Lead Free Cs2SnI6 Thin Films Using Solution Processing Technique for Perovskite Solar Cells
Hiroshi Segawa a, Gaurav Kapil a, Takeshi Ohta b, Yuhei Ogomi b, Shuzi Hayase b, Tsuguo Koyanagi b, Kenji Yoshino c, Qin Shen d, Taro Toyoda d, Takashi Minemoto e, Takurou N. Murakami f
a Kyushu Institute of Technology, 204 Hibikino Wakamatsu-ku, Kitakyushu - Fukuoka, 808, Japan
b University of Miyazaki, 1-1 Gakuen Kibanadai, Miyazaki, 889, Japan
c University of Electro Communication, 1-5-1 Chofugaoka, Chofu,Tokyo,182-8585, Japan
d Ritsumaekan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan
e The National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference Asia-Pacific Hybrid and Organic Photovoltaics (AP-HOPV17)
Yokohama-shi, Japan, 2017 February 2nd - 4th
Organizers: Tsutomu Miyasaka and Iván Mora-Seró
Poster, Gaurav Kapil, 133
Publication date: 7th November 2016

Cs2SnI6 has been successfully incorporated as an efficient hole transport material (HTM)[1] for dye sensitized solar cells (DSSCs), indicating its p-type semiconductor behavior. However, some of the reports claimed its n-type behavior only [2]. It has also been reported that the formation of pure, dense and thin films of desired thickness of Cs2SnI6 by solution processable method is difficult task to perform due to its poor solubility in any solvent [2] . Hence, in this work first time we fabricated pure thin films of Cs2SnI6 by improvising solution process method.  Despite the use of Cs2SnI6 as a hole transporter, the quantitative information on the charge transfer at the interface of different n-type and p-type semiconductor is still lacking and investigation for detailed information is needed. This work investigates the Cs2SnI6 film for utilizing as an absorber layer where facile electron and hole mobility is important.  In our work, we realized the interfacial charge transfer for Cs2SnI6 with n-type PCBM layer and p-type P3HT layer by photoluminescence (PL) as well as transient absorption spectroscopy ( TA) data, supporting for both intrinsic electron and hole mobility. However, no change of absorption decay signal in case of PCBM when measured in microsecond scale unravel the slow electron mobility compared to hole mobility.The absorption coefficient for Cs2SnI6 was estimated to be 8 * 103 cm-1 at 700 nm, indicating that the penetration depth for 700 nm light is 1.25 μm or at least 1.25 μm thin film need to absorb light effectively, which is comparable to conventional Pb based solar cells. Excitation carrier life time was monitored by time resolved PL decay which revealed fast decay of 0.717 ns followed by a slow decay lasting for 900 ns within the material. Mobile charge carrier life time as measured by time resolved microwave photoconductivity (TRMP) suggested for values of more than 300 ns. This was further supported by nanosecond transient absorption spectroscopy (ns TA) indicating slow charge decay lasting up to 20μs.


1. B. Lee and M. G. Kanatzidis et.al, Jour. Am. Chem. Soc., 2014, 136, 15379-15385.

2. B. Saparov and D. B. Mitzi, Chem. Mater., 2016, 28, 2315-2322.

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