source Data for "Tuning charge transport dynamics via clustering of doping in organic semiconductor thin films"
(2019-01-01) Boyle, Connor J.; Upadhyaya, Meenakshi; Lu-Díaz, Michael; Venkataraman, Dhandapani; Aksamija, Zlatan
Open Access
Data for "Interplay Between Ion Transport, Applied Bias and Degradation under Illumination in Hybrid Perovskite p-i-n Devices"
(2018-01-01) Smith, Emily C.; Ellis, Christie L.C.; Javaid, Hamza; Renna, Lawrence A.; Liu, Yao; Russell, Thomas P.; Bag, Monojit; Venkataraman, Dhandapani; Venkataraman, Dhandapani; Venkataraman, Dhandapani
We studied ion transport in hybrid organic inorganic perovskite p-i-n devices as a function of applied bias under device operating conditions. Using electrochemical impedance spectroscopy (EIS) and equivalent circuit modeling, we elucidated various resistive and capacitive elements in the device. We show that ion migration is predictably influenced by a low applied forward bias, characterized by an increased capacitance at the hole transporting (HTM) and electron transporting material (ETM) interfaces, as well as through the bulk. However, unlike observations in n-i-p devices, we found that there is a capacitive discharge leading to ion redistribution in the bulk at high forward biases. Furthermore, we show that a chemical double layer capacitance buildup as a result of ion accumulation impacts the electronic properties of the device, likely by either inducing charge pinning or charge screening, depending on the direction of the ion induced field. Lastly, we extrapolate ion diffusion coefficients (~10-7 cm2 s-1) and ionic conductivities (~10-7 S cm-1) from the Warburg mass (ion) diffusion response, and show that, as the device degrades, there is an overall depletion of capacitive effects coupled with an increased ion mobility.