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 (TiO2) have been applied as the ETL in conventional structure of perovskite solar cells (PSCs). Device structures of FTO/TiO2 compact layer/TiO2 NS layer/Perovskite/Spiro-OMeTAD/Au are used for the fabrication of PSCs in ambient conditions. Zero and one-dimensional structures of TiO2 including TiO2 nanocrystals (NCs) with the dominant size of 25 nm, TiO2 nanorods (NRs) with diameters and lengths about 80 nm and 1–2 µm, and TiO2 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 Cs0.05(MA0.17-FA0.83)0.95Pb(I0.83Br0.17)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) TiO2 nanostructures with medium size released the best current density of 21.9 mA/cm2 and maximum filling factor of 0.7. That is while the incomplete pore filling of the sublayer and lower open circuit voltage (VOC) 0.905 V had negative impacts on the power conversion efficiency of TiO2 NRs included perovskite solar cells. Remarkable results were achieved for the PSC with zero-dimensional (0D) TiO2 nanostructures as the compact ETL and highest VOC of 1.02 V led to the maximum power conversion efficiency of 14.88 % in ambient conditions.