Potential improvement in power factor of (Bi0.98Ge0.02)2Te2.7Se0.3 compound due to defect engineering

In recent years, thermoelectricity has gained popularity as a renewable energy source, with applications including Peltier coolers and thermoelectric generators, particularly focusing on materials, like bismuth telluride and its doped derivatives. This study investigates Bi 2 Te 3 , (Bi 0.98 Ge 0.02 ) 2 Te 2.7 Se 0.3 , and (Bi 0.98 Ge 0.02 ) 2 Te 2.7 Se 0.3 /Bi 2 Te 3 synthesized via solid-state reaction, revealing a rhombohedral structure in the XRD pattern and confirming chemical composition and composite homogeneity through EDS and porosity, density, and selenium integration via FESEM. Electrical resistivity decreases with rising temperature, while the Seebeck coefficient shows a linear increase, indicating n-type semiconductor behaviour. The highest power factor of 108 μW/mK 2 is achieved by (Bi 0.98 Ge 0.02 ) 2 Te 2.7 Se 0.3 , contrasting with the lowest of 20 μW /mK 2 observed for the pristine sample at 250 °C. Ge atoms enhance the power factor of (Bi 0.98 Ge 0.02 ) 2 Te 2.7 Se 0.3 by 5.4 times compared to the pristine compound, making it ideal for thermoelectric applications through acceptor behaviour and defect engineering.