Carbon-based perovskite solar cells (C-PSCs) without hole transport layers offer acceptable stability while they suffer from low performance. In the current study, we fabricated a two-dimensional/three-dimensional (2D/3D) hybrid perovskite layer over a FAPbI₃ layer with the assistance of triethylbenzylammonium chloride (TBACl) vapor in HTL-free C-PSCs. The TBACl vapor by reaction with the surface residual PbI₂ of FAPbI₃ passivates the grain boundaries and promotes perovskite grain growth. The 2D/3D bilayer reduces surface defects and acts as an interface modifier, reduces charge recombination processes, facilitates charge transfer processes, and shields the FAPbI₃ layer from degradation. The fabricated HTL-free C-PSCs with 2D/3D bilayers show photovoltaic performance and record a champion efficiency of 16.10%, higher than the 11.78% recorded for control devices. In addition, the 2D/3D HTL-free C-PSCs show higher stability behavior against ambient air and heating.