Block ionomers cast from solution exhibit solvent-templated morphologies that can be altered by solvent-vapor annealing. When cast from a mixed solvent, a midblock-sulfonated pentablock ionomer self-assembles into spherical ionic microdomains that are loosely connected. Upon exposure to liquid water, nanoscale channels irreversibly develop between the microdomains due to swelling and form a continuous mesoscale network. We use electron tomography and real-time X-ray scattering to follow this transformation and show that the resultant morphology provides a highly effective diffusive pathway.

molecule absorbs a photon and becomes oxidized, electrons in the photosensitizer jump from their ground state to an excited state. These electrons, injected into the conduction band of TiO 2 nanoparticles, fl ow through a load to the anode where they are reintroduced into the cell and chemically reduce the dye so that the dye can absorb another photon and repeat the process. While liquid electrolytes yield high effi ciencies, [ 18 ] such devices suffer from solvent leakage and evaporation. [ 19 ] For this reason, DSSC research has shifted to using quasi-solid electrolytes, [ 20 ] and recent efforts have established [21][22][23] that the effi ciency and stability of DSSC devices containing electrolyte gels can exceed the performance of their liquid counterparts. Burschka et al. [ 24 ] have reported that solid-state DSSCs can achieve an effi ciency of 15% through the use of a hybrid perovskite dye.Ongoing demands to produce environment friendly, inexpensive, and reliable OPVs have likewise promoted the development of aqueous DSSCs. Using 1-methyl-3-propylimidazolium iodine with up to 10 wt% water has enabled a conversion effi ciency of up to 4.2%. [ 25 ] Combining a gel and dye with an aqueous environment has guided Velev and co-workers [ 26,27 ] to adopt a biomimetic approach by which to design OPVs on the basis of leaves. In this spirit, they have introduced the concept of hydrogel photovoltaic (HGPV) devices composed of an agarose gel containing 98 wt% water and exhibiting fi ll factor (FF) values up to 0.37 (the FF is a measure of the maximum power of a solar cell). Complementary FF values measured from biophotovoltaic HGPVs, inspired by the sequential charge-separation Z-scheme responsible for photosynthesis, have been recently reported by Schuhmann and co-workers [ 28,29 ] to range from 0.13 to 0.56. While the physical networks formed by natural gelling agents in HGPVs are stable, they are nonetheless mechanically fragile. Tough hydrogels substituted for this purpose tend to rely on chemical cross-linking and suffer from aging over time. To expand this biomimetic design with a physically cross-linkable macromolecule that exhibits excellent mechanical and stability attributes, we have chosen to fabricate HGPVs from self-organized multiblock copolymers, [ 30 ] each with a charged and thus hydrophilic midblock. These sulfonated block ionomers (SBIs), previously used in highly responsive ionic polymer-metal composites, [ 31 ] behave as thermoplastic elastomers (TPEs). For this reason and to retain consistency with the terminology we proposed earlier [ 32,33 ] for midblock-solvated TPE gels (as TPEGs), the resulting OPVs are hereafter referred to as photovoltaic elastomer gels (PVEGs).The PVEGs examined here are fabricated from poly[

As the threat of global climate change due to combustion emissions becomes increasingly alarming, the search for clean and sustainable alternative energy is of paramount importance. With this objective in mind, harnessing solar energy is particularly attractive due to ongoing improvements in silicon‐, perovskite‐, and organic‐based solar cells. Of these, dye‐sensitized solar cells (DSSCs) constitute a promising technology due to their relatively low cost, moderate conversion efficiency, and robust mechanical properties. An important breakthrough in the development of DSSCs is the use of polymer gel electrolytes. In this work, we employ amphi­philic thermoplastic elastomers (TPEs) in the form of sulfonated block ionomer (SBI) homologs for this purpose. Since the midblock of each charged copolymer is hydrophilic, the resultant microphase‐separated nanostructures consist of continuous ionic channels that facilitate electron diffusion. A unique characteristic of the SBI archetype studied here is that the morphology can be solvent‐templated. We exploit this feature by introducing either hydrophilic or hydrophobic photosensitizers into the DSSCs. When the SBI exhibits a primarily lamellar morphology, a hydrophilic dye yields the highest efficiency (7.0%), whereas the opposite is observed when the nanostructure consists of a solvent‐templated nonpolar matrix. Photosensi­tizer tunability is augmented by the intrinsic mechanical and adhesive properties of a TPE.

In this study, a sulfonated pentablock ionomer is considered for use as an aqueous gel electrolyte in photovoltaic elastomer gels (PVEGs) containing photosensitive dyes. Depending on the casting solvent employed, these materials order into different nanoscale morphologies, some of which inherently consist of a continuous pathway through which ions and other polar species are able to diffuse, while others transform into continuous channels upon exposure to water. Here, we examine the effect of solvent polarity during film casting, vapor annealing, and liquid immersion on block ionomer morphology and PVEG photovoltaic performance. Casting the block ionomers from a mixed nonpolar/polar solvent promotes the formation of dispersed ion-rich spherical microdomains. Alternatively, the use of a single polar solvent produces coexisting nonpolar cylinders and lamellae. Exposure of either morphology to polar solvent vapor causes the block ionomers to restructure into a lamellar morphology, whereas exposure of dispersed ion-rich microdomains to water induces a transformation to an irregular morphology composed of continuous ionic channels, which provide an effective pathway for ion diffusion and, consequently, the highest photovoltaic efficiency. In addition to their photovoltaic efficacy, these aqueous gels possess improved mechanical properties (in terms of tensile strength and elastic modulus) in the presence of photosensitive dyes. V C 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 85-95

To address the increasingly alarming threat of global climate change, Richard J. Spontak and co‐workers demonstrate dye‐sensitized solar cells, which are composed of amphiphilic, thermoplastic elastomeric block ionomers in article number http://doi.wiley.com/10.1002/solr.201700145. The midblock of each ionomer is hydrophilic and therefore the microphase‐ separated nanostructures are network‐forming and solvent‐templatable, consisting of continuous ionic channels that facilitate electron diffusion. The achieved effi ciency of these solar cells by using either hydrophilic or hydrophobic photosensitizers is as high as 7%.