Molecular aggregation method for perovskite–fullerene bulk heterostructure solar cells

We report morphological control with phenyl-C60-butyric acid methyl ester (PCBM) molecular aggregation for perovskite–PCBM bulk heterostructure (Pe–PCBM BHS) solar cells. Solar cells prepared via the Pe–PCBM BHS method exhibited a higher power conversion efficiency (PCE) of 18% than 11% from a device with a conventional planar heterojunction structure. The Pe–PCBM BHS can enhance device efficiency by improving electron transfer, shortening the electron transport length required for collection, and reducing the charge transfer resistance at the interface between the perovskite and PCBM through an increase of the perovskite crystal size and construction of a vertical perovskite–PCBM intermixing zone. To the best of our knowledge, the high PCE achieved by our Pe–PCBM BHS is the highest value to be reported in an inverted perovskite solar cell without buffer layers, such as metal oxides or low work function metals.