Improving the Performances of Perovskite Solar Cells via Modification of Electron Transport Layer

The commonly used electron transport material (6,6)-phenyl-C61 butyric acid methyl ester (PCBM) for perovskite solar cells (PSC) with inverted planar structures suffers from properties such as poor film-forming. In this manuscript, we demonstrate a simple method to improve the film-forming properties of PCBM by doping PCBM with poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) as the electron transport layer (ETL), which effectively enhances the performance of CH3NH3PbI3 based solar cells. With 5 wt % F8BT in PCBM, the short circuit current (J(SC)) and fill factor (FF) of PSC both significantly increased from 17.21 +/- 0.15 mAcm(-2) and 71.1 +/- 0.07% to 19.28 +/- 0.22 mAcm(-2) and 74.7 +/- 0.21%, respectively, which led to a power conversion efficiency (PCE) improvement from 12.6 +/- 0.24% to 15 +/- 0.26%. The morphology investigation suggested that doping with F8BT facilitated the formation of a smooth and uniform ETL, which was favorable for the separation of electron-hole pairs, and therefore, an improved performance of PSC.