Solvent‐Mediated Dimension Tuning of Semiconducting Oxide Nanostructures as Efficient Charge Extraction Thin Films for Perovskite Solar Cells with Efficiency Exceeding 16%

The recent surge in efficiency and progress of organohalide perovskite solar cells (PSCs) has been significant. The PSC performance is significantly influenced by nanostructuring as this varies the intrinsic optical, electrical, and electrochemical properties. Diverse TiO 2 electron transport layers (ETLs) are solvothermally grown on the transparent conducting oxide substrate with different dimensionalities, 0D nanoparticles (TNP), 1D nanowires (TNW) to 2D nanosheets (TNS), by varying the organic solvent used. These layers feature enhanced optical transparency (≈2%–5% transmittance improvement compared to pristine fluorine doped tin oxide, FTO, glass) minimizing light absorption losses. PSCs constructed using 1D TNW or 2D TNS yield enhanced photovoltaic performance compared to the 0D TNP counterparts. This is a result of i) improved infiltration of the perovskite in the porous TNW or TNS network and ii) facilitated electron transport and charge extraction at the TNW/perovskite or TNS/perovskite interfaces, thus reduced interfacial recombination loss. Employing a bilayered ETL film consisting of a self‐assembled TiO 2 blocking layer and a subsequent TNW active layer, produces PSC devices with an efficiency exceeding 16%. This bilayered ETL film can simultaneously block the photogenerated holes and enhance electron ­extraction, therefore improving PSC performance.