Fig. 1: Strategy to improve thermoelectric performance via grain boundary and interface engineering.
From: High figure-of-merit for ZnO nanostructures by interfacing lowly-oxidized graphene quantum dots
a Illustration of graphene quantum dots (GQDs)-decorated 3D ZnO (3D GQD@ZnO) obtained by dipping the 3D ZnO into GQD solution. b Schematic of energy filtering and phonon scattering effect at grain boundaries and GQD/ZnO interfaces in the 3D GQD@ZnO. c Transmission electron microscopy (TEM) image showing decoration of GQDs in 3D ZnO. Yellow circles of Fast Fourier-Transform (FFT) patterns indicate a hexagonal pattern of GQD, and white circles show an atomic plane of wurtzite ZnO structure. The inset of c indicates a high-resolution (HR)-TEM image of GQD coated on 3D ZnO. Temperature-dependent d Seebeck coefficient, e thermal conductivity, and f Figure-of-merit (zT) for 3D ZnO with varying grain sizes and its heterostructure with GQDs (3D GQD@ZnO). Filled circles are measured values, and open circles indicate the estimated values obtained using a modified Debye-Callaway model. Error bars shown in the Fig. 1 represent the standard deviation (SD).
