Interface Engineering by Unsubstituted Pristine Nickel Phthalocyanine as Hole Transport Material for Efficient and Stable Perovskite Solar Cells.

Lead halide perovskite solar cells (PSCs) have been rapidly developed in the past decade. With the development of a PSC, interface engineering plays an increasingly important role in maximizing device performance and long-term stability. We report a simple and effective interface engineering method for achieving improvement of PSCs up to 20% by employing unsubstituted pristine nickel phthalocyanine (NiPc). Thermal annealing of NiPc improves the interface between NiPc and perovskite because of the incorporation of NiPc molecules into the perovskite grain boundaries, which creates improvements in hole extraction from the perovskite absorber layer, as evidenced by time-resolved photoluminescence measurements. This significantly improves the charge transfer and collection efficiency, which are closely related to the improvement of the interface between perovskite and NiPc.