High performance planar heterojunction perovskite solar cells with fullerene derivatives as the electron transport layer.

In this study, we report the utilization of solution-processed high electrical conductive [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) combined with solution-processed TiO2 as the electron transport layer (ETL) to overcome extremely low electrical conductivity of solution-processed TiO2 ETL in planar heterojunction (PHJ) perovskite hybrid solar cells (pero-HSCs). Due to the much more preferable electron extraction and transportation of PC61BM at the cathode side, a tremendously boosted short-circuit current density (JSC), fill factor (FF) and enhanced power conversion efficiency (PCE) are observed. To further address the wettability issues of perovskite materials on the top of PC61BM, water-soluble fullerene derivative is applied to modulate the surface of PC61BM. Consequently, further advanced FF with slightly enlarged JSC and open-circuit voltage (VOC) are observed. The resulted PCE is comparable with the meso-superstructured solar cells in which high PCEs can be produced. Our studies certainly provide a simple approach to boost the efficiency of PHJ pero-HSCs.