Abstract
In the quest for sustainable materials for quasi-solid-state (QS) electrolytes in aqueous dye-sensitized solar cells (DSSCs), novel bioderived polymeric membranes were prepared in this work by reaction of preoxidized kraft lignin with poly(ethylene glycol)diglycidylether (PEGDGE). The effect of the PEGDGE/lignin relative proportions on the characteristics of the obtained membranes was thoroughly investigated, and clear structure–property correlations were highlighted. In particular, the glass transition temperature of the materials was found to decrease by increasing the amount of PEGDGE in the formulation, indicating that polyethylene glycol chains act as flexible segments that increase the molecular mobility of the three-dimensional polymeric network. Concurrently, their swelling ability in liquid electrolyte was found to increase with the concentration of PEGDGE, which was also shown to influence the ionic transport efficiency within the membrane. The incorporation of these lignin-based cross-linked systems as QS electrolyte frameworks in aqueous DSSCs allowed the preparation of devices with excellent long-term stability under UV–vis light, which were found to be superior to benchmark QS-DSSCs incorporating state-of-the-art carboxymethylcellulose membranes. This study provides the first demonstration of lignin-based QS electrolytes for stable aqueous DSSCs, establishing a straightforward strategy to exploit the potential of lignin as a functional polymer precursor for the field of sustainable photovoltaic devices.
Highlights
The progressive reduction of fossil resources and the severe environmental problems associated with their extensive use are pushing both academia and industry to resort to different routes for the development of more sustainable added-value products and processes
This study reports on the preparation and characterization of hydrophilic lignin-based membranes produced by cross-linking a preoxidized kraft lignin with poly(ethylene glycol) diglycidyl ether (PEGDGE) and on their application as QS electrolytes in aqueous dye-sensitized solar cells (DSSCs)
Novel bioderived polymeric membranes based on the cross-linking reaction between preoxidized kraft lignin and poly(ethylene glycol)diglycidylether (PEGDGE) were fabricated, characterized, and employed as QS electrolytes in aqueous DSSC devices
Summary
The progressive reduction of fossil resources and the severe environmental problems associated with their extensive use are pushing both academia and industry to resort to different routes for the development of more sustainable added-value products and processes. Based on the characteristic figures introduced so far, the ratio between ṽ·φPEGDGE and ERd (ṽ·φPEGDGE/ERd, indicated with the letter Χ in the following) can be considered as a qualitative measure of the combined effect on device efficiency of macromolecular 3D structure of the membrane and ionic mass transport through the electrolyte, at varying lignin/ PEGDGE relative proportions. The aging test was carried out for 5 weeks on three batches of three devices each: one set fabricated with LM_1 membrane (the one providing the highest device efficiency as reported in Figure 6), one set incorporating a QS electrolyte based on a different polymeric matrix (NaCMC), and one set based on reference liquid-state DSSCs. NaCMC was proposed by our group for water-based some years ago,[41] demonstrating its good operation and remarkable stability and representing a valuable choice to gauge the properties of the lignin-based systems presented in this work. The potential motion of harmful, photogenerated radical species is largely restricted with consequent limitation in their interaction with the photoactive components of the device assembly
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