Porous rGO/ZnSe/CoSe2 dispersed in PEDOT:PSS as an efficient counter electrode for dye-sensitized solar cells

In this work, we employ a simple hydrothermal method to synthesize a metal-organic framework (MOF) derived selenide from a reduced graphene oxide (rGO)/structured zeolitic imidazolate framework (ZIF). The resulting MOF-derived selenide (rGO/ZnSe/CoSe2) consists of porous nanowires encapsulated in a carbon matrix and having a high surface area (169.30 m(2) g(-1)). This porous rGO/ZnSe/CoSe2 is combined with polystyrene sulfonate-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) for use as a CE for DSSCs. CEs based on different weight percentages (1, 3, and 5 wt%) of rGO/ZnSe/CoSe2 powder in PEDOT:PSS solution are compared with the commonly used platinum (Pt) based CE. The rGO/ZnSe/CoSe2-PEDOT:PSS composite benefits from the synergistic effects between porous rGO/ZnSe/CoSe2 having a high surface area and PEDOT:PSS which holds superior conductivity and strong binding capability with a fluorine-doped tin oxide (FTO) glass substrate. Therefore, the 3 wt% rGO/ZnSe/CoSe2-PEDOT:PSS composite based CE achieved a good stability and superior electrocatalytic activity compared to Pt CE. Furthermore, DSSCs based on a 3 wt% rGO/ZnSe/CoSe2-PEDOT:PSS composite CE achieved a higher power conversion efficiency (PCE) of 8.60%, compared to the PCE of the Pt CE based DSSC (7.14%) prepared under similar conditions. This work has revealed a new approach to prepare MOF-derived selenide based CEs with high electrocatalytic activity without any calcination. In addition, we demonstrated that the low-cost 3 wt% rGO/ZnSe/CoSe2-PEDOT:PSS composite CE is an excellent candidate to replace Pt CE in DSSCs.