Self-organizing patterns with micrometre-scale features are promising for the large-area fabrication of photonic devices and scattering layers in optoelectronics. Pattern formation would ideally occur in the active semiconductor to avoid the need for further processing steps. Here, we report an approach to form periodic patterns in single layers of organic semiconductors by a simple annealing process. When heated, a crystallization front propagates across the film, producing a sinusoidal surface structure with wavelengths comparable to that of near-infrared light. These surface features initially form in the amorphous region within a micrometre of the crystal growth front, probably due to competition between crystal growth and surface mass transport. The pattern wavelength can be tuned from 800 nm to 2,400 nm by varying the film thickness and annealing temperature, and millimetre-scale domain sizes are obtained. This phenomenon could be exploited for the self-assembly of microstructured organic optoelectronic devices.
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The data that support the findings of this study are available from the corresponding author on reasonable request.
The code used to analyse pattern periodicity and pattern quality is available at https://github.com/jsbangsund/pattern-image-analysis. The code and interactive graphical user interface used to extract crystal growth rates is provided at https://github.com/jsbangsund/crystal-growth-rate-analysis.
Schweikart, A., Horn, A., Böker, A. & Fery, A. in Complex Macromolecular Systems I 75–99 (Springer, 2009).
Chung, J. Y., Nolte, A. J. & Stafford, C. M. Surface wrinkling: a versatile platform for measuring thin-film properties. Adv. Mater. 23, 349–368 (2011).
Li, B., Cao, Y.-P., Feng, X.-Q. & Gao, H. Mechanics of morphological instabilities and surface wrinkling in soft materials: a review. Soft Matter 8, 5728–5745 (2012).
del Campo, A. & Arzt, E. Fabrication approaches for generating complex micro- and nanopatterns on polymeric surfaces. Chem. Rev. 108, 911–945 (2008).
Mei, Y., Kiravittaya, S., Harazim, S. & Schmidt, O. G. Principles and applications of micro and nanoscale wrinkles. Mater. Sci. Eng. R 70, 209–224 (2010).
Lacour, S. P., Wagner, S., Huang, Z. & Suo, Z. Stretchable gold conductors on elastomeric substrates. Appl. Phys. Lett. 82, 2404–2406 (2003).
Park, M., Harrison, C., Chaikin, P. M., Register, R. A. & Adamson, D. H. Block copolymer lithography: periodic arrays of ~1011 holes in 1 square centimeter. Science 276, 1401–1404 (1997).
Bates, C. M., Maher, M. J., Janes, D. W., Ellison, C. J. & Willson, C. G. Block copolymer lithography. Macromolecules 47, 2–12 (2014).
Segalman, R. A. Patterning with block copolymer thin films. Mater. Sci. Eng. R 48, 191–226 (2005).
Bowden, N., Huck, W. T. S., Paul, K. E. & Whitesides, G. M. The controlled formation of ordered, sinusoidal structures by plasma oxidation of an elastomeric polymer. Appl. Phys. Lett. 75, 2557–2559 (1999).
Palmer, C. & Loewen, E. Diffraction Grating Handbook (Newport Corporation, 2005).
Samuel, I. D. W. & Turnbull, G. A. Organic Semiconductor Lasers. Chem. Rev. 107, 1272–1295 (2007).
Lu, C., Möhwald, H. & Fery, A. A lithography-free method for directed colloidal crystal assembly based on wrinkling. Soft Matter 3, 1530–1536 (2007).
Kim, J. B. et al. Wrinkles and deep folds as photonic structures in photovoltaics. Nat. Photon. 6, 327–332 (2012).
Koo, W. H. et al. Light extraction from organic light-emitting diodes enhanced by spontaneously formed buckles. Nat. Photon. 4, 222–226 (2010).
Guo, C. F. et al. Path-guided wrinkling of nanoscale metal films. Adv. Mater. 24, 3010–3014 (2012).
Kim, J. & Lee, H. H. Wave formation by heating in thin metal film on an elastomer. J. Polym. Sci. B 39, 1122–1128 (2001).
Chan, P. E. et al. Viscoelastic properties of confined polymer films measured via thermal wrinkling. Soft Matter 5, 4638–4641 (2009).
Shtukenberg, A. G., Punin, Y. O., Gunn, E. & Kahr, B. Spherulites. Chem. Rev. 112, 1805–1838 (2012).
Woo, E. M. & Lugito, G. Origins of periodic bands in polymer spherulites. Eur. Polym. J. 71, 27–60 (2015).
Crist, B. & Schultz, J. M. Polymer spherulites: a critical review. Prog. Polym. Sci. 56, 1–63 (2016).
Poudel, P., Majumder, S., Chandran, S., Zhang, H. & Reiter, G. Formation of periodically modulated polymer crystals. Macromolecules 51, 6119–6126 (2018).
Sun, Y., Xi, H., Chen, S., Ediger, M. D. & Yu, L. Crystallization near glass transition: transition from diffusion-controlled to diffusionless crystal growth studied with seven polymorphs. J. Phys. Chem. B 112, 5594–5601 (2008).
Ohdaira, K., Fujiwara, T., Endo, Y., Nishizaki, S. & Matsumura, H. Explosive crystallization of amorphous silicon films by flash lamp annealing. J. Appl. Phys. 106, 044907 (2009).
Tao, Y., Yang, C. & Qin, J. Organic host materials for phosphorescent organic light-emitting diodes. Chem. Soc. Rev. 40, 2943–2970 (2011).
Meerholz, B. K. & Müller, D. C. Outsmarting waveguide losses in thin-film light-emitting diodes. Adv. Funct. Mater. 11, 251–253 (2001).
Fuchs, C. et al. Quantitative allocation of Bragg scattering effects in highly efficient OLEDs fabricated on periodically corrugated substrates. Opt. Express 21, 16319–16330 (2013).
Kuehne, A. J. C. & Gather, M. C. Organic lasers: recent developments on materials, device geometries, and fabrication techniques. Chem. Rev. 116, 12823–12864 (2016).
Fielitz, T. R. & Holmes, R. J. Crystal morphology and growth in annealed rubrene thin films. Cryst. Growth Des. 16, 4720–4726 (2016).
Xu, J. et al. Direct AFM observation of crystal twisting and organization in banded spherulites of chiral poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). Macromolecules 37, 4118–4123 (2004).
Fusella, M. A. et al. Use of an underlayer for large area crystallization of rubrene thin films. Chem. Mater. 29, 6666–6673 (2017).
Park, S.-W. et al. Amorphous-to-crystalline phase transformation of thin film rubrene. J. Phys. Chem. B 114, 5661–5665 (2010).
Liu, Y.-X. & Chen, E.-Q. Polymer crystallization of ultrathin films on solid substrates. Coord. Chem. Rev. 254, 1011–1037 (2010).
Hasebe, M., Musumeci, D. & Yu, L. Fast surface crystallization of molecular glasses: creation of depletion zones by surface diffusion and crystallization flux. J. Phys. Chem. B 119, 3304–3311 (2015).
Tao, J., Mao, G. & Daehne, L. Asymmetrical molecular aggregation in spherulitic dye films. J. Am. Chem. Soc. 121, 3475–3485 (1999).
Sun, Y., Zhu, L., Kearns, K. L., Ediger, M. D. & Yu, L. Glasses crystallize rapidly at free surfaces by growing crystals upward. Proc. Natl Acad. Sci. USA 108, 5990–5995 (2011).
Mullins, W. W. Flattening of a nearly plane solid surface due to capillarity. J. Appl. Phys. 30, 77–83 (1959).
Chai, Y. et al. A direct quantitative measure of surface mobility in a glassy polymer. Science 343, 994–999 (2014).
Li, Y., Yao, Z., Wu, L. & Wang, Z. Nonbirefringent bands in thin films of a copolymer melt: rapid rhythmic crystal growth with an unusual crystal–melt interface. CrystEngComm 20, 2221–2226 (2018).
Zhu, L. et al. Surface self-diffusion of an organic glass. Phys. Rev. Lett. 106, 256103 (2011).
Zhang, Y. et al. Effect of substrate interactions on the glass transition and length-scale of correlated dynamics in ultra-thin molecular glass films. J. Chem. Phys. 149, 184902 (2018).
Zhang, W., Brian, C. W. & Yu, L. Fast surface diffusion of amorphous o-terphenyl and its competition with viscous flow in surface evolution. J. Phys. Chem. B 119, 5071–5078 (2015).
Paeng, K., Powell, C. T., Yu, L. & Ediger, M. D. Fast crystal growth induces mobility and tension in supercooled o-terphenyl. J. Phys. Chem. Lett. 3, 2562–2567 (2012).
Zhang, W., Douglas, J. F. & Starr, F. W. Why we need to look beyond the glass transition temperature to characterize the dynamics of thin supported polymer films. Proc. Natl Acad. Sci. USA 115, 5641–5646 (2018).
Yin, S., Shuai, Z. & Wang, Y. A quantitative structure−property relationship study of the glass transition temperature of OLED materials. J. Chem. Inf. Comput. Sci. 43, 970–977 (2003).
Agata, Y., Shimizu, H. & Kido, J. Syntheses and properties of novel quarterphenylene-based materials for blue organic light-emitting devices. Chem. Lett. 36, 316–317 (2007).
Cheng, J.-A. & Cheng, P.-J. Crystal study of N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine. J. Chem. Crystallogr 40, 557–560 (2010).
Shin, J.-W. et al. Random nano-structures as light extraction functionals for organic light-emitting diode applications. Org. Electron. 15, 196–202 (2014).
Fielitz, T. R., Phenicie, C. M. & Holmes, R. J. Effects of additives on crystallization in thin organic films. Cryst. Growth Des. 17, 4522–4526 (2017).
Jones, J. et al. SciPy: Open source scientific tools for Python. SciPy http://www.scipy.org (2001).
Nečas, D. & Klapetek, P. Gwyddion: an open-source software for SPM data analysis. Cent. Eur. J. Phys. 10, 181–188 (2012).
Funding for this work was provided by the NSF Program in Solid-State and Materials Chemistry under grant numbers DMR-1307066 and DMR-1708177. J.S.B. acknowledges support from the NSF Graduate Research Fellowship under grant no. 00039202. The authors acknowledge helpful discussions with C. Teresi, as well as the groups of P. Dauenhauer, C. D. Frisbie and R. L. Penn for the use of their high-speed camera, atomic force microscope and X-ray diffractometer, respectively. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC programme.
The authors declare no competing interests.
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Bangsund, J.S., Fielitz, T.R., Steiner, T.J. et al. Formation of aligned periodic patterns during the crystallization of organic semiconductor thin films. Nat. Mater. 18, 725–731 (2019). https://doi.org/10.1038/s41563-019-0379-3
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