Highly-efficient thermoelectric pn-junction device based on bismuth telluride (Bi2Te3) and molybdenum disulfide (MoS2) thin films fabricated by RF magnetron sputtering technique

Abstract

Layered structure bismuth telluride and molybdenum disulfide thin films were successfully deposited on different substrates using radio-frequency magnetron sputtering technique. The structural, morphological, and thermoelectric transport properties of bismuth telluride and molybdenum disulfide thin films have been investigated systematically to fabricate high-efficient thermal energy harvesting thermoelectric device. The magnitude of the Seebeck coefficient of bismuth telluride thin films decreases with increase in film thickness. Bismuth telluride grown at 350 °C for 10 min, which is approximately 120 nm, displays a maximum Seebeck coefficient of −126 μV K−1 at 435 K. The performance shows strong temperature dependence when the films were deposited at 300 °C, 350 °C, and 400 °C. The power factor increases from 0.91 × 10−3 W/mK2 at 300 K to about 1.4 × 10−3 W/mK2 at 350 K. Molybdenum disulfide films show the positive Seebeck coefficient values and their Seebeck coefficient increases with film thickness. The AFM images of bismuth telluride thin films display a root-mean-square (rms) roughness of 32.3 nm and molybdenum disulfide thin films show an rms roughness of 6.99 nm when both films were deposited at 350 °C. The open-circuit voltage of the pn-junction thermoelectric generator (TEG) device increases with increase in ΔT to about 130 mV at ΔT = 120 °C. We have demonstrated a highly efficient pn-junction TEG device for waste heat recovery applications.

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

“…The individual planar patterns devices were placed 0.15 cm apart. The size of our entire thermoelectric structure with multiple planar legs was 7.5 cm × 3.6 cm 35 . Both MoS 2 and WS 2 films are deposited at the substrate temperature of 450 °C and annealed at 600 °C in Argon environments for 1 hour.…”

“…All the films are grown for different period of time from 10-45 minutes to obtain various film thickness. The films were annealed at 600 °C and 700 °C under argon atmosphere at a flow rate of 50 sccm to improve the crystallinity of the films 35 .…”

“…The devices was fabricated on glass substrate; first WS 2 films were deposited followed by MoS 2 films to make pn junction at one end of the structure which is considered as a hot end. Other end of the WS 2 and MoS 2 legs were connected using 60 nm of Cr metal contact using thermal evaporation technique 35 .…”

“…Total thermal conductivity was measured using TDTR, operated at modulation frequency of 0.824-9.68 MHz. For temperature dependent electrical study, the samples are inserted into the cryostat and standard linear four-probe technique was used for data acquisition 35 .…”

A high-efficient thermoelectric generator with a built-in field

“…Inspired by the success of the metallurgical junctions in transforming Silicon into many sophisticated semiconductor devices, they were attempted in transforming thermoelectric materials into cost-effective devices. By directly connecting the nand the p-type thermocouple's legs [16][17][18][19][20][21][22][23][24][25][26] , it was found that so formed p-n junction enhanced the device's lifetime and efficiency. Although the effect of such a p-n junction on the Seebeck coefficient is modest, it was proved to be effective in enhancing the device durability 27,28 .…”