Enhanced the thermoelectric power factor of n-type Bi2Te3 thin film via energy filtering effect

Abstract

In recent years, Bi2Te3 thin films have gained interest in the field of thermoelectric power generation due to their promising thermoelectric performance. However, the poor performance of Bi2Te3 has limited its widespread applicability. To address this, we deposited Bi2Te3 films on soda lime glass substrates via thermal evaporation and annealed them at different temperature ranges between 100 and 350 °C. Our X-ray diffraction analysis showed that the best quality film was produced at a post-annealing temperature of 350 °C, while the as-deposited sample yielded a low-quality film. We then analyzed the surface morphology of the prepared sample using scanning electron microscopy and found that the grains were highly intact with a uniformly aligned granular surface morphology and no porosity. By controlling the density and grain size, we were able to improve the Seebeck coefficient and electrical conductivity. Specifically, the Seebeck coefficient value increased up to 135 μV/°C due to the energy filtering effect at small grain boundaries, while the electrical conductivity improved by raising the charge carrier mobility and reducing grain size, thus increasing the conductivity of the tiny domain. Consequently, the Bi2Te3 thin film with a small grain size exhibited the highest thermoelectric power factor of 15.30 μW cm−1 C−2 at room temperature. Our findings suggest that the thermal evaporation technique is an effective method for growing Bi2Te3 thin films with improved thermoelectric properties.