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Inducing panchromatic absorption and photoconductivity in polycrystalline molecular 1D lead-iodide perovskites through #-stacked viologens Benny Febriansyah, Teck Ming Koh, Rohit Abraham John, Rakesh Ganguly, Yongxin Li, Annalisa Bruno, Subodh G. Mhaisalkar, and Jason England Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/acs.chemmater.8b02038 • Publication Date (Web): 08 Aug 2018 Downloaded from http://pubs.acs.org on August 9, 2018
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Chemistry of Materials
Inducing panchromatic absorption and photoconductivity in polycrystalline molecular 1D lead-iodide perovskites through π-stacked viologens Benny Febriansyah,†,‡,§ Teck Ming Koh,† Rohit Abraham John,†,|| Rakesh Ganguly,§ Yongxin Li,§ Annalisa Bruno,† Subodh G. Mhaisalkar,†,|| and Jason England.*,§ †
Energy Research Institute at Nanyang Technological University (ERI@N), Research Techno Plaza, X-Frontier Block Level 5, 50 Nanyang Drive, Singapore 637553, Singapore. ‡
Interdiscipinary Graduate School (IGS), Energy Research Institute at NTU, Singapore 639798 Singapore.
§
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore. ||
School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
ABSTRACT: As a consequence of their quantum- and elec-
tronically-confined inorganic lattices, molecular 1D leadiodide perovskites are ill suited to photovoltaic (PV) applications. In order to circumvent these problems we utilized electron accepting viologen (N,N’-dialkyl-4,4’-bipyridinium) dications incorporating hydrogen bond donor functionalities, which served to induce !-! stacking interactions. The resulting ‘viologen dimers’ display enhanced charge-transfer (CT) interactions with the 1D lead-iodide nanowires. This manifests in extended light absorption (up to 800 nm), reduced band gaps (1.74 eV to 1.77 eV), and longer photoluminescence lifetimes. More importantly, we demonstrate significant photoconductivity behavior in polycrystalline molecular 1D lead-iodide perovskites for the first time. Thus, this work offers a strategy for inducing the properties required for PV applications in molecular 1D lead-iodide perovskites.
Molecular one-dimensional (1D) lead-iodide hybrid perovskites are an interesting class of solution-processed materials.1-2 Relative to the corresponding 3D materials, they have the advantages of being thermally, mechanically, and chemically stable, especially against moisture,3 whilst also being able to incorporate a much wider range of organic cations.4-7 However, due to narrower light absorption ranges, high excitonic binding energies and band gaps, as well as greatly compromised electrical conductivity,8-10 molecular 1D perovskites based on inert organic cations are not suitable for photovoltaic (PV) applications. In particular, although good photoconductivity has been demonstrated in single crystals
of molecular 1D perovskites,11-13 it has never been observed in more defective settings, such as polycrystalline forms.
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