Impacts of Heterogeneous TiO₂ and Al₂O₃ Composite Mesoporous Scaffold on Formamidinium Lead Trihalide Perovskite Solar Cells

Heterogeneous TiO2 and Al2O3 composites were employed as a mesoporous scaffold in formamidinium lead trihalide (FAPbI3-xClx)-based perovskite solar cells to modify surface properties of a mesoporous layer. It was found that the quality and morphology of the perovskite film were strongly affected by the TiO2/Al2O3 ratio in the mesoporous film. The conversion efficiency of the perovskite solar cell was improved by using a composite of TiO2 and Al2O3 in comparison with TiO2- and Al2O3-based cells, yielding 11.0% for a cell with a 7:3 TiO2/Al2O3 composite. Our investigation shows a change of electron transport path depending on a composition ratio of insulating Al2O3 to n-type semiconducting TiO2 in a mesoporous layer.