Faculty Assistant

Jacqueline Armstrong
Engineering Quad, A213
Phone: (609) 258-1830

Research Focus

Our research is in the area of materials chemistry and physics of complex, soft materials. Specifically, we are interested in electrically-active polymeric and molecular materials.  We hope to elucidate the fundamental processing-structure-property relationships that govern these materials to generate design rules and guidelines for the rational synthesis of materials with tailored properties and the development of innovative processing and patterning technologies for the realization of low-cost, light weight, mechanically flexible thin-film devices, such as organic transistors and solar cells.

Currently, we are examining how specific processing conditions affect the structure evolution of organic and polymer materials, and how structural development can in turn impact applications-relevant macroscopic electrical and physical properties.

Work is being carried out on molecular and polymeric semiconductors, conducting polymers, solution-synthesized and structurally precise graphene nano ribbons, as well as organic-inorganic hybrid perovskites.


Solution-processable organic conductors and semiconductors for thin-film electronics

The ability to replace thermally-evaporated metal and organic semiconductors with solution-processable counterparts as active device components will lower capital and operational costs associated with thin-film electronics fabrication. We are examining the processing-structure-property relationships of these materials to assess their viability. Current research efforts in this area focus on water-dispersible, conductive polyaniline and several p-type solution-processable anthradithiophenes.  These materials, respectively, find use as electrodes and active layers in organic transistors and solar cells.

The channel region of solution-processed organic thin film transistors using triethylsilylethynyl anthradithiophene (TES-ADT)as the organic semiconductor. Grain size is controlled by the addition of fluorinated-TES-ADT, which acts as heterogeneous nuclei for TES-ADT crystallization. 

Soft lithography and soft-contact lamination for plastic electronics

The chemical- and mechanical fragility of organic semiconductors calls for the development of non-invasive patterning technologies for establishing efficient electrical contact. Our group has developed nanotransfer printing (nTP), soft-contact lamination (scL) and stamp-and-spin-cast as means to fabricate functional organic thin-film devices. Research in this area continues to explore elastomeric-stamp-based patterning schemes for creating high-resolution functional features on rigid and flexible substrates over large areas.  These features are either directly transferred onto or laminated against the electrically-active components to complete the circuits of organic transistors and solar cells.


Self-assembled monolayers facilitate interfacial engineering in organic solar cells

Previously, our efforts in this area entailed the understanding the assembly of conjugated molecules on metal and semiconductor surfaces. High-resolution spectroscopic techniques, including transmission and reflectance infra-red spectroscopy and synchrotron-based near-edge X-ray absorption fine structure spectroscopy were used to elucidate the ensemble-averaged structure and orientation of the molecular assembly. Current work builds on our previous know-how; we are exploiting the molecular dipoles induced by and surface energy presented by the organization of self-assembled monolayers to engineer the electrode-photo-active later interface in organic solar cells.


Research Areas

Fellow, American Physical Society (2013)

Young Global Leader, World Economic Forum (2012)

Owens Corning Award, American Institute of Chemical Engineers (2012)

John H. Dillon Medal, Division of Polymers, American Physical Society (2010)

US Young Scientist Delegate, World Economic Forum “Summer Davos”, Tianjin, China (2010)

Alfred Sloan Research Fellowship in Chemistry (2008)

Alan P. Colburn Award for Excellence in Publications by a Young Member of the Institute, American Institute of Chemical Engineers (2006)

The Inaugural Peter and Edith O’Donnell Award in Engineering, the Academy of Medicine, Engineering, and Science of Texas (2006)

Arnold and Mabel Beckman Foundation, Young Investigator Award (2005)

Camille and Henry Dreyfus New Faculty Award (2002)

Selected Recent Publications

G.E. Purdum, N. Yao, A. Wol, T. Gessner, R.T. Weitz, Y.-L. Loo, “Understanding Polymorph Transformations in Core-Chlorinated Naphthalene Diimides and Its Impact on Thin-Film Transistor Performance” Advanced Functional Materials accepted July 2015.

P.P. Khlyabich, A.E. Rudenko, B.C. Thompson, Y.-L. Loo, “Structural Origins for Tunable Open-Circuit Voltage in Ternary-Blend Solar Cells” Advanced Functional Materials, accepted July 2015.

A.K. Hailey, S.-Y. Wang, Y. Chen, M.M. Payne, J.E. Anthony, V. Podzorov, Y.-L. Loo, “Quantifying the Energy Barriers and Elucidating the Charge Transport Mechanisms across Interspherulite Boundaries in Solution-Processed Organic Semiconductor Thin Films” Advanced Functional Materials, accepted July 2015.

J. Berry, T. Bounassisi, D.A. Egger, G. Hodes, L. Kronik, Y.-L. Loo, I. Lubomirsky, S.R. Marder, Y. Mastai, J.S. Miller, D.B. Mitzi, Y. Paz, A.M. Rappe, I. Riess, B. Rybtchinski, O. Stafsudd, V. Stevanovic, M.F. Toney, D. Zitoun, A. Kahn, D. Gingley, D. Cahen, “Hybrid Organic Inorganic Perovskites (HOIPs): Opportunities and Challenges” Advanced Materials DOI:10.1002/adma.201502294

A.M. Hiszpanski, R. Baur, B. Kim, N. Tremblay, C. Nuckolls, A. Woll, Y.-L. Loo, “Tuning Polymorphism and Orientation in Organic Semiconductor Thin Films via Post-Deposition Processing” Journal of the American Chemical Society 2014, 136, 15749.

L. Whittaker-Brooks, W.E. McClain, J. Schwartz, Y.-L. Loo, “Donor-Acceptor Interfacial Interactios Dominate Device Performance in Hybrid P3HT-ZnO Nanowire Array Solar Cells” Advanced Functional Materials 20144, 1400585; featured on inside cover.

A.M. Hiszpanski, S.S. Lee, H. Wang, A.R. Woll, C. Nuckolls, Y.-L. Loo, “Post-Deposition Processing Methods to Induce Preferential Orientation in Contorted Hexabenzocoronene Thin Films for Transistor Applications” ACS Nano 2013, 7, 294.

S.S. Lee, J.M. Mativetsky, M. Loth, J.E. Anthony, Y.-L. Loo, “Quantifying Resistance Across Nanoscale Low- and High-Angle Interspherulite Boundaries in Solution-Processed Organic Semiconductors” ACS Nano 20126, 9879.

H. Wang, M. Shah, V. Ganesan, M. Chabinyc, Y.-L. Loo, “Tail State-Assisted Charge Injection and Recombination at the Electron-Collecting Interface of P3HT:PCBM Bulk-Heterojunction Polymer Solar Cells” Advanced Energy Materials 2012, 2, 1447.

S.S. Lee, S. Muralidharan, A. Woll, M. Loth, Z. Li, J.E. Anthony, M. Haataja, Y.-L. Loo, “Understanding Heterogeneous Nucleation in Binary, Solution-Processed Organic Semiconductor Thin Films” Chemistry of Materials 2012, 24, 2920.

S.S. Lee, S.B. Tang, D.M. Smilgies, A.R. Woll, M.A. Loth, J.M. Mativetsky, J.E. Anthony, Y.-L. Loo, “Guiding Crystallization Around Bends and Sharp Corners” Advanced Materials 2012, 24, 2692;

J.B. Kim, P. Kim, N.C. Pegard, S.J. Oh, C.R. Kagan, J.W. Fleischer, H.A. Stone, Y.-L. Loo, “Wrinkles and Folds as Photonic Structures in Polymer Photovoltaics” Nature Photonics 20126, 327.

K. Kuribara, H. Wang, N. Uchiyama, K. Fukuda, T. Yokota, U. Zschieschang, C. Jaye, D.A. Fischer, H. Klauk, T. Yamamoto, K. Takimiya, M. Ikeda, H. Kuwabara, T. Sekitani, Y.-L. Loo, T. Someya, “Organic Transistors with High Thermal Stability for Medical Applications” Nature Communications 20123, 723.

S.S. Lee, M.A. Loth, J.E. Anthony, Y.-L. Loo, “Orientation-Independent Charge Transport in Single Spherulites” Journal of the American Chemical Society 2012134, 5436. Appeared as feature cover.

J. Tarver, Y.-L. Loo, “Mesostructures of Polyaniline Films Affect Polyelectrochromic Switching” Chemistry of Materials 201123, 4402.

H. Wang, E.D. Gomez, J.B. Kim, Z. Guan, C. Jaye, D.A. Fischer, A. Kahn, Y.-L. Loo, “Device Characteristics of Bulk-Heterojunction Polymer Solar Cells are Independent of Interfacial Segregation of Active Layers” Chemistry of Materials 201123, 2020.

E.D. Gomez, K.P. Barteau, H. Wang, M.F. Toney, Y.-L. Loo, “Correlating the Scattered Intensities of P3HT and PCBM to the Current Densities of Polymer Solar Cells” Chemical Communications 201147, 436.

J.E. Yoo, K.S. Lee, A. Garcias, J.D. Tarver, E.D. Gomez, K. Baldwin, Y. Sun, H. Meng, T.-Q. Nguyen, Y.-L. Loo, “Directly Patternable, Highly Conducting Polymers for Broad Applications in Organic Electronics” Proceedings of the National Academy of Science USA 2010, 107, 5712; featured in PNAS “In the News” and Princeton University homepage; highlighted by multiple publications including Science and Chemical Engineering Progress.

S.S. Lee, C.S. Kim, E.D. Gomez, B. Purushothaman, M.F. Toney, C. Wang, A. Hexemer, J.E. Anthony, Y.-L. Loo, “Controlling Nucleation and Crystallization in Solution-Processed Organic Semiconductors for Thin-Film Transistors” Advanced Materials 2009, 21, 3605; featured on back cover of issue.

N. Mano, J.E. Yoo, J.D. Tarver, Y.-L. Loo, A. Heller, “An Electron-Conducting Crosslinked Polyaniline-Based Redox Hydrogel, Formed in One Step at pH 7.2, Wires Glucose Oxidase” Journal of the American Chemical Society 2007, 129, 7006.

J.E. Yoo, J.L. Cross, T.L. Bucholz, K.S. Lee, M.P. Espe, Y.-L. Loo, “Improving the Electrical Conductivity of Polymer-Acid-Doped Polyaniline by Controlling the Template Molecular Weight” Journal of Materials Chemistry 200717, 1268; featured on front cover of issue.

K.C. Dickey, J.E. Anthony, Y.-L. Loo, “Improving Organic Thin-Film Transistor Performance through Solvent Vapor Annealing of Solution-Processable Triethylsilylethynyl Anthradithiophene” Advanced Materials 200618, 2717; appeared as feature cover.

K.S. Lee, T.J. Smith, K.C. Dickey, J.E. Yoo, K.J. Stevenson, Y.-L. Loo, “High-Resolution Characterization of Pentacene-Polyaniline Interfaces in Thin-Film Transistors” Advanced Functional Materials 2006, 16, 2409.

Y.-L. Loo,  T. Someya, K.W. Baldwin, Z. Bao, P. Ho, A. Dodabalapur, H.E. Katz, J.A. Rogers, “Soft, Conformable Electrical Contacts for Organic Transistors: High-Resolution Circuits by Lamination” Proceedings of the National Academy of Science, USA 2002, 99, 10252.

Y.-L. Loo, R.L. Willett, K.W. Baldwin, J.A. Rogers, “Interfacial Chemistries for Nanoscale Transfer Printing” Journal of the American Chemical Society 2002, 124, 7654.

Y.-L. Loo, R.A. Register, A.J. Ryan, “Polymer Crystallization in 25 nm Spheres” Physical Review Letters 2000, 84, 4120.