A thin film efficient pn-junction thermoelectric device fabricated by self-align shadow mask

Large area highly crystalline MoS₂ and WS₂ thin films were successfully grown on different substrates using radio-frequency magnetron sputtering technique. Structural, morphological and thermoelectric transport properties of MoS_2, and WS₂ thin films have been investigated systematically to fabricate high-efficient thermal energy harvesting devices. X-ray diffraction data revealed that crystallites of MoS₂ and WS₂ films are highly oriented in 002 plane with uniform grain size distribution confirmed through atomic force microscopy study. Surface roughness increases with substrate temperature and it plays a big role in electron and phonon scattering. Interestingly, MoS₂ films also display low thermal conductivity at room temperature and strongly favors achievement of higher thermoelectric figure of merit value of up to 1.98. Raman spectroscopy data shows two distinct MoS₂ vibrational modes at 380 cm^-1 for E¹_2g and 410 cm^-1 for A_1g. Thermoelectric transport studies further demonstrated that MoS₂ films show p-type thermoelectric characteristics, while WS₂ is an n-type material. We demonstrated high efficient pn-junction thermoelectric generator device for waste heat recovery and cooling applications.