Ni and P co-doped WS2 nanosheets decorated on MWCNTs as an efficient counter electrode for dye-sensitized solar cells

Designing of inexpensive and robust counter electrode (CE) material without noble metals is of great essential for improving the overall power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). Herein, nickel (Ni) and phosphorus (P) co-doped WS2 nanosheets decorated on multi-walled carbon nanotubes (Ni/P-WS2@MWCNTs) was fabricated via single-step hydrothermal method and used as CE for DSSC. According to the electrochemical studies, the Ni/P-WS2@MWCNTs CE displayed remarkable catalytic activities, great electron transfer ability, and high durability in the I−/I3− electrolyte. More importantly, the device equipped with Ni/P-WS2@MWCNTs CE yielded an outstanding PCE of 8.62%, surpassing that of standard Pt (PCE=6.61%) and other corresponding counterparts. Such notable photovoltaic performance can be ascribed to the synergistic coupling effect of heteroatom doping and support role of conductive carbon network, which offer abundant catalytic active sites, high porosity, and exceptional electrical conductivity. Our work suggests a novel strategy to fabricate Pt-like CE materials based on metal and nonmetal heteroatoms co-doped in metal chalcogenides with excellent performances for large-scale energy conversion devices to reach the consumer market.