# Synergistically Optimizing the Thermoelectric Performance of n‑Type SnS through an Integrated Systematic Approach

## TL;DR

Researchers improved the thermoelectric performance of n-type SnS by addressing challenges related to native Sn vacancies and enhancing conductivity.

## Contribution

A novel integrated approach combining sulfur vacancies, Cl– and Se2– substitutions, and SnCl2 compensation to optimize n-type SnS thermoelectric performance.

## Key findings

- n-type SnS1−δ samples with sulfur vacancies and Cl–/Se2– substitutions showed enhanced thermoelectric performance.
- SnS0.455Se0.45Cl0.02 achieved a ZT max of ≈0.7 at 823 K, the highest reported for n-type SnS.
- Incorporating SnCl2 lowered thermal conductivity and improved power factor.

## Abstract

Tin­(II) sulfide (SnS) is a promising p-type semiconductor
known
for its high thermoelectric performance and eco-friendly properties,
offering a viable alternative to group IV–VI compounds. However,
achieving n-type conductivity in SnS has been challenging due to the
propensity for native Sn vacancies. This study addresses this challenge
by synthesizing polycrystalline n-type SnS1−δ (δ = 0.05 and 0.075) samples through solid-state reaction.
By introducing sulfur vacancies to counteract Sn vacancies, followed
by aliovalent (Cl–) and isoelectronic (Se2–) substitutions, we significantly enhance the thermoelectric performance
of n-type SnS. Chlorine doping further improves electrical conductivity,
with SnS0.455Se0.45Cl0.02 showing
superior performance. Additionally, incorporating 0.03 mol % SnCl2 in SnS0.475Se0.45 compensates for intrinsic
Sn vacancies, optimizing the power factor and lowering lattice thermal
conductivity. Consequently, we realized a figure of merit ZT (ZT
max) of ≈0.7 at
823 K and an average ZT (ZT
ave) of ≈0.2 from 308 to 823 K, the highest reported
values for n-type SnS. This work advances the optimization of n-type
SnS and lays the groundwork for developing SnS-based thermoelectric
devices.