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where S refers to the Seebeck coefficient, G represents the elec tronic conductance, T corresponds to the absolute temperature and σ = σ el + σ ph refers to the total thermal conductance,

The rapid development of synthesis and fabrication techniques has opened up a research upsurge in two-dimensional material heterostructures, which have received extensive attention due to their superior physical and chemical properties. Currently, thermoelectric energy conversion is an effective means to deal with the energy crisis and increasingly serious environmental pollution. Therefore, an in-depth understanding of thermoelectric transport properties in two-dimensional heterostructures is crucial for the development of micro-nano energy devices. In this review, the recent progress of two-dimensional heterostructures for thermoelectric applications is summarized in detail. Firstly, we systematically introduce diverse theoretical simulations and experimental measurements of the thermoelectric properties of two-dimensional heterostructures. Then, the thermoelectric applications and performance regulation of several common two-dimensional materials, as well as in-plane heterostructures and van der Waals heterostructures, are also discussed. Finally, the challenges of improving the thermoelectric performance of two-dimensional heterostructures materials are summarized, and related prospects are described.

Inspired by the novel mechanism of reducing thermal conductivity by local phonon resonance instead of by inducing structural defects, we investigate the effect of side branching on the thermoelectric properties of [Formula: see text] nanoribbons, and prove that side branching is a highly efficient mechanism for enhancing the thermoelectricity of different kinds of nanoribbons. For both armchair and zigzag [Formula: see text] nanoribbons, the side branches result in not only significant blocking of phonon transport but also notable increase of the Seebeck coefficient. Consequently, the thermoelectric figure of merit of the armchair [Formula: see text] nanoribbon is boosted from 0.72 to as high as 1.93, and the originally non-thermoelectric metallic zigzag [Formula: see text] nanoribbon is turned into a thermoelectric material due to the appearance of the band gap induced by the side branches. These results mean that the mechanism of branching is not only very efficient, but also takes effect regardless of the original properties of the nanoribbons, and thus will hold great promise for its application in the thermoelectric field.

In this work, we investigate the electronic properties and thermoelectric performance of triangulene π-dimer junctions with the twist angle from 0° to 60° by using first-principles calculations in combination with a non-equilibrium Green's function method. It is found that the triangulene π-dimer can be transformed between nonmagnetic state and antiferromagnetic or ferromagnetic state by varying the twist angle. The reason is that the relative rotation between the monomers weakens the overlap of two single occupied molecular orbital. More importantly, our theoretical analysis shows that the ferromagnetic states of the triangulene π-dimer junctions at the twist angle of 20°, 30°, and 60° have outstanding thermoelectric performance. The corresponding ZT value is as high as around 6, which is mainly contributed from the spin splitting nature. This work is instructive to improve the thermoelectric properties of π-stacking molecular junctions or organic polymers.