Electrospun and hydrothermal techniques to synthesize the carbon-coated nickel sulfide microspheres/carbon nanofibers nanocomposite for high performance liquid-state solar cells

Abstract To achieve optimal electrochemical performance, a highly efficient and stable noble-metal-free catalyst which consists of carbon-coated nickel sulfide microspheres (Ni 3 S 4 @C) and carbon nanofibers (CNFs) are synthesized through the electrospinning and hydrothermal method. The optimized sample provides a large amount of active sites that benefit electron transfer which is further applied as a counter electrode (CE) in dye-sensitized solar cells (DSSCs). A series of electrochemical measurements reveal that the resultant Ni 3 S 4 @C/CNFs show higher catalytic activity toward the reduction of I 3 − to I − in comparison to the benchmark Pt, Ni 3 S 4 @C, pure Ni 3 S 4 and CNFs. As a result, the DSSC device assembled with Ni 3 S 4 @C/CNFs-based CE affords a decent power conversion efficiency (PCE) of 8.29%, which surpasses the corresponding values of the device using the commercial Pt (7.35%), Ni 3 S 4 @C(6.81%), pure Ni 3 S 4 (6.51%) and CNFs (6.11%) CE under identical conditions. This work unfolds a new strategy for developing low-cost and effective CE materials in DSSCs.