TlBr and Tl2AgBr3 Nanocrystal Synthesis

Timothy Siegler^a^,^b, Tushti Shah^a, Daniel Houck^a, Mokshin Suri^a^,^c, Yangning Zhang^a, Brian Korgel^a

^aMcKetta Department of Chemical Engineering and Texas Materials Institute, University of Texas at Austin, United States

^bDepartment of Chemical Engineering and Clean Energy Institute, University of Washington, United States

^cCornell University, School of Chemical Engineering, United States

Online Meetups
Proceedings of Online Meetup - Beyond Lead Halide Perovskites: Syntheses and Applications of Metal Halide Semiconductors (MABP)

Online, Spain, 2020 April 23rd - 23rd

Organizer: Quinten Akkerman

Poster, Timothy Siegler, 021
Publication date: 23rd April 2020

ePoster:

Recently, thallium has attracted attention for use in halide perovskites, both in A-site and B-site substitutions. In particular, Cs₂AgTlBr₆ (CATB) double perovskite is of interest, as this material exhibits a direct band gap of 0.95 eV in single crystals, the lowest band gap in the halide perovskite family of materials. Here, we report progress on the development of thallium bromide nanocrystal chemistry, reporting a new chemical route to TlBr and Tl₂AgBr₃ nanocrystals yielding uniform particles with 13 + 2 nm and 15 + 3 nm diameters, respectively. TlBr particles are synthesized via injection of trimethylsilyl bromide (TMSBr) into a thallium (III) acetate solution in octadecene/oleic acid/oleylamine at 70 ^oC, while Tl₂AgBr₃ is synthesized using the same reaction conditions and a 2:1 molar ratio of thallium (III) acetate and silver (I) acetate in the precursor solution. Nanoparticle optical properties are characterized, and Tl₂AgBr₃ exhibits an indirect band gap of 3.1 eV. This is the first report of Tl₂AgBr₃nanoparticle synthesis and the first characterization of the band gap of Tl₂AgBr₃. TlBr is exhibited to have a direct optical band gap of 3.1 eV, consistent with literature. Then, the assembly of both particles are characterized. Both nanoparticles suffer from aggregation during solution drying, which limits the extent of superlattice formation; nonetheless, FCC superlattices of TlBr nanoparticles can be characterized with GISAXS and SEM, and smaller domains of Tl₂AgBr₃ superlattices are seen in SEM. Finally, size control between 10-20 nm average diameter is shown for TlBr nanoparticles via tuning of reaction temperature.

References:

[1] Siegler, T.D., Shah, T., Houck, D.W., Suri, M., Zhang, Y., and Korgel, B.A., (2020) “Synthesis of TlBr and Tl2AgBr3 Nanocrystals” ChemNanoMat. Early View.

[2] Slavney, A.H., Leppert, L., Valdes, A.S., Bartesaghi, D., Savenije, T.J., Neaton, J.B., Karunadasa, H.I. (2018) "Small-Band-Gap Halide Double Perovskites" Angew. Chem. 57, 12765-12770

Acknowledgements:

The authors acknowledge financial support of this work from the Robert A. Welch Foundation (F-1464), the NSF Industry/University Cooperative Research Center on Next Generation Photovoltaics (IIP-1822206), The Center for Dynamics and Control of Materials (CDCM) Materials Research Science and Engineering Center (MRSEC) supported by the NSF (DMR-1720595), and NSF grant CBET-1624659. We thank Hugo Celio for assistance with XPS and Karalee Jarvis for assistance with high resolution TEM

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