Efficient Perovskite Solar Cells by Reducing Interface-Mediated Recombination: a Bulky Amine Approach

The presence of non-radiative recombination at the perovskite surface/interface limits the overall efficiency of perovskite solar cells (PSCs). Surface passivation has been demonstrated as an efficient strategy to suppress such recombination in Si cells. Here, 1-naphthylmethylamine iodide (NMAI) is judiciously selected to passivate the surface of the perovskite film. In contrast to the popular phenylethylammonium iodide, NMAI post-treatment primarily leaves NMAI salt on the surface of the perovskite film. The formed NMAI layer not only efficiently decreases the defect-assisted recombination for chemical passivation, but also retards the charge accumulation of energy level mis-alignment for vacuum level bending and prevents minority carrier recombination due to the charge-blocking effect. Consequently, planar PSCs with high efficiency of 21.04% and improved long-term stability (98.9% of the initial efficiency after 3240 h) are obtained. Moreover, open-circuit voltage as high as 1.20 V is achieved at the absorption threshold of 1.61 eV, which is among the highest reported values in planar PSCs. This work provides new insights into the passivation mechanisms of organic ammonium salts and suggests future guidelines for developing improved passivation layers.