The porosity optimization of an electron transporting layer (ETL) in the perovskite solar cells (PSCs) can make the effective pathways for transporting electron and blocking the holes. In the present study, the porosity modification effect of TiO2 paste as the most efficient ETL using TiO2 hollow spheres (TiO2 - HSs) on the air-processed formation of perovskite films is studied. In this procedure, the TiO2 - HSs were synthesized using removable carbonaceous sphere templates, Our characterization results demonstrated that prepared TiO2 - HSs showed an external diameters less than 200 nm with shell thickness about 2030 nm. Due to the high porosity of the TiO2 - HSs, CH3NH3PbI3 sufficiently infiltrate into the modified ETL. Thus a high-quality perovskite film with large grain size and smooth surface fabricated on the modified ETL. Further time resolved photoluminescence (TRPL) investigation reveals that an increase in the electron injection and recombination resistance leading to the performance improvement of the PSCs. The best fully ambient processed device with a modified electron transporting layer exhibited an efficiency of 19.62%, which is 16.37% higher than the efficiency of the standard PSC. Application of TiO2-HSs in the ETL can help to the development of air-processed perovskite solar cells for commercialization in the future. (C) 2019 Elsevier Inc. All rights reserved.