[en] Titanium dioxide (TiO₂) is a widely used electron transport material in organic-inorganic hybrid perovskite solar cells (PSCs). In order to reveal the influence of an additional mesoporous TiO₂ (mp-TiO₂) layer on fabricating large-area perovskite solar cells using TiO₂ as the electron transport layer, we have conducted a comprehensive study on the solution-processed PSCs with or without an additional mp-TiO₂ layer. Photoemission spectroscopy measurement indicates that, compared with the compact TiO₂ (cp-TiO₂) layers, the mp-TiO₂ layers possess a slightly larger work function, which will improve the electron extraction efficiency at the perovskite-TiO₂ interface. The PSCs with an additional mp-TiO₂ layer exhibit better performances than those with only a cp-TiO₂ layer. They suffer from a smaller efficiency loss when enlarging the device area from 0.16 to 1.44 cm² and exhibit a better long-term stability. About 89% of the initial efficiency is retained after keeping in dry air for 1000 h for the device with an active area of 1.44 cm². For both cases, increasing the active device area is beneficial to long term stability, photoluminescence measurement indicates that this is result from the degradation of perovskite films starts at the margin of the cells. Our work implies the indispensable role of the additional mp-TiO₂ layer for optimizing the performances of large-area PSCs using TiO₂ as the electron transport layer. (paper)