More Like this

1. Examining the electron transport in chalcogenide perovskite BaZrS 3

   https://doi.org/10.1039/d1tc00374g  

   Osei-Agyemang, Eric ; Koratkar, Nikhil ; Balasubramanian, Ganesh ( March 2021 , Journal of Materials Chemistry C)

   null (Ed.)

   Orthorhombic BaZrS 3 is a potential optoelectronic material with prospective applications in photovoltaic and thermoelectric devices. While efforts exist on understanding the effects of elemental substitution and material stability, fundamental knowledge on the electronic transport properties are sparse. We employ first principles calculations to examine the electronic band structure and optical band gap and interrogate the effect of electron transport on electrical and thermal conductivities, and Seebeck coefficient, as a function of temperature and chemical potential. Our results reveal that BaZrS 3 has a band gap of 1.79 eV in proximity of the optimal 1.35 eV recommended for single junction photovoltaics. An absorption coefficient of 3 × 10 5 cm −1 at photon energies of 3 eV is coupled with an early onset to optical absorption at 0.5 eV, significantly below the optical band gap. The carrier effective mass being lower for electrons than holes, we find the Seebeck coefficient to be higher for holes than electrons. A notable (≈1.0 at 300 K) upper limit to the thermoelectric figure of merit, obtained due to high Seebeck coefficient (3000 μV K −1 ) and ultra-low electron thermal conductivity, builds promise for BaZrS 3 as a thermoelectric. 

   more » « less
2. New Zintl Phase Yb 10 MgSb 9 with High Thermoelectric Performance

   https://doi.org/10.1002/aenm.202300393  

   Borgsmiller, Leah ; Li, Qingyuan ; Toriyama, Michael Y. ; Snyder, G. Jeffrey ( April 2023 , Advanced Energy Materials)

   Yb₁₀MgSb₉is a new Zintl compound (with a composition closer to Yb_10.5MgSb₉) and a promising thermoelectric material first reported in this work. Undoped Yb₁₀MgSb₉has an ultralow thermal conductivity due to crystallographic complexity and exhibits a relatively high peak p‐type Seebeck coefficient and high electrical resistivity. This is consistent with Zintl counting and density functional theory (DFT) calculations that the composition Yb_10.5MgSb₉should be a semiconductor. Na is found experimentally to be an effective p‐type dopant potentially due to the replacement of Na⁺for Yb²⁺, allowing for a significant decrease in electrical resistivity. With doping, a dramatic improvement of electrical conductivity is observed and the glass‐like thermal conductivity remains low, allowing for a significant enhancement of the thermoelectric figure of merit,zT. Doping increases thezTfrom 0.23 in undoped Yb₁₀MgSb₉to 1.06 in 7 at% Na‐doped Yb₁₀MgSb₉at 873K. This high thermoelectric performance found through Na‐doping places this material amongst the leading p‐type Zintl thermoelectrics, making it a promising candidate for future studies and high‐temperature thermoelectric applications.

    

   more » « less
3. Transport Properties of Ag‐doped ZnSb

   https://doi.org/10.1002/zaac.202000314  

   Eklöf, Daniel ; Fischer, Andreas ; Grins, Jekabs ; Scherer, Wolfgang ; Häussermann, Ulrich ( November 2020 , Zeitschrift für anorganische und allgemeine Chemie)

   The intermetallic compound ZnSb is a (II‐V) narrow gap semiconductor with interesting thermoelectric properties. Electrical resistivity, Hall coefficient, thermopower and thermal conductivity were measured up to 400 K on Ag‐doped samples with concentrations 0.2, 0.5, 1, 2, and 3 at.%, which were consolidated to densities in excess of 99.5 % by spark plasma sintering. The work confirms a huge improvement of the thermoelectric Figure‐of‐merit,ZT, upon Ag doping. The optimum doping level is near 0.5 at.% Ag and results inZTvalues around 1.05 at 390 K. The improvement stems from a largely decreased resistivity, which in turn relates to an increase of the hole charge carrier concentration by two orders of magnitude. It is argued that Ag can replace minute concentrations of Zn (on the order of 0.2 at.%) in the crystal structure which enhances the intrinsic impurity band of ZnSb. Excess Ag was found to segregate in grain boundaries. So the best performing material may be considered as a composite Zn_~0.998Ag_~0.002Sb/Ag_~0.003.

    

   more » « less
4. High Thermoelectric Performance in Supersaturated Solid Solutions and Nanostructured n‐Type PbTe–GeTe

   https://doi.org/10.1002/adfm.201801617  

   Luo, Zhong‐Zhen ; Zhang, Xiaomi ; Hua, Xia ; Tan, Gangjian ; Bailey, Trevor P. ; Xu, Jianwei ; Uher, Ctirad ; Wolverton, Chris ; Dravid, Vinayak P. ; Yan, Qingyu ; et al ( June 2018 , Advanced Functional Materials)

   Sb‐doped and GeTe‐alloyed n‐type thermoelectric materials that show an excellent figure of meritZTin the intermediate temperature range (400–800 K) are reported. The synergistic effect of favorable changes to the band structure resulting in high Seebeck coefficient and enhanced phonon scattering by point defects and nanoscale precipitates resulting in reduction of thermal conductivity are demonstrated. The samples can be tuned as single‐phase solid solution (SS) or two‐phase system with nanoscale precipitates (Nano) based on the annealing processes. The GeTe alloying results in band structure modification by widening the bandgap and increasing the density‐of‐states effective mass of PbTe, resulting in significantly enhanced Seebeck coefficients. The nanoscale precipitates can improve the power factor in the low temperature range and further reduce the lattice thermal conductivity (κ_lat). Specifically, the Seebeck coefficient of Pb_0.988Sb_0.012Te–13%GeTe–Nano approaches −280 µV K⁻¹at 673 K with a low κ_latof 0.56 W m⁻¹K⁻¹at 573 K. Consequently, a peakZTvalue of 1.38 is achieved at 623 K. Moreover, a high averageZT_avgvalue of ≈1.04 is obtained in the temperature range from 300 to 773 K for n‐type Pb_0.988Sb_0.012Te–13%GeTe–Nano.

    

   more » « less
5. Unassisted Water Splitting Using a GaSb x P (1− x ) Photoanode

   https://doi.org/10.1002/aenm.201703247  

   Martinez‐Garcia, Alejandro ; Russell, Harry B. ; Paxton, William ; Ravipati, Srikanth ; Calero‐Barney, Sonia ; Menon, Madhu ; Richter, Ernst ; Young, James ; Deutsch, Todd ; Sunkara, Mahendra K. ( February 2018 , Advanced Energy Materials)

   Here, unbiased water splitting with 2% solar‐to‐hydrogen efficiency under AM 1.5 G illumination using new materials based on GaSb_0.03P_0.97alloy is reported. Freestanding GaSb_xP_1−xis grown using halide vapor phase epitaxy. The native conductivity type of the alloy is modified by silicon doping, resulting in an open‐circuit potential (OCP) of 750 mV, photocurrents of 7 mA cm⁻²at 10 sun illumination, and corrosion resistance in an aqueous acidic environment. Alloying GaP with Sb at 3 at% improves the absorption of high‐energy photons above 2.68 eV compared to pure GaP material. Electrochemical Impedance Spectroscopy and illuminated OCP measurements show that the conduction band of GaSb_xP_1−xis at −0.55 V versus RHE irrespective of the Sb concentration, while photocurrent spectroscopy indicates that only radiation with photon energies greater than 2.68 eV generate mobile and extractable charges, thus suggesting that the higher‐laying conduction bands in the Γ 1 valley of the alloys are responsible for exciton generation.

    

   more » « less