Metallophthalocyanine-Based Molecular Dipole Layer as a Universal and Versatile Approach to Realize Efficient and Stable Perovskite Solar Cells.

ABSTRACT

It is well known that tailoring the interfacial structure is very important for perovskite solar cells, especially for its performance and stability. Here, we report a universal and versatile method of modulating the energetic alignment between the perovskite and hole-transporting layer by introducing a multifunctional dipole layer based on metallophthalocyanine derivatives copperphthalocyanine (CuPc) or highly fluorinated copper hexadecafluorophthalocyanine (F16CuPc). Both molecules were introduced through an "antisolution" process to treat the surface of organic-inorganic CH3NH3PbI3 perovskite. The dipole layer can well align the interfacial energy levels, passivate the CH3NH3PbI3 surface, and fill the grain boundaries, resulting in greatly suppressed charge recombination. As a result, our planar CH3NH3PbI3 perovskite devices exhibit the best power conversion efficiency of 20.2%, with significantly enhanced open-circuit voltages ( Voc) of 1.112 V (CuPc) and 1.145 V (F16CuPc), which is a record high Voc value for CH3NH3PbI3 thin-film solar cells. More importantly, the use of highly fluorinated F16CuPc produces a significantly more hydrophobic surface, leading to drastically improved long-term stability under ambient conditions. We believe that our study offers a general approach to making multifunctional dipole layers, which are necessary for achieving both stable and efficient perovskite solar cells.