Ultrafast Flame Annealing of TiO 2 Paste for Fabricating Dye‐Sensitized and Perovskite Solar Cells with Enhanced Efficiency

Mesoporous TiO 2 nanoparticle (NP) films are broadly used as electrodes in photoelectrochemical cells, dye‐sensitized solar cells (DSSCs), and perovskite solar cells (PSCs). State‐of‐the‐art mesoporous TiO 2 NP films for these solar cells are fabricated by annealing TiO 2 paste‐coated fluorine‐doped tin oxide glass in a box furnace at 500 °C for ≈30 min. Here, the use of a nontraditional reactor, i.e., flame, is reported for the high throughput and ultrafast annealing of TiO 2 paste (≈1 min). This flame‐annealing method, compared to conventional furnace annealing, exhibits three distinct benefits. First, flame removes polymeric binders in the initial TiO 2 paste more completely because of its high temperature (≈1000 °C). Second, flame induces strong interconnections between TiO 2 nanoparticles without affecting the underlying transparent conducting oxide substrate. Third, the flame‐induced carbothermic reduction on the TiO 2 surface facilitates charge injection from the dye/perovskite to TiO 2 . Consequently, when the flame‐annealed mesoporous TiO 2 film is used to fabricate DSSCs and PSCs, both exhibit enhanced charge transport and higher power conversion efficiencies than those fabricated using furnace‐annealed TiO 2 films. Finally, when the ultrafast flame‐annealing method is combined with a fast dye‐coating method to fabricate DSSC devices, its total fabrication time is reduced from over 3 h to ≈10 min.