Optimization of Thermoelectric Power Factor of Bilayer Graphene by Vertical Electric Field

We theoretically investigated thermoelectric (TE) effects in bilayer graphene (BLG) in the presence of a vertical electric field E-perpendicular to based on linear response theory combined with a Green's function technique. We found that the room-temperature Seebeck coefficient S and power factor PF for a fixed E-perpendicular to have maximum values (S-max and PFmax) at certain chemical potentials, and that both S-max and PFmax monotonically increase with increasing E-perpendicular to in the weak-E-perpendicular to region. Moreover, we analyzed recent experiments on the chemical potential dependence of S and PF of BLG with E-perpendicular to= 0 finding that experimental results are nicely reproduced by introducing the energy-dependent relaxation time tau(epsilon) = z(infinity) +A/vertical bar epsilon vertical bar(r) where e = 0 is the charge-neutral point. By applying the energy-dependent relaxation time to the finite E-perpendicular to cases, we predict PFmax -20 mW/(K-2 m) at 300 K when E-perpendicular to= 0.35 V/nm, which is approximately three times larger than that in the case of E-perpendicular to= 0.