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Tuning the Seebeck Effect in C60-based Hybrid Thermoelectric Devices through Temperature-dependent Surface Polarization and Thermally-modulated Interface Dipoles

Abstract

Fullerene (C60) is an important n-type organic semiconductor with high electron mobility and low thermal conductivity. In this work, we report the experimental result on the tunable Seebeck effect of C60 hybrid thin-film devices by adopting different oxide layers. After inserting n-type high dielectric titanium oxide (TiOx) and zinc oxide (ZnO) layers, we observe significantly enhanced n-type Seebeck effect in oxide/C60 hybrid devices with Seebeck coefficient of -5.8 mV/K for TiOx/C60 and -2.08 mV/K for ZnO/C60 devices at 100 °C, compared with the value of -400 μV/K for pristine C60 device. However, when a p-type nickel oxide (NiO) layer is inserted, the C60 hybrid devices show a p-type to n-type Seebeck effect transition when temperature increases. The remarkable Seebeck effect and change of Seebeck coefficient in different oxide/C60 hybrid devices can be attributed to two reasons: temperature-dependent surface polarization difference and thermally-dependent interface dipoles. Firstly, the surface polarization difference due to temperature-dependent electron-phonon coupling can be enhanced by inserting oxide layer and function as an additional driving force for the Seebeck effect development. Secondly, thermally-dependent interface dipoles formed at electrode/oxide interface play important role in modifying the density of interface states and affecting the charges diffusion in hybrid devices. The surface polarization difference and interface dipoles function in the same direction in hybrid devices with TiOx and ZnO dielectric layer, leading to enhanced n-type Seebeck effect, while the surface polarization difference and interface dipoles generate opposite impact on electrons diffusion in ITO/NiO/C60/Al, leading to the p-type to n-type transition in Seebeck effect. Therefore, inserting different oxide layers could effectively modulate the Seebeck effect of C60-based hybrid devices through the surface polarization difference and thermally-dependent interface dipoles, which presents as an effective approach to tune the vertical Seebeck effect in other organic functional devices.

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Publication details

The article was received on 18 Mar 2017, accepted on 17 May 2017 and first published on 17 May 2017


Article type: Paper
DOI: 10.1039/C7CP01736G
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Tuning the Seebeck Effect in C60-based Hybrid Thermoelectric Devices through Temperature-dependent Surface Polarization and Thermally-modulated Interface Dipoles

    Y. Liu, L. Xu, C. Zhao, M. Shao and B. Hu, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP01736G

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