fig12

Figure 12. (A-D) Cross-sectional microstructure characterization of the PVP/Ag₂Se composite films: (A) a typical cross-sectional TEM image indicating the existence of pores surrounded by several grains (grains A-G); (B) the enlarged image of the red square marked in (A) showing a coherent interface and a PVP layer; (C) the enlarged image of the green square marked in (A) containing four Ag₂Se grains coated with PVP; (D) an HRTEM image of the white square marked in (C) containing a coherent interface, with a corresponding FFT image given in the inset; Temperature dependent (E) Seebeck coefficient, electrical conductivity and power factor; and (F) carrier mobility and concentration of the composite film; (G-I) Flexibility test of the composite film: (G) The electrical conductivity and Seebeck coefficient of the composite film as a function of bending times with a bending radius of 4 mm; (H) the degradation of power factor of the composite films as a function of bending times with a bending radius of 4 mm; (I) the stress-strain curve of the composite films (P0: hot-pressed Ag₂Se films; P1: hot-pressed PVP/Ag₂Se films). Reproduced with permission from Ref^[97]. Copyright^© 2021. Elsevier. FFT: Fast Fourier transform; HRTEM: high-resolution transmission electron microscopy; PVP: poly(vinylpyrrolidone); TEM: transmission electron microscopes.