Polarization Effect of MoO₃ Increases the Thermoelectric Properties Based on the PbS Quantum-Dots Doped P3HT Devices

In this article, we fabricated PbS quantum-dots doped P3HT thin films, and their thermoelectric properties were enhanced by introducing the MoO3 interface layer into the ITO/PbS-doped P3HT/Al device. We found that the electrical conductivity of the P3HT thin film increased after only doping PbS quantum-dots, while its Seebeck coefficient decreased. After introducing the MoO3 interface layer into the device forming the ITO/P3HT/MoO3/Al structure, its electrical conductivity and the Seebeck coefficient increased simultaneously. Since the dielectric constant of MoO3 increases with rising temperature, we considered that the MoO3 interface layer brings a polarization effect with temperature changes. A polarization difference occurs between the MoO3 layer and the electron–phonon coupling in the P3HT material. The polarization difference and the entropy difference together drive the carriers to transport from the high temperature to the low temperature. The capacitance–frequency (C–F) characteristic results further confirmed that the polarization effect of MoO3 increases as temperature rises. The polarization effect promotes the enhancement of thermoelectric properties in the ITO/P3HT/MoO3/Al device, leading to a big Power Factor (PF) of 0.203 μW/mK2 at 90 °C. We presuppose that the introduction of a similar metal oxide interface layer may be an effective enhancement for the thermoelectric properties of materials and devices.