Thin-Film Deposition and Characterization of a Sn-Deficient Perovskite Derivative Cs2SnI6

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• 作者：Bayrammurad Saparov ; Jon-Paul Sun ; Weiwei Meng ; Zewen Xiao ; Hsin-Sheng Duan ; Oki Gunawan ; Donghyeop Shin ; Ian G. Hill ; Yanfa Yan ; David B. Mitzi
• 刊名：Chemistry of Materials
• 出版年：2016
• 出版时间：April 12, 2016
• 年：2016
• 卷：28
• 期：7
• 页码：2315-2322
• 全文大小：413K
• 年卷期：0
• ISSN：1520-5002

文摘

In this work, we describe details of a two-step deposition approach that enables the preparation of continuous and well-structured thin films of Csb>2b>SnIb>6b>, which is a one-half Sn-deficient 0-D perovskite derivative (i.e., the compound can also be written as CsSnb>0.5b>Ib>3b>, with a structure consisting of isolated SnIb>6b>^4– octahedra). The films were characterized using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), UV–vis spectroscopy, photoluminescence (PL), photoelectron spectroscopy (UPS, IPES, XPS), and Hall effect measurements. UV–vis and PL measurements indicate that the obtained Csb>2b>SnIb>6b> film is a semiconductor with a band gap of 1.6 eV. This band gap was further confirmed by the UPS and IPES spectra, which were well reproduced by the calculated density of states with the HSE hybrid functional. The Csb>2b>SnIb>6b> films exhibited n-type conduction with a carrier density of 6(1) × 10¹⁶ cm^–3 and mobility of 2.9(3) cm²/V·s. While the computationally derived band structure for Csb>2b>SnIb>6b> shows significant dispersion along several directions in the Brillouin zone near the band edges, the valence band is relatively flat along the Γ–X direction, indicative of a more limited hole minority carrier mobility compared to analogous values for the electrons. The ionization potential (IP) and electron affinity (EA) were determined to be 6.4 and 4.8 eV, respectively. The Csb>2b>SnIb>6b> films show some enhanced stability under ambient air, compared to methylammonium lead(II) iodide perovskite films stored under similar conditions; however, the films do decompose slowly, yielding a CsI impurity. These findings are discussed in the context of suitability of Csb>2b>SnIb>6b> for photovoltaic and related optoelectronic applications.