High efficiency graded band gap perovskite solar cells

We report high efficiency graded band gap perovskite solar cells with very large current output and high power conversion efficiencies (PCE) by using simultaneously mixed halides (CH$_{\mathrm{3}}$NH$_{\mathrm{3}}$SnI3 and CH$_{\mathrm{3}}$NH$_{\mathrm{3}}$PbI$_{\mathrm{3}}$-$_{\mathrm{x}}$Br$_{\mathrm{x}})$ perovskite absorber layers. An analysis of the experimental data yields a high fill factor (FF) of \textasciitilde 75{\%} and high short circuit current density (J$_{\mathrm{sc}})$ of up to 46.2 mA/cm$^{\mathrm{2}}$. These devices provide the highest current output aiming above 20{\%} PCE.