Periodic Acid Modification of Chemical-Bath Deposited SnO 2 Electron Transport Layers for Perovskite Solar Cells and Mini Modules.

Chemical bath deposition (CBD) has been demonstrated as a remarkable technology to fabricate high-quality SnO 2 electron transport layer (ETL) for large-area perovskite solar cells (PSCs). However, surface defects always exist on the SnO 2 film coated by the CBD process, impairing the devices' performance. Here, a facile periodic acid post-treatment (PAPT) method is developed to modify the SnO 2 layer. Periodic acid can react with hydroxyl groups on the surface of SnO 2 films and oxidize Tin(II) oxide to Tin(IV) oxide. With the help of periodic acid, a better energy level alignment between the SnO 2 and perovskite layers is achieved. In addition, the PAPT method inhibits interfacial nonradiative recombination and facilitates charge transportation. Such a multifunctional strategy enables to fabricate PSC with a champion power conversion efficiency (PCE) of 22.25%, which remains 93.32% of its initial efficiency after 3000 h without any encapsulation. Furthermore, 3 × 3 cm 2 perovskite mini-modules are presented, achieving a champion efficiency of 18.10%. All these results suggest that the PAPT method is promising for promoting the commercial application of large-area PSCs.