Cu2ZnSnS4 (CZTS) ink was synthesized from metal chloride precursors, sulfur, and oleylamine (OLA), as a ligand by a simple and low-cost hot-injection method. Thin films of CZTS were then prepared by spin coating, followed by thermal annealing. The effects of the fabrication parameters, such as ink concentration, spinning rate, and thermal treatment temperatures on the morphology and structural, optical, and electrical properties of the films were investigated. As expected, very thin films, for which the level of transmittance and band-gap values increase, can be obtained either by reducing the concentration of the inks or by increasing the rate of spinning. Moreover, the thermal treatment affects the phase formation and crystallinity of the film, as well as the electrical conductivity, which decreases at a higher temperature.
Cu-Zn disorder is known to deeply affect kesterite (Cu2ZnSnS4, CZTS) due to the low temperature order-disorder phase transition, leading to a random occupation of the two cations in the shared crystallographic planes. This defect complex has been extensively studied in the thin film photovoltaic sector, with considerable efforts in developing methods to quantify disorder. In this study, a preliminary investigation of thermoelectric properties in temperature for thin film CZTS is presented. It is found that Cu-Zn disorder enhances both electrical conductivity and Seebeck coefficient. This can positively affect the thermoelectric performance, showing a mechanism of potential interest for a broad class of quaternary chalcogenides. The order-disorder transition is clearly visible in the electronic properties. This feature is repeatable, with samples from different preparations and groups showing consistent results, qualitatively suggesting electronic measurements as possible methods to quantify disorder. Furthermore, the reversibility of the transition allows the electronic properties to be tuned via specific thermal treatments, pointing to interesting applications in tunable electronics.
Correction for 'Thermoelectric properties of CZTS thin films: effect of Cu-Zn disorder' by E. Isotta et al., Phys. Chem. Chem. Phys., 2021, DOI: 10.1039/d1cp01327k.