Mixed aliphatic and aromatic ammonium halides passivation in a chloride-iodide perovskite solar cell

Three-dimensional and two-dimensional perovskite solar cells are becoming popular due to their simultaneous improvements in efficiency and stability. The deposition of long aliphatic or bulky aromatic ammonium halide precursors promotes the formation of a quasi-two-dimensional perovskite layer on top of the three-dimensional perovskite. This quasi-two-dimensional layer serves two leading roles: passivation, which enhances efficiency, and capping, which maintains stability. A thorough comparison of the passivation effects of aliphatic and aromatic organic precursors on the performance of perovskite solar cells is scarce in the literature. Additionally, studies on the passivation effects of mixed aliphatic and aromatic organic precursors are limited. In this work, tert-octylammonium chloride/bromide is used as an aliphatic organic precursor, while methoxy-phenethylammonium chloride/bromide is selected as an aromatic organic precursor. We achieved an excellent device using a mixed passivation strategy comprising 70% methoxy-phenethylammonium chloride and 30% tert-octylammonium bromide. The device demonstrates a power conversion efficiency of around 22% and retains approximately 96% of its initial efficiency after 1000 hours. • Top interface passivation using mixed aliphatic and aromatic halides • Effective 2D perovskite capping layer formation on top of the chloride-iodide 3D perovskite • Effective self-formation of SnCl 2 passivation layer at the buried interface • Higher efficiency of about 22% and longer stability of about 96% efficiency after 1000 hours