4.2.5. Fabrication of PCBM-PSCs with nanopatterned
TiO2 layer
The fluorine-doped tin oxide (FTO) glass was cleaned using water,
ethanol, and acetone. Then, the compact TiO2 layer was
created by spin-coating a precursor solution made of 1 ml of titanium
diisopropoxide bis(acetylacetonate) (75 wt% in isopropanol, Sigma
Aldrich, St. Louis, MO, USA) in 6 ml of butanol (99%, Daejung
Chemicals, Siheung-si, Korea) onto the FTO at 4000 rpm for 20 s,
followed by annealing at 250°C for 10 min. This process was repeated
twice. To form the mp-TiO2 layer, 1 g of
TiO2 paste (Ti-Nanoxide T/SP, Solaronix, Aubonne,
Switzerland) was diluted in 12 ml of anhydrous ethanol (99.9%, Daejung
Chemicals, Siheung-si, Korea), and spin-coated on a compact
TiO2/FTO. After slightly evaporating the solvent by
prebaking on a hotplate at 70°C for 1 min, the PFPE mold was placed on
the mp-TiO2/compact TiO2/FTO substrate
and heat-pressed for 5 min at 70°C with a pressure of 2 bar. After
removing the mold, the resulting nanopatterned
mp-TiO2/compact TiO2/FTO substrate was
then annealed at 500 °C for 1 hour. The PCBM-perovskite layer was
created by spin coating the PCBM-perovskite precursor solution at 700
rpm onto the nanopatterned mp-TiO2 layer through the
hot-casting technique at 90 °C, followed by annealing at 130 °C for 1
hour. The HTM layer was spin coated at 4000 rpm for 60 s and dried
overnight in a glovebox. All the procedure were conducted inside a dried
air-filled glovebox. Finally, the Au electrode was deposited through
thermal evaporation.