The strength of electrostatic interactions within semiconductors strongly affects their performance in optoelectronic devices. An important target is the tuning of a material’s exciton binding energy—the energy binding an electron–hole pair through the electrostatic Coulomb force—independent of its electronic band gap. Here, we report on the doping of a family of two-dimensional hybrid perovskites, in which inorganic lead halide sheets alternate with naphthalene-based organic layers, with tetrachloro-1,2-benzoquinone (TCBQ). For four out of seven n = 1 perovskites, the incorporation of the electron-accepting TCBQ dopant into the organic sublattice containing the electron-donating naphthalene species enabled the tuning of the materials’ 1s exciton binding energy. The naphthalene–TCBQ electron donor–acceptor interactions increased the electrostatic screening of the exciton, in turn lowering its binding energy relative to the undoped perovskite—by almost 50% in one system. Structural and optical characterization showed that the inorganic lattice is not significantly perturbed even though the layer-to-layer spacing increases upon molecular dopant incorporation.
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The data that support this work are available in the manuscript and its Supplementary Information files. Further raw data are available from the corresponding authors upon request. X-ray crystallographic data have been deposited at the Cambridge Crystallographic Data Centre (http://www.ccdc.cam.ac.uk/) with CCDC references 1934873 (3), 1934874 (4), 1934872 (5), 1934871 (6), 1934875 (7) and 1934876 (8). A copy of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/.
The custom MATLAB code used for the Markov chain Monte Carlo method fit of absorption data can be found at https://github.com/tisdalelab/tunable_exciton_binding_energy, and is also available upon request from W.A.T.
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This work was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, under awards numbers DE-FG02-00ER45810 (for synthesis at Northwestern University) and DE-SC0019345 (for spectroscopic studies at the Massachusetts Institute of Technology). Additional support for the X-ray characterization at Northwestern University was provided by the Center for Bio-Inspired Energy Science (CBES), an Energy Frontier Research Center (EFRC) funded by the US Department of Energy, Office of Science, Basic Energy Sciences under award number DE-SC0000989. J.V.P. acknowledges support from Northwestern University through a Ryan Fellowship. C.M.M. was supported by a Postdoctoral Fellowship in Environmental Chemistry from the Camille and Henry Dreyfus Foundation. C.F.P. was funded by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering (award number DE-FG02-07ER46454). NMR and mass spectrometry experiments made use of the Integrated Molecular Structure Education and Research Center at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental Resource (NSF ECCS-1542205), State of Illinois and International Institute for Nanotechnology (IIN). This work also made use of the Electron Probe Instrumentation Center, Keck-II and Scanned Probe Imaging and Development facilities of Northwestern University’s Atomic and Nanoscale Characterization Experimental Center, which has received support from the Soft and Hybrid Nanotechnology Experimental Resource (NSF ECCS-1542205), the Materials Research Science and Engineering Centers programme (DMR-1720139) at the Materials Research Center, the IIN, the Keck Foundation and the State of Illinois, through the IIN. This work made use of the Jerome B. Cohen X-ray Diffraction Facility supported by the Materials Research Science and Engineering Centers programme of the National Science Foundation (DMR-1720139) at the Materials Research Center of Northwestern University (LCP1). GIWAXS experiments were performed at the Advanced Photon Source (Sector 8-ID-E)—a US Department of Energy Office of Science User Facility operated for the Department of Energy Office of Science by Argonne National Laboratory under contract number DE-AC02-06CH11357.
The authors declare no competing interests.
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Experimental details regarding the synthesis and characterization of the molecules used in this work; additional characterization data for the perovskite compounds with and without molecular dopant; and extended discussion of incorporation regimes and optical characterization.
1 CIF for compound 3; CCDC reference 1934873.
2 CIF for compound 4; CCDC reference 1934874.
3 CIF for compound 5; CCDC reference 1934872.
4 CIF for compound 6; CCDC reference 1934871.
5 CIF for compound 7; CCDC reference 1934875.
6 CIF for compound 8; CCDC reference 1934876.
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Passarelli, J.V., Mauck, C.M., Winslow, S.W. et al. Tunable exciton binding energy in 2D hybrid layered perovskites through donor–acceptor interactions within the organic layer. Nat. Chem. 12, 672–682 (2020). https://doi.org/10.1038/s41557-020-0488-2
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