Transparent Cobalt Selenide/Graphene Counter Electrode for Efficient Dye-Sensitized Solar Cells with Co²⁺/³⁺-Based Redox Couple

Abstract

In this study, we demonstrate a facile, one-pot, and low-temperature (∼85 °C) chemical bath method for the preparation of a composite of cobalt selenide/graphene (Co 0.85 Se/Gr) as the electrocatalyst for the counter electrode (CE) of dye-sensitized solar cells (DSSCs) with a cobalt-based electrolyte. The Co 0.85 Se/Gr composite film was envisaged to have the advantages of both components, that is, the high electrochemical surface area of Co 0.85 Se and the straight paths for electron transfer from Gr. The DSSCs with Co 0.85 Se/Gr exhibited a power conversion efficiency (η) of 11.26%. According to the results of the rotating disk electrode, the film of Co 0.85 Se/Gr showed a high electrocatalytic surface area (A e ) and an extremely large intrinsic heterogeneous rate constant (k 0 ). Furthermore, the composite film of Co 0.85 Se/Gr exhibits a high transparency in the wavelength region of 400−800 nm (>82%), which implied that the corresponding electrode shall be a potential CE in rear-side illuminated DSSCs. The photovoltaic parameters of the DSSCs with Pt, Co 0.85 Se, Gr, and Co 0.85 Se/Gr were obtained for rear-side illumination and additionally for front-and rear-side illuminations (AM 1.5, 100 mW/ cm 2 ) using different electrolytes. As the cobalt-based electrolyte of [Co(bpy) 3 ] 2+/3+ exhibited a low light absorption and low overpotential for dye regeneration, a rear-side illuminated DSSC with a cobalt-based electrolyte showed the highest efficiency of 9.43 ± 0.02%, which is greater than that of the DSSC with an I − /I 3 − -based electrolyte (η = 7.63 ± 0.04%).

Low-Cost and Efficient Nickel Nitroprusside/Graphene Nanohybrid Electrocatalysts as Counter Electrodes for Dye-Sensitized Solar Cells

“…Platinum (Pt) is widely used as a conventional CE material in DSSCs due to its superior catalytic activity toward the redox reaction of conventional I − /I 3 − electrolyte and high electrical conductivity (9.43 × 10 6 S/m) [ 9 ]. However, the high cost of Pt (4.6 USD/m 2 for a 5 nm-thick Pt film) hinders its large-scale application in DSSCs [ 10 , 11 ].…”

“…For the replacement of Pt-CE, numerous studies have demonstrated, using, for example, carbonaceous materials (e.g., graphene, carbon nanotubes, active carbon, graphite, carbon black) [ 12 ], conducting polymers (CPs) (e.g., polyaniline, polypyrrole, and poly(3,4-ethylene dioxythiophene) (PEDOT: PSS)) [ 13 ], transition metal compounds (e.g., carbides, nitrides, oxides) [ 14 ], and various hybrids or composites materials [ 15 ], which are about 10 to 10,000 times cheaper than that of Pt-CE [ 10 ]. Among them, nanostructures of metallic Ni and its compounds (e.g., oxides, sulfides, ternary sulfides, phosphides) are potentially suitable CE materials because of their decent corrosion resistance to the I − /I 3 − redox mediator and low cost [ 11 , 16 , 17 , 18 , 19 , 20 ].…”

High-Level Oxygen Reduction Catalysts Derived from the Compounds of High-Specific-Surface-Area Pine Peel Activated Carbon and Phthalocyanine Cobalt

“…These results suggest that the rich distribution and size of nanopores can be regulated and controlled by pyrolysis temperature and activation, thereby forming more nanopores to expose more active areas and promote the ability of electron transfer [35,36], but the appropriate temperature and proportion are more conducive to the recombination of AC and CoPc, as well as providing more adhesion sites for CoPc. The XRD patterns of AC/CoPc series composite catalysts (Figure 3a) all correspond to Co (JCPDS 15-0806) [37] and graphite (JCPDS 01-0646) [38]. AC/CoPc-800-1-2 and AC/CoPc-900-1-2 exhibit that the broadened peak at 25.7 • is ascribed to the (002) plane of graphite (JCPDS 01-0646), but AC/CoPc-800-1-2 has a larger broad peak at 25.7 • , which manifests that the carbonization temperature of 800 °C is more conducive to the formation of carbon with small graphite domains [39].…”

Influence of chemical composition and doping on optical properties of thallium selenide layers prepared by adsorption/diffusion method

“…Polymers modified by thin films of binary d-metal chalcogenides belong to the composite materials as well. These composites promise to be valuable in solar energy conversion [1,2], thermoelectrics [3,4], photocatalysis [5], photodetectors [6], light-emitting diodes [7] and so on. Group III metal (Ga, In and Tl) composite materials binary or ternary compounds combined with group VI nonmetals (S, Se and Te) have very important and unique physical properties to technology and modern science.…”