International Journal of Physics

International Journal of Physics | Vol. 1, No. 10, October 2010 | pp. 78–86

DOI: 10.46882/2010/IJP/000010

Article Type: Original Research Paper

Title: Thermoelectric Power Factor Enhancement in Nanostructured Silicon-Germanium Alloys via Energy Filtering Effects

Names of Authors: O. S. Adeyemi¹, K. N. Gupta²

Authors’ Affiliations: ¹Department of Physics, University of Abuja, Abuja, Nigeria; ²Department of Physics, Indian Institute of Science, Bangalore, India

Abstract: Silicon-germanium (Si-Ge) alloys are widely used in high-temperature thermoelectric generators, such as radioisotope thermoelectric generators for space exploration. However, their conversion efficiency remains limited by a coupled relationship between electrical conductivity and the Seebeck coefficient. This work presents a transport model designed to enhance the thermoelectric power factor of nanostructured n-type Si_0.8Ge_0.2 alloys by utilizing energy filtering effects at grain boundaries. The carrier transport equations were resolved using the Boltzmann transport equation under the relaxation time approximation. The model incorporates a series of potential barriers designed to scatter low-energy carriers while allowing high-energy electrons to pass unhindered. Our calculations indicate that introducing a potential barrier height of 0.15 eV increases the Seebeck coefficient from -140 μV/K to -215 μV/K at 900 K. Although the filtering barriers cause a 25% drop in total electrical conductivity, the net power factor (S²σ) rises by 38%, reaching a maximum value of 4.2 x 10^-3 W/(mK²). This enhancement is highly sensitive to the spatial distribution of doping impurities and the average grain size, with an optimal grain boundary spacing identified at 25 nm. These results suggest that tailoring grain boundary potential heights can optimize the power factor of bulk Si-Ge materials.

Keywords: Thermoelectric materials; Silicon-germanium alloys; Power factor; Seebeck coefficient; Energy filtering; Boltzmann transport equation; Grain boundaries; Carrier relaxation time.

Manuscript Timeline: Received: July 19, 2010; Revised: September 04, 2010; Accepted: September 29, 2010; Published: October 22, 2010.

Citation: Adeyemi, O. S., & Gupta, K. N. (2010). Thermoelectric Power Factor Enhancement in Nanostructured Silicon-Germanium Alloys via Energy Filtering Effects. International Journal of Physics, 1(10), 78–86.

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