Lead‐Free Double Perovskite Cs₂SnX₆: Facile Solution Synthesis and Excellent Stability

Abstract

Long‐term instability and possible lead contamination are the two main issues limiting the widespread application of organic–inorganic lead halide perovskites. Here a facile and efficient solution‐phase method is demonstrated to synthesize lead‐free Cs2SnX6 (X = Br, I) with a well‐defined crystal structure, long‐term stability, and high yield. Based on the systematic experimental data and first‐principle simulation results, Cs2SnX6 displays excellent stability against moisture, light, and high temperature, which can be ascribed to the unique vacancy‐ordered defect‐variant structure, stable chemical compositions with Sn4+, as well as the lower formation enthalpy for Cs2SnX6. Additionally, photodetectors based on Cs2SnI6 are also fabricated, which show excellent performance and stability. This study provides very useful insights into the development of lead‐free double perovskites with high stability.

Stability enhancement of lead‐free CsSnI3 perovskite photodetector with reductive ascorbic acid additive

“…88‐1175). As for the hybrid samples, besides the diffraction peaks originating from TiO 2 and FTO, almost all rest peaks are in good agreement with the reported orthorhombic (Pnam) structure of CsSnI 3 , and the peak at 13.2° in CsSnI 3 /TiO 2 sample corresponds to Cs 2 SnI 6 . After 6 hours of exposure to air, CsSnI 3 is converted to Cs 2 SnI 6 for the CsSnI 3 /TiO 2 sample, while the CsSnI 3 ‐x/TiO 2 samples remain almost unchanged (Figure S5A).…”

“…Additionally, there are high‐density intrinsic defects related to Sn vacancies in the crystal structure, which will produce highly mobile holes and make CsSnI 3 appear to be metallic . Due to these disadvantages, the reported inorganic Sn‐based photodetectors exhibit poor performance with large dark current, seriously limiting the further development of Sn‐based halide perovskite …”

Lead-Free Perovskites for Lighting and Lasing Applications: A Minireview

“…To replace Pb (II) in halide perovskites, several low-toxic cations from the same group of periodical table and those closest to it were proposed, including Sn(II) [28,29,30,31,32], In (III) [33,34], Bi(III) [35,36,37,38,39,40], Sb(III) [41], and others. At the same time, the double perovskite structure gained distribution in lead-free perovskites due to the wide range of cations from III group mixed with Ag(I) [42,43,44,45,46,47,48,49].…”

“…Thus, the tin-based perovskites are potentially applicable in the field of optoelectronic devices. In the work [31], a simple and efficient solution-phase method to synthesize Cs 2 SnX 6 (X = Br, I) with a good yield, well-defined crystal structure, and long-term stability was demonstrated (Figure 2a,b). Cs 2 SnX 6 single crystals show excellent stability against light and moisture due to the unique vacancy-ordered defect-variant structure, stable Sn 4+ chemical compositions, as well as the lower formation enthalpy for Cs 2 SnX 6 .…”

Indium Doping of Lead-Free Perovskite Cs2SnI6

“…Upon replacement of Cl − by I − , the optical absorption coefficient increases, the bandgap decreases, stability decreases, and the materials color changes from pale yellow (or white) to black. The Cs 2 SnI 6 phase is also used as photodetectors (Han et al, 2019 ), for photoelectrochemical water splitting (Dang et al, 2019 ), as photocatalysts (Wang X.-D. et al, 2019 ), and the efficiency of the SCs based on it has reached ~11.2%. In this work, we have demonstrated the preparation of solid solutions based on Cs 2 SnI 6 by doping with indium.…”