Tuning Structure and Function: Metal-Ion Induced Phase Transformation in Copper Antimony Sulphide Nanosheets

a. Kimberly Weston¹; b. Richard A. Taylor¹

 ¹The University of the West Indies, St Augustine Campus

Email: a. kimberly.weston@my.uwi.edu, b. richard.taylor@uwi.edu

Introduction

Cu-Sb-S for photovoltaics/energy storage since it has:

• Structure, composition, and stoichiometry versatility
• Excellent, broad variation of intrinsic functional properties
• Earth abundance, low cost, environmental and benign health effects
• Tunable optical & electrochemical properties

Colloidal (Hot-Injection) Synthesis

• Injection of Cu(acac)₂ + sulfonated OAm (Oleylamine) solution into a reaction flask containing Sb(ddtc)₃ + OAm solution held at 50 °C. The mixture was quickly ramped to 200 °C and NPs were grown for 30 minutes.

Metal ion-induced fCAS to cCAS Phase Transformation

• p-XRD data confirm a novel phase transformation from a tetragonal structure to an orthorhombic one with heavier metal ion dopant.
• Representative Raman spectroscopy data reveal a mixed phase system.
• HR-S/TEM and SAED data corroborate with p-XRD data and confirm the tetragonal and orthorhombic structures of doped CAS NPs.
• TEM and EDS suggest a correlation of morphology and composition of NPs with dopant ion.

Dopant-Induced Photophysical Variation

• Doped NPs:
  • bandgaps decrease from 2.58 eV (undoped) to range between 2.17 to 2.38 eV.
  • show blueshifted emission (~537 nm) with narrower FWHM.
  • have lengthened fast triple radiative recombination.

Phase-dependent Pseudocapacitance

• Metal ion doping - especially with Zn²⁺ - enhances pseudocapacitance through a phase transition to chalcostibite, improving redox activity, conductivity, and ion transport.

Conclusions

• Metal-ion induced phase transformation results in bandgap tunability (narrowed) and enhanced pseudocapacitance (almost 3-fold).

References

1. Suehiro, S.; et. al; Inorganic Chemistry 2015, 54 (16), 7840-7845.
2. Ramasamy, K.; et. al; Chemistry Materials 2015, 27 (1), 379-386.
3. Zakutayev, A; et. al; Conference Paper, 2014.