Effect of Cross-Linking on the Performances of Starch-Based Biopolymer as Gel Electrolyte for Dye-Sensitized Solar Cell Applications

Abstract

Dye-sensitized solar cells (DSSCs) have become a validated and economically credible competitor to the traditional solid-state junction photovoltaic devices. DSSCs based on biopolymer gel electrolyte systems offer the perspective of competitive conversion efficiencies with a very low-cost fabrication. In this paper, a new starch-based biopolymer gel electrolyte system is prepared by mixing lithium iodide and iodine with bare and citric acid cross-linked potato starches with glycerol as the plasticizing agent. The effect of the preparation methods on the starch cross-linking degree as well as the photoconversion efficiency of the resulting DSSC cells is carefully analyzed. Fourier transform spectroscopy, X-ray diffraction, and scanning electron microscopy were used to characterize the morphology and conformational changes of starch in the electrolytes. The conductivity of the biopolymer electrolytes was determined by electrochemical impedance spectroscopy. DSSC based on the starch-gel polymer electrolytes were characterized by photovoltaic measurements and electrochemical impedance spectroscopy. Results clearly show that the cross-linking increases the recombination resistance and open circuit voltage (V OC ) of the DSSC, and thereby the photoconversion efficiency of the cell. In particular, electrolytes containing 1.4 g bare and cross-linked starches showed ionic conductivities of σ = 1.61, 0.59, 0.38, and 0.35 S cm −1 , and the corresponding DSSCs showed efficiencies of 1.2, 1.4, 0.93, and 1.11%, respectively.

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

“…Interestingly, the darkening disappeared during the hot-press sealing and slowly appeared again while the cell cooled down to ambient temperature, finally stabilizing to the initial color after few hours. This phenomenon, in addition to the blue-greenish shades, suggests a possible "starch effect" due to the interactions between triiodide in the electrolyte and the polymer [37]. Further investigation of this effect will be discussed in a forthcoming paper.…”

“…Bearing in mind the idea to investigate the feasibility of stable, but sustainable solar cells with safe and truly nontoxic components, we decided to focus our efforts on low-cost, abundant bio-derived polymers and critical raw material (CRM)-free redox couples as attractive and feasible alternatives to common organic electrolyte redox mediators [ 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. In this context, we employed a standard Pt-based counter-electrode, but a further improvement in the sustainability of aqueous DSSCs should consider the development of alternative counter-electrodes [ 40 , 41 , 42 ].…”

Electrochemically Deposited NiO Films as a Blocking Layer in p-Type Dye-Sensitized Solar Cells with an Impressive 45% Fill Factor

“…DSSCs are usually made by sandwiching a photoactive electrode (i.e., anode) and a counter-electrode (CE). The latter should show a good catalytic activity toward the regeneration of a liquid [5] or quasi-solid electrolyte [6]. This configuration has two main drawbacks: on one hand, it involves the use of platinum, as a stable and efficient catalyst, which seriously undermines the sustainability of the devices [7]; on the other hand, just one of the electrodes is actively involved in light conversion.…”

Organosoluble Starch-Cellulose Binary Polymer Blend as a Quasi-Solid Electrolyte in a Dye-Sensitized Solar Cell

“…Despite the presence of additives, the energy conversion efficiency of these systems did not exceed 1%. Thus in recent studies, a novel approach of chemically modifying starch via grafting or cross-linking reactions has been adapted prior to electrolyte fabrication [8,9]. However, these methods could not resolve the high crystallinity and low mechanical strength of starch based quasi-solid electrolytes.…”