All Room‐Temperature‐Processed Carbon‐Based Flexible Perovskite Solar Cells with TiO2 Electron Collection Layer

Herein, low‐cost, solution‐based, all room‐temperature‐processed carbon‐based triple‐cation perovskite solar cells (C‐PSC) with TiO 2 electron transport layer (ETL) are reported. The hydrothermally synthesized anatase TiO 2 nanoparticles with titanium diisopropoxide bis(acetylacetonate) doping results in high‐quality and uniform ETL with improved interparticle connectivity. The room‐temperature crystallization of pure photoactive α‐phase perovskite absorber layer MA 0.14 FA 0.77 Cs 0.09 PbI 2.5 Br 0.5 is achieved with the combination of diethyl ether anti‐solvent treatment and nitrogen gas‐assisted drying. The resultant film is dense and smooth with pinhole‐free uniform grain distribution. The C‐PSCs with TiO 2 processed at 500 °C give 12.07% efficiency, whereas the room‐temperature‐processed TiO 2 (RT TiO 2 ) ETL‐based device shows 10.57% efficiency. Furthermore, this RT TiO 2 and room‐temperature crystallized perovskite layer are employed in all room‐temperature‐processed flexible C‐PSC with ≈8% efficiency. The fabricated C‐PSCs exhibit significant stability for more than 1 month, with a T 80 of 335 h.