Improved performance in dye-sensitized solar cells via controlling crystalline structure of nickel selenide

Probing the stoichiometry dependent catalytic activity of nickel selenide counter electrodes in the redox reaction of iodide/triiodide electrolyte in dye sensitized solar cells

“…From the curves, the J 0 and the J lim can be derived from the slope for anodic or cathodic branch and the intersection of anodic branch with y axis respectively. 2,37 As summarized in Table 4, the values of J 0 and J lim increased in a following the order: Pt < NS-1 < NS-2 < NS-3 < NS-5 < NS-4 which is similar to the EIS order. Usually the J 0 value increases with increasing slope of cathodic or anodic branches and eqn (3) suggest that J 0 is inversely proportional to R ct .…”

“…Previous reports indicate that the larger the J sc value the higher the generation of the iodide ions thus the higher the catalytic activity of the CE material. 2,7 Therefore, based on the above observations, NS-1 was a better electrocatalyst towards the reduction of triiodide ion while NS-5 was the weakest. Similarly, the device with NS-1 CE exhibited stronger charge separation and transferability compared to the other stoichiometries, thus the high J sc it generated.…”

“…S1 †) and this is with these CEs as a result of weak adhesion of the nanostructures on FTO. 2,40 The values of the V oc of all the as-synthesized CEs including Pt were seen to be relatively the same, about 0.7 V. This can be attributed to the fact that the V oc across a DSSC is thermodynamically determined by the difference between the quasi-Fermi level of the semiconductor (TiO 2 ) and the redox potential of the electrolyte. 41 Thus the value of the V oc is independent to the nature of the counter electrode material but dependent on the charge recombination and electron injection efficiency.…”

“…Generally, the stronger the electrocatalytic ability, the larger |J _Red-1 | and lower E pp values. 2,7,33 As shown in Fig. 6 and Table 4, most of the Ni x Se y CEs exhibited superior current response (J) than the Pt-CE for the reduction of I 3 À in order of NS-1 > NS-2 > NS-3 > Pt > NS-4 > NS-5, indicating that the rate of this reaction is relative higher for the NS-1, NS-2, NS-3 than the Pt.…”

“…The high cost of and low abundance of platinum have hindered its large-scale practical application despite its excellent electrocatalytic activities. 1,2 Moreover, the long-term stability of a Pt counter electrode (CE) can be destroyed in a liquid electrolyte composed of the triiodide/iodide (I À /I À 3 ) redox couple in dye sensitized solar cells (DSSCs). As a result, tremendous efforts are being made to nd alternative catalysts to Pt for use as CEs in DSSCs and for electro-catalytic oxygen-hydrogen reduction in fuel cells.…”