Towards an efficient p-n heterojunction in ternary composite material based polypyrrole, metal oxide and surface functionalized graphene for thermoelectric properties enhancement

The thermoelectric properties of ternary p-n heterojunction composites based on [p-type polymer/surface treated graphene/metal oxide in ceramic form] were investigated in this study. In the presence of ceramic tungsten oxide (WO ₃) particles and diazonium salt surface treated graphene, a simple in-situ pyrrole polymerization method was carried out. FTIR, Raman scattering, X-ray diffraction analysis (XRD), diffuse reflectance UV-Vis spectroscopy, I-V characteristics, and scanning electron microscopy - energy dispersive spectrometer (SEM-EDS) have all been used to characterize composites. Based on the comparison of observed thermoelectric parameters, the ternary composite created by PPy-FrGO (DS-SO ₃H)-WO ₃ based on functionalized graphene with diazonium salt (DS-SO ₃H) was chosen as having superior thermoelectric capabilities than the other samples. This advancement was made possible by combining two strategies: graphene functionalization with a conjugated diazonium salt and thermochemical treatment of tungsten oxide with the sol-gel method and sintering procedure. Functionalization reduced thermal conductivity (= 0.127 W.m ⁻¹. K ⁻¹) while adding ceramic tungsten oxide boosted electrical conductivity ( = 1087 S/m), resulting in a merit coefficient (ZT) of 1.63 × 10 ⁻⁴.