Stable Hydrophobic Ionic Liquid Gel Electrolyte for Stretchable Fiber‐Shaped Dye‐Sensitized Solar Cell

Abstract

Fiber-shaped dye-sensitized solarc ells have attracted increasingi nteresti np owering wearable and portable electronic devices. However,t he use of liquid electrolytes gives rise to vulnerabilities, greatly limiting their practical applications. Here we develop as table gel electrolyte based on polymer-ionic liquid gel with high nonvolatility and durability.T he gel electrolyte maintains aq uasi-solid state from room temperature to 98 8Ca nd can sustain high temperatures up to 300 8C. Based on this gel electrolyte, the resulting fiber-shaped dye-sensitized solar cell achieves ap ower conversion efficiency of 5.47 % that remains at 90 %a fter 30 days. The gel electrolyte makes the device more environmentally adaptive and compatible to bending and stretching deformations.With the rapid development in moderne lectronics, portable and wearabled evices attractm ore and more attention in our life. Yeti tr emains challenging to power them as the current power systems appear in planar or bulky structures that are incompatible with the required weaveability.Anew family of fiber-shaped energy harvesting and storage devices have been recently created to solve this problem.[1] For instance, fibershaped dye-sensitized solar cells (DSSCs) have been widely studied to produce high powerc onversion efficiencies up to 8.45 %.[2] However,t he use of liquid electrolytes bringss everal drawbacks, including the toxicitya nd inflammability of organic solvents and the leakage and vaporization of liquid electrolytes with the decay of powerc onversion efficiencies.[3] On one hand, many efforts have been devoted to explore ionic liquids (ILs), which are nonvolatile and avoid vaporization,b ut still suffer from the problem of leakage. [3,4] On the other hand, gel electrolytes employing solvents with high boilingp oints such as 3-methoxypropionitrile (MPN) have been studied due to ad eformable structure with no fluidity, [5] avoiding leakage as well as making them promising candidates for flexible devices.[6] However,t he vaporization problem which is detrimental for practical applications still remains due to the volatile nature of organics olvents.[7] Furthermore,t he hygroscopicity of nitrile or other solvents used in gel electrolytes would also shorten the lifetimeo fD SSCs.[8] Replacing the organic solvents by solid-state electrolytes such as IL crystalsc an sufficiently avoid the leakagea nd vaporizationp roblem, [9] and the hydrophobic nature of plastic crystals also provides resistance to water, [10] but the largely decreased current carrierm obility generally lowerst he power conversion efficiencies of DSSCs.[11] In addition, the hardnesso fI Lc rystals sacrifices the flexibility and stretchability of the resulting devices, which is disadvantageous for wearable and portable applications.Herein, an ovel gel electrolyte is developedf rom polymer and hydrophobic ionic liquid to fabricate stretchable fibershaped DSSCs. Poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) copolymer has been chosen to be the gelata in this...

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