Performance of 4‑Subsituted Pyridine Based Additive and Cobalt Redox in Poly(ethylene glycol)–Hydroxyethylcellulose Polymer Electrolytes with DTTCY Acid Sensitizer on Dye Sensitized Solar Cells

The photovoltaic performance of dye-sensitized solar cells fabricated with newly designed and synthesized heterocyclic aromatic pyridine based additive is described. The incorporation of the 4-subsituted pyridine based additive into the quasi-solid state polymer blend of poly­(ethylene glycol)–hydroxyethylcellulose (PEG-HEC) with Co^2+/3+[bnbip] redox mediator as electrolyte and (E)-3-(5-((E)-2-(1-(5-(2,2-bis­(4-(dimethylamino)­phenyl)­vinyl)­thiophen-2-yl)-1H-indol-3-yl)-1-cyanovinyl)­thiophen-2-yl)-2-cyanoacrylic acid (DTTCY) as organic photosensitizer has been investigated. The influences of synthesized additives in current–voltage characteristics and photoelectro behavior of devices assembled with [TiO₂/DTTCY/Co^2+/3+[bnbip]/additive/PEG-HEC/Pt] device were investigated. The presence of different additives in the gel polymer matrix enhanced the photovoltage and was related to the negative shift that occurred in the Quasi Fermi level of TiO₂ and also higher charge relaxation time. These additives probably reduce the recombination reaction between the TiO₂ surface and the Co³⁺ ion that boosts the photocurrent (J_SC) and PCE of the DSSCs. Furthermore, additives affect the catalytic behavior of the Pt electrode, trap diffusion of the Co³⁺ species, and charge transfer resistance that limits J_sc produced by the device. The PAZ additive possesses an azaindole moiety with bicyclic ring attached on the fourth position of the pyridine, which greatly supports the device for exhibiting good ionic conductivity (1.46 × 10^–3 S cm^–1), high chemical capacitance (C_μ = 11.96 μF), high recombination resistance (9.78 Ω), and lower charge transfer resistance (54.98 Ω) compared with other pyridine based additives. The overall results were also sustained with dielectric constant, dielectric loss, and electrical modulus studies. The cell integrated with PAZ additive generates a maximum J_SC of 13.59 mA cm^–2 and V_oc of 912 mV, yielding an overall power conversion efficiency η of 5.82% under simulated sunlight with 1.5AM condition (i.e., 100 mW cm^–2). These QS-DSSCs possess long-term stability for 196 h at ambient conditions.