Electron transport engineering with different types of titanium dioxide nanostructures in perovskite solar cells

The light-harvesting effects and electron transport engineering could be achieved by manipulating electron transport layer (ETL) morphology. In This research, three variant nanostructures (NSs) of titanium dioxide (TiO ₂ ) have been applied as the ETL in conventional structure of perovskite solar cells (PSCs). Device structures of FTO/TiO ₂ compact layer/TiO ₂ NS layer/Perovskite/Spiro-OMeTAD/Au are used for the fabrication of PSCs in ambient conditions. Zero and one-dimensional structures of TiO ₂ including TiO ₂ nanocrystals (NCs) with the dominant size of 25 nm, TiO ₂ nanorods (NRs) with diameters and lengths about 80 nm and 1–2 µm, and TiO ₂ nanofibers (NFs) with the same dimensional parameters of 100 nm and 2–12 µm were prepared through the hydrothermal method. Then the effects of ETL morphology on the electron transporting process, interfacial engineering, surface quality and cell performance have been investigated. Triple Cation Cs _0.05(MA _0.17-FA _0.83) _0.95Pb(I _0.83Br _0.17) ₃ perovskite is also used as the light harvester layer in PSCs due to its proper band gap energy, crystalline quality and longtime stability. According to the results, one-dimensional (1D) TiO ₂ nanostructures with medium size released the best current density of 21.9 mA/cm ² and maximum filling factor of 0.7. That is while the incomplete pore filling of the sublayer and lower open circuit voltage (V _OC) 0.905 V had negative impacts on the power conversion efficiency of TiO ₂ NRs included perovskite solar cells. Remarkable results were achieved for the PSC with zero-dimensional (0D) TiO ₂ nanostructures as the compact ETL and highest V _OC of 1.02 V led to the maximum power conversion efficiency of 14.88 % in ambient conditions.