Enhanced Thermoelectric Power Factor in Carrier‐Type‐Controlled Platinum Diselenide Nanosheets by Molecular Charge‐Transfer Doping

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. Unambiguous signatures of n‐type and p‐type doping behaviors are observed by solution‐depositing strong molecular reductant (benzyl viologen) and oxidant (magic blue), respectively, on the surface of PtSe2 nanosheets with various layer thicknesses. The thermoelectric power factor value corresponds to relatively one of the highest values among doped transition metal dichalcogenides and higher than those achieved by electrostatically doped PtSe2 nanosheets.