Hydrogel Electrolytes Based on Xanthan Gum: Green Route towards Stable Dye-Sensitized Solar Cells

Abstract

The investigation of innovative electrolytes based on nontoxic and nonflammable solvents is an up-to-date, intriguing challenge to push forward the environmental sustainability of dye-sensitized solar cells (DSSCs). Water is one of the best choices, thus 100% aqueous electrolytes are proposed in this work, which are gelled with xanthan gum. This well-known biosourced polymer matrix is able to form stable and easily processable hydrogel electrolytes based on the iodide/triiodide redox couple. An experimental strategy, also supported by the multivariate chemometric approach, is used here to study the main factors influencing DSSCs efficiency and stability, leading to an optimized system able to improve its efficiency by 20% even after a 1200 h aging test, and reaching an overall performance superior to 2.7%. In-depth photoelectrochemical investigation demonstrates that DSSCs performance based on hydrogel electrolytes depends on many factors (e.g., dipping conditions, redox mediator concentrations, etc.), that must be carefully quantified and correlated in order to optimize these hydrogels. Photovoltaic performances are also extremely reproducible and stable in an open cell filled in air atmosphere, noticeably without any vacuum treatments.

Photoanodes for Aqueous Solar Cells: Exploring Additives and Formulations Starting from a Commercial TiO2 Paste

“…PV parameters were almost comparable between these two types of electrolytes, suggesting that the polymeric matrix of the gel ensured a good charge transport and did not hinder the redox shuttle ions motion. [15] As evidenced in Figure 5, J sc and PCE trends followed a similar trend, where it emerged that the devices assembled with photoanodes prepared from the 20 wt% PEG-based paste achieved the best efficiency, both with liquid and quasi-solid-state electrolytes. The corresponding average PV parameters under 1 sun irradiation were: J sc = 5.2 mA cm À 2 , V oc = 0.64 V, FF = 0.69 and PCE = 2.3 % for the cell based on the liquid electrolyte; J sc = 5.1 mA cm À 2 , V oc = 0.64 V, FF = 0.71 and PCE = 2.3 % for the cell based on the quasi-solid-state electrolyte.…”

“…Conversely, in the case of hydrogel-based devices, 1.6-1.7 mg of quasi-solid electrolyte were deposited on photoanodes. [15] Then, they were faced to counterelectrodes using the Meltonix 1170-60 thermoplastic film as both spacer and sealant, subsequently hot pressed at 97°C for 15 s.…”

“…When working with aqueous quasi-solid electrolytes (hydrogels), two further issues must be considered with respect to the traditional commercial paste: i) to prepare an electrode surface being highly wettable by water; ii) to allow the permeation of hydrogel-based electrolytes in the electrode bulk. [15] Herein, we propose a study of the effects promoted by different polymeric (i. e. xanthan gum, polyethylene oxide, carboxymethyl cellulose and polyethylene glycol) and molecular (i. e. α-terpineol and propylene carbonate) species added to the commercial 18NR-T paste by Greatcell Solar (formerly Dyesol), one of the TiO 2 pastes most used in the scientific literature; we adopted the simple doctor-blade deposition method, easily accessible in all laboratories and very close to the industrial printing process. When thermally treated, these additives burn in air, leading to the formation of precise morphologies and thickness values to the resulting TiO 2 electrodes.…”

Fundamental Concepts of Hydrogels: Synthesis, Properties, and Their Applications

“…After careful designing of experiments, a few selected experiments were conducted. The fabricated DSSCs showed a power conversion efficiency of 2.7% and the efficiency was dependent on the dipping conditions and redox mediator concentration [220]. Numerous sensitizers have been used in sensitized solar cells (SSCs).…”

Highly Ordered TiO2 Nanotube Electrodes for Efficient Quasi-Solid-State Dye-Sensitized Solar Cells

“…Because of these attractive properties, anodic NT electrodes have also been investigated for solid-state or quasi-solid-state DSSC applications employing gel, polymer electrolytes, or solid organic hole conductors [21][22][23][24][25][26][27][28][29][30][31]. The development of these solid-state DSSCs is important for the commercialization of DSSCs because of the evaporation problems for the conventional liquid electrolytes [8,32].…”