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Investigation of Interfacial Charge Transfer in Solution Processed Cs2SnI6 Thin Films
journal contribution
posted on 2017-06-01, 00:00 authored by Gaurav Kapil, Takeshi Ohta, Tsuguo Koyanagi, Murugan Vigneshwaran, Yaohong Zhang, Yuhei Ogomi, Shyam S. Pandey, Kenji Yoshino, Qing Shen, Taro Toyoda, Md. Mijanur Rahman, Takashi Minemoto, Takurou N. Murakami, Hiroshi Segawa, Shuzi HayaseCesium
tin halide based perovskite Cs2SnI6 has been
subjected to in-depth investigations owing to its potentiality
toward the realization of environment benign Pb free and stable solar
cells. In spite of the fact that Cs2SnI6 has
been successfully utilized as an efficient hole transport material
owing to its p-type semiconducting nature, however, the nature of
the majority carrier is still under debate. Therefore, intrinsic properties
of Cs2SnI6 have been investigated in detail
to explore its potentiality as light absorber along with facile electron
and hole transport. A high absorption coefficient (5 × 104 cm–1) at 700 nm indicates the penetration
depth of 700 nm light to be 0.2 μm, which is comparable to conventional
Pb based solar cells. Preparation of pure and CsI impurity free dense
thin films with controllable thicknesses of Cs2SnI6 by the solution processable method has been reported to be
difficult owing to its poor solubility. An amicable solution to circumvent
such problems of Cs2SnI6 has been provided utilizing
spray-coating in combination with spin-coating. The presence of two
emission peaks at 710 and 885 nm in the prepared Cs2SnI6 thin films indicated coexistence of quantum dot and bulk
parts which were further supported by transmission electron microscopy
(TEM) investigations. Time-resolved photoluminescence (PL) and transient
absorption spectroscopy (TAS) were employed to investigate the excitation
carrier lifetime, which revealed fast decay kinetics in the picoseconds
(ps) to nanoseconds (ns) time domains. Time-resolved microwave photoconductivity
decay (MPCD) measurement provided the mobile charge carrier lifetime
exceeding 300 ns, which was also in agreement with the nanosecond
transient absorption spectroscopy (ns-TAS) indicating slow charge
decay lasting up to 20 μs. TA assisted interfacial charge transfer
investigations utilizing Cs2SnI6 in combination
with n-type PCBM and p-type P3HT exhibited both intrinsic electron
and hole transport.
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transmission electron microscopyInterfacial Charge TransferSolution Processed Cs 2 SnI 6TASCs 2 SnI 6MPCDabsorption spectroscopy700 nm lightPLcharge carrier lifetimesolution processable methodPCBMTime-resolved microwave photoconductivity decayFilms Cesium tin halideperovskite Cs 2 SnI 6TEMp-type P 3HThole transport materialcharge transfer investigationshole transport0.2 μ mTAp-type semiconducting natureexcitation carrier lifetime
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