[1] STRANKS S D, EPERON G E, GRANCINI G et al. Electron- hole diffusion lengths exceeding trihalide perovskite absorber[J]. Science, 341-344(2013).

[2] HEO J H, IM S H, NOH J H et al. Efficient inorganic-organic hybrid heterojunction solar cells containing perovskite compound and polymeric hole conductors[J]. Nature Photonics, 486-491(2013).

[3] SHAO Y, XIAO Z, BI C et al. Origin and elimination of photocurrent hysteresis by fullerene passivation in CH₃NH₃PbI₃ planar heterojunction solar cells[J]. Nature Communications, 5784(2014).

[4] XING G, MATHEWS N, LIM S S et al. Long-range balanced electron- and hole-transport lengths in organic-inorganic CH₃NH₃PbI₃[J]. Science, 344-347(2013).

[5] TAN Z K, MOGHADDAM R S, LAI M L et al. Bright light- emitting diodes based on organometal halide perovskite[J]. Nature Nanotechnology, 687-692(2014).

[6] GAO L, ZENG K, GUO J et al. Passivated single-crystalline CH₃NH₃PbI₃ nanowire photodetector with high detectivity and polarization sensitivity[J]. Nano Letters, 7446-7454(2016).

[7] HAO F, STOUMPOS C C, CAO D H et al. Lead-free solid-state organic-inorganic halide perovskite solar cells[J]. Nature Photonics, 489-494(2014).

[8] STOUMPOS C C, MALLIAKAS C D, KANATZIDIS M G. Semiconducting tin and lead iodide perovskites with organic cations: phase transitions, high mobilities, and near-infrared photoluminescent properties[J]. Inorganic Chemistry, 9019-9038(2013).

[9] NOEL N K, STRANKS S D, ABATE A et al. Lead-free organic- inorganic tin halide perovskites for photovoltaic applications[J]. Energy and Environmental Science, 3061-3068(2014).

[10] CHUNG I, LEE B, HE J et al. All-solid-state dye-sensitized solar cells with high efficiency[J]. Nature, 486-489(2012).

[11] KUMAR M H, DHARANI S, LEONG W L et al. Lead-free halide perovskite solar cells with high photocurrents realized through vacancy modulation[J]. Advanced Materials, 7122-7127(2014).

[12] MARSHALL K P, WALKER M, WALTON R I et al. Enhanced stability and efficiency in hole-transport-layer-free CsSnI₃ perovskite photovoltaics[J]. Nature Energy, 16178(2016).

[13] CHUNG I, SONG J H, IM J et al. CsSnI₃: semiconductor or metal? high electrical conductivity and strong near-infrared photoluminescence from a single material. high hole mobility and phase-transitions[J]. Journal of the American Chemical Society, 8579-8587(2012).

[14] LEE B, STOUMPOS C C, ZHOU N et al. Air-stable molecular semiconducting iodosalts for solar cell applications: Cs₂SnI₆ as a hole conductor[J]. Journal of the American Chemical Society, 15379-15385(2014).

[15] SAPAROV B, SUN J P, MENG W et al. Thin-film deposition and characterization of a Sn-deficient perovskite derivative Cs₂SnI₆[J]. Chemistry of Materials, 2315-2322(2016).

[16] QIU X, CAO B, YUAN S et al. From unstable CsSnI₃ to air-stable Cs₂SnI₆: a lead-free perovskite solar cell light absorber with bandgap of 1.48 eV and high absorption coefficient[J]. Solar Energy Materials and Solar Cells, 227-234(2017).

[17] WANG X D, HUANG Y H, LIAO J F et al. In situ construction of a Cs₂SnI₆ perovskite nanocrystal/SnS₂ nanosheet heterojunction with boosted interfacial charge transfer[J]. Journal of the American Chemical Society, 13434-13441(2019).

[18] LIU F, DING C, ZHANG Y et al. Colloidal synthesis of air-stable alloyed CsSn_1-xPbxI₃ perovskite nanocrystals for use in solar cells[J]. Journal of the American Chemical Society, 16708-16719(2017).

[19] DOLZHNIKOV D S, WANG C, XU Y et al. Ligand-free, quantum- confined Cs₂SnI₆ perovskite nanocrystals[J]. Chemistry of Materials, 7901-7907(2017).

[20] MAUGHAN A E, GANOSE A M, BORDELON M M et al. Defect tolerance to intolerance in the vacancy-ordered double perovskite semiconductors Cs₂SnI₆ and Cs₂TeI₆[J]. Journal of the American Chemical Society, 8453-8464(2016).

[21] XIAO Z, ZHOU Y, HOSONO H et al. Intrinsic defects in a photovoltaic perovskite variant Cs₂SnI₆[J]. Physical Chemistry Chemical Physics, 18900-18903(2015).

[22] KAPIL G, OHTA T, KOYANAGI T et al. Investigation of interfacial charge transfer in solution processed Cs₂SnI₆ thin films[J]. Journal of Physical Chemistry C, 13092-13100(2017).

[23] SHIN H O, KIM B M, JANG T et al. Surface state-mediated charge transfer of Cs₂SnI₆ and its application in dye-sensitized solar cells[J]. Advanced Energy Materials, 18032(2019).

[24] XU Y, LI S, ZHANG Z et al. Ligand-mediated synthesis of colloidal Cs₂SnI₆ three-dimensional nanocrystals and two-dimensional nanoplatelets[J]. Nanotechnology, 2956(2019).

[25] ZHU W, SHEN J, LI M et al. Kinetically controlled growth of sub-millimeter 2D Cs₂SnI₆ nanosheets at the liquid-liquid interface[J]. Small, 2006(2021).

[26] LUO R, ZHANG S, ZHAO S et al. Ultrasmall blueshift of near-infrared fluorescence in phase-stable Cs₂SnI₆ thin films[J]. Physical Review Applied, 014048(2020).

[27] ZHOU P, CHEN H, CHAO Y et al. Single-atom Pt-I₃ sites on all-inorganic Cs₂SnI₆ perovskite for efficient photocatalytic hydrogen production[J]. Nature Communications, 4412(2021).

[28] ULLAH S, ULLAH S, WANG J et al. Investigation of air-stable Cs₂SnI₆ films prepared by the modified two-step process for lead-free perovskite solar cells[J]. Semiconductor Science and Technology, 125027(2020).

[29] KRESSE G, FURTHMÜLLER J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set[J]. Physical Review B, 11169-11186(1996).

[30] KRESSE G, JOUBERT D. From ultrasoft pseudopotentials to the projector augmented-wave method[J]. Physical Review B, 1758-1775(1999).

[31] PENG H, YANG Z H, PERDEW J P et al. Versatile van der Waals density functional based on a meta-generalized gradient approximation[J]. Physical Review X, 041005(2016).

[32] XIAO Z, LEI H, ZHANG X et al. Ligand-hole in [SnI₆] unit and origin of band gap in photovoltaic perovskite variant Cs₂SnI₆[J]. Bulletin of the Chemical Society of Japan, 1250-1255(2015).

[33] ZHANG S B, NORTHRUP J E. Chemical potential dependence of defect formation energies in GaAs: application to Ga self-diffusion[J]. Physical Review Letters, 2339-2342(1991).

[34] VAN DE WALLE C G, NEUGEBAUER J. First-principles calculations for defects and impurities: applications to III-nitrides[J]. Journal of Applied Physics, 3851-3879(2004).

[35] CHEN H, DING Y H, YU H T et al. First-principles investigation of the electronic properties and stabilities of the LaAlO₃ (001) and (110) (1 × 1) polar terminations[J]. Journal of Physical Chemistry C, 9364-9374(2015).

[36] HUANG X, PAUDEL T R, DOWBEN P A et al. Electronic structure and stability of the CH₃NH₃PbBr₃ (001) surface[J]. Physical Review B, 195309(2016).