Abstract
Thermoelectric junctions are often made of components of different materials characterized by distinct transport properties. Single material junctions, with the same type of charge carriers, have also been considered to investigate various classical and quantum effects on the thermoelectric properties of nanostructured materials. We here introduce the concept of defect-induced thermoelectric voltage, namely, thermodefect voltage, in graphene nanoribbon (GNR) junctions under a temperature gradient. Our thermodefect junction is formed by two GNRs with identical properties except the existence of defects in one of the nanoribbons. At room temperature the thermodefect voltage is highly sensitive to the types of defects, their locations, as well as the width and edge configurations of the GNRs. We computationally demonstrate that the thermodefect voltage can be as high as 1.7 mV K−1 for 555–777 defects in semiconducting armchair GNRs. We further investigate the Seebeck coefficient, electrical conductance, and electronic thermal conductance, and also the power factor of the individual junction components to explain the thermodefect effect. Taken together, our study presents a new pathway to enhance the thermoelectric properties of nanomaterials.
Highlights
Thermoelectricity is the phenomenon of induced electrical potential difference due to a temperature gradient and vice versa
Depending on the position of the line vacancy we call it symmetrical, asymmetrical, or edge longitudinal vacancy when the vacancy line is situated in the middle i.e., (W + 1)/2-th line, in the (W + 3)/2-th line, or at the edge of the armchair GNRs (AGNRs), respectively
We see that 13-AGNR stands out with considerably higher voltages for dislocation defects compared to the others. The reason for this can be attributed to the appearance of a wide resonance associated with quasi-localized states around the zero energy within the semiconducting gap of the 13-AGNR, whereas the presence of dislocations do not to the same degree affect the electronic structure with already existing flat bands in the zigzag GNRs (ZGNRs) or the metallic state in the AGNR
Summary
Thermoelectricity is the phenomenon of induced electrical potential difference due to a temperature gradient and vice versa. To establish the concept of the thermodefect voltage, we choose graphene nanoribbons (GNRs) where both GNRs have exactly the same size (both length and width) and edge configurations, the only difference being the existence of crystallographic defects in one of the GNRs. The pristine GNR acts as the reference component with respect to the defective GNR, in order to isolate and analyze the effect of different defects on the thermoelectric properties. In order to explain and understand the behavior of the thermodefect voltage, we investigate the thermoelectric properties of single GNRs, both in absence and presence of various defects These analyses allow us to identify which defects result in higher performance in terms of thermo-
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