Fabrication of low cost kesterite Cu2ZnSnS4 (CZTS) thin films as counter-electrode for dye sensitised solar cells (DSSCs)

Cu2ZnSnS4 (CZTS) thin films were prepared by a low cost and large scale slurry sulphurisation process. The structure and morphology of the CZTS powders and films were characterised by X-ray diffraction, transmission electron microscopy and field emission–scanning electron microscopy respectively. The thermal behaviour of the CZTS slurry mixture was analysed by thermogravimetry coupled with differential scanning calorimetry. The absorption spectra of the thin film were characterised using an ultraviolet–visible–near infrared spectrophotometer. The effects of the sulphurisation temperature and soaking time on the structural, morphological, compositional and optical properties of the samples were investigated in detail. The results indicated that the crystals grew during sulphurisation, leading to some pores and cracks in the films, and the film possessed the optical band gap values between 1.45 and 1.48 eV. Under one sun (100 mW cm− 2) illumination, the dye sensitised solar cells with the CZTS counter-electrode (CE) showed comparable photovoltaic conversion efficiency (Eff = 3.141%) to that with a Pt CE (Eff = 2.761%). It is indicated that the as prepared CZTS films had potential for developing low cost and high efficient CE.