3P052
Structure and charge transport properties of tin-iodide perovskites(Division of Chemistry, Graduate School of Science, Hokkaido University, Japan 1, School ofBioengineering, Jimei University, Xiamen, China 2)! Zheng-Zhong Lin1,2㧘Yukari Takahashi1, Yukihiro Takahashi1, Yukihisa Sakurada1,Tamotsu Inabe*,1Introduction
Tin and iodide can be employed to construct a series of perovskites; the composition isdenoted by A2(Me-NH3)n-1SnnI3n+1A2SnIII4, where A=organic ammonium cation, and thenumber of the layer (n) can be adjusted. The compounds with n = 1 are primarily
semiconductors with wide energy gaps (Eg > 1 eV), but the electrical conductivity was foundto be tunable by doping treatment (Sn(II) is partly replaced with Sn(IV)). Therefore, relatively
high conductivity of as-grown A2SnI4 was interpreted by spontaneous hole-doping [1]. It
should be noted that even Me-NH3SnI3 (n=!) is also a semiconductor as shown by recent
theoretical calculations, though the pressed powder sample showed metallic conductivity [2].
Therefore, the high conductivity of cubic perovskite Me-NH3SnI3 is also considered to be due
to spontaneous hole doping. In the present study, doping effects on the transport properties inthe double layer Sn-I perovskite, (PhEtNH3)2(Me-NH3)Sn2I7 (n=2) and cubic perovskite
Me-NH3SnI3 (n=!) have been investigated.
Experiment
The double layer perovskite of (PhEtNH3)2(Me-NH3)Sn2I7 was prepared by adding
anhydrous ethanol to stoichiometric amounts of purified SnI2, PhEtNH3I, and Me-NH3I under
nitrogen atmosphere, followed by slow cooling of the solution (from 65 ûC to 5 ûC at a rate of2 ûC h-1). Black aggregated platelet crystals with size as large as 1.5 ! 1.5 ! 1 mm3 wereobtained. The same method was employed to prepare Me-NH3SnI3 (black and block crystalswith size 1.2 ! 1.2 ! 1 mm3) by just using

stoichiometric SnI2 and Me-NH3I.

Results and analysis
According to the single crystal X-ray diffraction at 153 K, (PhEtNH3)2(Me-NH3)Sn2I7 has
the space group of P-1 with cell parameters: a = 8.683, b = 8.659, c = 22.409 Å, " = 93.74, #= 97.42, $ = 90.24û. Although the diffraction data of the crystal were not good enough, its
double-layer feature was confirmed as shown in Fig. 1. The PhEtNH3+ ions are locatedbetween the tin-iodide perovskite double layers while Me-NH3+ ions are embedded into theintra-layer. The band calculation based from the inorganic framework indicates its
semiconducting electronic structure with an approximate Eg of 1.0 eV. The primary electricalconductivity experiment (four-probe method) indicates that (PhEtNH3)2(Me-NH3)Sn2I7 has
the resistivity of 30-75 "· cm at 300K, comparable with that of the single layer perovskite(PhEtNH3)2SnI4 [1].
In the following work, we will further carry out the electrical conductivity measurements ofthe single crystals of these two perovskites and their artificial Sn(IV)-doping, and investigate
the relationship between the conductivity and the doping level.

Fig.1 double layer configuration (left) of the (PhEtNH3)2(Me-NH3)Sn2I7 (the PhEtNH3+ cations are not wellresolved) and its band structure (right).

References[1] Y. Takahashi, R. Obara, K. Nakagawa, M. Nakano, J. Tokita, and T. Inabe: Chem. Mater.,
2007, 19, 6312-6316.
[2] D. B. Mitzi, C. A. Field, Z. Schlesinger, and R. B. Laibowitz, J. Solid State Chem., 1995,114, 159.