Low cost Ni-based electrodeposited pn-junction thermoelectric device for thermoelectric sensor application

This paper proposes a novel low cost atoxic Ni-based pn-junction thermoelectric device. The device fabrication begins with the growth of Ni-CuI and Ni-ZnO films on ITO by electrodeposition method followed by exploring their structural, morphological and thermoelectric properties. XRD and SEM analysis revealed high crystallinity and uniform nano grains in both layers. Hot probe confirmed the p-type Ni-CuI and n-type Ni-ZnO. These high conductive films exhibited thermoelectric energy that was calculated using the Seebeck effect. The thermoelectric effect showed that an increase in temperature result in an increase in induced electromotive force (emf). From the thermo emf measurements, the induced emf for Ni-CuI film was found to be 2.2 mV/K and 2.2 mV/K for Ni-ZnO film at 300 °C. The Seebeck values of Ni-CuI and Ni-ZnO were calculated to be 83 μVK⁻¹ and −98 μVK⁻¹ respectively. The hot probe method showed that the p-type Ni-CuI and n-type Ni-ZnO thin films were dense and exhibited thermoelectric figure of merit (ZT) of 1.2 and 1.5 up to the temperature of 300 ̊ C. The temperature-dependent power factor of Ni-CuI and Ni-ZnO was found to be 436 µWm^-1K⁻² and 977 µWm^-1K⁻² respectively. The fabricated pn-junction device produced the temperature-dependent output voltage 500 mV at 300 °C. The thermoelectric device generated a maximum power of 1250 pW that reveals that the Ni-CuI/Ni-ZnO pn-junction devices are likely suitable for thermoelectric sensor applications.