In recent years, hybrid organic–inorganic perovskite light absorbers have attracted much
attention in the field of solar cells due to their optoelectronic characteristics that enable high power
conversion efficiencies. Perovskite-based solar cells’ efficiency has increased dramatically from
3.8% to more than 20% in just a few years, making them a promising low-cost alternative for
photovoltaic applications. The deposition of perovskite into a mesoporous metal oxide is an
influential factor affecting solar cell performance. Full coverage and pore filling into the porous metal
oxide are important issues in the fabrication of highly-efficient mesoporous perovskite solar cells.
In this work, we carry out a structural and quantitative investigation of CH3NH3PbI3 pore filling
deposited via sequential two-step deposition into two different mesoporous metal oxides—TiO2
and Al2O3. We avoid using a hole conductor in the perovskite solar cells studied in this work to
eliminate undesirable end results. Filling oxide pores with perovskite was characterized by Energy
Dispersive X-ray Spectroscopy (EDS) in Transmission Electron Microscopy (TEM) on cross-sectional
focused ion beam (FIB) lamellae. Complete pore filling of CH3NH3PbI3 perovskite into the metal
oxide pores was observed down to X-depth, showing the presence of Pb and I inside the pores.
The observations reported in this work are particularly important for mesoporous Al2O3 perovskite
solar cells, as pore filling is essential for the operation of this solar cell structure. This work presents
structural and quantitative proof of complete pore filling into mesoporous perovskite-based solar
cells, substantiating their high power conversion efficiency.