Effect of humidity on the a.c. impedance of CH3NH3SnCl3 hybrid films |
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Authors: | Mosca R Ferro P Besagni T Calestani D Chiarella F Licci F |
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Institution: | (1) Department of Physics, Technical University, bul. Dacia 41, MD-2060 Chisinau, Moldova; |
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Abstract: | Impedance spectroscopy measurements show that complex conductivity of thermally ablated CH3NH3SnCl3 films is strongly enhanced when humidity increases. Coplanar two-electrode test devices are modeled through an equivalent
circuit comprising one resistance and two constant phase elements. It is shown that the influence of ambient humidity is mainly
resistive. The dynamic responses of the devices to humidification/dehumidification cycles point out that the a.c. current
varies by more than three orders of magnitude when humidity is varied between dry air and 80% relative humidity. The rise
times are few hundred seconds while fall times are as short as few tens of seconds. This observation suggests that impedance
variations are determined by mechanisms involving loosely bound water molecules physisorbed at the surface of the hybrid film.
The results obtained are discussed in terms of protonic conduction. |
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