Metal-Free Phthalocyanine as a Hole Transporting Material and a Surface Passivator for Efficient and Stable Perovskite Solar Cells

Abstract

Perovskite solar cells in an n-i-p structure record high power conversion efficiency, but issues of insufficient thermal stability and the high cost of p-type hole transporting materials have been raised as drawbacks. H-2-phthalocyanine (Pc) is introduced as a hole transport material to ensure the thermal stability and simultaneously have served surface passivation effects on hybrid halide perovskites as a Lewis base. Pyrrolic nitrogen in the Pc reacts with uncoordinated Pb2+ ions on the perovskite surface. Upon enhancing the interfacial interaction between phthalocyanine and the perovskite, the open circuit voltage in devices increases as compared to that of devices using a metal-phthalocyanine complex. While the phthalocyanine-applied device maintains superior thermal long-term stability, the power conversion efficiency also exceeds 20%.