Water-Based Thixotropic Polymer Gel Electrolyte for Dye-Sensitized Solar Cells

Abstract

For the practical application of dye-sensitized solar cells (DSSCs), it is important to replace the conventional organic solvents based electrolyte with environmentally friendly and stable ones, due to the toxicity and leakage problems. Here we report a noble water-based thixotropic polymer gel electrolyte containing xanthan gum, which satisfies both the environmentally friendliness and stability against leakage and water intrusion. For application in DSSCs, it was possible to infiltrate the prepared electrolyte into the mesoporous TiO2 electrode at the fluidic state, resulting in sufficient penetration. As a result, this electrolyte exhibited similar conversion efficiency (4.78% at 100 mW cm(-2)) and an enhanced long-term stability compared to a water-based liquid electrolyte. The effects of water on the photovoltaic properties were examined elaborately from the cyclic voltammetry curves and impedance spectra. Despite the positive shift in the conduction band potential of the TiO2 electrode, the open-circuit voltage was enhanced by addition of water in the electrolyte due to the greater positive shift in the I(-)/I3(-) redox potential. However, due to the dye desorption and decreased diffusion coefficient caused by the water content, the short-circuit photocurrent density was reduced. These results will provide great insight into the development of efficient and stable water-based electrolytes.

Aqueous dye-sensitized solar cells

“…316,317 To this purpose, Ko and coworkers used xanthan gum (M n = 2 Â 10 6 ), a water soluble and environmentally friendly polysaccharide rich in hydroxyl groups ready to form a 3D network, the viscosity of which reversibly decreases upon application of an external stress. 318 After a thorough optimization of the stability of all the ingredients in the reactive formulation -a key aspect in this field, where apolar, polar and ionic substances are concurrently used -a 1 : 1 mixture of xanthan gum (3 wt% in H 2 O) and liquid electrolyte (PMII 4.0 M, I 2 0.30 M, TBP 1.5 M and GuSCN 0.20 M in MPN) was selected. As reported in Table 19, resulting aqueous DSSCs, both liquid and quasi-solid, showed higher V oc and FF, but lower J sc values with respect to the MPNbased liquid counterpart.…”

The Effect of the Scattering Layer in Dye‐Sensitized Solar Cells Employing a Cobalt‐Based Aqueous Gel Electrolyte

“…We previously reported that aqueous DSCs stored in the dark fort hree months maintained 90 %i nitial efficiency. [25] Nevertheless, the devices maintain over 80 %o ft heir originale fficiency after illumination for 90 h, whereas the value for liquid counterparts was 57 %a fter the same period,s uggesting that the stability for the gel type DSCs is improved. One of the well documented reasons for the improveds tability is ar eduction in the evaporation of solvents present in the electrolytes.…”

“…O'Regan and co-workersr ecently examined the stabilityofDSCs assembled with an acetonitrile electrolyte containing the [Co(bpy) 3 ] 2 + /3 + redox couple over ap eriod of 2000h of light soaking at 20 8Ca nd 1sun light intensity. [25,44] Witht his in mind,w ec arried out experiments to comparethe stability of the devices assembled with the aqueous gel electrolyte with that of devices made with corresponding aqueous electrolyte under white LED light illumination correspondingt o1sun (Figure 9a). We previously reported that aqueous DSCs stored in the dark fort hree months maintained 90 %i nitial efficiency.…”

“…[19] Stability is ak ey factor for the applicationo fD SCs. [25] A1 :1 water/ 3-methoxypropionitrile (MPN) solvent mixture wasused to pre-We developed an aqueous gel electrolyte based on the [Co(bpy) 3 ] 2 + /3 + (bpy = 2,2'-bipyridine) redox mediator for use in n-type dye-sensitized solar cells. [20][21][22][23] Chen et al studied the in situ gelation of liquid electrolytes in the mesoporousm atrix of DSCs induced by the addition of poly(acrylonitrile-co-vinyl acetate) as ag elator.T hey found that after a1 000 ha ging test, the gelstate cell retained9 5% of its initial efficiency.…”

Perspectives for solid biopolymer electrolytes in dye sensitized solar cell and battery application

“…Gum XanthanþPVP, Gum tragacanth þ PVP and Gum Acacia þ PVP, Gum Acacia þ PVP presents better compatibility as it has stronger intermolecular interaction. In the same manner, among Gum Xanthan þ PEG, Gum Acacia þ PEG and Gum tragacanth þ PEG systems, Gum Tragacanth þ PEG has better compatibility [171].…”