Surface treatment of triple cation mixed perovskite for highly stable lateral photodetectors with low dark current

Owing to their remarkable optoelectronic properties, three-dimensional (3D) organic-inorganic hybrid perovskites are considered as promising candidate materials for highly sensitive photodetectors (PDs). However, intrinsic instability and high dark current of bare 3D perovskite-based PDs are limiting their potential applications. In this paper, we utilized three different ammonium salts, including the alkyl methylammonium iodide (MAI), single-ring aromatic phenylmethylammonium iodide (PMAI), and fused-ring aromatic 1-naphthylmethylamine iodide (NMAI), to treat the 3D triple cation (Cs/FA/MA) mixed perovskite film, respectively. Most notably, the PMAI treatment generates a two-dimensional (2D) (PMA)2PbI4 capping layer on the top of the 3D mixed perovskite film. The 2D layer not only passivates the surface undercoordinated iodide ions defects of the 3D perovskite film, but also protects the film from oxygen and water penetration. As a result, the PMAI-treated perovskite PD exhibits an ultra-low dark current (5.49 × 10−11 A at a 10 V bias), a high on/off ratio (∼4 × 103) and good long-term air stability. The imaging capability is also demonstrated in the bilayer device.