High-Efficiency Flexible Perovskite Solar Cells Enabled by an Ultrafast Roomerature Reactive Ion Etching Process

Perovskite solar cells (PSCs), which have surprisingly emerged in recent years, are now aiming at commercialization. Rapid, lowerature, and continuous fabrication processes that can produce high-efficiency PSCs with a reduced fabrication cost and shortened energy payback time are important challenges on the way to commercialization. Herein, we report a reactive ion etching (RIE) method, which is an ultrafast roomerature technique, to fabricate mesoporous TiO₂ (mp-TiO₂) as an electron transport layer for high-efficiency PSCs. Replacing the conventional higherature annealing process by RIE reduces the total processing time for fabricating 20 PSCs by 40%. Additionally, the RIE-processed mp-TiO₂ exhibits enhanced electron extraction, whereupon the optimized RIE-mp-TiO₂-based PSC exhibits a power conversion efficiency (PCE) of 19.60% without J-V hysteresis, when the devices were optimized with a TiCl₄ surface treatment process. Finally, a flexible PSC employing RIE-mp-TiO₂ is demonstrated with 17.29% PCE. Considering that the RIE process has been actively used in the semiconductor industry, including for the fabrication of silicon photovoltaic modules, the process developed in this work could be easily applied toward faster, simpler, and cheaper manufacturing of PSC modules.