A comparative study has been attempted on 1-substituted 2-(pyridin-2-yl)-1H-benzo­[d]­imidazole ligand-coordinated copper and cobalt metal complex electrolytes Cu+/2+[nbpbi]2(PF6 –)1/2, Cu+/2+[npbi]2(PF6 –)1/2, Co2+/3+[nbpbi]3(PF6 –)2/3, and Co2+/3+[npbi]3(PF6 –)2/3 in dry acetonitrile coupled with both N3 and N719 dyes in dye-sensitized solar cell (DSSC) devices. Impressively, the copper metal sites coordinated with ligands nbpbi (L1) and npbi (L2) shift the redox potential about 190–200 mV and pave the way to achieve remarkably higher power current efficiency, which is clarified with cyclic voltammetry, electrochemical impedance spectrum, electron lifetime, and quasi Fermi-level experimental results. Overall efficiencies of 4.99, 4.82, 3.26, and 3.19% under 1 sun conditions (100 mW cm–2) were obtained for Cu+/2+[nbpbi]2(PF6 –)1/2 and Cu+/2+[npbi]2(PF6 –)1/2 electrolytes coupled with the sensitizers (N3 and N719 dyes), which are considerably higher than those acquired for devices containing the cobalt electrolytes. These results signify a record for copper complex-based electrolytes coupled with ruthenium dyes in liquid DSSCs. In particular, bulky acceptor 4-nitro benzyl moiety-substituted 2-(pyridin-2-yl)-benzimidazole (on the N–H position) (ligand L1)-coordinated copper metal complex electrolytes achieved higher efficiency, approaching a suitable redox potential of 0.68 V versus NHE. At the same time, the napthyl moiety-substituted 2-(pyridin-2-yl)-benzimidazole (ligand L2)-coordinated copper metal complex electrolytes showed less redox potential due to its donating nature. It was determined that the J sc and PCE increment of the devices consisting of Cu+/2+[nbpbi]2(PF6 –)1/2 electrolytes was mainly attributed to various factors such as higher chemical capacitance, larger charge, longer electron life time, a downward shift in the quasi Fermi level of TiO2, the slow recombination process, and fast dye regeneration. These results make easily tunable metal complexes bearing a new sort of 1-substituted 2-(pyridin-2-yl)-1H-benzo­[d]­imidazole ligand-based electrolytes as very promising copper electrolytes for further improvements of extremely efficient liquid DSSCs.

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One of the most important tasks in improving supercapacitor (SC) efficiency is the quest for advanced electrode and electrolyte materials. For the first time, we propose using a metal organic framework (MOF) as an electrode and a cobalt redox pair as an electrolyte to increase the cell voltage of a SC. We successfully synthesized the octahedron structure of the cobalt MOF using a simple annealing treatment process, and we prepared a Co-redox couple incorporated along with the KOH electrolyte for the fabrication of a SC and dye-sensitized solar cell (DSSC). The redox couple-aided N-MOF exhibits an excellent electrochemical performance that is attributed to the highest specific capacitance value of 1150.61 F g–1 (517.77 C g–1) and capacitance retentions of 98.4% in the three-electrode system. Meanwhile, it shows 98.4 F g–1 in a two-electrode system at 1 A g–1 in current density. The two-electrode system redox couple-aided SC device had reached a high energy density of 70.8 W h kg–1 with a power density of 515.75 W kg–1. At the same time, it showed good cyclic stability and could retain 94.3% of the initial capacitance after 11,200 charge and discharge cycles. The DSSC devices were fabricated using N719 dyes coupled with the Co2+/3+[npbi]3 redox pair as an electrolyte and Co-MOF as a counter electrode, which exhibits a short circuit current (J sc = 4.73 mA cm–2), and open circuit voltage (V oc = 0.25 V), which gives a power conversion efficiency of 0.33% under 1 sun illumination with AM 1.5 G. The combination of the N-MOF electrode material with a Co-redox mediator paved the way to improve the efficient material for energy conversion of DSSCs and energy storage of SCs.

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In this study, we report the first application of (4-(tert-butyl) benzyl or 4-methyl benzyl)-substituted 2-(pyridin-2-yl)-1Hbenzo[d]-imidazole coordinated copper and cobalt redox shuttles Cu [((tbb) pbi) 2 ] + 1/ + 2 , Cu [(mbpbi) 2 ] + 1/ + 2 , Co [((tbb) pbi) 3 ] + 2/ + 3 and Co [(mbpbi) 3 ] + 2/ + 3 based xanthan gum gel electrolytes (XGE-1, XGE-2, XGE-3 and XGE-4) in fabrication of Dye sensitized solar cells. Interestingly, XGE-1 and XGE-2 obtained higher efficiency of 4.08 and 3.04 % under 1sun illumination. Specifically, highly donor moiety 4-(tertbutyl)benzyl)-substituted (on NÀ H position) 2-(pyridin-2-yl)-1H-benzo[d]-imidazole ligands coordinated, Cu [((tbb) pbi) 2 ] + 1/ + 2 gel electrolyte achieved best performance due to its appropriate redox potential of 0.80 V versus Normal Hydrogen Electrode. This high performance also confirmed with the interfacial studies of the devices. As per the computational results, the copper redox mediators conquered lower reorganization energy and free energy about (0.11-0.20 & 0.18-0.27 eV) due to the effect of ligands structure. Overall, Cu [((tbb) pbi) 2 ] + 1/ + 2 act as redox shuttle for highly proficient DSSCs.