Nanoscale homojunction thermoelectric generator built in defect-engineered MoS2

The relatively low efficiency and costly composition of conventional thermoelectric generators (TEGs) hinder pragmatic usage despite their high Carnot efficiency. A PN-junction-based TEG is one candidate to resolve the noted drawbacks, but electron-hole recombination at the junction severely reduces the efficiency and limits the compactness. Here, we propose the nanoscale homojunction thermoelectric generator by engineering the ${\mathrm{MoS}}_{2}$ grain boundary. Ab initio scanning Seebeck microscopy revealed that the influence of deep-level wave functions of atomic defects broadens out to a nanoscale, leading to the doping-tunable Seebeck domain with a different magnitude or even inverted sign. This thermopower utilization using vestiges of localized defect states enables exceptional integration density in a single material, while the simple oxygen substitution inflates the efficiency by barricading the recombination at the junction. Our finding suggests that inevitable structural defects could pave the way for actualizing productive thermoelectric energy recycling at the nanoscale.