Thin-Film Preparation and Characterization of Cs 3 Sb 2 I 9 : A Lead-Free Layered Perovskite Semiconductor
- Department of Mechanical Engineering and Materials Science, Duke University, Box 90300 Hudson Hall, Durham, North Carolina 27708, United States, Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
- Department of Physics and Astronomy and Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo, Ohio 43606, United States, Department of Physics, Shanghai University, Shanghai 200444, China
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 3J5, Canada
- Department of Mechanical Engineering and Materials Science, Duke University, Box 90300 Hudson Hall, Durham, North Carolina 27708, United States
- Department of Physics and Astronomy and Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo, Ohio 43606, United States
In this study, computational, thin-film deposition and characterization approaches have been used to examine the ternary halide semiconductor Cs3Sb2I9. Cs3Sb2I9 has two known structural modifications, the 0-D dimer form (space group P63/mmc, No. 194) and the 2-D layered form (P$$\bar{3}$$m1, No. 164), which can be prepared via solution and solid state or gas phase reactions, respectively. Our computational investigations suggest that the layered form, which is a one-third Sb-deficient derivative of the ubiquitous perovskite structure, is a potential candidate for high-band-gap photovoltaic (PV) applications. In this work, we describe details of a two-step deposition approach that enables the preparation of large grain (>1 µm) and continuous thin films of the lead-free layered perovskite derivative Cs3Sb2I9. Depending on the deposition conditions, films that are c-axis oriented or randomly oriented can be obtained. The fabricated thin films show enhanced stability under ambient air, compared to methylammonium lead (II) iodide perovskite films stored under similar conditions, and an optical band gap value of 2.05 eV. Photoelectron spectroscopy study yields an ionization energy of 5.6 eV, with the valence band maximum approximately 0.85 eV below the Fermi level, indicating near-intrinsic, weakly p-type character. Density Functional Theory (DFT) analysis points to a nearly direct band gap for this material (less than 0.02 eV difference between the direct and indirect band gaps) and a similar high-level of absorption compared to CH3NH3PbI3. The photoluminescence peak intensity of Cs3Sb2I9 is substantially suppressed compared to that of CH3NH3PbI3, likely reflecting the presence of deep level defects that result in non-radiative recombination in the film, with computational results pointing to Ii, ISb, and VI as being likely candidates. A key further finding from this study is that, despite a distinctly layered structure, the electronic transport anisotropy is less pronounced due to the high ionicity of the I atoms and the strong anti-bonding interactions between the Sb s lone pair states and I p states, which leads to a moderately dispersive valence band.
- Research Organization:
- Duke Univ., Durham, NC (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- Grant/Contract Number:
- EE0006712
- OSTI ID:
- 1209164
- Alternate ID(s):
- OSTI ID: 1222454
- Journal Information:
- Chemistry of Materials, Journal Name: Chemistry of Materials Vol. 27 Journal Issue: 16; ISSN 0897-4756
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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