Spin polarized thermoelectric feature of graphitic carbon nitride nanoribbon: An in-silico study

Abstract

Herein, we report very large spin polarized thermoelectric figure merit (ZsT = 20) in the ferromagnetic configuration of a two-probe system formed by a two-dimensional nanosheet of graphitic carbon nitride [g-C4N3]. In addition, we observed that the Seebeck coefficient of the system is completely spin polarized in FM configuration. Our non-equilibrium Green's function-based density functional theoretical study reveals that, due to spin flipping of one of the electrodes, this spin dependence of thermoelectric figure merit (ZsT) vanishes. Interestingly, charge dependent thermoelectric figure of merit (ZcT = 0.14) is reported to be 102 times lower than that of its spin dependent counterpart in the ferromagnetic configuration. The observed spin polarized thermoelectric feature is attributed to the ferromagnetic ground state of the two-dimensional nanosheet of g-C4N3.. In ferromagnetic configuration, the central molecule favours better charge transport indicating high degree of electrical conductance (Ge), low charge Seebeck coefficient and eventually low ZcT of the system. However, ZsT is much higher due to large spin polarized Seebeck coefficient in the spin up channel of the ferromagnetic state. All these observations have been supported by the spin polarized transmission spectra analyses and its slope at Fermi level which establishes the system as spin dependent p-type thermoelectric material with promising ZsT.