Aerogel Films as Electrolyte Absorbers in DSSCs.CNC−POEGMA aerogels (1 wt % sol−gel concentration, 1:1 CNC:POEGMA weight ratio) were cast on DSSC counter electrode substrates and patterned into 5 × 8 mm2 shapes (corresponding to dimensions of the photoelectrode) by using a stencil lift-off approach as described in previous work (see Figure S1 for schematic of protocol).40 This aerogel composition and density were chosen due to its high porosity (>99%, Figure 1),44 solvent stability (Figure 2A), minimal swelling (Figure 2B), high capacity for liquid uptake (Figure 2C), and flexible shape-recovery mechanical properties.44 Aerogels at two thicknesses were fabricated by using a 7 or 85 μm thick patterning mold, resulting in aerogel thicknesses of 10 ± 4 and 44 ± 4 μm, respectively. Liquid electrolyte was rapidly absorbed and retained by the aerogel after drop-casting, allowing for the preparation of the DSSCs without the postelectrolyte filling step. Because of the high porosity of the aerogel scaffold, the liquid electrolyte within the scaffold can wet the nanoporous TiO2 photoelectrode in a similar manner with the reference (conventional) cells. It should be noted that the thicker aerogel was compressed when assembling the cell, as the FTO-glass was kept apart using a 25 μm thick spacer. A schematic of the assembled DSSCs is shown in Figure S2.