Interface Modification Using Li-Doped Hollow Titania Nanospheres for High-Performance Planar Perovskite Solar Cells

Titania nanospheres have been utilized as building blocks of electron transporting layers (ETLs) for mesoscopic perovskite solar cells (PSCs). Nevertheless, the power conversion efficiencies (PCEs) reported so far for the mesoscopic PSCs containing titania nanospheres are generally lower than those of the state-of-the-art planar PSCs. Here, we have prepared Li-doped hollow titania nanospheres (Li-HTS) through a "cation-exchange" approach and used them for the first time to modify the SnO₂ ETL/perovskite interfaces of planar PSCs. The Li-HTS-modified PSC delivered a PCE of 23.28% with a fill factor (FF) of over 80%, which is significantly higher than the PCE of the control device (20.51%). This is the best PCE achieved for PSCs containing titania nanospheres. Moreover, interfacial modification using Li-HTS greatly improves the stability of the PSCs. This work demonstrates the potential of interface modification using inorganic nanostructures for enhancing the efficiency and stability of planar PSCs.