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2D transition metal dichalcogenides (TMDCs) have revealed great promise for realizing electronics at the nanoscale. Despite significant interests that have emerged for their thermoelectric applications due to their predicted high thermoelectric figure of merit, suitable doping methods to improve and optimize the thermoelectric power factor of TMDCs have not been studied extensively. In this respect, molecular charge-transfer doping is utilized effectively in TMDC-based nanoelectronic devices due to its facile and controllable nature owing to a diverse range of molecular designs available for modulating the degree of charge transfer. In this study, the power of molecular charge-transfer doping is demonstrated in controlling the carrier-type (n- and p-type) and thermoelectric power factor in platinum diselenide (PtSe2) nanosheets. This, combined with the tunability in the band overlap by changing the thickness of the nanosheets, allows a significant increase in the thermoelectric power factor of the n- and p-doped PtSe2 nanosheets to values as high as 160 and 250 µW mK−2, respectively. The methodology employed in this study provides a simple and effective route for the molecular doping of TMDCs that can be used for the design and development of highly efficient thermoelectric energy conversion systems.

This study presents an investigation of the band structure in a semimetallic two-dimensional (2D) PtSe2 nanosheet based on thermoelectric transport phenomena. Mechanically exfoliated PtSe2 nanosheets, including naturally doped nonneutral samples, were studied. The gate-tuned electrical conductivity and thermoelectric power were measured by varying the temperature. Based on the combined effects of gate-tuning and shifting of zero-gate energy level, the semimetallic band structure of 2D PtSe2 was confirmed in the band over a wide energy range. Furthermore, the temperature dependence of transport properties was investigated to determine the band structure and intrinsic properties.