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Properties and Improvements of Chlorine-Doped Methylamine-Based Perovskites

Photoactive lead halide perovskites with high crystalline structure and low well-state density are prerequisites for achieving high photovoltaic performance, and methylammonium lead iodide (MAPbI3), regarded as the standard perovskite model compound, has been extensively studied. In recent years, the photoelectric conversion efficiency (PCE) devices of organic-inorganic halide perovskite solar cells have also been greatly improved. However, methylammonium lead iodide is structurally unstable, which affects the long-term stability of the device and limits its practical application. Due to the advantages of mixed halide perovskites such as high light absorption capacity, long carrier diffusion length, high carrier mobility, and tunable band gap, the use of mixed halide perovskites has become a promising candidate for improving the efficiency of organometallic halides. A crucial strategy for the optoelectronic device performance of perovskite materials is to modify their optoelectronic properties by changing the halide used or by a mixture of halides. Adding a small amount of chlorine to MAPbI3 can trigger perovskite crystallization and stabilize the MAPbI3 lattice, which can improve device performance and greatly improve the stability of perovskite materials to moisture and heat. Although perovskites containing chlorine precursors have been successful in perovskite solar cells, how chloride ions affect the structural and electronic properties of these films has been a long-standing puzzle. In this paper, we experimentally compared the performance and difference of the red-brown perovskite thin film (MAPbI2Cl) obtained by one-step spin coating using MACl and PbI2 with traditional MAPbI3 perovskite solar cells. For the first time, a two-phase coexistence perovskite of MAPbI3 and MAPbCl3 was discovered. A series of tests and characterizations were carried out on this two-phase perovskite. It was found that it has the advantages of good crystallinity and long life, and its power conversion efficiency has also been significantly improved. This paper provides a new method for the preparation of efficient and stable perovskite solar cells.