- Title
- Effect of native defects on thermoelectric properties of copper iodide films
- Creator
- Murmu, Peter P.; Karthik, Varun; Chong, Shen V.; Rubanov, Sergey; Liu, Zihang; Mori, Takao; Yi, Jiabao; Kennedy, John
- Relation
- Emergent Materials Vol. 4, Issue 3, p. 761-768
- Publisher Link
- http://dx.doi.org/10.1007/s42247-021-00190-w
- Publisher
- Springer
- Resource Type
- journal article
- Date
- 2021
- Description
- Copper iodide (CuI) is a promising p-type wide bandgap semiconductor for optoelectronic and thermoelectric applications. Its p-type conductivity is due to the existence of native defect copper vacancy (VCu). We report the effect of native defects on microstructural, optical, and thermoelectric properties of ion beam sputtered CuI films via vacuum annealing. X-ray diffraction results showed that the CuI film is a γ-phase with zinc blende crystal structure, further confirmed by Raman spectroscopy analysis. Cu-rich region was observed in vacuum-annealed films by cross-section transmission electron microscopy and element mapping, while as-deposited film is very uniform. As-deposited film exhibited an electrical conductivity σ = 22.9 S cm−1, hole density p = 3.3 × 1019 cm−3, hole mobility μp = 4.3 cm2 V−1 s−1, and the Seebeck coefficient α = 244.9 μV K−1 which yielded a power factor of α2σ = 137.8 μW m−1 K−2, whereas vacuum annealing led to the large increase in Seebeck coefficient α = 561.8 μV K−1 and a strongly increased power factor, α2σ = 443.5 μW m−1 K−2 along with the slightly decreased conductivity, σ = 14.0 S cm−1 when the film was annealed at 100 °C. The increase in Seebeck coefficient is attributed to the decrease in hole density along with energy-dependent scattering of charge carriers at the grain boundaries between CuI and Cu-rich region. The decreased hole density is due to the formation of less VCu in high vacuum annealing condition. In addition, the film exhibited 60–85% transmission in the visible region. The results demonstrated that by a simple vacuum annealing, a high performance transparent thermoelectric material could be achieved, which provides a simple strategy for improving the properties of thermoelectric materials.
- Subject
- thermoelectric; copper iodide; conductivity; seekbeck coefficient; power factor; x-ray transmission
- Identifier
- http://hdl.handle.net/1959.13/1474841
- Identifier
- uon:49395
- Identifier
- ISSN:2522-5731
- Language
- eng
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