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Dean M. DeLongchamp

Research

I lead a project focused on measurements to accelerate the development of organic films and devices for flexible circuits, displays, and solar cells. We apply a suite of techniques to reveal the micro- and nano-scale structure features that control performance, including polarized spectroscopies (IR, vis, and X-ray), ellipsometry and reflectivity, wide and small angle scattering, and electron and scanning probe microscopy. (link: Organic Electronics and Photovoltaics Project)

My work includes a specialization in Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy, which is a powerful synchrotron-based tool that measures the composition and orientation of organic systems. (link: NIST NEXAFS capabilities)

I also specialize in electrochemical measurements and devices, including self assembled systems for energy storage and displays.

Honors and Awards

  • Presidential Early Career Award for Scientists and Engineers (PECASE) (2009)
  • NIST Bronze Medal Award (2008)
  • Sigma Xi young Investigator Award (2008
  • NRC/NIST Postdoctoral Fellow Appointment (2003)
  • NSF/KOSEF Korea Summer Institute Award (2002)
  • MRS Graduate Student Award (2002)
  • National Defense Science and Engineering Graduate Fellowship Appointment (1998)

Research Opportunities

National Research Council Postdoctoral Fellowship – Open to U.S. citizens with an annual stipend of $63,400 per year (as of 2009). link: NRC video

   

Highlights

Polymer Semiconductor Film Structure

We determined the detailed film structure in pBTTTs, a series of thiophene ring semiconductors with alkyl side chains and record-setting charge mobilities. We determined the substrate-relative tilts of the pBTTT conjugated plane, side chains, and backbones using our suite of spectroscopies. By combining orientation information with crystal spacings from X-ray diffraction and microscopy, we could discern important structure details.  Notably, the conjugated planes have a preferred tilt, and the side chains are highly interdigitated.

pBTTT packing

Advanced Materials, 2007, 19, (6), 833-837. (link)

   

Polymer Semiconductor Phase Transitions

We determined the mechanism of performance enhancement in the thermal annealing of pBTTTs.  The layer structure dramatically improved when the film entered a mesophase at ≈ 140°C.  Polarized IR revealed that the molecular mechanism of performance enhancement was the melting of alkane side chains.  Once the side chains melt, the backbones move to eliminate packing defects in a smectic-like liquid crystalline state.  Upon cooling, the side chains recrystallize.  Side chain interdigitation therefore provides a general mechanism to achieve and then preserve layer order, because it allows "repairs" to defective crystals and then “locks in” the order.

pBTTT transitions

Macromolecules, 2008, 41, (15), 5709-5715. (link)

   

Oriented Polymer Semiconductors

Oriented domains of pBTTT are created with a flow-coating technique, where films are cast by mechanically spreading a solution with slow and directional drying.  Cast films initially exhibit little in-plane orientation, but orientation increases dramatically after films are heated to a liquid-like state and then cooled.  The oriented domains appear as terraced ribbons with a terrace height of 2.1 nm and a ribbon width equivalent to the length of a fully extended pBTTT chain.  The ribbon interiors have high levels of molecular order and surface-relative orientation.

pBTTT transitions

ACS Nano, 2009, 3, (4), 780-787. (link)

   

Publications

  1. DS Germack, CK Chan, BH Hamadani, LJ Richter, DA Fischer, DJ Gundlach, DM DeLongchamp, "Substrate-dependent interface composition and charge transport in films for organic photovoltaics." Applied Physics Letters, 2009, 94, 233303. (link)
  2. DM DeLongchamp, RJ Kline, Y Jung, DS Germack, EK Lin, AJ Moad, LJ Richter, MF Toney, M Heeney, L McCulloch, "Controlling the Orientation of Terraced Nanoscale "Ribbons" of a Poly(thiophene) Semiconductor." ACS Nano, 2009, 3, (4), 780-787. (link)
  3. CE Mauldin, K Puntambekar, AR Murphy, F Laio, JMJ Fréchet, V Subramanian, DM DeLongchamp, DA Fischer, MF Toney, "Solution Processible alpha, omega-Distyryl Oligothiophene Semiconductors with Enhanced Environmental Stability." Chemistry of Materials, 2009, (ASAP). (link)
  4. DM DeLongchamp, RJ Kline, Y Jung, EK Lin, DA Fischer, DJ Gundlach, SK Cotts, AJ Moad, LJ Richter, MF Toney, M Heeney, I McCulloch, "Molecular Basis of Mesophase Ordering in a Thiophene-Based Copolymer." Macromolecules, 2008, 41, (15), 5709-5715. (link)
  5. I McCulloch, M Heeney, M Chabinyc, DM DeLongchamp, JR Kline, M Cölle, W Duffy, DA Fischer, DJ Gundlach, B Hamadani, R Hamilton, LJ Richter, A Salleo, M Shkunov, D Sparrowe, S Tierney, W Zhang, "Semiconducting Thienothiophene Copolymers: Design, Synthesis, Morphology and Performance in Thin Film Organic Transistors." Advanced Materials, 2008, in press. (link)
  6. BM Vogel, DM DeLongchamp, CM Mahoney, LA Lucas, DA Fischer, EK Lin, "Interfacial modification of silica surfaces through gamma-isocyanatopropyl triethoxy silane-amine coupling reactions." Applied Surface Science, 2008, 254, (6), 1789-1796. (link)
  7. O Esenturk, RJ Kline, DM Delongchamp, EJ Heilweil, "Conjugation Effects on Carrier Mobilities of Polythiophenes Probed by Time-Resolved Terahertz Spectroscopy." Journal of Physical Chemistry C, 2008, 112, (29), 10587-10590. (link)
  8. J Park, RQ Yang, CV Hoven, A Garcia, DA Fischer, TQ Nguyen, GC Bazan, DM DeLongchamp, "Structural characterization of conjugated polyelectrolyte electron transport layers by NEXAFS spectroscopy." Advanced Materials, 2008, 20, (13), 2491. (link)
  9. Y Quan, SCB Mannsfeld, ML Tang, M Roberts, MF Toney, DM DeLongchamp, Z Bao, "Microstructure of oligofluorene asymmetric derivatives in organic thin film transistors." Chemistry of Materials, 2008, 20, (8), 2763-2772. (link)
  10. Y Jung, RJ Kline, EK Lin, DA Fischer, MF Toney, M Heeney, I McCulloch, DM DeLongchamp, "The Impact of the Dielectric/Semiconductor Interface on Microstructure and Charge Carrier Transport in High-Performance Polythiophene Transistors." Electrochemical Society Transactions, 2008, 13, (2), 113-122.
  11. LA Lucas, DM DeLongchamp, LJ Richter, RJ Kline, DA Fischer, BR Kaafarani, GE Jabbour, "Thin Film Microstructure of a Solution Processable Pyrene-Based Organic Semiconductor." Chemistry of Materials, 2008, 20, (18), 5743-5749. (link)
  12. Y Jung, RJ Kline, DA Fischer, EK Lin, M Heeney, I McCulloch, DM DeLongchamp, "The Effect of Interfacial Roughness on the Thin Film Morphology and Charge Transport of High-Performance Polythiophenes." Advanced Materials, 2008, 18, (5), 742-750. (link)
  13. RJ Kline, DM DeLongchamp, DA Fischer, EK Lin, LJ Richter, ML Chabinyc, MF Toney, M Heeney, I McCulloch, "Critical role of side-chain attachment density on the order and device performance of polythiophenes." Macromolecules, 2007, 40, (22), 7960-7965. (link)
  14. DM DeLongchamp, RJ Kline, EK Lin, DA Fischer, LJ Richter, LA Lucas, M Heeney, I McCulloch, JE Northrup, "High carrier mobility polythiophene thin films: Structure determination by experiment and theory." Advanced Materials, 2007, 19, (6), 833-837. (link)
  15. TH Epps, DM DeLongchamp, MJ Fasolka, DA Fischer, EL Jablonski, "Substrate surface energy dependent morphology and dewetting in an ABC triblock copolymer film." Langmuir, 2007, 23, (6), 3355-3362. (link)
  16. NS Zacharia, DM DeLongchamp, M Modestino, PT Hammond, "Controlling diffusion and exchange in layer-by-layer assemblies." Macromolecules, 2007, 40, (5), 1598-1603. (link)
  17. DM DeLongchamp, EK Lin, DA Fischer, "Near Edge X-ray Absorption Fine Structure (NEXAFS) Spectroscopy." In Organic Field-Effect Transistors, Bao, Z.; Locklin, J., Eds. CRC Press: New York, 2007; pp 277-300.
  18. RJ Kline, DM DeLongchamp, DA Fischer, EK Lin, M Heeney, I McCulloch, MF Toney, "Significant dependence of morphology and charge carrier mobility on substrate surface chemistry in high performance polythiophene semiconductor films." Applied Physics Letters, 2007, 90, (6). (link)
  19. MC Gurau, DM Delongchamp, BM Vogel, EK Lin, DA Fischer, S Sambasivan, LJ Richter, "Measuring Molecular Order in Poly(3 alkylthiophene) Thin Films with Polarizing Spectroscopies." Langmuir, 2007, 23, (2), 834 -842. (link)
  20. LA Lucas, DM DeLongchamp, BM Vogel, EK Lin, MJ Fasolka, DA Fischer, I McCulloch, M Heeney, GE Jabbour, "Combinatorial screening of the effect of temperature on the microstructure and mobility of a high performance polythiophene semiconductor." Applied Physics Letters 2007, 90, (1). (link)<
  21. DM DeLongchamp, MM Ling, Y Jung, DA Fischer, ME Roberts, EK Lin, ZN Bao, "Thickness dependence of microstructure in semiconducting films of an oligofluorene derivative." Journal of the American Chemical Society, 2006, 128, (51), 16579-16586. (link)
  22. C Xu, SE Barnes, T Wu, DA Fischer, DM DeLongchamp, JD Batteas, KL Beers, "Solution and surface composition gradients via microfluidic confinement: Fabrication of a statistical-copolymer-brush composition gradient." Advanced Materials, 2006, 18, (11), 1427. (link)
  23. ML Chabinyc, F Endicott, BD Vogt, DM DeLongchamp, EK Lin, YL Wu, P Liu, BS Ong, "Effects of humidity on unencapsulated poly(thiophene) thin-film transistors." Applied Physics Letters 2006, 88, (11), 3. (link)
  24. DM DeLongchamp, YS Jung, DA Fischer, EK Lin, P Chang, V Subramanian, AR Murphy, JMJ Frechet, "Correlating molecular design to microstructure in thermally convertible oligothiophenes: The effect of branched versus linear end groups." Journal of Physical Chemistry B, 2006, 110, (22), 10645-10650. (link)
  25. DM DeLongchamp, BM Vogel, Y Jung, MC Gurau, CA Richter, OA Kirillov, J Obrzut, DA Fischer, S Sambasivan, LJ Richter, EK Lin, "Variations in semiconducting polymer microstructure and hole mobility with spin-coating speed." Chemistry Of Materials, 2005, 17, (23), 5610-5612. (link)
  26. DM DeLongchamp, S Sambasivan, DA Fischer, EK Lin, P Chang, AR Murphy, JMJ Frechet, V Subramanian, "Direct correlation of organic semiconductor film structure to field-effect mobility." Advanced Materials, 2005, 17, (19), 2340-+. (link)
  27. AR Murphy, PC Chang, P VanDyke, JS Liu, JMJ Frechet, V Subramanian, DM DeLongchamp, S Sambasivan, DA Fischer, EK Lin, "Self-assembly, molecular ordering, and charge mobility in solution-processed ultrathin oligothiophene films." Chemistry Of Materials, 2005, 17, (24), 6033-6041. (link)
  28. DM DeLongchamp, EK Lin, DA Fischer, "Organic semiconductor structure and chemistry from near-edge X-ray absorption fine structure (NEXAFS) spectroscopy." Proceedings of the SPIE, 2005, 5940, 54-64.
  29. BD Vogt, HJ Lee, VM Prabhu, DM DeLongchamp, EK Lin, WL Wu, SK Satija, "X-ray and neutron reflectivity measurements of moisture transport through model multilayered barrier films for flexible displays." Journal of Applied Physics, 2005, 97, (11). (link)
  30. DM DeLongchamp, BD Vogt, CM Brooks, K Kano, J Obrzut, CA Richter, OA Kirillov, EK Lin, "Influence of a water rinse on the structure and properties of poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate) films." Langmuir, 2005, 21, (24), 11480-11483. (link)
  31. DM DeLongchamp, PT Hammond, "Electrochromic polyaniline films from layer-by-layer assembly." In Chromogenic Phenomena in Polymers, 2005; Vol. 888, pp 18-33.
  32. DM DeLongchamp, PT Hammond, "High-contrast electrochromism and controllable dissolution of assembled Prussian blue/polymer nanocomposites." Advanced Functional Materials, 2004, 14, (3), 224-232. (link)
  33. DM DeLongchamp, PT Hammond, "Highly ion conductive poly(ethylene oxide)-based solid polymer electrolytes from hydrogen bonding layer-by-layer assembly." Langmuir, 2004, 20, (13), 5403-5411. (link)
  34. DM DeLongchamp, PT Hammond, "Multiple-color electrochromism from layer-by-layer-assembled polyaniline/Prussian Blue nanocomposite thin films." Chemistry of Materials, 2004, 16, (23), 4799-4805. (link)
  35. DM DeLongchamp, M Kastantin, PT Hammond, "High-contrast electrochromism from layer-by-layer polymer films." Chemistry of Materials, 2003, 15, (8), 1575-1586. (link)
  36. DM DeLongchamp, PT Hammond, "Fast ion conduction in layer-by-layer polymer films." Chemistry of Materials, 2003, 15, (5), 1165-1173. (link)
  37. D DeLongchamp, PT Hammond, "Layer-by-layer assembly of PEDOT/polyaniline electrochromic devices." Advanced Materials, 2001, 13, (19), 1455-+. (link)
Dean M. DeLongchamp

Position:

Project Leader: Organic Electronics and Photovoltaics
Polymers Division
Electronics Materials Group

Education:

  • Ph.D., MIT Chemical Engineering, 2003.
    Advisor: Paula T. Hammond
    (link: Paula's Group)
  • M.S.C.E.P. MIT Chemical Engineering, 2000.
    (link: Practice School)
  • B.S. Georgia Tech Chemical Engineering, 1998.
Contact

Phone: 301-975-5599
Email: dean.delongchamp@nist.gov
Fax: 301-975-3928