Multi-dimensional anatase TiO2 materials: Synthesis and their application as efficient charge transporter in perovskite solar cells

Recently, organo-metal halide perovskite (e.g., CH 3 NH 3 PbI 3 ) solar cells have shown a significant surge in progress and efficiency. The photovoltaic performance of perovskite solar cells (PSC) extensively depends on the morphology of the materials at nano-level, because the intrinsic electrical, optical and electrochemical properties also change with a change in morphology. Different TiO 2 nanostructures with diverse dimensionalities, 0D hollow TiO 2 nanoparticles (HTNPs), 3D hollow TiO 2 mesospheres (HTMSs) and 3D hierarchical TiO 2 spheres (HTSs) were synthesized hydrothermally. The PSCs based on 3D HTSs or 3D HTMSs as electron transport layers (ETLs) shows better performance than the PSCs fabricated with 0D HTNPs as ETL. The enhanced results can be attributed to the better penetration of the perovskite materials in the porous network of the HTSs or HTMSs and decreased interfacial recombination due to superior charge extraction and electron transport at the HTSs/CH 3 NH 3 PbI or HTMSs/CH 3 NH 3 Pb interfaces. By using a self-assembled TiO 2 compact layer (c-TiO 2 ), followed by a mesoporous layer of HTSs, produces PSCs with an excellent efficiency of 15.08%. Such c-TiO 2 -ETL films may improve PSCs performance by enhancing electron extraction and block the photogenerated holes.