Capacitance of the double layers of the Pt electrode/electrolyte interface was chiefly determined by capacitance of the compact layer according to the Helmoholtz theory.
After cooling down to room temperature naturally, a 1 μm TiO2 nanocrystalline layer (PASOL HPW-18NR) was deposited on top of the compact layer by screen printing and then sintered at 500°C for 30 min.
Figure 5b shows the SEM image of the film containing 30NR-D and UC-TiO2 deposited on the compact layer by spin-coating method.
After drying, mesoporous TiO2 (mp-TiO2) film with thickness of ~200 nm was deposited on the compact layer by spin-coating TiO2 paste (Dyesol 18NR-T) diluted in ethanol at 1 5 by weight at 5000 rpm for 30 s.
A mesoporous TiO2 film was obtained by spin-coating TiO2 solution on the compact layer at 4000 rpm for 30 s, followed by annealing at 100 °C for 10 min and 500 °C for 30 min, respectively.
The compact layer was prepared by the diluted sol through the layer-by-layer (LBL) self assembly technique to control its thickness.
A mechanism whereby the compact layer is formed by re-deposition of the pyrolysis gas in the char layer skeleton, which is initially relatively porous, is proposed to explain the formation of the compact/porous structure.
Compared with the traditional DSSCs without this compact layer, the solar energy-to-electricity conversion efficiency, short-circuit current and open-circuit potential of the DSSCs with the compact layer were improved by 33.3%, 20.3%, and 10.2%, respectively.
The morphology and microstructure of the compact layer were observed by field emission scanning electron microscope (FESEM, JEM-7001F, JEOL) and scanning probe microscope (Multimode 8, Bruker, America).
At this higher tyre pressure the first pass broke up the compact layer, which was then re-compacted by the second pass and broken up again by the first pass.
