Details

Autor(en) / Beteiligte

• James, Derak
• Lu, Xu
• Nguyen, Alexander Chi
• Morelli, Donald
• Brock, Stephanie L

Titel

Design of Lead Telluride Based Thermoelectric Materials through Incorporation of Lead Sulfide Inclusions or Ligand Stripping of Nanosized Building Blocks

Ist Teil von

• Journal of physical chemistry. C, 2015-03, Vol.119 (9), p.4635-4644

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2015

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Design of thermoelectric materials focuses on the optimization of several unfavorably coupled factors: electrical conductivity, Seebeck coefficient, and thermal conductivity. Recent work in thermoelectrics has focused on decreasing lattice thermal conductivity by nanostructuring thermoelectric materials, while recent work in photovoltaics has demonstrated ligand stripping as a means to increased electron mobility in thin films of nanoparticles. In the present work, these two features are combined. A multigram scale synthesis of dispersible, lead telluride nanocrystals (25–50 nm) is developed using hot-injection methods in common organic solvents. These nanocrystals (NCs) are ligand stripped with sulfide (PbTe-S) or iodide (PbTe-I) sources to result in p-type or n-type materials with large Seebeck coefficients at room temperature of 520 or −540 μV·K–1, respectively. Sequential stripping with sulfide and then iodide (PbTe-SI) resulted in a small Seebeck due to counter doping. PbTe-S and PbTe-SI are found to generate nanostructured composites by growth of lead sulfide nanocrystals (∼50–60 nm) in situ upon annealing. However, the electrical conductivities are low (<1 S·cm–1) due to excess doping during the ligand stripping. Intentional formation of a nanocomposite (PbTe–PbS) is achieved by combining PbTe NCs with 4–6 nm diameter lead sulfide particles via mixing by incipient wetness with a target of 8 mol % lead sulfide. The resulting nanocomposite is n-type with a Seebeck coefficient of −160 μV·K–1 and an electrical conductivity of 42 S·cm–1 at room temperature. The lattice thermal conductivities of all materials at room temperature are substantially lower than those of bulk lead telluride (2.0 W m–1·K–1). However, thermoelectric figure of merit (ZT) values are low for all samples (maximum ZT = 0.03 for PbTe–PbS), attributed primarily to the low electrical conductivities. This work underscores the importance of developing new methods for augmenting electrical conductivity if nanoparticle assemblies are to be practically employed in thermoelectrics.