Enhanced Photovoltaic Performance of Perovskite Solar Cells by Tuning Alkaline Earth Metal-Doped Perovskite-Structured Absorber and Metal-Doped TiO₂ Hole Blocking Layer

The perovskite solar cells (PSCs), bearing advantages including low cost of materials and solution process and high power conversion efficiency, have drawn intensive attention. Alkaline earth metal can replace the toxic lead in the perovskite-structured absorber (PSA) due to the approximate ionic radius. Some of these metals can fit an octahedral factor and Goldschmidt's tolerance factor. In this study, we partially replaced various alkaline earth metals (such as Mg, Ca, Sr, and Ba) for lead. We found that Ba was most suitable for Pb replacement in PSA and exhibited the highest photovoltaic performance. In addition, we adopted the various hole blocking layers (HBLs), including pristine TiO₂, Ag-doped TiO₂, and Zn-doped TiO₂, to enhance the photovoltaic performance. Furthermore, we replaced gold with silver for the electrode material of n-i-p PSCs, because silver exhibits high conductivity and can drastically reduce manufacturing costs. We systematically studied the photovoltaic effects of the various amount and type of alkaline earth metal doped PSAs and metal-doped TiO₂ HBLs had on PSCs. The PSCs with 5.0 mol % Ba-doped PSA and 1.0 mol % Zn-doped TiO₂ HBL enhanced the power conversion efficiency (PCE) from 11.0 to 14.1%, and its champion device reached a PCE of as high as 14.4%. Our study provides a series of innovative materials to be adopted in the fabrication of high stability PSCs.