Abstract
Thermal annealing represents an important stage for the fabrication of active layers for organic solar cells. The crystalline organization improves charge carrier mobility and induces the proper morphology of the electron donor and electron acceptor. In this work, the optimal annealing time for maximization of crystalline volume fraction and the crystallization mechanisms of conjugated polymer films synthesized in our group for solar cell application has been determined by grazing incidence wide-angle X-ray scattering (GIWAXS). By following the evolution of the diffraction peak position, the peak area, and the full width at half maximum (FWHM), it was possible to determine the proper annealing time and to identify the stages corresponding to crystallites formation and growth for poly(butyl octyl benzodithiophene-co-benzothiadiazole) (PBOBDTBTD), poly(butyl octyl benzodithiophene-co-thiophene) (PBOBDTTh), and two different poly(3-hexylthiophene), one of lower molar mass synthesized through Kumada mechanism (P3HTA) and other of higher molar mass through Grimm mechanism (P3HTB). The results show that annealing time increases with polymer backbone rigidity, around 1200 s, 800 s, and 400 s for PBOBDTBTD, PBOBDTTh, and P3HT, respectively. Thus, crystallization in PBOBDTBTD and P3HT mainly occurs through several stages of crystallite formation. In contrast, crystallite growth is significant in PBOBDTTh, promoted both by the flexibility of the polymer chain and the symmetry of the structural unit position in the backbone. For all polymers, an unexpected increase of interplanar distance during crystallites formation and growth has been detected. We attribute this behavior to the confinement of the chains in thin films, which may inhibit the interdigitation effect usually observed in bulk polymer and associated with increased packing between side chains, diminishing the average distance among conjugated backbones. Such inhibition seems to be more pronounced for PBOBDTBTD due to the greater rigidity of the polymer backbone, and less intense for PBOBDTTh, due to the higher molar mass of this polymer than P3HT.
Similar content being viewed by others
References
A. Anctil, E. Lee, R.R. Lunt, Net energy and cost benefit of transparent organic solar cells in building-integrated applications. Appl. Ener. 261, 114429 (2020)
L.K. Jagadamma, M.T. Sajjad, V. Savikhin, M.F. Toney, I.D.W. Samuel, Correlating photovoltaic properties of a PTB7-Th:PC71BM blend to photophysics and microstructure as a function of thermal annealing. J. Mater. Chem. A 5, 14646 (2017)
J.L. Wang, K.K. Liu, J. Yan, Z. Wu, F. Liu, F. Xiao, Z.F. Chang, H.B. Wu, Y. Cao, T.P. Russell, Series of multifluorine substituted oligomers for organic solar cells with efficiency over 9% and fill factor of 0.77 by combination thermal and solvent vapor annealing. J. Am. Chem. Soc. 138, 7687 (2016)
C.H. To, A. Ng, Q. Dong, A.B. Djurišić, J.A. Zapien, W.K. Chan, C. Surya, Effect of PTB7 properties on the performance of PTB7:PC71BM solar cells. ACS Appl. Mater. Inter. 7, 13198 (2015)
H. Sirringhaus, P. Brown, P. Friend, M. Nielsen, K. Bechgaard, A.J.H. Spiering, Two-dimensional charge transport in conjugated polymers. Nature 401, 685 (1999)
K.R. Amundson, B.J. Sapjeta, A.J. Lovinger, Z. Bao, An in-plane anisotropic organic semiconductor based upon poly(3-hexyl thiophene). Thin Solid Films 414, 143 (2002)
B. Fluegel, Y. Zhang, A. Mascarenhas, X. Huang, J. Li, Electronic properties of hybrid organic-inorganic semiconductors. Phys. Rev. B – Conden. Matt. Mater. Phys. 70, 2 (2004)
J.J.R. Arias, L. Crociani, I.T. Soares, I.C. Mota, B.P.S. Santos, R. Valaski, M.D.F.V. Marques, Synthesis of conjugated polymers with directly coupled 2-butyloctyloxybenzodithiophene and benzothiadazole units for application as active layers in organic solar cells. React. Func. Polym. 144, 104355 (2019)
M. Aryal, K. Trivedi, W. Hu, Nano-confinement induced chain alignment in ordered P3HT nanostructures defined by nanoimprint lithography. ACS Nano 3, 3085 (2009)
C. Shen, Y.H. Lee, Y.P. Lee, C.J. Chiang, F.K. Wei, C.H. Wu, K.C. Kau, H.W. Liu, C.C. Hsieh, L. Wang, C.A. Dai, Self-organization and phase transformation of all π-conjugated diblock copolymers and its applications in organic solar cells. React. Funct. Polym. 108, 94 (2016)
S.C. Chang, Y.J. Hsiao, T.S. Li, Selecting annealing temperature of P3HT/PCBM incorporated with nano-diamonds using thermal desorption spectroscopy. Int. J. Electrochem. Sci. 10, 1658 (2015)
D.M. González, C.J. Schaffer, S. Pröller, J. Schlipf, L. Song, S. Bernstorff, E.M. Herzig, P. Müller-Buschbaum, Codependence between crystalline and photovoltage evolutions in P3HT:PCBM solar cells probed with in-operando GIWAXS. ACS Appl. Mater. Inter. 9, 3282 (2017)
C.D. Liman, S. Choi, D.W. Breiby, J.E. Cochran, M.F. Toney, E.J. Kramer, M.L. Chabinyc, Two-dimensional GIWAXS reveals a transient crystal phase in solution-processed thermally converted tetrabenzoporphyrin. J. Phys. Chem. B 117, 14557 (2013)
M. Jeffries-El, G. Sauvé, R.D. McCullough, Facile synthesis of end-functionalized regioregular poly(3-alkylthiophene)s via modified Grignard metathesis reaction. Macromolecules 38, 10346 (2005)
B.P.S. Santos, J.J.R. Arias, M.F.V. Marques, J.G.M. Furtado, L.A. Silva, R.A. Simão, Synthesis and characterization of poly(3-Hexylthiophene) for organic solar cells. Macromol. Symp. 383, 1 (2019)
P. Müller-Buschbaum, The active layer morphology of organic solar cells probed with grazing incidence scattering techniques. Adv. Mater. 26, 7692 (2014)
Hammersley AP (1997) ESRF Internal Report, ESRF97HA02T, FIT2D: An Introduction and Overview.
Hammersley AP (1998) ESRF Internal Report, ESRF98HA01T, FIT2D V9.129 Reference Manual 3.1.
M.A. Ruderer, S.M. Prams, M. Rawolle, Q. Zhong, J. Perlich, S.V. Roth, P. Müller-Buschbaum, Influence of annealing and blending of photoactive polymers on their crystalline structure. J. Phys. Chem. B 114, 15451 (2010)
S. Londono-Restrepo, R. Jeronimo-Cruz, B. Millan-Malo, E. Rivera-Munoz, M. Rodriguez-Garcia, Effect of the nano crystal size on the X-ray diffraction patterns of biogenic hydroxyapatite from human, bovine, and porcine bones. Sci. Rep. 9, 5915 (2019)
J. Rubio Arias, I.C. Mota, M.F.V. Marques, Synthesis of thiophene-benzodithiophene wide bandgap polymer and GIWAXS evaluation of thermal annealing with potential for application in ternary polymer solar cells. Polym. Adv. Technol. 32(1507), 1517 (2020)
K.Y. Wu, C.C. Chiu, W.T. Chuang, C.L. Wang, C.S. Hsu, The backbone rigidity and its influence on the morphology and charge mobility of FBT based conjugated polymers. Polym. Chem. 6, 1309 (2015)
M. Moroni, J. Le Moigne, T.A. Pham, J.Y. Bigot, Rigid rod conjugated polymers for nonlinear optics. 3. Intramolecular H bond effects on poly(phenyleneethynylene) chains. Macromolecules 30, 1964 (1997)
M. Aldissi, Effect of chain rigidity on conductivity of conjugated polymers. Synth. Met. 17, 235 (1987)
S. Debnath, S. Chithiravel, S. Sharma, A. Bedi, K. Krishnamoorthy, S.S. Zade, Selenium-containing fused bicyclic heterocycle diselenolodiselenole: field effect transistor study and structure-property relationship. ACS Appl. Mater. Interfaces. 8, 18222 (2016)
K.S. Ahn, H. Jo, J.B. Kim, I. Seo, H.H. Lee, D.R. Lee, Structural transition and interdigitation of alkyl side chains in the conjugated polymer poly (3-hexylthiophene) and their effects on the device performance of the associated organic field-effect transistor. ACS Appl. Mater. Interfaces. 12(1), 1142–1150 (2019)
J.J.R. Arias, M.D.F.V. Marques, Performance of poly(3-hexylthiophene) in bulk heterojunction solar cells: Influence of polymer size and size distribution. React. Funct. Polym. 113, 58 (2017)
K.M. Knoblock, C.J. Silvestri, D.M. Collard, Stacked conjugated oligomers as molecular models to examine interchain interactions in conjugated materials. J. Am. Chem. Soc. 128, 13680 (2006)
D.A.M. Egbe, S. Türk, S. Rathgeber, F. Kühnlenz, R. Jadhav, A. Wild, E. Birckner, G. Adam, A. Pivrikas, V. Cimrova, G. Knör, N.S. Sariciftci, H. Hoppe, Anthracene based conjugated polymers: Correlation between π-π- Stacking ability, photophysical properties, charge carrier mobility, and photovoltaic performance. Macromolecule 43, 1261 (2010)
J.H. Dou, Y.Q. Zheng, T. Lei, S.D. Zhang, Z. Wang, W.B. Zhang, J.Y. Wang, J. Pei, Systematic investigation of side-chain branching position effect on electron carrier mobility in conjugated polymers. Adv. Func. Mater. 24, 6270 (2014)
P. Keg, A. Lohani, D. Fichou, Y.M. Lam, Y. Wu, B.S. Ong, S.G. Mhaisalkar, Direct observation of alkyl chain interdigitation in conjugated polyquarterthiophene self-organized on graphite surfaces. Macromol. Rapid Commun. 29, 1197 (2008)
B.G. Kim, E.J. Jeong, J.W. Chung, S. Seo, B. Koo, J. Kim, A molecular design principle of lyotropic liquid-crystalline conjugated polymers with directed alignment capability for plastic electronics. Nat. Mater. 12, 659 (2013)
Y. Olivier, D. Niedzialek, V. Lemaur, W. Pisula, K. Müllen, U. Koldemir, J.R. Reynolds, R. Lazzaroni, J. Cornil, D. Beljonne, 25th anniversary article: High-mobility hole and electron transport conjugated polymers: How structure defines function. Adv. Mater. 26, 2119 (2014)
L. Xu, Y. Liu, S. Lei, Self Assembly of conjugated oligomers and polymers at the interface: structure and properties. Nanoscale 4, 4399 (2010)
Y. Pan, J. Huang, D. Gao, Z. Chen, W. Zhang, G. Yu, An insight into the role of side chains in the microstructure and carrier mobility of high-performance conjugated polymers. Polym. Chem. 12(16), 2471–2480 (2021)
Y.W. Huang, Y.C. Lin, H.C. Yen, C.K. Chen, W.Y. Lee, W.C. Chen, C.C. Chueh, High mobility preservation of near amorphous conjugated polymers in the stretched states enabled by biaxially-extended conjugated side-chain design. Chem. Mater. 32(17), 7370–7382 (2020)
Acknowledgements
This research used resources of the Brazilian Synchrotron Light Laboratory (LNLS), an open national facility operated by the Brazilian Center for Research in Energy and Materials (CNPEM), supported by the Brazilian Ministry of Science, Technology, Innovations, and Communications (MCTIC). The XRD2 beamline staff is acknowledged for their assistance during the experiments, especially Dr. Antonio Gasperini, who made possible data reduction. We also thank the funding agency FAPERJ for the financial support.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
The authors declare no conflict of interest.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Rubio Arias, J.J., Custodio Mota, I., Schmidt Albuquerque, L. et al. A GIWAXS study of crystallization in annealed conjugated polymers presenting technological interest for organic solar cell applications. J Mater Sci: Mater Electron 33, 1838–1850 (2022). https://doi.org/10.1007/s10854-021-07383-3
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10854-021-07383-3