Engineering thermoelectric performance in copper-doped graphene nanoribbons for energy-aware electronics.

Armchair graphene nanoribbons (AGNRs) are promising candidates for nanoscale thermoelectric applications due to their tunable bandgap and high electrical conductance. However, their inherently high thermal conductance limits thermoelectric efficiency. In this study, we investigate the effects of vacancy defects and copper (Cu) doping on the thermoelectric performance of AGNRs using the extended Hückel method combined with nonequilibrium Green's function (NEGF) formalism. The results show that the introducing vacancy defects reduces both the bandgap and phononic thermal conductance, thereby creating a favorable platform for thermoelectric enhancement. Low-concentration Cu doping, especially single-atom doping, improves electrical conductance and the Seebeck coefficient, resulting in a peak ZT value exceeding 1.5 at room temperature. The power factor is also significantly improved under optimized doping conditions. In contrast, high doping levels lead to reduced Seebeck coefficients and increased electronic thermal losses, lowering overall efficiency. These findings highlight the importance of precise control over dopant concentration and placement. Overall, this work demonstrates a viable approach for engineering high-performance thermoelectric materials using defect and dopant strategies, supporting future development of low-power, energy-harvesting devices in electrical and electronic systems.