Toward Highly Reproducible, Efficient, and Stable Perovskite Solar Cells via Interface Engineering with CoO Nanoplates.

It is well-known that solution-processed polycrystalline perovskite films show a high density of parasitic traps and the defects mainly exist at grain boundaries and surfaces of polycrystal perovskite films, which would limit potential device performance by triggering the undesired recombination and impair device long-term stability by accelerating the degradation of perovskite films. In this regard, defect passivation is highly desirable for achieving efficient and stable perovskite solar cells (PSCs). Here, we report the fabrication of highly reproducible, efficient, and stable PSCs via interface engineering with CoO nanoplates. When a suitable concentration of CoO nanoplates solution is spin-coated on perovskite film, a discontinuous CoO nanoplates modified layer is obtained, which is advantageous to achieving highly photovoltaic performance of the device because the uncovered perovskite crystalline grains can guarantee the unobstructed transport of holes from perovskite layers to hole transport layers. Furthermore, the hydrophobic oleylamine ligands capped CoO nanoplates are well filled in the boundaries of perovskite crystalline grains to effectively passivate the trap states, suppress dark recombination, and enhance moisture-resistance. These benefits are propitious to achieving a 20.72% champion efficiency and a 20.20% steady-state efficiency of the devices with good reproducibility and stability.