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Impact of hole-doping on the thermoelectric properties of pyrite FeS2

Anustup Mukherjee, Alaska Subedi

TL;DR

This work addresses the thermoelectric viability of hole-doped FeS2 pyrite by performing first-principles transport calculations that include electron-phonon interactions. Using DFT and DFPT with Boltzmann transport theory, it documents a consistently large positive Seebeck coefficient $S$ across hole concentrations up to $n_h=10^{21}$ cm$^{-3}$, while electrical conductivity remains moderate and lattice-dominated thermal conductivity keeps $ZT$ below 0.1. The analysis attributes the limited $ZT$ to a combination of low $\sigma$ and high $\kappa_{ph}$, with bipolar conduction further affecting $S$ at elevated temperatures. The results suggest that while hole-doping yields strong thermopower, substantial improvements in electrical transport or reductions in lattice thermal conductivity would be required for FeS2 to become a competitive thermoelectric material, and experimental work is essential to validate and potentially enhance these predictions.

Abstract

We present a comprehensive first-principles analysis of the thermoelectric transport properties of hole-doped pyrite FeS$_2$ that includes electron-phonon interactions. This work was motivated by the observed variations in the magnitude of thermopower reported in previous experimental and theoretical studies of hole-doped FeS$_2$ systems. Our calculations reveal that hole-doped FeS$_2$ exhibits large positive room-temperature thermopower across all doping levels, with a room-temperature thermopower of 608 $μ$V/K at a low hole-doping concentration of 10$^{19}$ cm$^{-3}$. This promising thermopower finding prompted a comprehensive investigation of other key thermoelectric parameters governing the thermoelectric figure of merit $ZT$. The calculated electrical conductivity is modest and remains below 10$^5$ S/m at room-temperature for all doping levels, limiting the achievable power factor. Furthermore, the thermal conductivity is found to be phonon driven, with a high room-temperature lattice thermal conductivity of 40.5 W/mK. Consequently, the calculated $ZT$ remains below 0.1, suggesting that hole-doped FeS$_2$ may not a viable candidate for effective thermoelectric applications despite its promising thermopower.

Impact of hole-doping on the thermoelectric properties of pyrite FeS2

TL;DR

This work addresses the thermoelectric viability of hole-doped FeS2 pyrite by performing first-principles transport calculations that include electron-phonon interactions. Using DFT and DFPT with Boltzmann transport theory, it documents a consistently large positive Seebeck coefficient across hole concentrations up to cm, while electrical conductivity remains moderate and lattice-dominated thermal conductivity keeps below 0.1. The analysis attributes the limited to a combination of low and high , with bipolar conduction further affecting at elevated temperatures. The results suggest that while hole-doping yields strong thermopower, substantial improvements in electrical transport or reductions in lattice thermal conductivity would be required for FeS2 to become a competitive thermoelectric material, and experimental work is essential to validate and potentially enhance these predictions.

Abstract

We present a comprehensive first-principles analysis of the thermoelectric transport properties of hole-doped pyrite FeS that includes electron-phonon interactions. This work was motivated by the observed variations in the magnitude of thermopower reported in previous experimental and theoretical studies of hole-doped FeS systems. Our calculations reveal that hole-doped FeS exhibits large positive room-temperature thermopower across all doping levels, with a room-temperature thermopower of 608 V/K at a low hole-doping concentration of 10 cm. This promising thermopower finding prompted a comprehensive investigation of other key thermoelectric parameters governing the thermoelectric figure of merit . The calculated electrical conductivity is modest and remains below 10 S/m at room-temperature for all doping levels, limiting the achievable power factor. Furthermore, the thermal conductivity is found to be phonon driven, with a high room-temperature lattice thermal conductivity of 40.5 W/mK. Consequently, the calculated remains below 0.1, suggesting that hole-doped FeS may not a viable candidate for effective thermoelectric applications despite its promising thermopower.

Paper Structure

This paper contains 7 sections, 5 equations, 10 figures, 1 table.

Table of Contents

  1. Introduction
  2. Computational Details
  3. Structural Details
  4. Results and Discussions
  5. Electronic Structure
  6. Transport Properties
  7. Conclusions

Figures (10)

  • Figure 1: (Left) Electronic band structure and (right) density of states of stoichiometric FeS$_2$. The Fermi energy is shifted to the valence band maximum.
  • Figure 2: Seebeck coefficient $S$ of hole-doped FeS$_2$ in the concentration range 10$^{19}$--10$^{21}$ cm$^{-3}$.
  • Figure 3: Electrical conductivity $\sigma$ of hole-doped FeS$_2$ in the concentration range 10$^{19}-$10$^{21}$ cm$^{-3}$.
  • Figure 4: Electron-phonon scattering rates (the inverse of relaxation time) as a function of energy at 300 and 700 K for carrier concentration $n_h$ = 1$\times$10$^{19}$ cm$^{-3}$. The Fermi energy is shifted to the valence band maximum.
  • Figure 5: Power factor of hole-doped FeS$_2$ in the concentration range 10$^{19}$--10$^{21}$ cm$^{-3}$.
  • ...and 5 more figures