Ligand exchange in Cu_2ZnSnS_4 nanoparticles and its effect on counter electrode performance in dye-sensitized solar cells

摘要

Ligand-exchanged Cu2ZnSnS4 (CZTS) nanoparticles (NPs) were successfully synthesized from colloidal NPs by replacing the long chain organic ligand from the surface of NPs via a bi-phasic method. It was found that ammonium sulphide salt ((NH4)2S) plays a key role in changing the surface of the NPs from hydrophobic to hydrophilic. The efficacy of the ligand exchange process over the surface of the CZTS NPs was analysed using X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy and scanning electron microscopy with energy dispersive X-ray. The ligand-exchanged CZTS NP-based counter electrodes (CEs) were fabricated by drop casting the inorganic ligand (ammonium sulphide)-capped CZTS nanoink onto the conducting substrate. Our result indicates that dye-sensitized solar cells (DSSCs) with inexpensive CZTS NP-based CEs show 2.42% efficiency. The present result indicates that CZTS CEs will be helpful as an alternative CE to a Pt CE in DSSC application.