Efficient planar CH3NH3PbBr3 perovskite solar cells prepared at room temperature with ionic-liquids/fullerene as an electron transport bilayer

A room temperature solution processed ionic liquids (1-benzyl-3-methylimidazolium chloride)/C-60 bilayer were used as the electron transport layer in planar n-i-p structure CH3NH3PbBr3 perovskite solar cells. The ionic liquids could effectively decrease the work function and improve the wettability of the perovskite precursor solution on the C-60 layer. Moreover, C-60 guarantees the excellent electron mobility. In comparison with devices with different ETLs, the IL/C-60-based solar cells show greatly improved performance, achieving the PCE of 5.88% with a J(sc )of 6.14 mA/cm(2) , a V-oc of 1.39 V, and a FF of 69.94%.