TY - JOUR
T1 - The Origin of Lower Hole Carrier Concentration in Methylammonium Tin Halide Films Grown by a Vapor-Assisted Solution Process
AU - Yokoyama, Takamichi
AU - Song, Tze Bin
AU - Cao, Duyen H.
AU - Stoumpos, Constantinos C.
AU - Aramaki, Shinji
AU - Kanatzidis, Mercouri G.
N1 - Funding Information:
T.-B.S. acknowledges financial support from Mitsubishi Chemical Group Science & Technology Research Center, Inc. D.H.C. acknowledges support from the Link Foundation through the Link Foundation Energy Fellowship Program. This work was supported in part by the ANSER Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under Award Number DE-SC0001059. This work made use of the EPIC facility (NUANCE Center-Northwestern University), which has received support from the MRSEC program (NSF DMR-1121262) at the Materials Research Center, and the Nanoscale Science and Engineering Center (EEC-0118025/ 003), both programs of the National Science Foundation; the State of Illinois; and Northwestern University.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2017/1/13
Y1 - 2017/1/13
N2 - A low hole carrier concentration in methylammonium tin halide (MASnX3) perovskite semiconductors is a prerequisite for a nonshorting solar cell device. In-depth film characterizations were performed on MASnI3-xBrx films, fabricated by both a low-temperature vapor-assisted solution process (LT-VASP) and conventional one-step methods, to reveal the origin of the lower hole carrier concentration from films of the former approach. We found that the vaporization of CH3NH3I solid at 150 °C, the temperature at which the LT-VASP occurs, does not supply iodine to the SnX2 (X = Br, I) films. As a result, secondary phases form aside from the desired MASnX3 perovskite; the secondary phases are suggested to be SnO and Sn(OH)2 via a proposed reaction pathway and are further supported by X-ray photoemission spectroscopy (XPS). These nonperovskite Sn2+ phases are beneficial because they assist in achieving the lower hole-doping levels in LT-VASP films. Remarkably, LT-VASP devices demonstrate improved air stability. Overall, our findings suggest that not only the commonly used SnF2 but also other divalent Sn compounds could serve as Sn vacancy suppressors. Further work on modulating the perovskite film compositions could realize more efficient and stable tin-based perovskite solar cells.
AB - A low hole carrier concentration in methylammonium tin halide (MASnX3) perovskite semiconductors is a prerequisite for a nonshorting solar cell device. In-depth film characterizations were performed on MASnI3-xBrx films, fabricated by both a low-temperature vapor-assisted solution process (LT-VASP) and conventional one-step methods, to reveal the origin of the lower hole carrier concentration from films of the former approach. We found that the vaporization of CH3NH3I solid at 150 °C, the temperature at which the LT-VASP occurs, does not supply iodine to the SnX2 (X = Br, I) films. As a result, secondary phases form aside from the desired MASnX3 perovskite; the secondary phases are suggested to be SnO and Sn(OH)2 via a proposed reaction pathway and are further supported by X-ray photoemission spectroscopy (XPS). These nonperovskite Sn2+ phases are beneficial because they assist in achieving the lower hole-doping levels in LT-VASP films. Remarkably, LT-VASP devices demonstrate improved air stability. Overall, our findings suggest that not only the commonly used SnF2 but also other divalent Sn compounds could serve as Sn vacancy suppressors. Further work on modulating the perovskite film compositions could realize more efficient and stable tin-based perovskite solar cells.
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U2 - 10.1021/acsenergylett.6b00513
DO - 10.1021/acsenergylett.6b00513
M3 - Article
AN - SCOPUS:85018926395
SN - 2380-8195
VL - 2
SP - 22
EP - 28
JO - ACS Energy Letters
JF - ACS Energy Letters
IS - 1
ER -
