Achieving Boosted Thermoelectric Power Factor of MoS₂ through Selective Charged-Impurity-Free Doping.

Abstract

Ultrathin two-dimensional (2D) transition metal dichalcogenides (TMDs) exhibit unique band structures, allowing promising thermoelectric properties. Achieving a high power factor (<i>PF</i>) for thermoelectric generators (TEGs) requires optimizing both the Seebeck coefficient (<i>S</i>) and electrical conductivity (<i>σ</i>). Conventional surface charge-transfer doping can be a solution to enhance <i>σ</i> by introducing additional electrons. However, residual organic dopants act as charged impurities, degrading charge transport and lowering <i>PF</i> due to the intensified trade-off between carrier concentration and <i>S</i>. We propose a charged-impurity-free diffusion doping method for CVD-grown molybdenum disulfide (MoS₂) to enhance <i>PF</i>. By depositing organic dopants on the contact region and enabling electron diffusion into the channel via carrier concentration gradients, <i>σ</i> is improved while maintaining high <i>S</i>. This approach achieves a record-high <i>PF</i> of 1698 μW/mK² for CVD-grown TMDs. Our strategy offers a promising pathway to enhance thermoelectric performance, not limited by the exacerbated trade-off relationship observed in conventional doping methods.