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Workshops

Fabrication processes and molecular organization in organic thin films: theory and simulation meet experiments

July 17, 2019 to July 20, 2019
Location : CECAM-IT-SIMUL, Politecnico di Milano, Polo Territoriale di Lecco, Via G. Previati, 23900 Lecco, Italy

Organisers

  • Guido Raos (Politecnico di Milano, Italy)
  • Claudio Zannoni (Universita' di Bologna, Dipartimento di Chimica Industriale "Toso Montanari", Italy)
  • Giuseppe Milano (Dept. Of Organic Materials Science, Yamagata University, Italy)

Supports

   CECAM

Lampre s.r.l.

Description

The computational study and design of soft, functional organic materials, has made huge progresses in the last twenty years. Single molecule properties can now be calculated reliably and routinely by quantum chemical methods. The application of force-field-based Monte Carlo (MC) and Molecular Dynamics (MD) simulations is not so straightforward, but nonetheless they have progressed to a point where they can predict some basic properties of bulk condensed phases (e.g., the structure and transition temperatures of liquid crystals [1]). However, many technologically relevant applications of functional organic materials do not involve bulk phases but micro- or nano-thick films[2]. Examples range from Organic Solar Cells (OSC) [3,4,5], Organic Field Effect Transistors (OFET) [7,8,9], Organic Light Emitting Diodes (OLED) [10] to Liquid Crystal Displays (LCD) [11,12] and polymeric films for optical applications, non-wetting surfaces,[13] sensors and stimuli-responsive surfaces[14,15].
The computational study and design of these organic thin-films is much more complex than that of bulk phases, for a number of reasons:
(1) surfaces and interfaces (also within the organic film) play a key role. A realistic model of molecular organization on a solid substrate may have to include its chemical composition, morphology and roughness.[16] Modelling the delicate balance of intermolecular interactions may be a problem, especially for organic-inorganic interfaces.
(2) there is generally a significant change in properties of organic materials (structure, morphology, melting, glass transition, etc.) from the bulk to the nano-scale level relevant for modern applications[17,18];
(3) the molecular organization within a film may strongly depend on its history and fabrication technology. Actually, the purpose of some fabrication processes (e.g. shearing[8]) may be to generate and stabilize specific out-of-equilibrium structures with favorable properties (e.g., charge transport[19,20]).
A further source of complication resides in the variety of technologically relevant organic materials that range from low molar mass to polymeric, and moreover are often employed as multi-component mixtures. The preparation processes are also different. For low molar mass molecules, vapor deposition and molecular beam epitaxy are often preferred.[21,22] Thin films of polymers and block copolymers are instead usually produced by wet deposition techniques, including spin-coating, inkjet or roll-to-roll printing.[23,24,25] In all cases, the process parameters and post-deposition treatments (e.g., solvent evaporation and annealing) can have a major effect on the final structure and properties of the films and should be accounted for by simulations.[26,27]
The aim of the workshop is to bring together computational scientists, theorists and experimentalists, to define the state of the art and push forward the boundaries in the field of organic thin films. The theme is broad and ambitious. Speakers and participants will be encouraged to address key questions, including:
• What are the criteria for validating a simulation of an organic thin film, when the film itself may be in some non-equilibrium metastable state and information about its structure incomplete?
• What level of coarse-graining and scale-bridging strategies can make the simulations of organic thin film production processes feasible and closer to experiment?
• How can simulations be made more relevant to the interpretation of experiments? How can experimental information be used to constrain the outcome of the numerical simulations?
• What level of detail in a model is required to reproduce or predict specific properties of the films (e.g., charge transport)?
• What are the best techniques for extending simulations from the study of equilibrium molecular organizations to that of nonequilibrium ones produced by the processing techniques practically used in technology?

 

References

[1] Palermo, M. F., Pizzirusso, A., Muccioli, L., & Zannoni, C. (2013). An atomistic description of the nematic and smectic phases of 4-n-octyl-4′ cyanobiphenyl (8CB). The Journal of chemical physics, 138(20), 204901.
[2] Richardson, J. J., Björnmalm, M., & Caruso, F. (2015). Technology-driven layer-by-layer assembly of nanofilms. Science, 348(6233), aaa2491.
[3] Huang, Y., Kramer, E. J., Heeger, A. J., & Bazan, G. C. (2014). Bulk heterojunction solar cells: morphology and performance relationships. Chemical reviews, 114(14), 7006-7043.
[5] Idé, J., Méreau, R., Ducasse, L., Castet, F., Bock, H., Olivier, Y., ... & Muccioli, L. (2014). Charge dissociation at interfaces between discotic liquid crystals: the surprising role of column mismatch. Journal of the American Chemical Society, 136(7), 2911-2920.
[6] Casalegno, M., Pastore, R., Idé, J., Po, R., & Raos, G. (2017). Origin of charge separation at organic photovoltaic heterojunctions: a mesoscale quantum mechanical view. The Journal of Physical Chemistry C, 121(31), 16693-16701.
[7] Noh, Y. Y., Zhao, N., Caironi, M., & Sirringhaus, H. (2007). Downscaling of self-aligned, all-printed polymer thin-film transistors. Nature nanotechnology, 2(12), 784.
[8] Giri, G., Verploegen, E., Mannsfeld, S. C., Atahan-Evrenk, S., Kim, D. H., Lee, S. Y., ... & Bao, Z. (2011). Tuning charge transport in solution-sheared organic semiconductors using lattice strain. Nature, 480(7378), 504.
[9] Minemawari, H., Yamada, T., Matsui, H., Tsutsumi, J. Y., Haas, S., Chiba, R., ... & Hasegawa, T. (2011). Inkjet printing of single-crystal films. Nature, 475(7356), 364.
[11] Geffroy, B., Le Roy, P., & Prat, C. (2006). Organic light‐emitting diode (OLED) technology: materials, devices and display technologies. Polymer International, 55(6), 572-582.
[12] Ricci, M., Mazzeo, M., Berardi, R., Pasini, P., & Zannoni, C. (2010). A molecular level simulation of a twisted nematic cell. Faraday discussions, 144, 171-185.
[13] Tuteja, A., Choi, W., Ma, M., Mabry, J. M., Mazzella, S. A., Rutledge, G. C., ... & Cohen, R. E. (2007). Designing superoleophobic surfaces. Science, 318(5856), 1618-1622.
[14] Torsi, L., Magliulo, M., Manoli, K., & Palazzo, G. (2013). Organic field-effect transistor sensors: a tutorial review. Chemical Society Reviews, 42(22), 8612-8628.
[15] Byshkin, M. S., Buonocore, F., Di Matteo, A., & Milano, G. (2015). A unified bottom up multiscale strategy to model gas sensors based on conductive polymers. Sensors and Actuators B: Chemical, 211, 42-51.
[16] Roscioni, O. M., Muccioli, L., Della Valle, R. G., Pizzirusso, A., Ricci, M., & Zannoni, C. (2013). Predicting the anchoring of liquid crystals at a solid surface: 5-cyanobiphenyl on cristobalite and glassy silica surfaces of increasing roughness. Langmuir, 29(28), 8950-8958.
[17] Kim, C., Facchetti, A., & Marks, T. J. (2007). Polymer gate dielectric surface viscoelasticity modulates pentacene transistor performance. Science, 318(5847), 76-80.
[18] Jones, A. O., Chattopadhyay, B., Geerts, Y. H., & Resel, R. (2016). Substrate‐Induced and Thin‐Film Phases: Polymorphism of Organic Materials on Surfaces. Advanced functional materials, 26(14), 2233-2255.
[19] Troisi, A. (2011). Charge transport in high mobility molecular semiconductors: classical models and new theories. Chemical Society Reviews, 40(5), 2347-2358.
[20] Noriega, R., Rivnay, J., Vandewal, K., Koch, F. P., Stingelin, N., Smith, P., ... & Salleo, A. (2013). A general relationship between disorder, aggregation and charge transport in conjugated polymers. Nature materials, 12(11), 1038.
[21] Sassella, A., Campione, M., Papagni, A., Goletti, C., Bussetti, G., Chiaradia, P., ... & Raos, G. (2006). Strategies for two-dimensional growth of organic molecular films. Chemical physics, 325(1), 193-206
[22] Muccioli, L., D'Avino, G., & Zannoni, C. (2011). Simulation of Vapor‐Phase Deposition and Growth of a Pentacene Thin Film on C60 (001). Advanced Materials, 23(39), 4532-4536.
[23] Krebs, F. C. (2009). Fabrication and processing of polymer solar cells: a review of printing and coating techniques. Solar energy materials and solar cells, 93(4), 394-412.
[24] Gentili, D., Foschi, G., Valle, F., Cavallini, M., & Biscarini, F. (2012). Applications of dewetting in micro and nanotechnology. Chemical Society Reviews, 41(12), 4430-4443.
[25] Rossander, L. H., Dam, H. F., Carlé, J. E., Helgesen, M., Rajkovic, I., Corazza, M., ... & Andreasen, J. W. (2017). In-line, roll-to-roll morphology analysis of organic solar cell active layers. Energy & Environmental Science, 10(11), 2411-2419.
[26] Okuzono, T., Ozawa, K. Y., & Doi, M. (2006). Simple model of skin formation caused by solvent evaporation in polymer solutions. Physical review letters, 97(13), 136103.
[27] Sevink, G. J. A., Schmid, F., Kawakatsu, T., & Milano, G. (2017). Combining cell-based hydrodynamics with hybrid particle-field simulations: efficient and realistic simulation of structuring dynamics. Soft matter, 13(8), 1594-1623.