Fig. 8From: Enhanced Power Conversion Efficiency of Perovskite Solar Cells with an Up-Conversion Material of Er3+-Yb3+-Li+ Tri-doped TiO2a Nyquist plots of the devices based on mesoporous layers formed by 30NR-D without UC-TiO2 and 30NR-D with UC-TiO2. b Equivalent circuit applied to fit the EIS dataBack to article page