Photoelectrical properties of surfactant-free kesterite Cu2ZnSnSe4 hydrophilic nanocrystal ink and the stability in polar solvents

Colloidal semiconductor nanocrystals (NCs) with surfactant/ligand capping have easy solubility in nonpolar organic solvents but have hindered charge transport, diminishing the electrical efficiency of the material. In the present article, synthesis of bare Cu2ZnSnSe4 NCs of 20–30 nm average diameter with high quality and phase purity has been demonstrated by a simple hydrothermal route, without using any surfactant and hazardous organic solvents. As-synthesized samples can be easily dispersed in polar solvents by electrostatic stabilization and utilized for thin film fabrication. Photovoltaic cell made from the fine high-quality bare Cu2ZnSnSe4 NCs shows accountable fourfold photoresponse electrical conductivity upon illumination (AM 1.5) attributed to ligand-free nature of the synthesized nanoparticles. The dispersibility of the material in a variety of solvents providing electrostatic stabilization has been explored for application purpose which is useful for the material utilization without any pre- or post-deposition treatment for low-cost photovoltaic applications.