Compositional disorder and its effect on the thermoelectric performance of Zn₃P₂nanowire–copper nanoparticle composites

Abstract

Recent studies indicated that nanowire format of materials is ideal for enhancing the thermoelectric performance of materials. Most of these studies were performed using individual nanowires as the test elements. It is not currently clear whether bulk assemblies of nanowires replicate this enhanced thermoelectric performance of individual nanowires. Therefore, it is imperative to understand whether enhanced thermoelectric performance exhibited by individual nanowires can be extended to bulk assemblies of nanowires. It is also imperative to know whether the addition of metal nanoparticle to semiconductor nanowires can be employed for enhancing their thermoelectric performance further. Specifically, it is important to understand the effect of microstructure and composition on the thermoelectric performance on bulk compound semiconductor nanowire-metal nanoparticle composites. In this study, bulk composites composed of mixtures of copper nanoparticles with either unfunctionalized or 1,4-benzenedithiol (BDT) functionalized Zn₃P₂ nanowires were fabricated and analyzed for their thermoelectric performance. The results indicated that use of BDT functionalized nanowires for the fabrication of composites leads to interface-engineered composites that have uniform composition all across their cross-section. The interface engineering allows for increasing their Seebeck coefficients and electrical conductivities, relative to the Zn₃P₂ nanowire pellets. In contrast, the use of unfunctionalized Zn₃P₂ nanowires for the fabrication of composite leads to the formation of composites that are non-uniform in composition across their cross-section. Ultimately, the composites were found to have Zn₃P₂ nanowires interspersed with metal alloy nanoparticles. Such non-uniform composites exhibited very high electrical conductivities, but slightly lower Seebeck coefficients, relative to Zn₃P₂ nanowire pellets. These composites were found to show a very high zT of 0.23 at 770 K, orders of magnitude higher than either interface-engineered composites or Zn₃P₂ nanowire pellets. The results indicate that microstructural composition of semiconductor nanowire-metal nanoparticle composites plays a major role in determining their thermoelectric performance, and such composites exhibit enhanced thermoelectric performance.

Lead Chalcogenide Nanoparticles and Their Size-Controlled Self-Assemblies for Thermoelectric and Photovoltaic Applications

“…For the determination of the pellet thermal conductivity (κ), the following were measured experimentally: pellet density (ρ) using Archimedes principle, heat capacity (Cp) using differential scanning calorimetry (DSC), and thermal diffusivity (α) using laser flash measurement. On the basis of these measurements, κ was determined using the relationship, κ = αρCp. − All measurements were performed in a vacuum of 1 mTorr or lower. Finally, the thermoelectric figure of merit (zT) of the pellets was calculated using the well-known relationship, zT = ( S 2 σ T )/κ. − …”

“…On the basis of these measurements, κ was determined using the relationship, κ = αρCp. − All measurements were performed in a vacuum of 1 mTorr or lower. Finally, the thermoelectric figure of merit (zT) of the pellets was calculated using the well-known relationship, zT = ( S 2 σ T )/κ. − …”

Engineering Efficient Thermoelectrics from Large-Scale Assemblies of Doped ZnO Nanowires: Nanoscale Effects and Resonant-Level Scattering

“…However, a destructive technique involving chipping consolidated pellets, followed by loading these chips onto TEM grids was employed for the HRTEM characterization of the pellets. 50,51 Thermal conductivity measurements of the consolidated pellets were done in accordance with ASTM standard E1461. 52 The three parameters necessary for the determination of thermal conductivities of the pellets, density, heat capacity and thermal diffusivity, were respectively obtained using Archimedes' principle, differential scanning calorimetry (DSC) and laser flash analysis (LFA).…”

“…As-obtained pellets were directly employed for SEM, XRD, and EDS analysis of the samples. However, a destructive technique involving chipping consolidated pellets, followed by loading these chips onto TEM grids was employed for the HRTEM characterization of the pellets. , …”

Growth and characterization of indium-doped Zn3P2 bulk crystals

“…Zinc phosphide (Zn 3 P 2 ) is an earth-abundant II 3 V 2 -type compound semiconductor that has attractive physical properties for applications such as solar cells, [1][2][3] photodetectors, 4) thermoelectric devices, 5,6) and half-metallic dilute magnetic semiconductors. 7,8) Among these applications, Zn 3 P 2 has been vigorously studied as an absorber for solar cells because it has a direct band gap of around 1.5 eV, a high absorption coefficient (>10 4 cm −1 ) in the visible region, 9) and a long diffusion length of minority carriers.…”