posted on 2024-02-23, 13:37authored byYu Liu, Paul D. McNaughter, Xiaodong Liu, Andrey V. Kretinin, Jonathan M. Skelton, Feridoon Azough, David J. Lewis, Robert Freer
High-quality Cu2(Zn,Fe,Cd)SnS4 (CZFCTS) thin
films based on the parent CZTS were prepared by aerosol-assisted chemical
vapor deposition (AACVD). Substitution of Zn by Fe and Cd significantly
improved the electrical transport properties, and monophasic CZFCTS
thin films exhibited a maximum power factor (PF) of ∼0.22 μW
cm–1 K–2 at 575 K. The quality
and performance of the CZFCTS thin films were further improved by
postdeposition annealing. CZFCTS thin films annealed for 24 h showed
a significantly enhanced maximum PF of ∼2.4 μW cm–1 K–2 at 575 K. This is higher than
all reported values for single-phase quaternary sulfide (Cu2BSnS4, B = Mn, Fe, Co, Ni) thin films and even exceeds
the PF for most polycrystalline bulk materials of these sulfides.
Density functional theory (DFT) calculations were performed to understand
the impact of Cd and Fe substitution on the electronic properties
of CZTS. It was predicted that CZFCTS would have a smaller band gap
than CZTS and a higher density of states (DoS) near the Fermi level.
The thermal conductivity and thermoelectric figure of merit (zT) of the CZFCTS thin films have been evaluated, yielding
an estimated maximum zT range of 0.18–0.69
at 550 K. The simple processing route and improved thermoelectric
performance make CZFCTS thin films extremely promising for thermoelectric
energy generation.