Role of chlorine in the performance of mixed halide perovskite solar cells

Recently introduced mixed halide perovskite solar cells have attracted considerable attention due to the demonstrated high photoconversion efficiency and the anticipated low cost fabrication. The presence of chlorine in CH3NH3PbX3 (x $=$ halogen) apparently increased the carrier diffusion length to about 1 micron. Increase in carrier diffusion length enabled use of inorganic thin films instead of high surface area nanostructures as electron transport medium. However, due to the ferroelectric behavior of organic halides, the devices often give unreliable efficiency values and other solar cell parameters. We observed that chlorine play a significant role in the reliability of cell characteristics, We will present the result of our photo-impedance spectroscopy studies on chlorine-iodine based metalorganic perovskite cells.