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Crystal-structure of active layers of small molecule organic photovoltaics before and after solvent vapor annealing

  • Marvin Berlinghof , Stefan Langner , Christina Harreiß , Ella Mara Schmidt , Rita Siris , Florian Bertram , Chen Shen , Johannes Will , Torben Schindler , Annemarie Prihoda , Stefanie Rechberger , Georg S. Duesberg , Reinhard B. Neder , Erdmann Spiecker , Christoph J. Brabec and Tobias Unruh EMAIL logo
Published/Copyright: January 13, 2020
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Zeitschrift für Kristallographie - Crystalline Materials
From the journal Zeitschrift für Kristallographie - Crystalline Materials Volume 235 Issue 1-2

Abstract

It is demonstrated by a detailed structural analysis that the crystallinity and the efficiency of small molecule based organic photovoltaics can be tuned by solvent vapor annealing (SVA). Blends made of the small molecule donor 2,2′-[(3,3′″,3″″,4′-tetraoctyl[2,2′:5′,2″:5″,2′″:5′″,2″″-quinquethiophene]-5,5″″-diyl)bis[(Z)-methylidyne(3-ethyl-4-oxo-5,2-thiazolidinediylidene)]]bis-propanedinitrile (DRCN5T) and the acceptor [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) were annealed using solvent vapors with either a high solubility for the donor (tetrahydrofuran), the acceptor (carbon disulfide) or both (chloroform). The samples were analyzed by grazing-incidence wide-angle X-ray scattering (GIWAXS), electron diffraction, X-ray pole figures, and time-of-flight secondary ion mass spectrometry (ToF-SIMS). A phase separation of DRCN5T and PC71BM is induced by SVA leading to a crystallization of DRCN5T and the formation of a DRCN5T enriched layer. The DRCN5T crystallites possess the two dimensional oblique crystal system with the lattice parameters a = 19.2 Å, c = 27.1 Å, and β = 111.1° for the chloroform case. No major differences in the crystal structure for the other solvent vapors were observed. However, the solvent choice strongly influences the size of the DRCN5T enriched layer. Missing periodicity in the [010]-direction leads to the extinction of all Bragg reflections with k ≠ 0. The annealed samples are randomly orientated with respect to the normal of the substrate (fiber texture).

Keywords: crystal structure; DRCN5T; OPV; small molecule; SVA

Acknowledgements

The authors gratefully acknowledge the funding of the Deutsche Forschungsgemeinschaft (DFG) through the “Cluster of Excellence Engineering of Advanced Materials (EAM)”. M.B., C.H., J.W., A.P., T.S., S.R., E.S. and T.U. thank the research training group GRK 1896 “In-Situ Microscopy with Electrons, X-rays, and Scanning Probes” for funding. M.B., J.W., A.P., T.S., and T.U thankfully acknowledge the funding by the research unit FOR 1878 “Functional Molecular Structures on Complex Oxide Surfaces”, the German Federal Ministry of Education and Research (BMBF, project numbers: 05K16WEB, 05K16WE1), and the DFG (INST 90/825-1 FUGG, INST 90/751-1 FUGG, INST 90/827-1 FUGG). S.L., C.H., S.R., E.S., and C.J.B. gratefully thank for financial support provided by the Deutsche Forschungsgemeinschaft (DFG) in the framework of SFB 953 “Synthetic Carbon Allotropes” (project number 182849149). C.J.B. gratefully acknowledge “Solar Energy goes Hybrid” Initiative (SolTech) and the “Solar Factory of the Future” as part of the Energy Campus Nürnberg (EnCN), which is supported by the Bavarian State Government (FKZ 20.2-3410.5-4-5). E.M.S. and would like to thank the Bavarian Equal Opportunities Sponsorship – Förderung von Frauen in Forschung und Lehre (FFL) – promoting equal opportunities for women in research and teaching for funding. R.S. and G.S.D. thank the “High-Performance Center Connected Secure Systems, Munich” for its support. The authors thank Christian Bär, Herbert Lang, and Jürgen Grasser from the workshop of the Institute for Crystallography and Structural Physics (ICSP) at FAU for the construction of the in situ sample cell. We also thank Wolfgang Gruber and Johannes Dallmann (both: ICSP, FAU) for the fruitful discussions about the details of this article. We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at PETRA III and we would like to thank Milena Lippmann, Brit Heilmann, and René Kirchhof for assistance in using the P08 beamline and the chemical laboratory of the Deutsches Elektronen-Synchrotron (DESY).

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Supplementary Material

The online version of this article offers supplementary material (https://doi.org/10.1515/zkri-2019-0055).

Received: 2019-11-08
Accepted: 2019-12-19
Published Online: 2020-01-13
Published in Print: 2020-02-25

©2020 Walter de Gruyter GmbH, Berlin/Boston

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https://doi.org/10.1515/zkri-2019-0055
Keywords for this article
crystal structure; DRCN5T; OPV; small molecule; SVA

Articles in the same Issue

  1. Frontmatter
  2. Graphical Synopsis
  3. Inorganic Crystal Structures
  4. The polymorphs of the Na+ ion conductor Na3PS4 viewed from the perspective of a group-subgroup scheme
  5. Twinned olivenite from Cap Garonne, Mine du Pradet – structure and magnetic behavior
  6. Crystal-structure of active layers of small molecule organic photovoltaics before and after solvent vapor annealing
  7. Group-subgroup schemes for MoNi4, Nb4N5, KxFe2−ySe2, Nd10Au3As8O10 and CsInCl3: i5 superstructures of I 4/m allowing atom, charge or vacancy ordering
  8. Centrosymmetric LaRh2Ga2
  9. Organic and Metalorganic Crystal Structures
  10. Fibril formation through self-assembly of a simple glycine derivative and X-ray diffraction study
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