Self-assembled Ni0.98Li0.02O and Zn0.98Al0.02O composite interface for thermoelectrics

Thermoelectric generators (TEGs) offer flexible and robust conversion of waste heat to electricity. Among the thermoelectric materials candidates, oxides have been rapidly developed in the last decade because of potential... [ view full abstract ]

Thermoelectric generators (TEGs) offer flexible and robust conversion of waste heat to electricity. Among the thermoelectric materials candidates, oxides have been rapidly developed in the last decade because of potential advantages over non-oxides in terms of chemical and thermal stability at high temperatures. One of the factors limiting the ideal performance of a conventional oxide TEG arises from the use of metal interconnects to ensure ohmic contact, which are vulnerable to inter-diffusion, cracking, evaporation, and oxidation. To overcome these challenges, Span and co-workers proposed the use of a direct p-n junction ^[1], despite the expected high electrical contact resistance. Using a composite interconnect from the desired p- and n-type oxide material at the interface (p-c-n) can increase the effective contact area and reduce the electrical contact resistance.

p-type NiO and n-type ZnO are promising oxide materials for high-temperature thermoelectrics ^{[2, 3]}. In the present work, we investigate a composite consisting of Ni_0.98Li_0.02O and Zn_0.98Al_0.02O, prepared by a citric acid sol-gel combustion method ^[4]. X-ray diffraction and scanning electron microscopy confirm the presence of both NiO and ZnO phases. Current-voltage characteristic of p-n and p-c-n junctions were investigated, with the latter showing less resistive behaviour, attributed to the increased effective contact area.

References

1.         Span, G., et al. Thermoelectric Power Conversion using Generation of Electron-Hole Pairs in Large Area p-n Junctions. in 2006 25th International Conference on Thermoelectrics. 2006.

2.         Woosuck Shin and Norimitsu Murayama, Li-Doped Nickel Oxide as a Thermoelectric Material. Japanese Journal of Applied Physics, 1999. 38(11B)

3.         T. D. Desissa, M.S., T. Norby, Electrical properties of a p-n heterojunction of Li-doped NiO and Al-doped ZnO for thermoelectrics. Submitted 2018.

4.         Chen, K.J., et al., The crystallization and physical properties of Al-doped ZnO nanoparticles. Applied Surface Science, 2008. 254(18): p. 5791-5795.