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García-Benito I, Quarti C, Queloz VIE, Hofstetter YJ, Becker-Koch D, Caprioglio P, Neher D, Orlandi S, Cavazzini M, Pozzi G, Even J, Nazeeruddin MK, Vaynzof Y, Grancini G. Fluorination of Organic Spacer Impacts on the Structural and Optical Response of 2D Perovskites. Front Chem 2020; 7:946. [PMID: 32064245 PMCID: PMC6999157 DOI: 10.3389/fchem.2019.00946] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 12/31/2019] [Indexed: 11/13/2022] Open
Abstract
Low-dimensional hybrid perovskites have triggered significant research interest due to their intrinsically tunable optoelectronic properties and technologically relevant material stability. In particular, the role of the organic spacer on the inherent structural and optical features in two-dimensional (2D) perovskites is paramount for material optimization. To obtain a deeper understanding of the relationship between spacers and the corresponding 2D perovskite film properties, we explore the influence of the partial substitution of hydrogen atoms by fluorine in an alkylammonium organic cation, resulting in (Lc)2PbI4 and (Lf)2PbI4 2D perovskites, respectively. Consequently, optical analysis reveals a clear 0.2 eV blue-shift in the excitonic position at room temperature. This result can be mainly attributed to a band gap opening, with negligible effects on the exciton binding energy. According to Density Functional Theory (DFT) calculations, the band gap increases due to a larger distortion of the structure that decreases the atomic overlap of the wavefunctions and correspondingly bandwidth of the valence and conduction bands. In addition, fluorination impacts the structural rigidity of the 2D perovskite, resulting in a stable structure at room temperature and the absence of phase transitions at a low temperature, in contrast to the widely reported polymorphism in some non-fluorinated materials that exhibit such a phase transition. This indicates that a small perturbation in the material structure can strongly influence the overall structural stability and related phase transition of 2D perovskites, making them more robust to any phase change. This work provides key information on how the fluorine content in organic spacer influence the structural distortion of 2D perovskites and their optical properties which possess remarkable importance for future optoelectronic applications, for instance in the field of light-emitting devices or sensors.
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Affiliation(s)
- Inés García-Benito
- Group for Molecular Engineering of Functional Materials, Institute of Chemical Sciences and Engineering, EPFL Valais Wallis, Sion, Switzerland
| | - Claudio Quarti
- Laboratory for Chemistry of Novel Materials, Department of Chemistry, Université de Mons, Mons, Belgium.,Univ Rennes, ENSCR, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, Rennes, France
| | - Valentin I E Queloz
- Group for Molecular Engineering of Functional Materials, Institute of Chemical Sciences and Engineering, EPFL Valais Wallis, Sion, Switzerland
| | - Yvonne J Hofstetter
- Integrated Centre for Applied Physics and Photonic Materials and Centre for Advancing Electronics Dresden (CFAED), Technical University of Dresden, Dresden, Germany
| | - David Becker-Koch
- Integrated Centre for Applied Physics and Photonic Materials and Centre for Advancing Electronics Dresden (CFAED), Technical University of Dresden, Dresden, Germany
| | - Pietro Caprioglio
- Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany.,Young Investigator Group Perovskite Tandem Solar Cells, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
| | - Dieter Neher
- Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany
| | - Simonetta Orlandi
- CNR - Istituto di Scienze e Tecnologie Chimiche "G. Natta" (CNR-SCITEC), Milan, Italy
| | - Marco Cavazzini
- CNR - Istituto di Scienze e Tecnologie Chimiche "G. Natta" (CNR-SCITEC), Milan, Italy
| | - Gianluca Pozzi
- CNR - Istituto di Scienze e Tecnologie Chimiche "G. Natta" (CNR-SCITEC), Milan, Italy
| | - Jacky Even
- Univ Rennes, INSA Rennes, CNRS, Institut FOTON - UMR 6082, Rennes, France
| | - Mohammad Khaja Nazeeruddin
- Group for Molecular Engineering of Functional Materials, Institute of Chemical Sciences and Engineering, EPFL Valais Wallis, Sion, Switzerland
| | - Yana Vaynzof
- Integrated Centre for Applied Physics and Photonic Materials and Centre for Advancing Electronics Dresden (CFAED), Technical University of Dresden, Dresden, Germany
| | - Giulia Grancini
- Group for Molecular Engineering of Functional Materials, Institute of Chemical Sciences and Engineering, EPFL Valais Wallis, Sion, Switzerland.,Dipartimento di Chimica Fisica, University of Pavia, Pavia, Italy
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