Effect of poly (ethylene glycol) gel polymer electrolyte consist of novel heteroleptic cobalt redox shuttle and pyridine based organic additive on performance of dye sensitized solar cells

Abstract

A newly designed heteroleptic cobalt I/II [2,6-bis (1-(naphthalen-2-ylmethyl)-1H-benzo[d] imidazole-2-yl)pyridine) (2,6-bis (1-(4-(tert-butyl)benzyl)-1H-benzo [d] imidazole-2-yl)pyridine)] redox shuttle (Co2+/3+[(bnbip) (b(tbb)bip)]) and pyridine based organic additive 2, 6-bis(pyridin-2-ylthio)pyridine (BPTP) was introduced first time into the Poly(ethylene glycol) (PEG) gel polymer electrolyte to improvise power conversion efficiency (PCE) of Dye sensitized solar cells (DSSCs). Interestingly gel electrolytes (PEG/Co2+/3+[(bnbip) (b(tbb)bip)]/BPTP) attained an improved conductivity of 11.54 × 10−4 S cm−1higher than the gel polymer electrolyte without additive BPTP. Mainly, the redox potential (Emed = 0.64 V Vs NHE) of cobalt redox pair sustains the gel polymer electrolyte to conquer a higher open circuit voltage of devices. The PCE of device with PEG/Co2+/3+[(bnbip) (b(tbb)bip)]/BPTP gel electrolyte achieved up to 5.12% under 1 sun (100 mW/cm2) condition which was superior than the device with PEG gel polymer electrolyte without BPTP. This enhancement of PCE was confirmed via certain consequences such as longer electron life time (1.3 ms), lower charge transfer resistance (217 Ω), lower charge transfer kinetics (0.77 ms−1), higher Chemical capacitance (5.99 × 10−3 F), high diffusion coefficient (2.59 × 10−5 cm2 s−1) and a shift in Quasi Fermi level of TiO2. The newly integrated Co2+/3+[(bnbip) (b(tbb)bip)] redox and BPTP additive in PEG gel polymer electrolytes readily suppress the recombination reaction between TiO2 and Co3+ species of Cobalt redox pair. An opening of PEG gel electrolytes with new organic additive and Cobalt redox pair paved a way to replacement of liquid electrolytes with usual Iodine/Iodide redox pair, homoleptic cobalt redox pair and commercial costly additive in DSSCs.