Fig. 3.

a Current–voltage curve for planar perovskite solar cells using TiO₂/CH₃NH₃PbI_3-xCl_x/Spiro-OMeTAD/Au architecture, the perovskite films prepared by mixing with different concentrations of Cl ions. The measurements are carried out under 100 mW cm⁻². b Plots of $-\text{d}V/\text{d}J\text{versus}\left(\frac{1+R_{\text{sh}}^{-1}\frac{\text{d}V}{\text{d}J}}{J_{\text{sc}}-J-V/R_{\text{sh}}}\right)$ (symbols) and the linear fitted curve (solid lines). c Plots of ln(J _sc − J − V/R _sh) versus V + JR _s (symbols) and the linear fitted curve (solid lines). (Color figure online)