Abstract: The self-assembly process for compatible functional layers of devices is a simple, feasible, and energy-saving strategy. In mesoporous perovskite solar cells (PSCs), compact and scaffold TiO₂ films generally function as the hole-blocking and electron-transporting layers, respectively. However, both of these layers are usually generated through a high-temperature annealing process. Here, we deposited TiO₂ compact films through a room-temperature self-assembly process as effective hole-blocking layers for PSCs. The thickness of TiO₂ compact films can be easily controlled by the deposition time. Through the optimization of TiO₂ compact films (80 nm), the power conversion efficiency (PCE) of mesoporous PSCs without and with hole conductor layers increases up to 10.66% and 17.95%, respectively. Notably, an all-low-temperature planar PSC with the self-assembled TiO₂ layer exhibits a PCE of 16.41%.